#
cargo_credential/
lib.rs

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    //! Helper library for writing Cargo credential providers.
    //!
    //! A credential process should have a `struct` that implements the `Credential` trait.
    //! The `main` function should be called with an instance of that struct, such as:
    //!
    //! ```rust,ignore
    //! fn main() {
    //!     cargo_credential::main(MyCredential);
    //! }
    //! ```
    //!
    //! While in the `perform` function, stdin and stdout will be re-attached to the
    //! active console. This allows credential providers to be interactive if necessary.
    //!
    //! > This crate is maintained by the Cargo team for use by the wider
    //! > ecosystem. This crate follows semver compatibility for its APIs.
    //!
    //! ## Error handling
    //! ### [`Error::UrlNotSupported`]
    //! A credential provider may only support some registry URLs. If this is the case
    //! and an unsupported index URL is passed to the provider, it should respond with
    //! [`Error::UrlNotSupported`]. Other credential providers may be attempted by Cargo.
    //!
    //! ### [`Error::NotFound`]
    //! When attempting an [`Action::Get`] or [`Action::Logout`], if a credential can not
    //! be found, the provider should respond with [`Error::NotFound`]. Other credential
    //! providers may be attempted by Cargo.
    //!
    //! ### [`Error::OperationNotSupported`]
    //! A credential provider might not support all operations. For example if the provider
    //! only supports [`Action::Get`], [`Error::OperationNotSupported`] should be returned
    //! for all other requests.
    //!
    //! ### [`Error::Other`]
    //! All other errors go here. The error will be shown to the user in Cargo, including
    //! the full error chain using [`std::error::Error::source`].
    //!
    //! ## Example
    //! ```rust,ignore
    #![doc = include_str!("../examples/file-provider.rs")]
    //! ```

    #![allow(clippy::print_stderr)]
    #![allow(clippy::print_stdout)]

    use serde::{Deserialize, Serialize};
    use std::{fmt::Display, io};
    use time::OffsetDateTime;

    mod error;
    mod secret;
    mod stdio;

    pub use error::Error;
    pub use secret::Secret;
    use stdio::stdin_stdout_to_console;

    /// Message sent by the credential helper on startup
    #[derive(Serialize, Deserialize, Clone, Debug, PartialEq, Eq)]
    pub struct CredentialHello {
        // Protocol versions supported by the credential process.
        pub v: Vec<u32>,
    }

    /// Credential provider that doesn't support any registries.
    pub struct UnsupportedCredential;
    impl Credential for UnsupportedCredential {
        fn perform(
            &self,
            _registry: &RegistryInfo<'_>,
            _action: &Action<'_>,
            _args: &[&str],
        ) -> Result<CredentialResponse, Error> {
            Err(Error::UrlNotSupported)
        }
    }

    /// Message sent by Cargo to the credential helper after the hello
    #[derive(Serialize, Deserialize, Clone, Debug, PartialEq, Eq)]
    #[serde(rename_all = "kebab-case")]
    pub struct CredentialRequest<'a> {
        // Cargo will respond with the highest common protocol supported by both.
        pub v: u32,
        #[serde(borrow)]
        pub registry: RegistryInfo<'a>,
        #[serde(borrow, flatten)]
        pub action: Action<'a>,
        /// Additional command-line arguments passed to the credential provider.
        #[serde(skip_serializing_if = "Vec::is_empty", default)]
        pub args: Vec<&'a str>,
    }

    #[derive(Serialize, Deserialize, Clone, Debug, PartialEq, Eq)]
    #[serde(rename_all = "kebab-case")]
    pub struct RegistryInfo<'a> {
        /// Registry index url
        pub index_url: &'a str,
        /// Name of the registry in configuration. May not be available.
        /// The crates.io registry will be `crates-io` (`CRATES_IO_REGISTRY`).
        #[serde(skip_serializing_if = "Option::is_none")]
        pub name: Option<&'a str>,
        /// Headers from attempting to access a registry that resulted in a HTTP 401.
        #[serde(skip_serializing_if = "Vec::is_empty", default)]
        pub headers: Vec<String>,
    }

    #[derive(Serialize, Deserialize, Clone, Debug, PartialEq, Eq)]
    #[non_exhaustive]
    #[serde(tag = "kind", rename_all = "kebab-case")]
    pub enum Action<'a> {
        #[serde(borrow)]
        Get(Operation<'a>),
        Login(LoginOptions<'a>),
        Logout,
        #[serde(other)]
        Unknown,
    }

    impl<'a> Display for Action<'a> {
        fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
            match self {
                Action::Get(_) => f.write_str("get"),
                Action::Login(_) => f.write_str("login"),
                Action::Logout => f.write_str("logout"),
                Action::Unknown => f.write_str("<unknown>"),
            }
        }
    }

    #[derive(Serialize, Deserialize, Clone, Debug, PartialEq, Eq)]
    #[serde(rename_all = "kebab-case")]
    pub struct LoginOptions<'a> {
        /// Token passed on the command line via --token or from stdin
        #[serde(skip_serializing_if = "Option::is_none")]
        pub token: Option<Secret<&'a str>>,
        /// Optional URL that the user can visit to log in to the registry
        #[serde(skip_serializing_if = "Option::is_none")]
        pub login_url: Option<&'a str>,
    }

    /// A record of what kind of operation is happening that we should generate a token for.
    #[derive(Serialize, Deserialize, Clone, Debug, PartialEq, Eq)]
    #[non_exhaustive]
    #[serde(tag = "operation", rename_all = "kebab-case")]
    pub enum Operation<'a> {
        /// The user is attempting to fetch a crate.
        Read,
        /// The user is attempting to publish a crate.
        Publish {
            /// The name of the crate
            name: &'a str,
            /// The version of the crate
            vers: &'a str,
            /// The checksum of the crate file being uploaded
            cksum: &'a str,
        },
        /// The user is attempting to yank a crate.
        Yank {
            /// The name of the crate
            name: &'a str,
            /// The version of the crate
            vers: &'a str,
        },
        /// The user is attempting to unyank a crate.
        Unyank {
            /// The name of the crate
            name: &'a str,
            /// The version of the crate
            vers: &'a str,
        },
        /// The user is attempting to modify the owners of a crate.
        Owners {
            /// The name of the crate
            name: &'a str,
        },
        #[serde(other)]
        Unknown,
    }

    /// Message sent by the credential helper
    #[derive(Serialize, Deserialize, Clone, Debug, PartialEq, Eq)]
    #[serde(tag = "kind", rename_all = "kebab-case")]
    #[non_exhaustive]
    pub enum CredentialResponse {
        Get {
            token: Secret<String>,
            #[serde(flatten)]
            cache: CacheControl,
            operation_independent: bool,
        },
        Login,
        Logout,
        #[serde(other)]
        Unknown,
    }

    #[derive(Serialize, Deserialize, Clone, Debug, PartialEq, Eq)]
    #[serde(tag = "cache", rename_all = "kebab-case")]
    #[non_exhaustive]
    pub enum CacheControl {
        /// Do not cache this result.
        Never,
        /// Cache this result and use it for subsequent requests in the current Cargo invocation until the specified time.
        Expires {
            #[serde(with = "time::serde::timestamp")]
            expiration: OffsetDateTime,
        },
        /// Cache this result and use it for all subsequent requests in the current Cargo invocation.
        Session,
        #[serde(other)]
        Unknown,
    }

    /// Credential process JSON protocol version.
    ///
    /// If the protocol needs to make
    /// a breaking change, a new protocol version should be defined (`PROTOCOL_VERSION_2`).
    /// This library should offer support for both protocols if possible, by signaling
    /// in the `CredentialHello` message. Cargo will then choose which protocol to use,
    /// or it will error if there are no common protocol versions available.
    pub const PROTOCOL_VERSION_1: u32 = 1;
    pub trait Credential {
        /// Retrieves a token for the given registry.
        fn perform(
            &self,
            registry: &RegistryInfo<'_>,
            action: &Action<'_>,
            args: &[&str],
        ) -> Result<CredentialResponse, Error>;
    }

    /// Runs the credential interaction
    pub fn main(credential: impl Credential) {
        let result = doit(credential).map_err(|e| Error::Other(e));
        if result.is_err() {
            serde_json::to_writer(std::io::stdout(), &result)
                .expect("failed to serialize credential provider error");
            println!();
        }
    }

    fn doit(
        credential: impl Credential,
    ) -> Result<(), Box<dyn std::error::Error + Send + Sync + 'static>> {
        let hello = CredentialHello {
            v: vec![PROTOCOL_VERSION_1],
        };
        serde_json::to_writer(std::io::stdout(), &hello)?;
        println!();

        loop {
            let mut buffer = String::new();
            let len = std::io::stdin().read_line(&mut buffer)?;
            if len == 0 {
                return Ok(());
            }
            let request = deserialize_request(&buffer)?;
            let response = stdin_stdout_to_console(|| {
                credential.perform(&request.registry, &request.action, &request.args)
            })?;

            serde_json::to_writer(std::io::stdout(), &response)?;
            println!();
        }
    }

    /// Deserialize a request from Cargo.
    fn deserialize_request(
        value: &str,
    ) -> Result<CredentialRequest<'_>, Box<dyn std::error::Error + Send + Sync>> {
        let request: CredentialRequest<'_> = serde_json::from_str(&value)?;
        if request.v != PROTOCOL_VERSION_1 {
            return Err(format!("unsupported protocol version {}", request.v).into());
        }
        Ok(request)
    }

    /// Read a line of text from stdin.
    pub fn read_line() -> Result<String, io::Error> {
        let mut buf = String::new();
        io::stdin().read_line(&mut buf)?;
        Ok(buf.trim().to_string())
    }

    /// Prompt the user for a token.
    pub fn read_token(
        login_options: &LoginOptions<'_>,
        registry: &RegistryInfo<'_>,
    ) -> Result<Secret<String>, Error> {
        if let Some(token) = &login_options.token {
            return Ok(token.to_owned());
        }

        if let Some(url) = login_options.login_url {
            eprintln!("please paste the token found on {url} below");
        } else if let Some(name) = registry.name {
            eprintln!("please paste the token for {name} below");
        } else {
            eprintln!("please paste the token for {} below", registry.index_url);
        }

        Ok(Secret::from(read_line().map_err(Box::new)?))
    }

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

        #[test]
        fn unsupported_version() {
            // This shouldn't ever happen in practice, since the credential provider signals to Cargo which
            // protocol versions it supports, and Cargo should only attempt to use one of those.
            let msg = r#"{"v":999, "registry": {"index-url":""}, "args":[], "kind": "unexpected"}"#;
            assert_eq!(
                "unsupported protocol version 999",
                deserialize_request(msg).unwrap_err().to_string()
            );
        }

        #[test]
        fn cache_control() {
            let cc = CacheControl::Expires {
                expiration: OffsetDateTime::from_unix_timestamp(1693928537).unwrap(),
            };
            let json = serde_json::to_string(&cc).unwrap();
            assert_eq!(json, r#"{"cache":"expires","expiration":1693928537}"#);

            let cc = CacheControl::Session;
            let json = serde_json::to_string(&cc).unwrap();
            assert_eq!(json, r#"{"cache":"session"}"#);

            let cc: CacheControl = serde_json::from_str(r#"{"cache":"unknown-kind"}"#).unwrap();
            assert_eq!(cc, CacheControl::Unknown);

            assert_eq!(
                "missing field `expiration`",
                serde_json::from_str::<CacheControl>(r#"{"cache":"expires"}"#)
                    .unwrap_err()
                    .to_string()
            );
        }

        #[test]
        fn credential_response() {
            let cr = CredentialResponse::Get {
                cache: CacheControl::Never,
                operation_independent: true,
                token: Secret::from("value".to_string()),
            };
            let json = serde_json::to_string(&cr).unwrap();
            assert_eq!(
                json,
                r#"{"kind":"get","token":"value","cache":"never","operation_independent":true}"#
            );

            let cr = CredentialResponse::Login;
            let json = serde_json::to_string(&cr).unwrap();
            assert_eq!(json, r#"{"kind":"login"}"#);

            let cr: CredentialResponse =
                serde_json::from_str(r#"{"kind":"unknown-kind","extra-data":true}"#).unwrap();
            assert_eq!(cr, CredentialResponse::Unknown);

            let cr: CredentialResponse =
                serde_json::from_str(r#"{"kind":"login","extra-data":true}"#).unwrap();
            assert_eq!(cr, CredentialResponse::Login);

            let cr: CredentialResponse = serde_json::from_str(r#"{"kind":"get","token":"value","cache":"never","operation_independent":true,"extra-field-ignored":123}"#).unwrap();
            assert_eq!(
                cr,
                CredentialResponse::Get {
                    cache: CacheControl::Never,
                    operation_independent: true,
                    token: Secret::from("value".to_string())
                }
            );
        }

        #[test]
        fn credential_request() {
            let get_oweners = CredentialRequest {
                v: PROTOCOL_VERSION_1,
                args: vec![],
                registry: RegistryInfo {
                    index_url: "url",
                    name: None,
                    headers: vec![],
                },
                action: Action::Get(Operation::Owners { name: "pkg" }),
            };

            let json = serde_json::to_string(&get_oweners).unwrap();
            assert_eq!(
                json,
                r#"{"v":1,"registry":{"index-url":"url"},"kind":"get","operation":"owners","name":"pkg"}"#
            );

            let cr: CredentialRequest<'_> =
                serde_json::from_str(r#"{"extra-1":true,"v":1,"registry":{"index-url":"url","extra-2":true},"kind":"get","operation":"owners","name":"pkg","args":[]}"#).unwrap();
            assert_eq!(cr, get_oweners);
        }

        #[test]
        fn credential_request_logout() {
            let unknown = CredentialRequest {
                v: PROTOCOL_VERSION_1,
                args: vec![],
                registry: RegistryInfo {
                    index_url: "url",
                    name: None,
                    headers: vec![],
                },
                action: Action::Logout,
            };

            let cr: CredentialRequest<'_> = serde_json::from_str(
                r#"{"v":1,"registry":{"index-url":"url"},"kind":"logout","extra-1":true,"args":[]}"#,
            )
            .unwrap();
            assert_eq!(cr, unknown);
        }

        #[test]
        fn credential_request_unknown() {
            let unknown = CredentialRequest {
                v: PROTOCOL_VERSION_1,
                args: vec![],
                registry: RegistryInfo {
                    index_url: "",
                    name: None,
                    headers: vec![],
                },
                action: Action::Unknown,
            };

            let cr: CredentialRequest<'_> = serde_json::from_str(
                r#"{"v":1,"registry":{"index-url":""},"kind":"unexpected-1","extra-1":true,"args":[]}"#,
            )
            .unwrap();
            assert_eq!(cr, unknown);
        }
    }