scratchstack_aws_signature/

canonical.rs

//! Canonicalization functionality for signature generation and validation.
//!
//! This includes various URL and header canonicalization functions, as well as the ability to
//! create an AWS SigV4 canonical request.
//!
//! **Stability of this module is not guaranteed except for items exposed at the crate root**.
//! The functions and types are subject to change in minor/patch versions. This is exposed for
//! testing purposes only.

use {
    crate::{
        auth::{SigV4Authenticator, SigV4AuthenticatorBuilder},
        chronoutil::ParseISO8601,
        crypto::{sha256, sha256_hex, SHA256_OUTPUT_LEN},
        SignatureError, SignatureOptions,
    },
    bytes::Bytes,
    chrono::{offset::FixedOffset, DateTime, Utc},
    encoding_rs::UTF_8,
    http::{
        header::{HeaderMap, HeaderValue},
        request::Parts,
        uri::Uri,
    },
    lazy_static::lazy_static,
    log::trace,
    qualifier_attr::qualifiers,
    regex::Regex,
    std::{
        borrow::Cow,
        collections::HashMap,
        fmt::{Debug, Formatter, Result as FmtResult},
        str::from_utf8,
    },
};

/// Content-Type string for HTML forms
const APPLICATION_X_WWW_FORM_URLENCODED: &str = "application/x-www-form-urlencoded";

/// Header parameter for the authorization
const AUTHORIZATION: &str = "authorization";

/// Algorithm for AWS SigV4
const AWS4_HMAC_SHA256: &str = "AWS4-HMAC-SHA256";

/// Algorithm for AWS SigV4 (bytes)
const AWS4_HMAC_SHA256_BYTES: &[u8] = b"AWS4-HMAC-SHA256";

/// Content-Type parameter for specifying the character set
const CHARSET: &str = "charset";

/// Header field for the content type
const CONTENT_TYPE: &str = "content-type";

/// Signature field for the access key
const CREDENTIAL: &[u8] = b"Credential";

/// Header parameter for the date.
const DATE: &str = "date";

/// Uppercase hex digits.
const HEX_DIGITS_UPPER: [u8; 16] =
    [b'0', b'1', b'2', b'3', b'4', b'5', b'6', b'7', b'8', b'9', b'A', b'B', b'C', b'D', b'E', b'F'];

/// Error message: `"Authorization header requires 'Credential' parameter."`
const MSG_AUTH_HEADER_REQ_CREDENTIAL: &str = "Authorization header requires 'Credential' parameter.";

/// Error message: `"Authorization header requires existence of either a 'X-Amz-Date' or a 'Date' header."`
const MSG_AUTH_HEADER_REQ_DATE: &str =
    "Authorization header requires existence of either a 'X-Amz-Date' or a 'Date' header.";

/// Error message: `"Authorization header requires 'Signature' parameter."`
const MSG_AUTH_HEADER_REQ_SIGNATURE: &str = "Authorization header requires 'Signature' parameter.";

/// Error message: `"Authorization header requires 'SignedHeaders' parameter."`
const MSG_AUTH_HEADER_REQ_SIGNED_HEADERS: &str = "Authorization header requires 'SignedHeaders' parameter.";

/// Error message: `"'Host' or ':authority' must be a 'SignedHeader' in the AWS Authorization."`
const MSG_HOST_AUTHORITY_MUST_BE_SIGNED: &str =
    "'Host' or ':authority' must be a 'SignedHeader' in the AWS Authorization.";

/// Error message: `"Illegal hex character in escape % pattern: %"`
const MSG_ILLEGAL_HEX_CHAR: &str = "Illegal hex character in escape % pattern: %";

/// Error message: `"Incomplete trailing escape % sequence"`
const MSG_INCOMPLETE_TRAILING_ESCAPE: &str = "Incomplete trailing escape % sequence";

/// Error message: `"AWS query-string parameters must include 'X-Amz-Credential'"`
const MSG_QUERY_STRING_MUST_INCLUDE_CREDENTIAL: &str = "AWS query-string parameters must include 'X-Amz-Credential'.";

/// Error message: `"AWS query-string parameters must include 'X-Amz-Sigature'"`
const MSG_QUERY_STRING_MUST_INCLUDE_SIGNATURE: &str = "AWS query-string parameters must include 'X-Amz-Signature'.";

/// Error message: `"AWS query-string parameters must include 'X-Amz-SignedHeaders'"`
const MSG_QUERY_STRING_MUST_INCLUDE_SIGNED_HEADERS: &str =
    "AWS query-string parameters must include 'X-Amz-SignedHeaders'.";

/// Error message: `"AWS query-string parameters must include 'X-Amz-Date'"`
const MSG_QUERY_STRING_MUST_INCLUDE_DATE: &str = "AWS query-string parameters must include 'X-Amz-Date'.";

/// Error message: `"Re-examine the query-string parameters."`
const MSG_REEXAMINE_QUERY_STRING_PARAMS: &str = "Re-examine the query-string parameters.";

/// Error message: `"Request is missing Authentication Token"`
const MSG_REQUEST_MISSING_AUTH_TOKEN: &str = "Request is missing Authentication Token";

/// Error message: `"Unsupported AWS 'algorithm': "`
const MSG_UNSUPPORTED_ALGORITHM: &str = "Unsupported AWS 'algorithm': ";

/// Signature field for the signature itself
const SIGNATURE: &[u8] = b"Signature";

/// Authorization header parameter specifying the signed headers
const SIGNED_HEADERS: &[u8] = b"SignedHeaders";

/// Query parameter for the signature algorithm
const X_AMZ_ALGORITHM: &str = "X-Amz-Algorithm";

/// Query parameter for delivering the access key
const X_AMZ_CREDENTIAL: &str = "X-Amz-Credential";

/// Query parameter for delivering the date
const X_AMZ_DATE: &str = "X-Amz-Date";

/// Header for delivering the alternate date
const X_AMZ_DATE_LOWER: &str = "x-amz-date";

/// Query parameter for delivering the session token
const X_AMZ_SECURITY_TOKEN: &str = "X-Amz-Security-Token";

/// Header for delivering the session token
const X_AMZ_SECURITY_TOKEN_LOWER: &str = "x-amz-security-token";

/// Query parameter for delivering the signature
const X_AMZ_SIGNATURE: &str = "X-Amz-Signature";

/// Query parameter specifying the signed headers
const X_AMZ_SIGNED_HEADERS: &str = "X-Amz-SignedHeaders";

lazy_static! {
    /// Multiple slash pattern for condensing URIs
    static ref MULTISLASH: Regex = Regex::new("//+").unwrap();

    /// Multiple space pattern for condensing header values
    static ref MULTISPACE: Regex = Regex::new("  +").unwrap();

    /// Pattern for the start of an AWS4 signature Authorization header.
    static ref AWS4_HMAC_SHA256_RE: Regex = Regex::new(r"\s*AWS4-HMAC-SHA256(?:\s+|$)").unwrap();
}

/// Authentication parameters extracted from the header or query string.
#[cfg_attr(doc, doc(cfg(feature = "unstable")))]
#[cfg_attr(any(doc, feature = "unstable"), qualifiers(pub))]
#[cfg_attr(not(any(doc, feature = "unstable")), qualifiers(pub(crate)))]
#[derive(Debug)]
struct AuthParams {
    /// Builder for creating an authenticator.
    pub builder: SigV4AuthenticatorBuilder,

    /// The headers that are required to be signed in the request.
    pub signed_headers: Vec<String>,

    /// The timestamp string for the request in YYYYMMDD'T'HHMMSS'Z' format.
    pub timestamp_str: String,
}

/// A canonicalized request for AWS SigV4.
///
/// This is mainly used internally for generating the canonical request for signing, but is
/// exposed for testing and debugging purposes.
///
/// **The stability of this struct is not guaranteed.** The fields and methods are subject to
/// change in minor/patch versions.
#[cfg_attr(doc, doc(cfg(feature = "unstable")))]
#[cfg_attr(any(doc, feature = "unstable"), qualifiers(pub))]
#[cfg_attr(not(any(doc, feature = "unstable")), qualifiers(pub(crate)))]
#[derive(Clone)]
struct CanonicalRequest {
    /// The HTTP method for the request (e.g., "GET", "POST", etc.)
    request_method: String,

    /// The canonicalized path from the HTTP request. This is guaranteed to be ASCII.
    canonical_path: String,

    /// Query parameters from the HTTP request. Values are ordered as they appear in the URL. If a
    /// request body is present and of type `application/x-www-form-urlencoded` and
    /// [`SignatureOptions`] includes `url_encode_form`, the request body is parsed and added as
    /// query parameters.
    query_parameters: HashMap<String, Vec<String>>,

    /// Headers from the HTTP request. Values are ordered as they appear in the HTTP request.
    ///
    /// The encoding of header values is Latin 1 (ISO 8859-1), apart from a few oddities like Content-Disposition.
    headers: HashMap<String, Vec<Vec<u8>>>,

    /// The SHA-256 hash of the body.
    body_sha256: String,
}

impl CanonicalRequest {
    /// Create a CanonicalRequest from an HTTP request [Parts] and a body of [Bytes].
    #[cfg_attr(doc, doc(cfg(feature = "unstable")))]
    #[cfg_attr(any(doc, feature = "unstable"), qualifiers(pub))]
    #[cfg_attr(not(any(doc, feature = "unstable")), qualifiers(pub(crate)))]
    fn from_request_parts(
        mut parts: Parts,
        mut body: Bytes,
        options: SignatureOptions,
    ) -> Result<(Self, Parts, Bytes), SignatureError> {
        let canonical_path = canonicalize_uri_path(parts.uri.path(), options.s3)?;
        let content_type = get_content_type_and_charset(&parts.headers);
        let mut query_parameters = query_string_to_normalized_map(parts.uri.query().unwrap_or(""))?;

        if options.url_encode_form {
            // Treat requests with application/x-www-form-urlencoded bodies as if they were passed into the query string.
            if let Some(content_type) = content_type {
                if content_type.content_type == APPLICATION_X_WWW_FORM_URLENCODED {
                    trace!("Body is application/x-www-form-urlencoded; converting to query parameters");

                    let encoding = match &content_type.charset {
                        Some(charset) => match encoding_rs::Encoding::for_label(charset.as_bytes()) {
                            Some(encoding) => encoding,
                            None => {
                                return Err(SignatureError::InvalidBodyEncoding(format!(
                                    "application/x-www-form-urlencoded body uses unsupported charset '{}'",
                                    charset
                                )))
                            }
                        },
                        None => {
                            trace!("Falling back to UTF-8 for application/x-www-form-urlencoded body");
                            UTF_8
                        }
                    };

                    let (body_query, _, has_errors) = encoding.decode(&body);
                    if has_errors {
                        return Err(SignatureError::InvalidBodyEncoding(format!(
                            "Invalid body data encountered parsing application/x-www-form-urlencoded with charset '{}'",
                            encoding.name()
                        )));
                    }

                    query_parameters.extend(query_string_to_normalized_map(&body_query)?);
                    // Rebuild the parts URI with the new query string.
                    let qs = canonicalize_query_to_string(&query_parameters);
                    trace!("Rebuilding URI with new query string: {}", qs);

                    let mut pq = canonical_path.clone();
                    if !qs.is_empty() {
                        pq.push('?');
                        pq.push_str(&qs);
                    }

                    parts.uri =
                        Uri::builder().path_and_query(pq).build().expect("failed to rebuild URI with new query string");
                    body = Bytes::from("");
                }
            }
        }

        let headers = normalize_headers(&parts.headers);
        let body_sha256 = sha256_hex(body.as_ref());

        Ok((
            CanonicalRequest {
                request_method: parts.method.to_string(),
                canonical_path,
                query_parameters,
                headers,
                body_sha256,
            },
            parts,
            body,
        ))
    }

    /// Retrieve the HTTP request method.
    #[cfg_attr(doc, doc(cfg(feature = "unstable")))]
    #[cfg_attr(any(doc, feature = "unstable"), qualifiers(pub))]
    #[cfg_attr(not(any(doc, feature = "unstable")), qualifiers(pub(crate)))]
    #[inline(always)]
    fn request_method(&self) -> &str {
        &self.request_method
    }

    /// Retrieve the canonicalized URI path from the request.
    #[cfg_attr(doc, doc(cfg(feature = "unstable")))]
    #[cfg_attr(any(doc, feature = "unstable"), qualifiers(pub))]
    #[cfg_attr(not(any(doc, feature = "unstable")), qualifiers(pub(crate)))]
    #[inline(always)]
    fn canonical_path(&self) -> &str {
        &self.canonical_path
    }

    /// Retrieve the query parameters from the request. Values are ordered as they appear in the URL, followed by any
    /// values in the request body if the request body is of type `application/x-www-form-urlencoded`. Values are
    /// normalized to be percent-encoded.
    #[cfg_attr(doc, doc(cfg(feature = "unstable")))]
    #[cfg_attr(any(doc, feature = "unstable"), qualifiers(pub))]
    #[cfg_attr(not(any(doc, feature = "unstable")), qualifiers(pub(crate)))]
    #[inline(always)]
    fn query_parameters(&self) -> &HashMap<String, Vec<String>> {
        &self.query_parameters
    }

    /// Retrieve the headers from the request. Values are ordered as they appear in the HTTP request.
    #[cfg_attr(doc, doc(cfg(feature = "unstable")))]
    #[cfg_attr(any(doc, feature = "unstable"), qualifiers(pub))]
    #[cfg_attr(not(any(doc, feature = "unstable")), qualifiers(pub(crate)))]
    #[inline(always)]
    fn headers(&self) -> &HashMap<String, Vec<Vec<u8>>> {
        &self.headers
    }

    /// Retrieve the SHA-256 hash of the request body.
    #[cfg_attr(doc, doc(cfg(feature = "unstable")))]
    #[cfg_attr(any(doc, feature = "unstable"), qualifiers(pub))]
    #[cfg_attr(not(any(doc, feature = "unstable")), qualifiers(pub(crate)))]
    #[inline(always)]
    fn body_sha256(&self) -> &str {
        &self.body_sha256
    }

    /// Get the canonical query string from the request.
    #[cfg_attr(doc, doc(cfg(feature = "unstable")))]
    #[cfg_attr(any(doc, feature = "unstable"), qualifiers(pub))]
    #[cfg_attr(not(any(doc, feature = "unstable")), qualifiers(pub(crate)))]
    fn canonical_query_string(&self) -> String {
        canonicalize_query_to_string(&self.query_parameters)
    }

    /// Get the [canonical request to hash](https://docs.aws.amazon.com/general/latest/gr/sigv4-create-canonical-request.html)
    /// for the request.
    #[cfg_attr(doc, doc(cfg(feature = "unstable")))]
    #[cfg_attr(any(doc, feature = "unstable"), qualifiers(pub))]
    #[cfg_attr(not(any(doc, feature = "unstable")), qualifiers(pub(crate)))]
    fn canonical_request(&self, signed_headers: &Vec<String>) -> Vec<u8> {
        let mut result = Vec::with_capacity(1024);
        result.extend(self.request_method().as_bytes());
        result.push(b'\n');
        result.extend(self.canonical_path().as_bytes());
        result.push(b'\n');
        result.extend(self.canonical_query_string().as_bytes());
        result.push(b'\n');

        for header in signed_headers {
            let values = self.headers.get(header);
            if let Some(values) = values {
                for (i, value) in values.iter().enumerate() {
                    if i == 0 {
                        result.extend(header.as_bytes());
                        result.push(b':');
                    } else {
                        result.push(b',');
                    }
                    result.extend(value);
                }
                result.push(b'\n')
            }
        }

        result.push(b'\n');
        result.extend(signed_headers.join(";").as_bytes());
        result.push(b'\n');
        result.extend(self.body_sha256().as_bytes());

        trace!("Canonical request:\n{}", String::from_utf8_lossy(&result));

        result
    }

    /// Get the SHA-256 hash of the [canonical request](https://docs.aws.amazon.com/general/latest/gr/sigv4-create-canonical-request.html).
    #[cfg_attr(doc, doc(cfg(feature = "unstable")))]
    #[cfg_attr(any(doc, feature = "unstable"), qualifiers(pub))]
    #[cfg_attr(not(any(doc, feature = "unstable")), qualifiers(pub(crate)))]
    fn canonical_request_sha256(&self, signed_headers: &Vec<String>) -> [u8; SHA256_OUTPUT_LEN] {
        let canonical_request = self.canonical_request(signed_headers);
        let result_digest = sha256(&canonical_request);
        let result_slice = result_digest.as_ref();
        assert!(result_slice.len() == SHA256_OUTPUT_LEN);
        let mut result: [u8; SHA256_OUTPUT_LEN] = [0; SHA256_OUTPUT_LEN];
        result.as_mut_slice().clone_from_slice(result_slice);
        result
    }

    /// Create a [SigV4Authenticator] for the request. This performs steps 1-8 from the AWS Auth Error Ordering
    /// workflow.
    #[cfg_attr(doc, doc(cfg(feature = "unstable")))]
    #[cfg_attr(any(doc, feature = "unstable"), qualifiers(pub))]
    #[cfg_attr(not(any(doc, feature = "unstable")), qualifiers(pub(crate)))]
    fn get_authenticator<S>(&self, signed_header_requirements: &S) -> Result<SigV4Authenticator, SignatureError>
    where
        S: SignedHeaderRequirements,
    {
        let auth_params = self.get_auth_parameters(signed_header_requirements)?;
        self.get_authenticator_from_auth_parameters(auth_params)
    }

    /// Create an authenticator based on the provided [`AuthParams`].
    #[cfg_attr(doc, doc(cfg(feature = "unstable")))]
    #[cfg_attr(any(doc, feature = "unstable"), qualifiers(pub))]
    #[cfg_attr(not(any(doc, feature = "unstable")), qualifiers(pub(crate)))]
    fn get_authenticator_from_auth_parameters(
        &self,
        auth_params: AuthParams,
    ) -> Result<SigV4Authenticator, SignatureError> {
        // Rule 9: The date must be in ISO 8601 format.
        let timestamp_str = auth_params.timestamp_str.as_str();
        let timestamp = DateTime::<FixedOffset>::parse_from_iso8601(timestamp_str)
            .map_err(|_| {
                SignatureError::IncompleteSignature(format!(
                    "Date must be in ISO-8601 'basic format'. Got '{}'. See http://en.wikipedia.org/wiki/ISO_8601",
                    auth_params.timestamp_str
                ))
            })?
            .with_timezone(&Utc);
        let mut builder = auth_params.builder;
        builder.request_timestamp(timestamp);

        let signed_headers = auth_params.signed_headers;

        // Create the canonical request.
        builder.canonical_request_sha256(self.canonical_request_sha256(&signed_headers));

        Ok(builder.build().expect("all fields should be set"))
    }

    /// Create an [AuthParams] structure, either from the `Authorization` header or the query strings as appropriate.
    /// This performs step 5 and either performs steps 6a-6d or 7a-7d from the AWS Auth Error Ordering workflow.
    #[cfg_attr(doc, doc(cfg(feature = "unstable")))]
    #[cfg_attr(any(doc, feature = "unstable"), qualifiers(pub))]
    #[cfg_attr(not(any(doc, feature = "unstable")), qualifiers(pub(crate)))]
    fn get_auth_parameters<S>(&self, signed_header_requirements: &S) -> Result<AuthParams, SignatureError>
    where
        S: SignedHeaderRequirements,
    {
        let auth_header = self.headers().get(AUTHORIZATION);
        let sig_algs = self.query_parameters().get(X_AMZ_ALGORITHM);

        // Rule 5: Either the Authorization header or X-Amz-Algorithm query parameter must be present, not both.
        let params = match (auth_header, sig_algs) {
            // Use first header (per rule 6a).
            (Some(auth_header), None) => self.get_auth_parameters_from_auth_header(&auth_header[0])?,
            // Use first algorithm (per rule 7a).
            (None, Some(sig_algs)) => self.get_auth_parameters_from_query_parameters(&sig_algs[0])?,
            (Some(_), Some(_)) => return Err(SignatureError::SignatureDoesNotMatch(None)),
            (None, None) => {
                return Err(SignatureError::MissingAuthenticationToken(MSG_REQUEST_MISSING_AUTH_TOKEN.to_string()))
            }
        };

        // Rule 8: SignedHeaders must include "Host" or ":authority".
        let mut found_host = false;
        for header in &params.signed_headers {
            if header == "host" || header == ":authority" {
                found_host = true;
                break;
            }
        }
        if !found_host {
            return Err(SignatureError::SignatureDoesNotMatch(Some(MSG_HOST_AUTHORITY_MUST_BE_SIGNED.to_string())));
        }

        for header in signed_header_requirements.always_present() {
            let header_lower = header.to_lowercase();
            if !params.signed_headers.contains(&header_lower) {
                return Err(SignatureError::SignatureDoesNotMatch(Some(format!(
                    "'{}' must be a 'SignedHeader' in the AWS Authorization.",
                    header
                ))));
            }
        }

        for header in signed_header_requirements.if_in_request() {
            let header_lower = header.to_lowercase();
            if self.headers.contains_key(&header_lower) && !params.signed_headers.contains(&header_lower) {
                return Err(SignatureError::SignatureDoesNotMatch(Some(format!(
                    "'{}' must be a 'SignedHeader' in the AWS Authorization.",
                    header
                ))));
            }
        }

        for header in signed_header_requirements.prefixes() {
            let header_lower = header.to_lowercase();
            for http_header in self.headers.keys() {
                if http_header.starts_with(&header_lower) && !params.signed_headers.contains(http_header) {
                    return Err(SignatureError::SignatureDoesNotMatch(Some(format!(
                        "'{}' must be a 'SignedHeader' in the AWS Authorization.",
                        http_header
                    ))));
                }
            }
        }

        Ok(params)
    }

    /// Create an [`AuthParams`] structure from the `Authorization` header. This performs steps 6a-6d of the AWS Auth
    /// Error Ordering workflow.
    #[cfg_attr(doc, doc(cfg(feature = "unstable")))]
    #[cfg_attr(any(doc, feature = "unstable"), qualifiers(pub))]
    #[cfg_attr(not(any(doc, feature = "unstable")), qualifiers(pub(crate)))]
    fn get_auth_parameters_from_auth_header<'a>(&'a self, auth_header: &'a [u8]) -> Result<AuthParams, SignatureError> {
        // Interpret the header as Latin-1, trimmed.
        let auth_header = trim_ascii(auth_header);

        // Rule 6a: Make sure the Authorization header starts with "AWS4-HMAC-SHA256".
        let parts = auth_header.splitn(2, |c| *c == b' ').collect::<Vec<&'a [u8]>>();
        let algorithm = parts[0];
        if algorithm != AWS4_HMAC_SHA256_BYTES {
            return Err(SignatureError::IncompleteSignature(format!(
                "{}'{}'.",
                MSG_UNSUPPORTED_ALGORITHM,
                String::from_utf8_lossy(algorithm)
            )));
        }

        let parameters = if parts.len() > 1 {
            parts[1]
        } else {
            b""
        };

        // Split the parameters by commas; trim each one; then split into key=value pairs.
        let mut parameter_map = HashMap::new();
        for parameter_untrimmed in parameters.split(|c| *c == b',') {
            let parameter = trim_ascii(parameter_untrimmed);

            // Needed if we have no parameters at all; this loop will always run at least once.
            if parameter.is_empty() {
                continue;
            }

            let parts = parameter.splitn(2, |c| *c == b'=').collect::<Vec<&'a [u8]>>();

            // Rule 6b: All parameters must be in key=value format.
            if parts.len() != 2 {
                return Err(SignatureError::IncompleteSignature(format!(
                    "'{}' not a valid key=value pair (missing equal-sign) in Authorization header: '{}'",
                    latin1_to_string(parameter),
                    latin1_to_string(auth_header)
                )));
            }

            // Rule 6c: Use the last value for each key; overwriting is ok.
            parameter_map.insert(parts[0], parts[1]);
        }

        // Rule 6d: ensure all authorization header parameters/headers are present.
        let mut missing_messages = Vec::new();
        let mut builder = SigV4Authenticator::builder();

        if let Some(credential) = parameter_map.get(CREDENTIAL) {
            builder.credential(latin1_to_string(credential));
        } else {
            missing_messages.push(MSG_AUTH_HEADER_REQ_CREDENTIAL);
        }

        if let Some(signature) = parameter_map.get(SIGNATURE) {
            builder.signature(latin1_to_string(signature));
        } else {
            missing_messages.push(MSG_AUTH_HEADER_REQ_SIGNATURE);
        }

        let mut signed_headers = if let Some(signed_headers) = parameter_map.get(SIGNED_HEADERS) {
            signed_headers.split(|c| *c == b';').map(latin1_to_string).collect()
        } else {
            missing_messages.push(MSG_AUTH_HEADER_REQ_SIGNED_HEADERS);
            Vec::new()
        };
        signed_headers.sort();

        let mut timestamp_str = None;

        if let Some(date) = self.headers.get(X_AMZ_DATE_LOWER) {
            // Rule 6e: Use the first X-Amz-Date header (per rule 6a).
            timestamp_str = Some(latin1_to_string(&date[0]));
        } else if let Some(date) = self.headers.get(DATE) {
            // Rule 6e: Use the first Date header (per rule 6a).
            timestamp_str = Some(latin1_to_string(&date[0]));
        } else {
            missing_messages.push(MSG_AUTH_HEADER_REQ_DATE);
        }

        if !missing_messages.is_empty() {
            return Err(SignatureError::IncompleteSignature(format!(
                "{} Authorization={}",
                missing_messages.join(" "),
                latin1_to_string(algorithm)
            )));
        }

        // Get the session token if present.
        if let Some(token) = self.headers.get(X_AMZ_SECURITY_TOKEN_LOWER) {
            builder.session_token(latin1_to_string(&token[0]));
        }

        // Return the builder and the date.
        let timestamp_str = timestamp_str.expect("date_str should be set");
        Ok(AuthParams {
            builder,
            signed_headers,
            timestamp_str,
        })
    }

    /// Create an [`AuthParams`] structure from the query parameters. This performs steps 7a-7d of the AWS Auth
    /// Error Ordering workflow.
    #[cfg_attr(doc, doc(cfg(feature = "unstable")))]
    #[cfg_attr(any(doc, feature = "unstable"), qualifiers(pub))]
    #[cfg_attr(not(any(doc, feature = "unstable")), qualifiers(pub(crate)))]
    fn get_auth_parameters_from_query_parameters(&self, query_alg: &str) -> Result<AuthParams, SignatureError> {
        // Rule 7a: Make sure the X-Amz-Algorithm query parameter is "AWS4-HMAC-SHA256".
        if query_alg != AWS4_HMAC_SHA256 {
            return Err(SignatureError::MissingAuthenticationToken(MSG_REQUEST_MISSING_AUTH_TOKEN.to_string()));
        }

        let mut missing_messages = Vec::new();
        let mut builder = SigV4Authenticator::builder();

        // Rule 7c: Use the first value for each key.
        if let Some(credential) = self.query_parameters.get(X_AMZ_CREDENTIAL) {
            builder.credential(credential[0].clone());
        } else {
            missing_messages.push(MSG_QUERY_STRING_MUST_INCLUDE_CREDENTIAL);
        }

        if let Some(signature) = self.query_parameters.get(X_AMZ_SIGNATURE) {
            builder.signature(signature[0].clone());
        } else {
            missing_messages.push(MSG_QUERY_STRING_MUST_INCLUDE_SIGNATURE);
        }

        let mut signed_headers = if let Some(signed_headers) = self.query_parameters.get(X_AMZ_SIGNED_HEADERS) {
            let unescaped_signed_headers = unescape_uri_encoding(&signed_headers[0]);
            unescaped_signed_headers.split(';').map(|s| s.to_string()).collect::<Vec<String>>()
        } else {
            missing_messages.push(MSG_QUERY_STRING_MUST_INCLUDE_SIGNED_HEADERS);
            Vec::new()
        };
        signed_headers.sort();

        let timestamp_str = self.query_parameters.get(X_AMZ_DATE);
        if timestamp_str.is_none() {
            missing_messages.push(MSG_QUERY_STRING_MUST_INCLUDE_DATE);
        }

        if !missing_messages.is_empty() {
            return Err(SignatureError::IncompleteSignature(format!(
                "{} {}",
                missing_messages.join(" "),
                MSG_REEXAMINE_QUERY_STRING_PARAMS
            )));
        }

        // Get the session token if present.
        if let Some(token) = self.query_parameters.get(X_AMZ_SECURITY_TOKEN) {
            builder.session_token(token[0].clone());
        }

        let timestamp_str = timestamp_str.expect("date_str should be set")[0].clone();
        Ok(AuthParams {
            builder,
            signed_headers,
            timestamp_str,
        })
    }
}

impl Debug for CanonicalRequest {
    fn fmt(&self, f: &mut Formatter<'_>) -> FmtResult {
        let headers = debug_headers(&self.headers);

        f.debug_struct("CanonicalRequest")
            .field("request_method", &self.request_method)
            .field("canonical_path", &self.canonical_path)
            .field("query_parameters", &self.query_parameters)
            .field("headers", &headers)
            .field("body_sha256", &self.body_sha256)
            .finish()
    }
}

/// The Content-Type header value, along with the character set (if specified).
#[derive(Debug, Clone, PartialEq, Eq)]
#[cfg_attr(doc, doc(cfg(feature = "unstable")))]
#[cfg_attr(any(doc, feature = "unstable"), qualifiers(pub))]
#[cfg_attr(not(any(doc, feature = "unstable")), qualifiers(pub(crate)))]
struct ContentTypeCharset {
    /// The content type of the body.
    pub content_type: String,

    /// The encoding (charset) of the body.
    pub charset: Option<String>,
}

/// Trait for informing validation routines indicating which headers must be signed in addition to
/// the standard AWS SigV4 headers.
pub trait SignedHeaderRequirements {
    /// Return the headers that must always be present in SignedHeaders.
    fn always_present(&self) -> &[Cow<'_, str>];

    /// Return the headers that must be present in SignedHeaders if they are present in the request.
    fn if_in_request(&self) -> &[Cow<'_, str>];

    /// Return the prefixes that must be present in SignedHeaders if any headers with that prefix.
    fn prefixes(&self) -> &[Cow<'_, str>];
}

/// Static implementation of [SignedHeaderRequirements] that uses slices of string slices.
#[derive(Debug, Clone, Copy, Default, PartialEq, Eq)]
pub struct SliceSignedHeaderRequirements<'a, 'b, 'c> {
    /// Headers that must always be present in SignedHeaders.
    always_present: &'a [Cow<'a, str>],

    /// Headers that must be present in SignedHeaders if they are present in the request.
    if_in_request: &'b [Cow<'b, str>],

    /// Prefixes that must be present in SignedHeaders if any headers with that prefix are present in the request.
    prefixes: &'c [Cow<'c, str>],
}

impl<'a, 'b, 'c> SignedHeaderRequirements for SliceSignedHeaderRequirements<'a, 'b, 'c> {
    #[inline(always)]
    fn always_present(&self) -> &[Cow<'_, str>] {
        self.always_present
    }

    #[inline(always)]
    fn if_in_request(&self) -> &[Cow<'_, str>] {
        self.if_in_request
    }

    #[inline(always)]
    fn prefixes(&self) -> &[Cow<'_, str>] {
        self.prefixes
    }
}

impl<'a, 'b, 'c> SliceSignedHeaderRequirements<'a, 'b, 'c> {
    /// Create a new `SliceSignedHeaderRequirements` structure from the provided data.
    pub const fn new(
        always_present: &'a [Cow<'a, str>],
        if_in_request: &'b [Cow<'b, str>],
        prefixes: &'c [Cow<'c, str>],
    ) -> Self {
        SliceSignedHeaderRequirements {
            always_present,
            if_in_request,
            prefixes,
        }
    }
}

/// SignedHeaderRequirements from constant slices.
pub type ConstSignedHeaderRequirements = SliceSignedHeaderRequirements<'static, 'static, 'static>;

/// Constant [`SignedHeaderRequirements`] value to use when no additional signed headers are
/// required.
pub const NO_ADDITIONAL_SIGNED_HEADERS: ConstSignedHeaderRequirements =
    ConstSignedHeaderRequirements::new(&[], &[], &[]);

/// `SignedHeaderRequirements` that can be dynamically changed.
#[derive(Clone, Debug, Default, PartialEq, Eq)]
pub struct VecSignedHeaderRequirements {
    /// Headers that must always be present in SignedHeaders.
    always_present: Vec<Cow<'static, str>>,

    /// Headers that must be present in SignedHeaders if they are present in the request.
    if_in_request: Vec<Cow<'static, str>>,

    /// Prefixes that must be present in SignedHeaders if any headers with that prefix are present in the request.
    prefixes: Vec<Cow<'static, str>>,
}

impl SignedHeaderRequirements for VecSignedHeaderRequirements {
    #[inline(always)]
    fn always_present(&self) -> &[Cow<'_, str>] {
        &self.always_present
    }

    #[inline(always)]
    fn if_in_request(&self) -> &[Cow<'_, str>] {
        &self.if_in_request
    }

    #[inline(always)]
    fn prefixes(&self) -> &[Cow<'_, str>] {
        &self.prefixes
    }
}

impl VecSignedHeaderRequirements {
    /// Create a new `VecSignedHeaderRequirements` structure from the provided data.
    pub fn new<A, B, C>(always_present: &[&A], if_in_request: &[&B], prefixes: &[&C]) -> Self
    where
        for<'a> &'a A: Into<String>,
        for<'b> &'b B: Into<String>,
        for<'c> &'c C: Into<String>,
        A: ?Sized,
        B: ?Sized,
        C: ?Sized,
    {
        let always_present = always_present.iter().map(|s| Cow::Owned((*s).into())).collect();
        let if_in_request = if_in_request.iter().map(|s| Cow::Owned((*s).into())).collect();
        let prefixes = prefixes.iter().map(|s| Cow::Owned((*s).into())).collect();

        VecSignedHeaderRequirements {
            always_present,
            if_in_request,
            prefixes,
        }
    }

    /// Add a header that must always be present in `SignedHeaders`.
    pub fn add_always_present(&mut self, header: &str) {
        let header_lower = header.to_ascii_lowercase();

        for h in self.always_present.iter() {
            if h == &header_lower {
                return;
            }
        }

        self.always_present.push(Cow::Owned(header.to_string()));
    }

    /// Add a header that must be present in `SignedHeaders` if it is present in the request.
    pub fn add_if_in_request(&mut self, header: &str) {
        let header_lower = header.to_ascii_lowercase();

        for h in self.if_in_request.iter() {
            if h == &header_lower {
                return;
            }
        }

        self.if_in_request.push(Cow::Owned(header.to_string()));
    }

    /// Add a prefix that must be present in `SignedHeaders` if any headers with that prefix are
    /// present in the request.
    pub fn add_prefix(&mut self, prefix: &str) {
        let prefix_lower = prefix.to_ascii_lowercase();

        for h in self.prefixes.iter() {
            if h == &prefix_lower {
                return;
            }
        }

        self.prefixes.push(Cow::Owned(prefix.to_string()));
    }

    /// Remove a header that must always be present in `SignedHeaders`.
    pub fn remove_always_present(&mut self, header: &str) {
        let header = header.to_ascii_lowercase();
        self.always_present.retain(|h| h.to_ascii_lowercase() != header);
    }

    /// Remove a header that must be present in `SignedHeaders` if it is present in the request.
    pub fn remove_if_in_request(&mut self, header: &str) {
        let header = header.to_ascii_lowercase();
        self.if_in_request.retain(|h| h.to_ascii_lowercase() != header);
    }

    /// Remove a prefix that must be present in `SignedHeaders` if any headers with that prefix are
    /// present in the request.
    pub fn remove_prefix(&mut self, prefix: &str) {
        let prefix = prefix.to_ascii_lowercase();
        self.prefixes.retain(|h| h.to_ascii_lowercase() != prefix);
    }
}

/// Indicates whether we are normalizing a URI path element or a query string element. This is used to create the
/// correct error message.
#[cfg_attr(doc, doc(cfg(feature = "unstable")))]
#[cfg_attr(any(doc, feature = "unstable"), qualifiers(pub))]
#[cfg_attr(not(any(doc, feature = "unstable")), qualifiers(pub(crate)))]
enum UriElement {
    /// URI element represents a path
    Path,

    /// URI element represents a query string
    Query,
}

/// Convert a [`HashMap`] of query parameters to a string for the canonical request.
#[cfg_attr(doc, doc(cfg(feature = "unstable")))]
#[cfg_attr(any(doc, feature = "unstable"), qualifiers(pub))]
#[cfg_attr(not(any(doc, feature = "unstable")), qualifiers(pub(crate)))]
pub fn canonicalize_query_to_string(query_parameters: &HashMap<String, Vec<String>>) -> String {
    let mut results = Vec::new();

    for (key, values) in query_parameters.iter() {
        // Don't include the signature itself.
        if key != X_AMZ_SIGNATURE {
            for value in values.iter() {
                results.push(format!("{}={}", key, value));
            }
        }
    }

    results.sort_unstable();
    results.join("&")
}

/// Normalizes the specified URI path, removing redundant slashes and relative path components (unless performing S3
/// canonicalization).
#[cfg_attr(doc, doc(cfg(feature = "unstable")))]
#[cfg_attr(any(doc, feature = "unstable"), qualifiers(pub))]
#[cfg_attr(not(any(doc, feature = "unstable")), qualifiers(pub(crate)))]
pub fn canonicalize_uri_path(uri_path: &str, s3: bool) -> Result<String, SignatureError> {
    // Special case: empty path is converted to '/'; also short-circuit the usual '/' path here.
    if uri_path.is_empty() || uri_path == "/" {
        return Ok("/".to_string());
    }

    // All other paths must be abolute.
    if !uri_path.starts_with('/') {
        return Err(SignatureError::InvalidURIPath(format!("Path is not absolute: {}", uri_path)));
    }

    let uri_path = if s3 {
        Cow::Borrowed(uri_path)
    } else {
        // Replace double slashes; this makes it easier to handle slashes at the end.
        MULTISLASH.replace_all(uri_path, "/")
    };

    // Examine each path component for relative directories.
    let mut components: Vec<String> = uri_path.split('/').map(|s| s.to_string()).collect();
    let mut i = 1; // Ignore the leading "/"
    while i < components.len() {
        let component = normalize_uri_path_component(&components[i])?;

        if component == "." && !s3 {
            // Relative path: current directory; remove this.
            components.remove(i);

            // Don't increment i; with the deletion, we're now pointing to the next element in the path.
        } else if component == ".." && !s3 {
            // Relative path: parent directory.  Remove this and the previous component.

            if i <= 1 {
                // This isn't allowed at the beginning!
                return Err(SignatureError::InvalidURIPath(format!(
                    "Relative path entry '..' navigates above root: {}",
                    uri_path
                )));
            }

            components.remove(i - 1);
            components.remove(i - 1);

            // Since we've deleted two components, we need to back up one to examine what's now the next component.
            i -= 1;
        } else {
            // Leave it alone; proceed to the next component.
            components[i] = component;
            i += 1;
        }
    }

    assert!(!components.is_empty());
    match components.len() {
        1 => Ok("/".to_string()),
        _ => Ok(components.join("/")),
    }
}

/// Formats HTTP headers in a HashMap suitable for debugging.
#[cfg_attr(doc, doc(cfg(feature = "unstable")))]
#[cfg_attr(any(doc, feature = "unstable"), qualifiers(pub))]
#[cfg_attr(not(any(doc, feature = "unstable")), qualifiers(pub(crate)))]
fn debug_headers(headers: &HashMap<String, Vec<Vec<u8>>>) -> String {
    use std::io::Write;
    let mut result = Vec::new();
    for (key, values) in headers.iter() {
        for value in values {
            match String::from_utf8(value.clone()) {
                Ok(s) => writeln!(result, "{}: {}", key, s).unwrap(),
                Err(_) => writeln!(result, "{}: {:?}", key, value).unwrap(),
            }
        }
    }

    if result.is_empty() {
        return String::new();
    }

    // Remove the last newline.
    let result_except_last = &result[..result.len() - 1];
    String::from_utf8_lossy(result_except_last).to_string()
}

/// Get the content type and character set used in the body
#[cfg_attr(doc, doc(cfg(feature = "unstable")))]
#[cfg_attr(any(doc, feature = "unstable"), qualifiers(pub))]
#[cfg_attr(not(any(doc, feature = "unstable")), qualifiers(pub(crate)))]
fn get_content_type_and_charset(headers: &HeaderMap<HeaderValue>) -> Option<ContentTypeCharset> {
    let content_type_opts = match headers.get(CONTENT_TYPE) {
        Some(value) => value.as_ref(),
        None => return None,
    };

    let mut parts = content_type_opts.split(|c| *c == b';').map(trim_ascii);
    let content_type = latin1_to_string(parts.next().expect("split always returns at least one element"));

    for option in parts {
        let opt_trim = trim_ascii(option);
        let mut opt_parts = opt_trim.splitn(2, |c| *c == b'=');

        let opt_name = opt_parts.next().unwrap();
        if latin1_to_string(opt_name).to_lowercase() == CHARSET {
            if let Some(opt_value) = opt_parts.next() {
                return Some(ContentTypeCharset {
                    content_type,
                    charset: Some(latin1_to_string(opt_value)),
                });
            }
        }
    }

    Some(ContentTypeCharset {
        content_type,
        charset: None,
    })
}

/// Indicates whether the specified byte is RFC3986 unreserved -- i.e., can be represented without being
/// percent-encoded, e.g. '?' -> '%3F'.
#[cfg_attr(doc, doc(cfg(feature = "unstable")))]
#[cfg_attr(any(doc, feature = "unstable"), qualifiers(pub))]
#[cfg_attr(not(any(doc, feature = "unstable")), qualifiers(pub(crate)))]
#[inline(always)]
pub fn is_rfc3986_unreserved(c: u8) -> bool {
    c.is_ascii_alphanumeric() || c == b'-' || c == b'.' || c == b'_' || c == b'~'
}

/// Convert a Latin-1 slice of bytes to a UTF-8 string.
#[cfg_attr(doc, doc(cfg(feature = "unstable")))]
#[cfg_attr(any(doc, feature = "unstable"), qualifiers(pub))]
#[cfg_attr(not(any(doc, feature = "unstable")), qualifiers(pub(crate)))]
pub fn latin1_to_string(bytes: &[u8]) -> String {
    let mut result = String::new();
    for b in bytes {
        result.push(*b as char);
    }
    result
}

/// Returns a sorted dictionary containing the header names and their values.
#[cfg_attr(doc, doc(cfg(feature = "unstable")))]
#[cfg_attr(any(doc, feature = "unstable"), qualifiers(pub))]
#[cfg_attr(not(any(doc, feature = "unstable")), qualifiers(pub(crate)))]
pub fn normalize_headers(headers: &HeaderMap<HeaderValue>) -> HashMap<String, Vec<Vec<u8>>> {
    let mut result = HashMap::<String, Vec<Vec<u8>>>::new();
    for (key, value) in headers.iter() {
        let key = key.as_str().to_lowercase();
        let value = normalize_header_value(value.as_bytes());
        result.entry(key).or_default().push(value);
    }

    result
}

/// Normalizes a header value by trimming whitespace and converting multiple spaces to a single space.
#[cfg_attr(doc, doc(cfg(feature = "unstable")))]
#[cfg_attr(any(doc, feature = "unstable"), qualifiers(pub))]
#[cfg_attr(not(any(doc, feature = "unstable")), qualifiers(pub(crate)))]
pub fn normalize_header_value(value: &[u8]) -> Vec<u8> {
    let mut result = Vec::with_capacity(value.len());

    // Remove leading whitespace and reduce multiple spaces to a single space.
    let mut last_was_space = true;

    for c in value {
        if *c == b' ' {
            if !last_was_space {
                result.push(b' ');
                last_was_space = true;
            }
        } else {
            result.push(*c);
            last_was_space = false;
        }
    }

    if last_was_space {
        // Remove trailing spaces.
        while result.last() == Some(&b' ') {
            result.pop();
        }
    }

    result
}

/// Normalize a single element (key or value from key=value) of a query string.
#[cfg_attr(doc, doc(cfg(feature = "unstable")))]
#[cfg_attr(any(doc, feature = "unstable"), qualifiers(pub))]
#[cfg_attr(not(any(doc, feature = "unstable")), qualifiers(pub(crate)))]
pub fn normalize_query_string_element(element: &str) -> Result<String, SignatureError> {
    normalize_uri_element(element, UriElement::Query)
}

/// Normalizes a path element of a URI.
#[cfg_attr(doc, doc(cfg(feature = "unstable")))]
#[cfg_attr(any(doc, feature = "unstable"), qualifiers(pub))]
#[cfg_attr(not(any(doc, feature = "unstable")), qualifiers(pub(crate)))]
pub fn normalize_uri_path_component(path: &str) -> Result<String, SignatureError> {
    normalize_uri_element(path, UriElement::Path)
}

/// Normalize the URI or query string according to RFC 3986.  This performs the following operations:
/// * Alpha, digit, and the symbols `-`, `.`, `_`, and `~` (unreserved characters) are left alone.
/// * Characters outside this range are percent-encoded.
/// * Percent-encoded values are upper-cased (`%2a` becomes `%2A`)
/// * Percent-encoded values in the unreserved space (`%41`-`%5A`, `%61`-`%7A`, `%30`-`%39`, `%2D`, `%2E`, `%5F`,
///   `%7E`) are converted to normal characters.
///
/// If a percent encoding is incomplete, an error is returned.
#[cfg_attr(doc, doc(cfg(feature = "unstable")))]
#[cfg_attr(any(doc, feature = "unstable"), qualifiers(pub))]
#[cfg_attr(not(any(doc, feature = "unstable")), qualifiers(pub(crate)))]
fn normalize_uri_element(uri_el: &str, uri_el_type: UriElement) -> Result<String, SignatureError> {
    let path_component = uri_el.as_bytes();
    let mut i = 0;
    let result = &mut Vec::<u8>::new();

    while i < path_component.len() {
        let c = path_component[i];

        if is_rfc3986_unreserved(c) {
            result.push(c);
            i += 1;
        } else if c == b'%' {
            if i + 2 >= path_component.len() {
                // % encoding would go beyond end of string.
                return Err(match uri_el_type {
                    UriElement::Path => {
                        // AWS Auth Error Ordering Rule 1.
                        SignatureError::InvalidURIPath(MSG_INCOMPLETE_TRAILING_ESCAPE.to_string())
                    }
                    UriElement::Query => {
                        // AWS Auth Error Ordering Rule 4.
                        SignatureError::MalformedQueryString(MSG_INCOMPLETE_TRAILING_ESCAPE.to_string())
                    }
                });
            }

            let hex_digits = &path_component[i + 1..i + 3];
            match hex::decode(hex_digits) {
                Ok(value) => {
                    assert_eq!(value.len(), 1);
                    let c = value[0];

                    if is_rfc3986_unreserved(c) {
                        result.push(c);
                    } else {
                        // Rewrite the hex-escape so it's always upper-cased.
                        result.push(b'%');
                        result.extend(u8_to_upper_hex(c));
                    }
                    i += 3;
                }
                Err(_) => {
                    let message = format!("{}{}{}", MSG_ILLEGAL_HEX_CHAR, hex_digits[0] as char, hex_digits[1] as char);
                    return Err(match uri_el_type {
                        // AWS Auth Error Ordering Rule 1.
                        UriElement::Path => SignatureError::InvalidURIPath(message),
                        // AWS Auth Error Ordering Rule 4.
                        UriElement::Query => SignatureError::MalformedQueryString(message),
                    });
                }
            }
        } else if c == b'+' {
            // Plus-encoded space. Convert this to %20.
            result.extend_from_slice(b"%20");
            i += 1;
        } else {
            // Character should have been encoded.
            result.push(b'%');
            result.extend(u8_to_upper_hex(c));
            i += 1;
        }
    }

    Ok(from_utf8(result.as_slice()).unwrap().to_string())
}

/// Normalize the query parameters by normalizing the keys and values of each parameter and return a `HashMap` mapping
/// each key to a *vector* of values (since it is valid for a query parameters to appear multiple times).
///
/// The order of the values matches the order that they appeared in the query string -- this is important for SigV4
/// validation.
#[cfg_attr(doc, doc(cfg(feature = "unstable")))]
#[cfg_attr(any(doc, feature = "unstable"), qualifiers(pub))]
#[cfg_attr(not(any(doc, feature = "unstable")), qualifiers(pub(crate)))]
pub fn query_string_to_normalized_map(query_string: &str) -> Result<HashMap<String, Vec<String>>, SignatureError> {
    if query_string.is_empty() {
        return Ok(HashMap::new());
    }

    // Split the query string into parameters on '&' boundaries.
    let components = query_string.split('&');
    let mut result = HashMap::<String, Vec<String>>::new();

    for component in components {
        if component.is_empty() {
            // Empty component; skip it.
            continue;
        }

        // Split the parameter into key and value portions on the '='
        let parts: Vec<&str> = component.splitn(2, '=').collect();
        let key = parts[0];
        let value = if parts.len() > 1 {
            parts[1]
        } else {
            ""
        };

        // Normalize the key and value.
        let norm_key = normalize_query_string_element(key)?;
        let norm_value = normalize_query_string_element(value)?;

        // If we already have a value for this key, append to it; otherwise, create a new vector containing the value.
        if let Some(result_value) = result.get_mut(&norm_key) {
            result_value.push(norm_value);
        } else {
            result.insert(norm_key, vec![norm_value]);
        }
    }

    Ok(result)
}

/// Returns a byte slice with leading ASCII whitespace bytes removed.
///
/// ‘Whitespace’ refers to the definition used by u8::is_ascii_whitespace.
///
/// This is copied from the Rust standard library source until the
/// [`byte_slice_trim_ascii` feature](https://github.com/rust-lang/rust/issues/94035) is stabilized.
#[cfg_attr(doc, doc(cfg(feature = "unstable")))]
#[cfg_attr(any(doc, feature = "unstable"), qualifiers(pub))]
#[cfg_attr(not(any(doc, feature = "unstable")), qualifiers(pub(crate)))]
pub const fn trim_ascii_start(bytes: &[u8]) -> &[u8] {
    let mut bytes = bytes;
    // Note: A pattern matching based approach (instead of indexing) allows
    // making the function const.
    while let [first, rest @ ..] = bytes {
        if first.is_ascii_whitespace() {
            bytes = rest;
        } else {
            break;
        }
    }
    bytes
}

/// Returns a byte slice with trailing ASCII whitespace bytes removed.
///
/// ‘Whitespace’ refers to the definition used by u8::is_ascii_whitespace.
///
/// This is copied from the Rust standard library source until the
/// [`byte_slice_trim_ascii` feature](https://github.com/rust-lang/rust/issues/94035) is stabilized.
#[cfg_attr(doc, doc(cfg(feature = "unstable")))]
#[cfg_attr(any(doc, feature = "unstable"), qualifiers(pub))]
#[cfg_attr(not(any(doc, feature = "unstable")), qualifiers(pub(crate)))]
pub const fn trim_ascii_end(bytes: &[u8]) -> &[u8] {
    let mut bytes = bytes;
    // Note: A pattern matching based approach (instead of indexing) allows
    // making the function const.
    while let [rest @ .., last] = bytes {
        if last.is_ascii_whitespace() {
            bytes = rest;
        } else {
            break;
        }
    }
    bytes
}

/// Returns a byte slice with leading and trailing ASCII whitespace bytes removed.
///
/// ‘Whitespace’ refers to the definition used by u8::is_ascii_whitespace.
///
/// This is copied from the Rust standard library source until the
/// [`byte_slice_trim_ascii` feature](https://github.com/rust-lang/rust/issues/94035) is stabilized.
#[cfg_attr(doc, doc(cfg(feature = "unstable")))]
#[cfg_attr(any(doc, feature = "unstable"), qualifiers(pub))]
#[cfg_attr(not(any(doc, feature = "unstable")), qualifiers(pub(crate)))]
pub const fn trim_ascii(bytes: &[u8]) -> &[u8] {
    trim_ascii_end(trim_ascii_start(bytes))
}

/// Convert a byte to uppercase hex representation.
#[cfg_attr(doc, doc(cfg(feature = "unstable")))]
#[cfg_attr(any(doc, feature = "unstable"), qualifiers(pub))]
#[cfg_attr(not(any(doc, feature = "unstable")), qualifiers(pub(crate)))]
#[inline(always)]
pub const fn u8_to_upper_hex(b: u8) -> [u8; 2] {
    let result: [u8; 2] = [HEX_DIGITS_UPPER[((b >> 4) & 0xf) as usize], HEX_DIGITS_UPPER[(b & 0xf) as usize]];
    result
}

/// Unescapes a URI percent-encoded string.
///
/// This function panics if the input string contains invalid percent encodings.
#[cfg_attr(doc, doc(cfg(feature = "unstable")))]
#[cfg_attr(any(doc, feature = "unstable"), qualifiers(pub))]
#[cfg_attr(not(any(doc, feature = "unstable")), qualifiers(pub(crate)))]
pub fn unescape_uri_encoding(s: &str) -> String {
    let mut result = String::with_capacity(s.len());
    let mut chars = s.bytes();

    while let Some(c) = chars.next() {
        if c == b'%' {
            let mut hex_digits = [0u8; 2];
            hex_digits[0] = chars.next().expect(MSG_INCOMPLETE_TRAILING_ESCAPE);
            hex_digits[1] = chars.next().expect(MSG_INCOMPLETE_TRAILING_ESCAPE);
            match u8::from_str_radix(from_utf8(&hex_digits).unwrap(), 16) {
                Ok(c) => result.push(c as char),
                Err(_) => panic!("{}{}{}", MSG_ILLEGAL_HEX_CHAR, hex_digits[0] as char, hex_digits[1] as char),
            }
        } else {
            result.push(c as char);
        }
    }

    result
}

#[cfg(test)]
mod tests {
    use {
        super::{debug_headers, u8_to_upper_hex},
        crate::{
            canonical::{
                canonicalize_query_to_string, canonicalize_uri_path, normalize_uri_path_component,
                query_string_to_normalized_map, unescape_uri_encoding, CanonicalRequest,
            },
            SignatureError, SignatureOptions, NO_ADDITIONAL_SIGNED_HEADERS,
        },
        bytes::Bytes,
        http::{
            method::Method,
            request::Request,
            uri::{PathAndQuery, Uri},
        },
        scratchstack_errors::ServiceError,
        std::collections::HashMap,
    };

    macro_rules! expect_err {
        ($test:expr, $expected:ident) => {
            match $test {
                Ok(ref v) => panic!("Expected Err({}); got Ok({:?})", stringify!($expected), v),
                Err(ref e) => match e {
                    SignatureError::$expected(_) => e.to_string(),
                    _ => panic!("Expected {}; got {:#?}: {}", stringify!($expected), &e, &e),
                },
            }
        };
    }

    #[test_log::test]
    fn canonicalize_uri_path_empty() {
        assert_eq!(canonicalize_uri_path("", false).unwrap(), "/".to_string());
        assert_eq!(canonicalize_uri_path("/", false).unwrap(), "/".to_string());
    }

    #[test_log::test]
    fn canonicalize_valid() {
        assert_eq!(canonicalize_uri_path("/hello/world", false).unwrap(), "/hello/world".to_string());
        assert_eq!(canonicalize_uri_path("/hello///world", false).unwrap(), "/hello/world".to_string());
        assert_eq!(canonicalize_uri_path("/hello/./world", false).unwrap(), "/hello/world".to_string());
        assert_eq!(canonicalize_uri_path("/hello/foo/../world", false).unwrap(), "/hello/world".to_string());
        assert_eq!(canonicalize_uri_path("/hello/foo/%2E%2E/world", false).unwrap(), "/hello/world".to_string());
        assert_eq!(canonicalize_uri_path("/hello/%77%6F%72%6C%64", false).unwrap(), "/hello/world".to_string());
        assert_eq!(canonicalize_uri_path("/hello/w*rld", false).unwrap(), "/hello/w%2Arld".to_string());
        assert_eq!(canonicalize_uri_path("/hello/w%2arld", false).unwrap(), "/hello/w%2Arld".to_string());
        assert_eq!(canonicalize_uri_path("/hello/w+rld", false).unwrap(), "/hello/w%20rld".to_string());

        assert_eq!(canonicalize_uri_path("/hello/world", true).unwrap(), "/hello/world".to_string());
        assert_eq!(canonicalize_uri_path("/hello///world", true).unwrap(), "/hello///world".to_string());
        assert_eq!(canonicalize_uri_path("/hello/./world", true).unwrap(), "/hello/./world".to_string());
        assert_eq!(canonicalize_uri_path("/hello/foo/../world", true).unwrap(), "/hello/foo/../world".to_string());
        assert_eq!(canonicalize_uri_path("/hello/%77%6F%72%6C%64", true).unwrap(), "/hello/world".to_string());
        assert_eq!(canonicalize_uri_path("/hello/w*rld", true).unwrap(), "/hello/w%2Arld".to_string());
        assert_eq!(canonicalize_uri_path("/hello/w%2arld", true).unwrap(), "/hello/w%2Arld".to_string());
        assert_eq!(canonicalize_uri_path("/hello/w+rld", true).unwrap(), "/hello/w%20rld".to_string());
        assert_eq!(canonicalize_uri_path("/hello/../../world", true).unwrap(), "/hello/../../world".to_string());
        assert_eq!(
            canonicalize_uri_path("/hello/%2e%2e/%2e%2e/world", true).unwrap(),
            "/hello/../../world".to_string()
        );
    }

    #[test_log::test]
    fn canonicalize_invalid() {
        let e = expect_err!(canonicalize_uri_path("hello/world", false), InvalidURIPath);
        assert_eq!(e.to_string(), "Path is not absolute: hello/world");
        let e = canonicalize_uri_path("/hello/../../world", false).unwrap_err();
        if let SignatureError::InvalidURIPath(_) = e {
            assert_eq!(e.to_string(), "Relative path entry '..' navigates above root: /hello/../../world");
            assert_eq!(e.error_code(), "InvalidURIPath");
            assert_eq!(e.http_status(), 400);
        } else {
            panic!("Expected InvalidURIPath; got {:#?}", &e);
        }

        let e = canonicalize_uri_path("/hello/%2E%2E/%2E%2E/world", false).unwrap_err();
        if let SignatureError::InvalidURIPath(_) = e {
            assert_eq!(e.to_string(), "Relative path entry '..' navigates above root: /hello/%2E%2E/%2E%2E/world");
            assert_eq!(e.error_code(), "InvalidURIPath");
            assert_eq!(e.http_status(), 400);
        } else {
            panic!("Expected InvalidURIPath; got {:#?}", &e);
        }
    }

    #[test_log::test]
    fn canonicalize_query_excludes_signature() {
        let query = HashMap::from([
            ("X-Amz-Signature".to_string(), vec!["abcdef".to_string()]),
            ("b".to_string(), vec!["B".to_string()]),
            ("c".to_string(), vec!["C".to_string()]),
            ("a".to_string(), vec!["A".to_string()]),
            ("e".to_string(), vec!["E".to_string()]),
            ("d".to_string(), vec!["d".to_string()]),
        ]);

        let query = canonicalize_query_to_string(&query);
        assert_eq!(query, "a=A&b=B&c=C&d=d&e=E");
    }

    #[test_log::test]
    fn normalize_valid1() {
        let result = query_string_to_normalized_map("Hello=World&foo=bar&baz=bomb&foo=2&name").unwrap();
        let hello = result.get("Hello").unwrap();
        assert_eq!(hello.len(), 1);
        assert_eq!(hello[0], "World");

        let foo = result.get("foo").unwrap();
        assert_eq!(foo.len(), 2);
        assert_eq!(foo[0], "bar");
        assert_eq!(foo[1], "2");

        let baz = result.get("baz").unwrap();
        assert_eq!(baz.len(), 1);
        assert_eq!(baz[0], "bomb");

        let name = result.get("name").unwrap();
        assert_eq!(name.len(), 1);
        assert_eq!(name[0], "");
    }

    #[test_log::test]
    fn normalize_empty() {
        let result = query_string_to_normalized_map("Hello=World&&foo=bar");
        let v = result.unwrap();
        let hello = v.get("Hello").unwrap();

        assert_eq!(hello.len(), 1);
        assert_eq!(hello[0], "World");

        let foo = v.get("foo").unwrap();
        assert_eq!(foo.len(), 1);
        assert_eq!(foo[0], "bar");

        assert!(!v.contains_key(""));
    }

    #[test_log::test]
    fn normalize_invalid_hex() {
        let e = expect_err!(normalize_uri_path_component("abcd%yy"), InvalidURIPath);
        assert_eq!(e.as_str(), "Illegal hex character in escape % pattern: %yy");
        expect_err!(normalize_uri_path_component("abcd%yy"), InvalidURIPath);
        expect_err!(normalize_uri_path_component("abcd%0"), InvalidURIPath);
        expect_err!(normalize_uri_path_component("abcd%"), InvalidURIPath);
        assert_eq!(normalize_uri_path_component("abcd%65").unwrap(), "abcde");
    }

    struct PathAndQuerySimulate {
        data: Bytes,
        _query: u16,
    }

    #[test_log::test]
    fn normalize_invalid_hex_path_cr() {
        // The HTTP crate does its own validation; we need to hack into it to force invalid URI elements in there.
        for (path, error_message) in [
            ("/abcd%yy", "Illegal hex character in escape % pattern: %yy"),
            ("/abcd%0", "Incomplete trailing escape % sequence"),
            ("/abcd%", "Incomplete trailing escape % sequence"),
        ] {
            let mut fake_path = "/".to_string();
            while fake_path.len() < path.len() {
                fake_path.push('a');
            }

            let mut pq = PathAndQuery::from_maybe_shared(fake_path.clone()).unwrap();
            let pq_path = Bytes::from_static(path.as_bytes());

            unsafe {
                // Rewrite the path to be invalid. This can't be done with the normal PathAndQuery
                // API.
                let pq_ptr: *mut PathAndQuerySimulate = &mut pq as *mut PathAndQuery as *mut PathAndQuerySimulate;
                (*pq_ptr).data = pq_path;
            }

            let uri = Uri::builder().path_and_query(pq).build().unwrap();
            let request = Request::builder()
                .method(Method::GET)
                .uri(uri)
                .header("authorization", "AWS4-HMAC-SHA256 Credential=1234, SignedHeaders=date;host, Signature=5678")
                .header("authorization", "Basic foobar")
                .header("x-amz-date", "20150830T123600Z")
                .body(Bytes::new())
                .unwrap();
            let (parts, body) = request.into_parts();

            let e = CanonicalRequest::from_request_parts(parts, body, SignatureOptions::url_encode_form()).unwrap_err();
            if let SignatureError::InvalidURIPath(msg) = e {
                assert_eq!(msg.as_str(), error_message);
            }
        }
    }

    #[test_log::test]
    fn normalize_invalid_hex_query_cr() {
        // The HTTP crate does its own validation; we need to hack into it to force invalid URI elements in there.
        for (path, error_message) in [
            ("/?x=abcd%yy", "Illegal hex character in escape % pattern: %yy"),
            ("/?x=abcd%0", "Incomplete trailing escape % sequence"),
            ("/?x=abcd%", "Incomplete trailing escape % sequence"),
        ] {
            let mut fake_path = "/?x=".to_string();
            while fake_path.len() < path.len() {
                fake_path.push('a');
            }

            let mut pq = PathAndQuery::from_maybe_shared(fake_path.clone()).unwrap();
            let pq_path = Bytes::from_static(path.as_bytes());

            unsafe {
                // Rewrite the path to be invalid.
                let pq_ptr: *mut PathAndQuerySimulate = &mut pq as *mut PathAndQuery as *mut PathAndQuerySimulate;
                (*pq_ptr).data = pq_path;
            }

            let uri = Uri::builder().path_and_query(pq).build().unwrap();
            let request = Request::builder()
                .method(Method::GET)
                .uri(uri)
                .header("authorization", "AWS4-HMAC-SHA256 Credential=1234, SignedHeaders=date;host, Signature=5678")
                .header("authorization", "Basic foobar")
                .header("x-amz-date", "20150830T123600Z")
                .body(Bytes::new())
                .unwrap();
            let (parts, body) = request.into_parts();

            let e = CanonicalRequest::from_request_parts(parts, body, SignatureOptions::url_encode_form()).unwrap_err();
            if let SignatureError::MalformedQueryString(msg) = e {
                assert_eq!(msg.as_str(), error_message);
            }
        }
    }

    /// Check for query parameters without a value, e.g. ?Key2&
    /// https://github.com/dacut/scratchstack-aws-signature/issues/2
    #[test_log::test]
    fn normalize_query_parameters_missing_value() {
        let result = query_string_to_normalized_map("Key1=Value1&Key2&Key3=Value3");
        assert!(result.is_ok());
        let result = result.unwrap();
        assert_eq!(result["Key1"], vec!["Value1"]);
        assert_eq!(result["Key2"], vec![""]);
        assert_eq!(result["Key3"], vec!["Value3"]);
    }

    #[test_log::test]
    fn test_multiple_algorithms() {
        let uri = Uri::builder().path_and_query(PathAndQuery::from_static("/")).build().unwrap();
        let request = Request::builder()
            .method(Method::GET)
            .uri(uri)
            .header("authorization", "AWS4-HMAC-SHA256 Credential=1234, SignedHeaders=date;host, Signature=5678")
            .header("authorization", "Basic foobar")
            .header("x-amz-date", "20150830T123600Z")
            .body(Bytes::new())
            .unwrap();
        let (parts, body) = request.into_parts();

        let (cr, _, _) =
            CanonicalRequest::from_request_parts(parts, body, SignatureOptions::url_encode_form()).unwrap();

        // Ensure we can debug print the canonical request.
        let _ = format!("{:?}", cr);

        assert_eq!(cr.request_method(), "GET");
        assert_eq!(cr.canonical_path(), "/");
        assert!(cr.query_parameters().is_empty());
        assert_eq!(cr.headers().len(), 2);
        assert_eq!(cr.headers().get("authorization").unwrap().len(), 2);
        assert_eq!(
            cr.headers().get("authorization").unwrap()[0],
            b"AWS4-HMAC-SHA256 Credential=1234, SignedHeaders=date;host, Signature=5678"
        );
        assert_eq!(cr.body_sha256(), "e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855");

        let params = cr.get_auth_parameters(&NO_ADDITIONAL_SIGNED_HEADERS).unwrap();
        // Ensure we can debug print the auth parameters.
        let _ = format!("{:?}", params);
        assert_eq!(params.signed_headers, vec!["date", "host"]);
    }

    #[test_log::test]
    fn test_bad_form_urlencoded_charset() {
        let uri = Uri::builder().path_and_query(PathAndQuery::from_static("/")).build().unwrap();
        let request = Request::builder()
            .method(Method::POST)
            .uri(uri)
            .header("content-type", "application/x-www-form-urlencoded; hello=world; charset=foobar")
            .header("authorization", "AWS4-HMAC-SHA256 Credential=1234, SignedHeaders=date;host, Signature=5678")
            .header("x-amz-date", "20150830T123600Z")
            .body(Bytes::from_static(b"foo=ba\x80r"))
            .unwrap();
        let (parts, body) = request.into_parts();

        let e = CanonicalRequest::from_request_parts(parts, body, SignatureOptions::url_encode_form()).unwrap_err();
        if let SignatureError::InvalidBodyEncoding(_) = e {
            assert_eq!(e.to_string(), "application/x-www-form-urlencoded body uses unsupported charset 'foobar'");
            assert_eq!(e.error_code(), "InvalidBodyEncoding");
            assert_eq!(e.http_status(), 400);
        } else {
            panic!("Unexpected error: {:?}", e);
        }
    }

    #[test_log::test]
    fn test_empty_form() {
        let uri = Uri::builder().path_and_query(PathAndQuery::from_static("/")).build().unwrap();
        let request = Request::builder()
            .method(Method::POST)
            .uri(uri)
            .header("content-type", "application/x-www-form-urlencoded; charset=utf-8")
            .header("authorization", "AWS4-HMAC-SHA256 Credential=1234, SignedHeaders=date;host, Signature=5678")
            .header("x-amz-date", "20150830T123600Z")
            .body(Bytes::from_static(b""))
            .unwrap();
        let (parts, body) = request.into_parts();

        let (cr, _, _) =
            CanonicalRequest::from_request_parts(parts, body, SignatureOptions::url_encode_form()).unwrap();
        assert!(cr.query_parameters().is_empty());
    }

    #[test_log::test]
    fn test_default_form_encoding() {
        let uri = Uri::builder().path_and_query(PathAndQuery::from_static("/")).build().unwrap();
        let request = Request::builder()
            .method(Method::POST)
            .uri(uri)
            .header("content-type", "application/x-www-form-urlencoded")
            .header("authorization", "AWS4-HMAC-SHA256 Credential=1234, SignedHeaders=date;host, Signature=5678")
            .header("x-amz-date", "20150830T123600Z")
            .body(Bytes::from(b"foo=bar\xc3\xbf".to_vec()))
            .unwrap();
        let (parts, body) = request.into_parts();

        let (cr, _, _) =
            CanonicalRequest::from_request_parts(parts, body, SignatureOptions::url_encode_form()).unwrap();
        assert_eq!(cr.query_parameters().get("foo").unwrap(), &vec!["bar%C3%BF".to_string()]);

        let uri = Uri::builder().path_and_query(PathAndQuery::from_static("/")).build().unwrap();
        let request = Request::builder()
            .method(Method::POST)
            .uri(uri)
            .header("content-type", "application/x-www-form-urlencoded; hello=world")
            .header("authorization", "AWS4-HMAC-SHA256 Credential=1234, SignedHeaders=date;host, Signature=5678")
            .header("x-amz-date", "20150830T123600Z")
            .body(Bytes::from(b"foo=bar\xc3\xbf".to_vec()))
            .unwrap();
        let (parts, body) = request.into_parts();

        let (cr, _, _) =
            CanonicalRequest::from_request_parts(parts, body, SignatureOptions::url_encode_form()).unwrap();
        assert_eq!(cr.query_parameters().get("foo").unwrap(), &vec!["bar%C3%BF".to_string()]);
    }

    #[test_log::test]
    fn test_no_map_form() {
        let uri = Uri::builder().path_and_query(PathAndQuery::from_static("/")).build().unwrap();
        let request = Request::builder()
            .method(Method::POST)
            .uri(uri)
            .header("content-type", "application/x-www-form-urlencoded")
            .header("authorization", "AWS4-HMAC-SHA256 Credential=1234, SignedHeaders=date;host, Signature=5678")
            .header("x-amz-date", "20150830T123600Z")
            .body(Bytes::from(b"foo=bar\xc3\xbf".to_vec()))
            .unwrap();
        let (parts, body) = request.into_parts();

        let (cr, _, _) = CanonicalRequest::from_request_parts(parts, body, SignatureOptions::default()).unwrap();
        assert!(!cr.query_parameters().contains_key("foo"));
    }

    #[test_log::test]
    fn test_bad_debug_headers() {
        let mut headers = HashMap::new();
        headers.insert("Host".to_string(), vec![vec![0xffu8]]);
        let debug = debug_headers(&headers);
        assert_eq!(debug, "Host: [255]");

        assert_eq!(debug_headers(&HashMap::new()), "");
    }

    #[test_log::test]
    fn test_bad_form_encoding() {
        let uri = Uri::builder().path_and_query(PathAndQuery::from_static("/")).build().unwrap();
        let request = Request::builder()
            .method(Method::POST)
            .uri(uri)
            .header("content-type", "application/x-www-form-urlencoded; charset=utf-8")
            .header("authorization", "AWS4-HMAC-SHA256 Credential=1234, SignedHeaders=date;host, Signature=5678")
            .header("x-amz-date", "20150830T123600Z")
            .body(Bytes::from(b"foo=ba\x80r".to_vec()))
            .unwrap();
        let (parts, body) = request.into_parts();

        let e = CanonicalRequest::from_request_parts(parts, body, SignatureOptions::url_encode_form()).unwrap_err();
        if let SignatureError::InvalidBodyEncoding(msg) = e {
            assert_eq!(
                msg.as_str(),
                "Invalid body data encountered parsing application/x-www-form-urlencoded with charset 'UTF-8'"
            )
        } else {
            panic!("Unexpected error: {:?}", e);
        }
    }

    #[test_log::test]
    fn test_bad_form_charset_param() {
        let uri = Uri::builder().path_and_query(PathAndQuery::from_static("/")).build().unwrap();
        let request = Request::builder()
            .method(Method::POST)
            .uri(uri)
            .header("content-type", "application/x-www-form-urlencoded; charset")
            .header("authorization", "AWS4-HMAC-SHA256 Credential=1234, SignedHeaders=date;host, Signature=5678")
            .header("x-amz-date", "20150830T123600Z")
            .body(Bytes::from(b"foo=bar".to_vec()))
            .unwrap();
        let (parts, body) = request.into_parts();

        let (_, _, body) =
            CanonicalRequest::from_request_parts(parts, body, SignatureOptions::url_encode_form()).unwrap();
        assert_eq!(body.as_ref(), b"");
    }

    #[test_log::test]
    fn test_bad_form_urlencoding() {
        let uri = Uri::builder().path_and_query(PathAndQuery::from_static("/")).build().unwrap();
        let request = Request::builder()
            .method(Method::POST)
            .uri(uri)
            .header("content-type", "application/x-www-form-urlencoded; charset=utf-8")
            .header("authorization", "AWS4-HMAC-SHA256 Credential=1234, SignedHeaders=date;host, Signature=5678")
            .header("x-amz-date", "20150830T123600Z")
            .body(Bytes::from(b"foo=bar%yy".to_vec()))
            .unwrap();
        let (parts, body) = request.into_parts();

        let e = CanonicalRequest::from_request_parts(parts, body, SignatureOptions::url_encode_form()).unwrap_err();
        if let SignatureError::MalformedQueryString(msg) = e {
            assert_eq!(msg.as_str(), "Illegal hex character in escape % pattern: %yy")
        } else {
            panic!("Unexpected error: {:?}", e);
        }

        let uri = Uri::builder().path_and_query(PathAndQuery::from_static("/")).build().unwrap();
        let request = Request::builder()
            .method(Method::POST)
            .uri(uri)
            .header("content-type", "application/x-www-form-urlencoded; charset=utf-8")
            .header("authorization", "AWS4-HMAC-SHA256 Credential=1234, SignedHeaders=date;host, Signature=5678")
            .header("x-amz-date", "20150830T123600Z")
            .body(Bytes::from(b"foo%tt=bar".to_vec()))
            .unwrap();
        let (parts, body) = request.into_parts();

        let e = CanonicalRequest::from_request_parts(parts, body, SignatureOptions::url_encode_form()).unwrap_err();
        if let SignatureError::MalformedQueryString(msg) = e {
            assert_eq!(msg.as_str(), "Illegal hex character in escape % pattern: %tt")
        } else {
            panic!("Unexpected error: {:?}", e);
        }

        let uri = Uri::builder().path_and_query(PathAndQuery::from_static("/")).build().unwrap();
        let request = Request::builder()
            .method(Method::POST)
            .uri(uri)
            .header("content-type", "application/x-www-form-urlencoded; charset=utf-8")
            .header("authorization", "AWS4-HMAC-SHA256 Credential=1234, SignedHeaders=date;host, Signature=5678")
            .header("x-amz-date", "20150830T123600Z")
            .body(Bytes::from(b"foo=bar%y".to_vec()))
            .unwrap();
        let (parts, body) = request.into_parts();

        let e = CanonicalRequest::from_request_parts(parts, body, SignatureOptions::url_encode_form()).unwrap_err();
        if let SignatureError::MalformedQueryString(msg) = e {
            assert_eq!(msg.as_str(), "Incomplete trailing escape % sequence")
        } else {
            panic!("Unexpected error: {:?}", e);
        }
    }

    #[test_log::test]
    fn test_u8_to_upper_hex() {
        for i in 0..=255 {
            let result = u8_to_upper_hex(i);
            assert_eq!(String::from_utf8_lossy(result.as_slice()), format!("{:02X}", i));
        }
    }

    #[test_log::test]
    fn test_missing_auth_header_components() {
        for i in 0..15 {
            let uri = Uri::builder().path_and_query(PathAndQuery::from_static("/")).build().unwrap();
            let mut error_messages = Vec::with_capacity(4);
            let mut auth_header = Vec::with_capacity(3);

            if i & 1 != 0 {
                auth_header.push(" Credential=1234  ");
            } else {
                error_messages.push("Authorization header requires 'Credential' parameter.");
            }

            if i & 2 != 0 {
                auth_header.push(" Signature=5678  ");
            } else {
                error_messages.push("Authorization header requires 'Signature' parameter.");
            }

            if i & 4 != 0 {
                auth_header.push(" SignedHeaders=host;x-amz-date");
            } else {
                error_messages.push("Authorization header requires 'SignedHeaders' parameter.");
            }

            let auth_header = format!("AWS4-HMAC-SHA256 {}", auth_header.join(", "));
            let builder = Request::builder().method(Method::GET).uri(uri).header("authorization", auth_header);

            let builder = if i & 8 != 0 {
                builder.header("x-amz-date", "20150830T123600Z")
            } else {
                error_messages
                    .push("Authorization header requires existence of either a 'X-Amz-Date' or a 'Date' header.");
                builder
            };

            let request = builder.body(Bytes::new()).unwrap();
            let (parts, body) = request.into_parts();

            let (cr, _, _) =
                CanonicalRequest::from_request_parts(parts, body, SignatureOptions::url_encode_form()).unwrap();
            let e = cr.get_auth_parameters(&NO_ADDITIONAL_SIGNED_HEADERS).unwrap_err();
            if let SignatureError::IncompleteSignature(msg) = e {
                let error_message = format!("{} Authorization=AWS4-HMAC-SHA256", error_messages.join(" "));
                assert_eq!(msg.as_str(), error_message.as_str());
            } else {
                panic!("Unexpected error: {:?}", e);
            }
        }
    }

    #[test_log::test]
    fn test_malformed_auth_header() {
        let uri = Uri::builder().path_and_query(PathAndQuery::from_static("/")).build().unwrap();
        let request = Request::builder()
            .method(Method::GET)
            .uri(uri)
            .header("x-amz-date", "20150830T123600Z")
            .header("authorization", "AWS4-HMAC-SHA256 Credential=1234, SignedHeadersdate;host")
            .body(Bytes::new())
            .unwrap();

        let (parts, body) = request.into_parts();

        let (cr, _, _) =
            CanonicalRequest::from_request_parts(parts, body, SignatureOptions::url_encode_form()).unwrap();
        let e = cr.get_auth_parameters(&NO_ADDITIONAL_SIGNED_HEADERS).unwrap_err();
        if let SignatureError::IncompleteSignature(msg) = e {
            assert_eq!(msg.as_str(), "'SignedHeadersdate;host' not a valid key=value pair (missing equal-sign) in Authorization header: 'AWS4-HMAC-SHA256 Credential=1234, SignedHeadersdate;host'");
        } else {
            panic!("Unexpected error: {:?}", e);
        }
    }

    #[test_log::test]
    fn test_missing_auth_query_components() {
        for i in 0..15 {
            let mut error_messages = Vec::with_capacity(4);
            let mut auth_query = Vec::with_capacity(5);

            auth_query.push("X-Amz-Algorithm=AWS4-HMAC-SHA256");

            if i & 1 != 0 {
                auth_query.push("X-Amz-Credential=1234");
            } else {
                error_messages.push("AWS query-string parameters must include 'X-Amz-Credential'.");
            }

            if i & 2 != 0 {
                auth_query.push("X-Amz-Signature=5678");
            } else {
                error_messages.push("AWS query-string parameters must include 'X-Amz-Signature'.");
            }

            if i & 4 != 0 {
                auth_query.push("X-Amz-SignedHeaders=host;x-amz-date");
            } else {
                error_messages.push("AWS query-string parameters must include 'X-Amz-SignedHeaders'.");
            }

            if i & 8 != 0 {
                auth_query.push("X-Amz-Date=20150830T123600Z")
            } else {
                error_messages.push("AWS query-string parameters must include 'X-Amz-Date'.");
            };

            let query_string = auth_query.join("&");

            let pq = PathAndQuery::from_maybe_shared(format!("/?{}", query_string)).unwrap();
            let uri = Uri::builder().path_and_query(pq).build().unwrap();
            let builder = Request::builder().method(Method::GET).uri(uri);

            let request = builder.body(Bytes::new()).unwrap();
            let (parts, body) = request.into_parts();

            let (cr, _, _) =
                CanonicalRequest::from_request_parts(parts, body, SignatureOptions::url_encode_form()).unwrap();
            let e = cr.get_auth_parameters(&NO_ADDITIONAL_SIGNED_HEADERS).unwrap_err();
            if let SignatureError::IncompleteSignature(msg) = e {
                let error_message = format!("{} Re-examine the query-string parameters.", error_messages.join(" "));
                assert_eq!(msg.as_str(), error_message.as_str());
            } else {
                panic!("Unexpected error: {:?}", e);
            }
        }
    }

    #[test_log::test]
    fn test_auth_component_ordering() {
        let uri = Uri::builder().path_and_query(PathAndQuery::from_static("/")).build().unwrap();
        let request = Request::builder()
            .method(Method::GET)
            .uri(uri)
            .header("authorization", "AWS4-HMAC-SHA256 Credential=1234, SignedHeaders=date;host, Signature=5678, Credential=ABCD, SignedHeaders=foo;bar;host, Signature=DEFG")
            .header("authorization", "AWS3 Credential=1234, SignedHeaders=date;host, Signature=5678, Credential=ABCD, SignedHeaders=foo;bar;host, Signature=DEFG")
            .header("host", "example.amazonaws.com")
            .header("x-amz-date", "20150830T123600Z")
            .header("x-amz-date", "20161231T235959Z")
            .header("x-amz-security-token", "Test1")
            .header("x-amz-security-token", "Test2")
            .body(Bytes::new())
            .unwrap();
        let (parts, body) = request.into_parts();

        let (cr, _, _) =
            CanonicalRequest::from_request_parts(parts, body, SignatureOptions::url_encode_form()).unwrap();
        let auth = cr.get_auth_parameters(&NO_ADDITIONAL_SIGNED_HEADERS).unwrap();
        // Expect last component found
        assert_eq!(auth.builder.get_credential(), Some("ABCD"));
        assert_eq!(auth.builder.get_signature(), Some("DEFG"));
        assert_eq!(auth.signed_headers, vec!["bar", "foo", "host"]);
        // Expect first header found.
        assert_eq!(auth.builder.get_session_token(), Some("Test1"));
        assert_eq!(auth.timestamp_str, "20150830T123600Z");

        let uri = Uri::builder().path_and_query(PathAndQuery::from_static("/?X-Amz-Algorithm=AWS4-HMAC-SHA256&X-Amz-Algorithm=AWS3&X-Amz-Credential=1234&X-Amz-SignedHeaders=date%3Bhost&X-Amz-Signature=5678&X-Amz-Security-Token=Test1&X-Amz-Date=20150830T123600Z&X-Amz-Credential=ABCD&X-Amz-SignedHeaders=foo%3Bbar%3Bhost&X-Amz-Signature=DEFG&X-Amz-SecurityToken=Test2&X-Amz-Date=20161231T235959Z")).build().unwrap();
        let request = Request::builder()
            .method(Method::GET)
            .uri(uri)
            .header("host", "example.amazonaws.com")
            .body(Bytes::new())
            .unwrap();
        let (parts, body) = request.into_parts();

        let (cr, _, _) =
            CanonicalRequest::from_request_parts(parts, body, SignatureOptions::url_encode_form()).unwrap();
        let auth = cr.get_auth_parameters(&NO_ADDITIONAL_SIGNED_HEADERS).unwrap();
        // Expect first component found
        assert_eq!(auth.builder.get_credential(), Some("1234"));
        assert_eq!(auth.builder.get_signature(), Some("5678"));
        assert_eq!(auth.builder.get_session_token(), Some("Test1"));
        assert_eq!(auth.timestamp_str, "20150830T123600Z");
        assert_eq!(auth.signed_headers, vec!["date", "host"]);

        let auth = cr.get_authenticator(&NO_ADDITIONAL_SIGNED_HEADERS);
        assert!(auth.is_ok());
    }

    #[test_log::test]
    fn test_signed_headers_missing_host() {
        let uri = Uri::builder().path_and_query(PathAndQuery::from_static("/")).build().unwrap();
        let request = Request::builder()
            .method(Method::GET)
            .uri(uri)
            .header("x-amz-date", "20150830T123600Z")
            .header("host", "example.amazonaws.com")
            .header("authorization", "AWS4-HMAC-SHA256 Credential=1234, SignedHeaders=x-amz-date, Signature=5678")
            .body(Bytes::new())
            .unwrap();

        let (parts, body) = request.into_parts();

        let (cr, _, _) =
            CanonicalRequest::from_request_parts(parts, body, SignatureOptions::url_encode_form()).unwrap();
        let required_headers = NO_ADDITIONAL_SIGNED_HEADERS;
        let required_headers2 = required_headers;
        assert_eq!(&required_headers, &required_headers2);
        assert_eq!(format!("{:?}", required_headers), format!("{:?}", required_headers2));
        let e = cr.get_auth_parameters(&required_headers).unwrap_err();
        if let SignatureError::SignatureDoesNotMatch(msg) = e {
            let msg = msg.expect("Expected error message");
            assert_eq!(msg.as_str(), "'Host' or ':authority' must be a 'SignedHeader' in the AWS Authorization.");
        } else {
            panic!("Unexpected error: {:?}", e);
        }

        let uri = Uri::builder().path_and_query(PathAndQuery::from_static("/?X-Amz-Algorithm=AWS4-HMAC-SHA256&X-Amz-Credential=1234&X-Amz-SignedHeaders=&X-Amz-Signature=5678&X-Amz-Date=20150830T123600Z&X-Amz-SecurityToken=Foo")).build().unwrap();
        let request = Request::builder()
            .method(Method::GET)
            .uri(uri)
            .header("host", "example.amazonaws.com")
            .body(Bytes::new())
            .unwrap();

        let (parts, body) = request.into_parts();

        let (cr, _, _) =
            CanonicalRequest::from_request_parts(parts, body, SignatureOptions::url_encode_form()).unwrap();
        let e = cr.get_auth_parameters(&NO_ADDITIONAL_SIGNED_HEADERS).unwrap_err();
        if let SignatureError::SignatureDoesNotMatch(msg) = e {
            let msg = msg.expect("Expected error message");
            assert_eq!(msg.as_str(), "'Host' or ':authority' must be a 'SignedHeader' in the AWS Authorization.");
        } else {
            panic!("Unexpected error: {:?}", e);
        }
    }

    #[test_log::test]
    fn test_missing_signed_header() {
        let uri = Uri::builder().path_and_query(PathAndQuery::from_static("/")).build().unwrap();
        let request = Request::builder()
            .method(Method::GET)
            .uri(uri)
            .header("x-amz-date", "20150830T123600Z")
            .header("host", "example.amazonaws.com")
            .header(
                "authorization",
                "AWS4-HMAC-SHA256 Credential=1234, SignedHeaders=a;host;x-amz-date, Signature=5678",
            )
            .body(Bytes::new())
            .unwrap();

        let (parts, body) = request.into_parts();

        let (cr, _, _) =
            CanonicalRequest::from_request_parts(parts, body, SignatureOptions::url_encode_form()).unwrap();
        let a = cr.get_auth_parameters(&NO_ADDITIONAL_SIGNED_HEADERS).unwrap();
        assert_eq!(a.signed_headers, vec!["a", "host", "x-amz-date"]);
        let cr_bytes = cr.canonical_request(&a.signed_headers);
        assert!(!cr_bytes.is_empty());
    }

    #[test_log::test]
    fn test_bad_algorithms() {
        // No algorithm present (rule 5)
        let uri = Uri::builder().path_and_query(PathAndQuery::from_static("/")).build().unwrap();
        let request = Request::builder()
            .method(Method::POST)
            .uri(uri)
            .header("content-type", "application/json")
            .header("x-amz-date", "20150830T123600Z")
            .header("host", "example.amazonaws.com")
            .body(Bytes::from_static(b"{}"))
            .unwrap();

        let (parts, body) = request.into_parts();

        let (cr, _, _) =
            CanonicalRequest::from_request_parts(parts, body, SignatureOptions::url_encode_form()).unwrap();
        let e = cr.get_auth_parameters(&NO_ADDITIONAL_SIGNED_HEADERS).unwrap_err();
        if let SignatureError::MissingAuthenticationToken(msg) = e {
            assert_eq!(msg.as_str(), "Request is missing Authentication Token");
        } else {
            panic!("Unexpected error: {:?}", e);
        }

        // Both header and query string signatures present (rule 5)
        let uri = Uri::builder().path_and_query(PathAndQuery::from_static("/?X-Amz-Algorithm=AWS4-HMAC-SHA256&X-Amz-Credential=1234&X-Amz-SignedHeaders=&X-Amz-Signature=5678&X-Amz-Date=20150830T123600Z&X-Amz-SecurityToken=Foo")).build().unwrap();
        let request = Request::builder()
            .method(Method::GET)
            .uri(uri)
            .header("authorization", "AWS4-HMAC-SHA256 Credential=1234, SignedHeaders=x-amz-date, Signature=5678")
            .header("x-amz-date", "20150830T123600Z")
            .header("host", "example.amazonaws.com")
            .body(Bytes::new())
            .unwrap();

        let (parts, body) = request.into_parts();

        let (cr, _, _) =
            CanonicalRequest::from_request_parts(parts, body, SignatureOptions::url_encode_form()).unwrap();
        let e = cr.get_auth_parameters(&NO_ADDITIONAL_SIGNED_HEADERS).unwrap_err();
        if let SignatureError::SignatureDoesNotMatch(ref msg) = e {
            assert!(msg.is_none());
            assert_eq!(e.to_string(), "");
        } else {
            panic!("Unexpected error: {:?}", e);
        }

        // Wrong algorithm header (rule 6a)
        let uri = Uri::builder().path_and_query(PathAndQuery::from_static("/")).build().unwrap();
        let request = Request::builder()
            .method(Method::GET)
            .uri(uri)
            .header("authorization", "AWS3-HMAC-SHA256 Credential=1234, SignedHeaders=x-amz-date, Signature=5678")
            .header("x-amz-date", "20150830T123600Z")
            .header("host", "example.amazonaws.com")
            .body(Bytes::new())
            .unwrap();

        let (parts, body) = request.into_parts();

        let (cr, _, _) =
            CanonicalRequest::from_request_parts(parts, body, SignatureOptions::url_encode_form()).unwrap();
        let e = cr.get_auth_parameters(&NO_ADDITIONAL_SIGNED_HEADERS).unwrap_err();
        if let SignatureError::IncompleteSignature(msg) = e {
            assert_eq!(msg.as_str(), "Unsupported AWS 'algorithm': 'AWS3-HMAC-SHA256'.");
        } else {
            panic!("Unexpected error: {:?}", e);
        }

        // Wrong algorithm query string (rule 7a)
        let uri = Uri::builder().path_and_query(PathAndQuery::from_static("/?X-Amz-Algorithm=AWS3-HMAC-SHA256&X-Amz-Algorithm=AWS4-HMAC-SHA256&X-Amz-Credential=1234&X-Amz-SignedHeaders=date%3Bhost&X-Amz-Signature=5678&X-Amz-Security-Token=Test1&X-Amz-Date=20150830T123600Z&X-Amz-Credential=ABCD&X-Amz-SignedHeaders=foo%3Bbar%3Bhost&X-Amz-Signature=DEFG&X-Amz-SecurityToken=Test2&X-Amz-Date=20161231T235959Z")).build().unwrap();
        let request = Request::builder()
            .method(Method::GET)
            .uri(uri)
            .header("x-amz-date", "20150830T123600Z")
            .header("host", "example.amazonaws.com")
            .body(Bytes::new())
            .unwrap();

        let (parts, body) = request.into_parts();

        let (cr, _, _) =
            CanonicalRequest::from_request_parts(parts, body, SignatureOptions::url_encode_form()).unwrap();
        let e = cr.get_auth_parameters(&NO_ADDITIONAL_SIGNED_HEADERS).unwrap_err();
        if let SignatureError::MissingAuthenticationToken(msg) = e {
            assert_eq!(msg.as_str(), "Request is missing Authentication Token");
        } else {
            panic!("Unexpected error: {:?}", e);
        }
    }

    #[test_log::test]
    #[should_panic]
    fn unescape_uri_encoding_invalid_panics() {
        unescape_uri_encoding("%YY");
    }
}