b2-client 0.1.3

/* This Source Code Form is subject to the terms of the Mozilla Public
   License, v. 2.0. If a copy of the MPL was not distributed with this
   file, You can obtain one at http://mozilla.org/MPL/2.0/.
*/

//! Validation functions used throughout the crate.

use std::collections::HashMap;

use crate::{
    bucket::{LifecycleRule, ServerSideEncryption},
    error::*,
};

use http_types::{
    cache::{CacheControl, Expires},
    Trailers,
};


/// Returns the provided HTTP header if it's valid; otherwise a ValidationError.
///
/// An HTTP header:
///
/// * must be valid ASCII.
/// * must not include whitespace.
/// * must not include ASCII codes outside alphanumeric codes or any of
///   "!" "#" "$" "%" "&" "'" "*" "+" "-" "." "^" "_" "`" "|" or "~".
///
/// # Notes
///
/// We validate headers according to
/// [RFC 7230](https://www.rfc-editor.org/rfc/rfc7230), notably
/// [Section 3.2.6](https://www.rfc-editor.org/rfc/rfc7230#section-3.2.6). It is
/// possible that the B2 API is more lenient.
pub(crate) fn validated_http_header(header: &str) -> Result<&str, BadHeaderName>
{
    let is_valid = |c: char| "!#$%&'*+-.^_`|~".contains(c);

    let invalid = header.chars()
        .find(|c| !(c.is_ascii_alphanumeric() || is_valid(*c)));

    if let Some(ch) = invalid {
        Err(BadHeaderName {
            header: header.to_owned(),
            invalid_char: ch,
        })
    } else {
        Ok(header)
    }
}

pub(crate) fn validated_bucket_name(name: impl Into<String>)
-> Result<String, BucketValidationError> {
    let name = name.into();

    if name.len() < 6 || name.len() > 50 {
        return Err(BucketValidationError::BadNameLength(name.len()));
    }

    let invalid_char = |c: &char| !(c.is_ascii_alphanumeric() || *c == '-');

    match name.chars().find(invalid_char) {
        None => Ok(name),
        Some(ch) => Err(BucketValidationError::InvalidChar(ch)),
    }
}

/// Ensure a filename is valid.
///
/// Note that B2 disallows ASCII control characters, but other control
/// characters defined by Unicode are allowed.
pub(crate) fn validated_file_name(name: &str)
-> Result<&str, FileNameValidationError> {
    for ch in name.chars() {
        if ch.is_ascii_control() {
            return Err(FileNameValidationError::InvalidChar(ch));
        }
    }

    if name.len() < 1024 {
        Ok(name)
    } else {
        Err(FileNameValidationError::BadLength(name.len()))
    }
}

pub(crate) fn validated_cors_rule_name(name: impl Into<String>)
-> Result<String, CorsRuleValidationError> {
    // The rules are the same as for bucket names.
    validated_bucket_name(name)
}

/// Ensure that file metadata fits within the B2 length requirements.
pub(crate) fn validate_file_metadata_size(
    file_name: &str,
    file_info: Option<&serde_json::Value>,
    enc: Option<&ServerSideEncryption>
) -> Result<(), ValidationError> {
    let limit = match enc {
        Some(&ServerSideEncryption::NoEncryption) => 7000,
        _ => 2048,
    };

    // Only the keys and values count against the max limit, so we need to
    // add them up rather than convert the entire Value to a string and
    // check its length.
    let info_len = file_info
        .map(|v| v.as_object())
        .flatten()
        .map(|obj| obj.iter()
            .fold(0, |acc, (k, v)| acc + k.len() + v.to_string().len())
        )
        .unwrap_or(0);

    let name_len = file_name.len();

    if info_len + name_len <= limit {
        Ok(())
    } else {
        Err(ValidationError::OutOfBounds(format!(
            "file_name and file_info lengths must not exceed {} bytes",
            limit
        )))
    }
}

/// Ensure the keys and values of file metadata is correct.
///
/// We do not check the byte length limit since the limit applies to both the
/// file info and the name. Use [validate_file_metadata_size] to check the
/// length limit.
pub(crate) fn validated_file_info(info: serde_json::Value)
-> Result<serde_json::Value, ValidationError> {
    let obj = info.as_object()
        .ok_or_else(||
            ValidationError::BadFormat("file_info is not an object".into())
        )?;

    if obj.len() > 10 {
        return Err(ValidationError::BadFormat(
            "file_info cannot contain more than 10 items".into()
        ));
    }

    for (key, val) in obj {
        validate_info_key_val(key, val)?;
    }

    Ok(info)
}

fn validate_info_key_val(key: &str, val: &serde_json::Value)
-> Result<(), ValidationError> {
    if key.len() > 50 {
        return Err(ValidationError::BadFormat(format!(
            "Key cannot exceed 50 bytes, but is {}", key.len()
        )));
    }

    if key.starts_with("b2-") {
        validate_info_val(key, val)?
    }

    let is_valid = |c: char| c.is_alphanumeric()
        || ['-', '_', '.', '`', '~', '!', '#', '$', '%', '^', '&', '*', '\'',
            '|', '+'].contains(&c);

    for ch in key.chars() {
        if ! is_valid(ch) {
            return Err(ValidationError::BadFormat(format!(
                "Invalid character in key: '{}'", ch
            )));
        }
    }

    Ok(())
}

/// Validate the file_info for B2-specific metadata.
pub fn validate_info_val(key: &str, val: &serde_json::Value)
-> Result<(), ValidationError> {
    let val = val.as_str().ok_or_else(||
        ValidationError::BadFormat(format!("{} value must be a string", key))
    )?;

    // TODO: We can likely validate the stuff I'm using http_types to validate
    // more efficiently by doing it manually.
    match key {
        "b2-content-disposition" => {
            validate_content_disposition(val, false)
        },
        "b2-content-language" => {
            for ch in val.chars() {
                if ! (ch.is_ascii_alphabetic() || ch == '-') {
                    return Err(ValidationError::BadFormat(format!(
                        "Invalid character in Content-Language: {}", ch
                    )));
                }
            }
            Ok(())
        },
        "b2-expires" => {
            let mut hdr = Trailers::new();
            hdr.insert("Expires", val);

            Expires::from_headers(hdr.as_ref())
                .map_err(|_| ValidationError::BadFormat(format!(
                    "Invalid Expires value: {}", val
                )))?;

            Ok(())
        },
        "b2-cache-control" => {
            // TODO: CacheControl type doesn't seem to validate cache-extension
            // properly. See
            // https://datatracker.ietf.org/doc/html/rfc2616#section-14.9
            let mut hdr = Trailers::new();
            hdr.insert("CacheControl", val);

            CacheControl::from_headers(hdr.as_ref())
                .map_err(|_| ValidationError::BadFormat(format!(
                    "Invalid CacheControl value: {}", val
                )))?;

            Ok(())
        },
        "b2-content-encoding" => {
            // B2 documentation says this must conform to RFC 2616, which seems
            // to be more restrictive than RFC 7231, which supercedes it. We're
            // going to validate that the value is a valid token, but not worry
            // about the value itself.
            if is_valid_token(val) {
                Ok(())
            } else {
                Err(ValidationError::BadFormat(format!(
                    "Invalid ContentEncoding: {}", val
                )))
            }
        },
        _ => Err(ValidationError::BadFormat(format!(
            "Invalid key name: {}", key
        ))),
    }
}

pub fn validate_content_disposition(text: &str, allow_star: bool)
-> Result<(), ValidationError> {
    let sep_idx = text.find(';');

    if sep_idx.is_none() {
        // Lack of a ';' means the value is a simple token.
        return if is_valid_token(text) {
            Ok(())
        } else {
            Err(ValidationError::BadFormat(format!(
                "Illegal Content-Disposition type: {}", text
            )))
        };
    } else if text.ends_with(';') {
        return Err(ValidationError::BadFormat(
            "Content-Disposition cannot end with a semicolon".into()
        ));
    }
    let sep_idx = sep_idx.unwrap();

    for param in text[sep_idx+1..].split(';') {
        if let Some((field, value)) = param.split_once('=') {
            let field = field.trim();

            if ! is_valid_token(field) {
                return Err(ValidationError::BadFormat(format!(
                    "Illegal character in field name: {}", field
                )));
            }

            if ! allow_star && field == "*" {
                return Err(ValidationError::BadFormat(
                    "Asterisk ('*') is not allowed in a field name".into()
                ));
            }

            let value = value.trim();

            // TODO: We need to also verify that if the value is an ext-value as
            // defined at
            // https://datatracker.ietf.org/doc/html/rfc5987#section-3.2 that it
            // is valid. We currently assume it's valid. Also see restrictions
            // listed at https://www.backblaze.com/b2/docs/files.html
            if ! (is_valid_token(value) || is_valid_quoted_string(value)) {
                return Err(ValidationError::BadFormat(
                    "Invalid field value".into()
                ));
            }
        }
    }

    Ok(())
}

fn is_valid_token(s: &str) -> bool {
    let separators = [
        '(', ')', '<', '>', '@', ',', ';', ':', '\\', '"', '/', '[', ']', '?',
        '=', '{', '}', ' ', '\t',
    ];

    if s.is_empty() { return false; }

    for ch in s.chars() {
        if ! ch.is_ascii_alphanumeric() || ch.is_control()
            || separators.contains(&ch)
        {
            return false;
        }
    }

    true
}

fn is_valid_quoted_string(s: &str) -> bool {
    if ! (s.starts_with('"') && s.ends_with('"'))
    {
        return false;
    }

    let s = s.as_bytes();

    for i in 1..s.len() - 1 {
        if ! s[i].is_ascii() || s[i].is_ascii_control()
            || (s[i] == b'"' && s[i-1] != b'\\')
        {
            return false;
        }
    }

    true
}

/// Return the provided list of [LifecycleRule]s or a map of errors.
///
/// No file within a bucket can be subject to multiple lifecycle rules. If any
/// of the rules provided apply to multiple files or folders, we return the
/// conflicting rules. The map's key is the broadest rule (highest in the
/// hierarchy). The map may have duplicate entries when subfolders are
/// involved.
///
/// The empty string (`""`) matches all paths, so if provided it must be the
/// only lifecycle rule. If it is provided along with other rules, all of those
/// rules will be listed as a conflict.
pub(crate) fn validated_lifecycle_rules(rules: impl Into<Vec<LifecycleRule>>)
-> Result<Vec<LifecycleRule>, LifecycleRuleValidationError> {
    let mut rules = rules.into();

    if rules.len() <= 1 {
        Ok(rules)
    } else if rules.len() > 100 {
        Err(LifecycleRuleValidationError::TooManyRules(rules.len()))
    } else {
        rules.sort();

        // TODO: May be worthwhile to reserve rules.len()/2 or something.
        let mut checked: Vec<Vec<&LifecycleRule>> = vec![vec![&rules[0]]];

        for rule in rules.iter().skip(1) {
            for i in 0 .. checked.len() {
                let root = &checked[i][0];

                if rule.file_name_prefix.starts_with(&root.file_name_prefix) {
                    checked[i].push(rule);
                }  else {
                    checked.push(vec![rule]);
                }
            }
        }

        let mut map = HashMap::new();

        checked.into_iter()
            .filter(|list| list.len() > 1) // Keep only conflicts.
            .for_each(|list| {
                let key = list[0].file_name_prefix.to_owned();

                let val = list[1..].iter()
                    .map(|v| (*v).to_owned())
                    .collect::<Vec<LifecycleRule>>();

                map.insert(key, val);
            });

        if ! map.is_empty() {
            Err(LifecycleRuleValidationError::ConflictingRules(map))
        } else {
            Ok(rules)
        }
    }
}

/// Validate a list of origins for a CORS rule.
///
/// See [CorsRuleBuilder::with_allowed_origins] for the rules concerning a valid
/// origin.
pub(crate) fn validated_origins(origins: impl Into<Vec<String>>)
-> Result<Vec<String>, ValidationError> {
    let origins = origins.into();

    if origins.is_empty() {
        return Err(ValidationError::MissingData(
            "There must be at least one origin covered by the rule".into()
        ));
    }

    if ! (origins.len() == 1 && origins[0] == "*") {
        let mut found_https = false;

        for origin in origins.iter() {
            // `http` and `https` are valid origins, but `Url::parse()` won't
            // parse them, so we check them separately.
            if origin == "https" {
                if found_https {
                    return Err(ValidationError::Incompatible(
                        "There can only be one HTTPS rule".into()
                    ));
                }
                found_https = true;
            } else if origin != "http" {
                if origin.chars().filter(|c| *c == '*').count() > 1 {
                    return Err(ValidationError::BadFormat(
                        "A URL cannot have more than one '*'".into()
                    ));
                }

                let url = url::Url::parse(origin)?;

                if url.scheme() == "https" {
                    if found_https {
                        return Err(ValidationError::Incompatible(
                            "There can only be one HTTPS rule".into()
                        ));
                    }
                    found_https = true;
                }

                if ! (url.scheme() == "https" || url.scheme() == "http") {
                    return Err(ValidationError::BadUrl(url.to_string()));
                }
            }
        }
    }

    Ok(origins)
}

#[cfg(test)]
mod tests {
    use super::*;
    use serde_json::json;


    fn make_rule(prefix: &str) -> LifecycleRule {
        LifecycleRule::builder()
            .filename_prefix(prefix).unwrap()
            .delete_after_hide(chrono::Duration::days(3)).unwrap()
            .build().unwrap()
    }

    #[test]
    fn validate_good_lifecycle_rules() {
        let rules = vec![
            make_rule("Docs/Photos/"),
            make_rule("Legal/"),
            make_rule("Archive/"),
        ];

        let rules = validated_lifecycle_rules(rules).unwrap();
        assert_eq!(rules.len(), 3);
        assert_eq!(rules[0].file_name_prefix, "Archive/");
        assert_eq!(rules[1].file_name_prefix, "Docs/Photos/");
        assert_eq!(rules[2].file_name_prefix, "Legal/");
    }

    #[test]
    fn validate_single_rule() {
        let rules = vec![
            make_rule("Docs/Photos/"),
        ];

        let rules = validated_lifecycle_rules(rules).unwrap();
        assert_eq!(rules.len(), 1);
        assert_eq!(rules[0].file_name_prefix, "Docs/Photos/");
    }

    #[test]
    fn validate_one_lifecycle_rule_conflicts() {
        let rules = vec![
            make_rule("Docs/Photos/"),
            make_rule("Legal/"),
            make_rule("Legal/Taxes/"),
            make_rule("Archive/"),
        ];

        match validated_lifecycle_rules(rules).unwrap_err() {
            LifecycleRuleValidationError::ConflictingRules(conflicts) => {
                assert_eq!(conflicts.len(), 1);

                let conflicts = &conflicts["Legal/"];

                assert_eq!(conflicts.len(), 1);
                assert_eq!(conflicts[0].file_name_prefix, "Legal/Taxes/");
            },
            e => panic!("Unexpected error: {}", e),
        }
    }

    #[test]
    fn validate_many_lifecycle_rules_conflict() {
        let rules = vec![
            make_rule("Docs/Photos/"),
            make_rule("Docs/"),
            make_rule("Docs/Documents/"),
            make_rule("Archive/Temporary/"),
            make_rule("Legal/Taxes/"),
            make_rule("Legal/Other/"),
            make_rule("Docs/Photos/Vacations/"),
            make_rule("Archive/"),
        ];

        match validated_lifecycle_rules(rules).unwrap_err() {
            LifecycleRuleValidationError::ConflictingRules(c) => {
                assert_eq!(c.len(), 3);

                let conflicts = &c["Docs/"];

                assert_eq!(conflicts.len(), 3);
                assert_eq!(conflicts[0].file_name_prefix, "Docs/Documents/");
                assert_eq!(conflicts[1].file_name_prefix, "Docs/Photos/");
                assert_eq!(
                    conflicts[2].file_name_prefix,
                    "Docs/Photos/Vacations/"
                );

                // This is a duplicated record owing its existence to the way
                // we've happened to implement the loops. I don't want to
                // iterate the vectors yet again to eliminate it, and I think
                // I'm OK with the duplication.
                let conflicts = &c["Docs/Photos/"];

                assert_eq!(conflicts.len(), 1);
                assert_eq!(
                    conflicts[0].file_name_prefix,
                    "Docs/Photos/Vacations/"
                );

                let conflicts = &c["Archive/"];

                assert_eq!(conflicts.len(), 1);
                assert_eq!(conflicts[0].file_name_prefix, "Archive/Temporary/");
            },
            e => panic!("Unexpected error: {}", e),
        }
    }

    #[test]
    fn validate_many_lifecycle_rules_multiple_conflicts() {
        let rules = vec![
            make_rule("Docs/Photos/Vacations/"),
            make_rule("Docs/Photos/Buildings/"),
            make_rule("Docs/Photos/"),
            make_rule("Docs/"),
            make_rule("Docs/Documents/"),
        ];

        match validated_lifecycle_rules(rules).unwrap_err() {
            LifecycleRuleValidationError::ConflictingRules(conflicts) => {
                assert_eq!(conflicts.len(), 1);

                let conflicts = &conflicts["Docs/"];

                assert_eq!(conflicts.len(), 4);
                assert_eq!(conflicts[0].file_name_prefix, "Docs/Documents/");
                assert_eq!(conflicts[1].file_name_prefix, "Docs/Photos/");
                assert_eq!(
                    conflicts[2].file_name_prefix,
                    "Docs/Photos/Buildings/"
                );
                assert_eq!(
                    conflicts[3].file_name_prefix,
                    "Docs/Photos/Vacations/"
                );
            },
            e => panic!("Unexpected error: {}", e),
        }
    }

    #[test]
    fn validate_empty_lifecycle_rule_alone_is_good() {
        let rules = vec![
            make_rule(""),
        ];

        let rules = validated_lifecycle_rules(rules).unwrap();
        assert_eq!(rules.len(), 1);
        assert_eq!(rules[0].file_name_prefix, "");
    }

    #[test]
    fn validate_empty_lifecycle_rule_with_others_is_error() {
        let rules = vec![
            make_rule("Docs/Photos/"),
            make_rule(""),
            make_rule("Legal/"),
            make_rule("Legal/Taxes/"),
            make_rule("Archive/"),
        ];

        match validated_lifecycle_rules(rules).unwrap_err() {
            LifecycleRuleValidationError::ConflictingRules(conflicts) => {
                assert_eq!(conflicts.len(), 1);

                let conflicts = &conflicts[""];

                assert_eq!(conflicts.len(), 4);
                assert_eq!(conflicts[0].file_name_prefix, "Archive/");
                assert_eq!(conflicts[1].file_name_prefix, "Docs/Photos/");
                assert_eq!(conflicts[2].file_name_prefix, "Legal/");
                assert_eq!(conflicts[3].file_name_prefix, "Legal/Taxes/");
            },
            e => panic!("Unexpected error: {}", e),
        }
    }

    #[test]
    fn validate_quoted_string() {
        assert!(is_valid_quoted_string("\"\""));
        assert!(is_valid_quoted_string("\"a\""));
        assert!(is_valid_quoted_string("\"abcde\""));
        assert!(is_valid_quoted_string("\"ab\\\"cde\""));

        assert!(! is_valid_quoted_string("\"ab\"cd\""));
    }

    #[test]
    fn validate_info_key_val_filters_disallowed_chars() {
        validate_info_key_val("good-sep", &json!("asdf")).unwrap();
        validate_info_key_val("good#sep", &json!("asdf")).unwrap();
        validate_info_key_val("$goodsep", &json!("asdf")).unwrap();
        validate_info_key_val("good-sep%", &json!("asdf")).unwrap();

        validate_info_key_val("bad@sep", &json!("asdf")).unwrap_err();
        validate_info_key_val("bad(sep", &json!("asdf")).unwrap_err();
        validate_info_key_val("{badsep", &json!("asdf")).unwrap_err();
        validate_info_key_val("badsep]", &json!("asdf")).unwrap_err();
    }

    #[test]
    fn validate_content_disposition_fields() {
        validate_info_val("b2-content-disposition", &json!("inline")).unwrap();
        validate_info_val(
            "b2-content-disposition",
            &json!("attachment; filename=\"myfile.txt\"")
        ).unwrap();
        validate_info_val(
            "b2-content-disposition",
            &json!("attachment; something=value")
        ).unwrap();
        validate_info_val(
            "b2-content-disposition",
            &json!("attachment; filename=\"myfile.txt\"; something=value")
        ).unwrap();

        // RFC 6266 says that the semicolon without at least one field is
        // illegal. It wouldn't surprise me if many clients allow it, but we're
        // going to enforce the standard.
        validate_info_val("b2-content-disposition", &json!("inline;"))
            .unwrap_err();
        validate_info_val("b2-content-disposition", &json!("inline; f="))
            .unwrap_err();
    }

    #[test]
    fn validate_content_language() {
        validate_info_val("b2-content-language", &json!("en")).unwrap();
        validate_info_val("b2-content-language", &json!("lang-dialect"))
            .unwrap();

        validate_info_val("b2-content-language", &json!("bad-lang/text"))
            .unwrap_err();
        validate_info_val("b2-content-language", &json!("bad+lang"))
            .unwrap_err();
    }

    #[test]
    fn validate_expires() {
        validate_info_val("b2-expires", &json!("Thu, 01 Dec 1994 16:00:00 GMT"))
            .unwrap();

        validate_info_val("b2-expires", &json!("2021-1-1")).unwrap_err();
    }

    #[test]
    fn validate_cache_control() {
        validate_info_val("b2-cache-control", &json!("no-store")).unwrap();

        // TODO: Implement cache-extension validation to test:
        //validate_info_val("b2-cache-control", &json!("(not-valid-token)"))
        //    .unwrap_err();
    }
}