qcs_api_client_common/configuration/

secrets.rs

//! Models and utilities for managing QCS secret credentials.

use std::collections::HashMap;
use std::path::{Path, PathBuf};

use figment::Figment;
use figment::providers::{Format, Toml};
use serde::{Deserialize, Serialize};
use time::format_description::well_known::Rfc3339;
use time::{OffsetDateTime, PrimitiveDateTime};
use toml_edit::{DocumentMut, Item};

use crate::configuration::LoadError;

use super::error::{IoErrorWithPath, IoOperation, WriteError};
use super::tokens::ClientCredentials;
use super::{DEFAULT_PROFILE_NAME, expand_path_from_env_or_default};

pub use super::external_command::{ExternalCommandError, ExternallyManagedCredential};
pub use super::secret_string::{ClientSecret, SecretAccessToken, SecretRefreshToken};

/// Setting the `QCS_SECRETS_FILE_PATH` environment variable will change which file is used for loading secrets
pub const SECRETS_PATH_VAR: &str = "QCS_SECRETS_FILE_PATH";
/// `QCS_SECRETS_READ_ONLY` indicates whether to treat the `secrets.toml` file as read-only. Disabled by default.
/// * Access token updates will _not_ be persisted to the secrets file, regardless of file permissions, for any of the following values (case insensitive): "true", "yes", "1".  
/// * Access token updates will be persisted to the secrets file if it is writeable for any other value or if unset.
pub const SECRETS_READ_ONLY_VAR: &str = "QCS_SECRETS_READ_ONLY";
/// The default path that [`Secrets`] will be loaded from
pub const DEFAULT_SECRETS_PATH: &str = "~/.qcs/secrets.toml";

/// The structure of QCS secrets, typically serialized as a TOML file at [`DEFAULT_SECRETS_PATH`].
#[derive(Deserialize, Debug, PartialEq, Eq, Serialize)]
pub struct Secrets {
    /// All named [`Credential`]s defined in the secrets file.
    #[serde(default = "default_credentials")]
    pub credentials: HashMap<String, Credential>,
    /// The path to the secrets file this [`Secrets`] was loaded from,
    /// if it was loaded from a file. This is not stored in the secrets file itself.
    #[serde(skip)]
    pub file_path: Option<PathBuf>,
}

fn default_credentials() -> HashMap<String, Credential> {
    HashMap::from([(DEFAULT_PROFILE_NAME.to_string(), Credential::default())])
}

impl Default for Secrets {
    fn default() -> Self {
        Self {
            credentials: default_credentials(),
            file_path: None,
        }
    }
}

impl Secrets {
    /// Load [`Secrets`] from the path specified by the [`SECRETS_PATH_VAR`] environment variable if set,
    /// or else the default path at [`DEFAULT_SECRETS_PATH`].
    ///
    /// # Errors
    ///
    /// [`LoadError`] if the secrets file cannot be loaded.
    pub fn load() -> Result<Self, LoadError> {
        let path = expand_path_from_env_or_default(SECRETS_PATH_VAR, DEFAULT_SECRETS_PATH)?;
        #[cfg(feature = "tracing")]
        tracing::debug!("loading QCS secrets from {path:?}");
        Self::load_from_path(&path)
    }

    /// Load [`Secrets`] from the path specified by `path`.
    ///
    /// # Errors
    ///
    /// [`LoadError`] if the secrets file cannot be loaded.
    pub fn load_from_path(path: &PathBuf) -> Result<Self, LoadError> {
        let mut secrets: Self = Figment::from(Toml::file(path)).extract()?;
        secrets.file_path = Some(path.into());
        Ok(secrets)
    }

    /// Returns a bool indicating whether or not the QCS [`Secrets`] file is read-only.
    ///
    /// The file is considered read-only if the [`SECRETS_READ_ONLY_VAR`] environment variable is set,
    /// or if the file permissions indicate that it is read-only.
    ///
    /// # Errors
    ///
    /// [`WriteError`] if the file permissions cannot be checked.
    pub async fn is_read_only(
        secrets_path: impl AsRef<Path> + Send + Sync,
    ) -> Result<bool, WriteError> {
        // Check if the QCS_SECRETS_READ_ONLY environment variable is set
        let ro_env = std::env::var(SECRETS_READ_ONLY_VAR);
        let ro_env_lowercase = ro_env.as_deref().map(str::to_lowercase);
        if let Ok("true" | "yes" | "1") = ro_env_lowercase.as_deref() {
            return Ok(true);
        }

        // Check file permissions - a non-existent file is treated as writable if its
        // parent directory is writable
        for (i, ancestor) in secrets_path.as_ref().ancestors().enumerate() {
            match tokio::fs::metadata(ancestor).await {
                Ok(metadata) => return Ok(metadata.permissions().readonly()),
                Err(e) if e.kind() == std::io::ErrorKind::NotFound => continue,
                Err(error) if i == 0 => {
                    return Err(IoErrorWithPath {
                        error,
                        path: secrets_path.as_ref().to_path_buf(),
                        operation: IoOperation::GetMetadata,
                    }
                    .into());
                }
                Err(_) => return Ok(true), // Can't access ancestor = read-only
            }
        }
        Ok(true) // No existing ancestor found = read-only
    }

    /// Attempts to write a refresh and access token to the QCS [`Secrets`] file at
    /// the given path.
    ///
    /// The access token will only be updated if the access token currently stored in the file is
    /// older than the provided `updated_at` timestamp.
    ///
    /// # Errors
    ///
    /// - [`TokenError`] for possible errors.
    pub(crate) async fn write_tokens(
        secrets_path: impl AsRef<Path> + Send + Sync + std::fmt::Debug,
        credentials_name: &str,
        refresh_token: Option<&SecretRefreshToken>,
        access_token: &SecretAccessToken,
        updated_at: OffsetDateTime,
    ) -> Result<(), WriteError> {
        // Read the current contents of the secrets file
        let secrets_string = tokio::fs::read_to_string(&secrets_path)
            .await
            .map_err(|error| IoErrorWithPath {
                error,
                path: secrets_path.as_ref().to_path_buf(),
                operation: IoOperation::Read,
            })?;

        // Parse the TOML content into a mutable document
        let mut secrets_toml = secrets_string.parse::<DocumentMut>()?;

        // Navigate to the `[credentials.<credentials_name>.token_payload]` table
        let token_payload = Self::get_token_payload_table(&mut secrets_toml, credentials_name)?;

        let current_updated_at = token_payload
            .get("updated_at")
            .and_then(|v| v.as_str())
            .and_then(|s| PrimitiveDateTime::parse(s, &Rfc3339).ok())
            .map(PrimitiveDateTime::assume_utc);

        let did_update_access_token = if current_updated_at.is_none_or(|dt| dt < updated_at) {
            token_payload["access_token"] = access_token.secret().into();
            token_payload["updated_at"] = updated_at.format(&Rfc3339)?.into();
            true
        } else {
            false
        };

        let did_update_refresh_token = refresh_token.is_some_and(|new_refresh_token| {
            let current_refresh_token = token_payload.get("refresh_token").and_then(|v| v.as_str());
            let new_refresh_token = new_refresh_token.secret();

            let is_changed = current_refresh_token != Some(new_refresh_token);
            if is_changed {
                token_payload["refresh_token"] = new_refresh_token.into();
            }
            is_changed
        });

        if did_update_access_token || did_update_refresh_token {
            // Atomically overwrite the secrets file. The temporary buffer is
            // staged next to the destination so the rename stays atomic even when
            // the secrets file lives on a different mount point from the system
            // temporary directory (which previously caused `cross-device link` errors).
            super::fs::atomic_write(&secrets_path, secrets_toml.to_string().as_bytes()).await?;
        }

        Ok(())
    }

    /// Get the `[credentials.<credentials_name>.token_payload]` table from the TOML document
    fn get_token_payload_table<'a>(
        secrets_toml: &'a mut DocumentMut,
        credentials_name: &str,
    ) -> Result<&'a mut Item, WriteError> {
        secrets_toml
            .get_mut("credentials")
            .and_then(|credentials| {
                credentials
                    .get_mut(credentials_name)?
                    .get_mut("token_payload")
            })
            .ok_or_else(|| {
                WriteError::MissingTable(format!("credentials.{credentials_name}.token_payload"))
            })
    }
}

/// A QCS credential, containing or providing access to sensitive authentication secrets.
#[derive(Deserialize, Debug, PartialEq, Eq, Serialize)]
#[serde(rename_all = "snake_case")]
pub enum Credential {
    /// The [`TokenPayload`] for this credential.
    TokenPayload(TokenPayload),
    /// Defer to a subcommand to manage access tokens.
    ExternallyManaged(ExternallyManagedCredential),
    /// Exchange a client secret for access tokens.
    ClientCredentials(ClientCredentials),
}

impl Default for Credential {
    fn default() -> Self {
        Self::TokenPayload(TokenPayload::default())
    }
}

/// A QCS token payload, containing sensitive authentication secrets.
#[derive(Deserialize, Debug, Default, PartialEq, Eq, Serialize)]
pub struct TokenPayload {
    /// The refresh token for this credential.
    pub refresh_token: Option<SecretRefreshToken>,
    /// The access token for this credential.
    pub access_token: Option<SecretAccessToken>,
    /// The time at which this token was last updated.
    #[serde(
        default,
        deserialize_with = "time::serde::rfc3339::option::deserialize",
        serialize_with = "time::serde::rfc3339::option::serialize"
    )]
    pub updated_at: Option<OffsetDateTime>,

    // The below fields are retained for (de)serialization for compatibility with other
    // libraries that use token payloads, but are not relevant here.
    scope: Option<String>,
    expires_in: Option<u32>,
    id_token: Option<String>,
    token_type: Option<String>,
}

#[cfg(test)]
mod describe_load {
    #![allow(clippy::result_large_err, reason = "happens in figment tests")]

    #[cfg(unix)]
    use std::os::unix::fs::PermissionsExt;
    use std::path::PathBuf;

    use time::{OffsetDateTime, macros::datetime};

    use crate::configuration::secrets::{SECRETS_READ_ONLY_VAR, SecretAccessToken};

    use super::{Credential, SECRETS_PATH_VAR, Secrets};

    #[test]
    fn returns_err_if_invalid_path_env() {
        figment::Jail::expect_with(|jail| {
            jail.set_env(SECRETS_PATH_VAR, "/blah/doesnt_exist.toml");
            Secrets::load().expect_err("Should return error when a file cannot be found.");
            Ok(())
        });
    }

    #[test]
    fn loads_from_env_var_path() {
        figment::Jail::expect_with(|jail| {
            let mut secrets = Secrets {
                file_path: Some(PathBuf::from("env_secrets.toml")),
                ..Secrets::default()
            };
            secrets
                .credentials
                .insert("test".to_string(), Credential::default());
            let secrets_string =
                toml::to_string(&secrets).expect("Should be able to serialize secrets");

            _ = jail.create_file("env_secrets.toml", &secrets_string)?;
            jail.set_env(SECRETS_PATH_VAR, "env_secrets.toml");

            assert_eq!(secrets, Secrets::load().unwrap());

            Ok(())
        });
    }

    const fn max_rfc3339() -> OffsetDateTime {
        // PrimitiveDateTime::MAX can be larger than what can fit in a RFC3339 timestamp if the `time` crate's `large-dates` feature is enabled.
        // Instead of asserting that the `time` crate's `large-dates` feature is disabled, we use a hardcoded max value here.
        datetime!(9999-12-31 23:59:59.999_999_999).assume_utc()
    }

    #[test]
    fn test_write_access_token() {
        figment::Jail::expect_with(|jail| {
            let secrets_file_contents = r#"
[credentials]
[credentials.test]
[credentials.test.token_payload]
access_token = "old_access_token"
expires_in = 3600
id_token = "id_token"
refresh_token = "refresh_token"
scope = "offline_access openid profile email"
token_type = "Bearer"
"#;

            jail.create_file("secrets.toml", secrets_file_contents)
                .expect("should create test secrets.toml");
            let mut original_permissions = std::fs::metadata("secrets.toml")
                .expect("Should be able to get file metadata")
                .permissions();
            #[cfg(unix)]
            {
                assert_ne!(
                    0o666,
                    original_permissions.mode(),
                    "Initial file mode should not be 666"
                );
                original_permissions.set_mode(0o100_666);
                std::fs::set_permissions("secrets.toml", original_permissions.clone())
                    .expect("Should be able to set file permissions");
            }
            jail.set_env("QCS_SECRETS_FILE_PATH", "secrets.toml");
            jail.set_env("QCS_PROFILE_NAME", "test");

            let rt = tokio::runtime::Runtime::new().unwrap();
            rt.block_on(async {
                // Create array of token updates with different timestamps
                let token_updates = [
                    ("new_access_token", max_rfc3339()),
                    ("stale_access_token", OffsetDateTime::now_utc()),
                ];

                for (access_token, updated_at) in token_updates {
                    Secrets::write_tokens(
                        "secrets.toml",
                        "test",
                        None,
                        &SecretAccessToken::from(access_token),
                        updated_at,
                    )
                    .await
                    .expect("Should be able to write access token");
                }

                // Verify the final state
                let mut secrets = Secrets::load_from_path(&"secrets.toml".into()).unwrap();
                let Credential::TokenPayload(payload) = secrets.credentials.remove("test").unwrap()
                else {
                    panic!("expected a token payload credential");
                };

                assert_eq!(
                    payload.access_token.unwrap(),
                    SecretAccessToken::from("new_access_token")
                );
                assert_eq!(payload.updated_at.unwrap(), max_rfc3339());
                let new_permissions = std::fs::metadata("secrets.toml")
                    .expect("Should be able to get file metadata")
                    .permissions();
                assert_eq!(
                    original_permissions, new_permissions,
                    "Final file permissions should not be changed"
                );
            });

            Ok(())
        });
    }

    /// Set file permissions on Unix systems for jail-created files and directories
    fn set_mode(path: &PathBuf, mode: u32) {
        #[cfg(unix)]
        {
            use std::os::unix::fs::PermissionsExt;
            let perms = std::fs::Permissions::from_mode(mode);
            std::fs::set_permissions(path, perms).expect("Should be able to set permissions");
        }
    }

    #[test]
    fn test_is_read_only_missing_file_checks_parent_dir() {
        figment::Jail::expect_with(|jail| {
            jail.set_env(SECRETS_READ_ONLY_VAR, "false");

            let writable_dir = jail.create_dir("writable_dir")?;
            let readonly_dir = jail.create_dir("readonly_dir")?;

            set_mode(&writable_dir, 0o777);
            set_mode(&readonly_dir, 0o555);

            let rt = tokio::runtime::Runtime::new().unwrap();
            rt.block_on(async {
                // Missing file in writable directory should be writable (not read-only)
                let writable_path = writable_dir.join("missing_secrets.toml");
                let is_ro = Secrets::is_read_only(&writable_path)
                    .await
                    .expect("Should not error");
                assert!(
                    !is_ro,
                    "Missing file in writable directory should not be read-only: {}",
                    writable_path.display()
                );

                // Missing file in read-only directory should be read-only
                let readonly_path = readonly_dir.join("missing_secrets.toml");
                let is_ro = Secrets::is_read_only(&readonly_path)
                    .await
                    .expect("Should not error");
                assert!(
                    is_ro,
                    "Missing file in read-only directory should be read-only: {}",
                    readonly_path.display()
                );
            });

            Ok(())
        });
    }

    #[test]
    fn test_is_read_only_existing_file() {
        figment::Jail::expect_with(|jail| {
            jail.set_env(SECRETS_READ_ONLY_VAR, "false");

            jail.create_file("writable_secrets.toml", "")?;
            jail.create_file("readonly_secrets.toml", "")?;

            let writable_path = jail.directory().join("writable_secrets.toml");
            let readonly_path = jail.directory().join("readonly_secrets.toml");

            set_mode(&writable_path, 0o666);
            set_mode(&readonly_path, 0o444);

            let rt = tokio::runtime::Runtime::new().unwrap();
            rt.block_on(async {
                // Existing writable file should not be read-only
                let is_ro = Secrets::is_read_only(&writable_path)
                    .await
                    .expect("Should not error");
                assert!(
                    !is_ro,
                    "Writable file should not be read-only: {}",
                    writable_path.display()
                );

                // Existing read-only file should be read-only
                let is_ro = Secrets::is_read_only(&readonly_path)
                    .await
                    .expect("Should not error");
                assert!(
                    is_ro,
                    "Read-only file should be read-only: {}",
                    readonly_path.display()
                );
            });

            Ok(())
        });
    }
}