//! TLS configuration
//!
//! By default, a `Client` will make use of system-native transport layer
//! security to connect to HTTPS destinations. This means schannel on Windows,
//! Security-Framework on macOS, and OpenSSL on Linux.
//!
//! - Additional X509 certificates can be configured on a `ClientBuilder` with the
//!   [`Certificate`](Certificate) type.
//! - Client certificates can be add to a `ClientBuilder` with the
//!   [`Identity`][Identity] type.
//! - Various parts of TLS can also be configured or even disabled on the
//!   `ClientBuilder`.

#[cfg(feature = "__rustls")]
use rustls::{
    client::HandshakeSignatureValid, client::ServerCertVerified, client::ServerCertVerifier,
    internal::msgs::handshake::DigitallySignedStruct, Error as TLSError, ServerName,
};
use std::fmt;

/// Represents a server X509 certificate.
#[derive(Clone)]
pub struct Certificate {
    #[cfg(feature = "native-tls-crate")]
    native: native_tls_crate::Certificate,
    #[cfg(feature = "__rustls")]
    original: Cert,
}

#[cfg(feature = "__rustls")]
#[derive(Clone)]
enum Cert {
    Der(Vec<u8>),
    Pem(Vec<u8>),
}

/// Represents a private key and X509 cert as a client certificate.
#[derive(Clone)]
pub struct Identity {
    #[cfg_attr(not(any(feature = "native-tls", feature = "__rustls")), allow(unused))]
    inner: ClientCert,
}

#[derive(Clone)]
enum ClientCert {
    #[cfg(feature = "native-tls")]
    Pkcs12(native_tls_crate::Identity),
    #[cfg(feature = "native-tls")]
    Pkcs8(native_tls_crate::Identity),
    #[cfg(feature = "__rustls")]
    Pem {
        key: rustls::PrivateKey,
        certs: Vec<rustls::Certificate>,
    },
}

impl Certificate {
    /// Create a `Certificate` from a binary DER encoded certificate
    ///
    /// # Examples
    ///
    /// ```
    /// # use std::fs::File;
    /// # use std::io::Read;
    /// # fn cert() -> Result<(), Box<std::error::Error>> {
    /// let mut buf = Vec::new();
    /// File::open("my_cert.der")?
    ///     .read_to_end(&mut buf)?;
    /// let cert = reqwest::Certificate::from_der(&buf)?;
    /// # drop(cert);
    /// # Ok(())
    /// # }
    /// ```
    pub fn from_der(der: &[u8]) -> crate::Result<Certificate> {
        Ok(Certificate {
            #[cfg(feature = "native-tls-crate")]
            native: native_tls_crate::Certificate::from_der(der).map_err(crate::error::builder)?,
            #[cfg(feature = "__rustls")]
            original: Cert::Der(der.to_owned()),
        })
    }

    /// Create a `Certificate` from a PEM encoded certificate
    ///
    /// # Examples
    ///
    /// ```
    /// # use std::fs::File;
    /// # use std::io::Read;
    /// # fn cert() -> Result<(), Box<std::error::Error>> {
    /// let mut buf = Vec::new();
    /// File::open("my_cert.pem")?
    ///     .read_to_end(&mut buf)?;
    /// let cert = reqwest::Certificate::from_pem(&buf)?;
    /// # drop(cert);
    /// # Ok(())
    /// # }
    /// ```
    pub fn from_pem(pem: &[u8]) -> crate::Result<Certificate> {
        Ok(Certificate {
            #[cfg(feature = "native-tls-crate")]
            native: native_tls_crate::Certificate::from_pem(pem).map_err(crate::error::builder)?,
            #[cfg(feature = "__rustls")]
            original: Cert::Pem(pem.to_owned()),
        })
    }

    #[cfg(feature = "native-tls-crate")]
    pub(crate) fn add_to_native_tls(self, tls: &mut native_tls_crate::TlsConnectorBuilder) {
        tls.add_root_certificate(self.native);
    }

    #[cfg(feature = "__rustls")]
    pub(crate) fn add_to_rustls(
        self,
        root_cert_store: &mut rustls::RootCertStore,
    ) -> crate::Result<()> {
        use std::io::Cursor;

        match self.original {
            Cert::Der(buf) => root_cert_store
                .add(&rustls::Certificate(buf))
                .map_err(crate::error::builder)?,
            Cert::Pem(buf) => {
                let mut pem = Cursor::new(buf);
                let certs = rustls_pemfile::certs(&mut pem).map_err(|_| {
                    crate::error::builder(TLSError::General(String::from(
                        "No valid certificate was found",
                    )))
                })?;
                for c in certs {
                    root_cert_store
                        .add(&rustls::Certificate(c))
                        .map_err(crate::error::builder)?;
                }
            }
        }
        Ok(())
    }
}

impl Identity {
    /// Parses a DER-formatted PKCS #12 archive, using the specified password to decrypt the key.
    ///
    /// The archive should contain a leaf certificate and its private key, as well any intermediate
    /// certificates that allow clients to build a chain to a trusted root.
    /// The chain certificates should be in order from the leaf certificate towards the root.
    ///
    /// PKCS #12 archives typically have the file extension `.p12` or `.pfx`, and can be created
    /// with the OpenSSL `pkcs12` tool:
    ///
    /// ```bash
    /// openssl pkcs12 -export -out identity.pfx -inkey key.pem -in cert.pem -certfile chain_certs.pem
    /// ```
    ///
    /// # Examples
    ///
    /// ```
    /// # use std::fs::File;
    /// # use std::io::Read;
    /// # fn pkcs12() -> Result<(), Box<std::error::Error>> {
    /// let mut buf = Vec::new();
    /// File::open("my-ident.pfx")?
    ///     .read_to_end(&mut buf)?;
    /// let pkcs12 = reqwest::Identity::from_pkcs12_der(&buf, "my-privkey-password")?;
    /// # drop(pkcs12);
    /// # Ok(())
    /// # }
    /// ```
    ///
    /// # Optional
    ///
    /// This requires the `native-tls` Cargo feature enabled.
    #[cfg(feature = "native-tls")]
    pub fn from_pkcs12_der(der: &[u8], password: &str) -> crate::Result<Identity> {
        Ok(Identity {
            inner: ClientCert::Pkcs12(
                native_tls_crate::Identity::from_pkcs12(der, password)
                    .map_err(crate::error::builder)?,
            ),
        })
    }

    /// Parses a chain of PEM encoded X509 certificates, with the leaf certificate first.
    /// `key` is a PEM encoded PKCS #8 formatted private key for the leaf certificate.
    ///
    /// The certificate chain should contain any intermediate cerficates that should be sent to
    /// clients to allow them to build a chain to a trusted root.
    ///
    /// A certificate chain here means a series of PEM encoded certificates concatenated together.
    ///
    /// # Examples
    ///
    /// ```
    /// # use std::fs;
    /// # fn pkcs8() -> Result<(), Box<std::error::Error>> {
    /// let cert = fs::read("client.pem")?;
    /// let key = fs::read("key.pem")?;
    /// let pkcs8 = reqwest::Identity::from_pkcs8_pem(&cert, &key)?;
    /// # drop(pkcs8);
    /// # Ok(())
    /// # }
    /// ```
    ///
    /// # Optional
    ///
    /// This requires the `native-tls` Cargo feature enabled.
    #[cfg(feature = "native-tls")]
    pub fn from_pkcs8_pem(pem: &[u8], key: &[u8]) -> crate::Result<Identity> {
        Ok(Identity {
            inner: ClientCert::Pkcs8(
                native_tls_crate::Identity::from_pkcs8(pem, key).map_err(crate::error::builder)?,
            ),
        })
    }

    /// Parses PEM encoded private key and certificate.
    ///
    /// The input should contain a PEM encoded private key
    /// and at least one PEM encoded certificate.
    ///
    /// Note: The private key must be in RSA, SEC1 Elliptic Curve or PKCS#8 format.
    ///
    /// # Examples
    ///
    /// ```
    /// # use std::fs::File;
    /// # use std::io::Read;
    /// # fn pem() -> Result<(), Box<std::error::Error>> {
    /// let mut buf = Vec::new();
    /// File::open("my-ident.pem")?
    ///     .read_to_end(&mut buf)?;
    /// let id = reqwest::Identity::from_pem(&buf)?;
    /// # drop(id);
    /// # Ok(())
    /// # }
    /// ```
    ///
    /// # Optional
    ///
    /// This requires the `rustls-tls(-...)` Cargo feature enabled.
    #[cfg(feature = "__rustls")]
    pub fn from_pem(buf: &[u8]) -> crate::Result<Identity> {
        use std::io::Cursor;

        let (key, certs) = {
            let mut pem = Cursor::new(buf);
            let mut sk = Vec::<rustls::PrivateKey>::new();
            let mut certs = Vec::<rustls::Certificate>::new();

            for item in std::iter::from_fn(|| rustls_pemfile::read_one(&mut pem).transpose()) {
                match item.map_err(|_| {
                    crate::error::builder(TLSError::General(String::from(
                        "Invalid identity PEM file",
                    )))
                })? {
                    rustls_pemfile::Item::X509Certificate(cert) => {
                        certs.push(rustls::Certificate(cert))
                    }
                    rustls_pemfile::Item::PKCS8Key(key) => sk.push(rustls::PrivateKey(key)),
                    rustls_pemfile::Item::RSAKey(key) => sk.push(rustls::PrivateKey(key)),
                    rustls_pemfile::Item::ECKey(key) => sk.push(rustls::PrivateKey(key)),
                    _ => {
                        return Err(crate::error::builder(TLSError::General(String::from(
                            "No valid certificate was found",
                        ))))
                    }
                }
            }

            if let (Some(sk), false) = (sk.pop(), certs.is_empty()) {
                (sk, certs)
            } else {
                return Err(crate::error::builder(TLSError::General(String::from(
                    "private key or certificate not found",
                ))));
            }
        };

        Ok(Identity {
            inner: ClientCert::Pem { key, certs },
        })
    }

    #[cfg(feature = "native-tls")]
    pub(crate) fn add_to_native_tls(
        self,
        tls: &mut native_tls_crate::TlsConnectorBuilder,
    ) -> crate::Result<()> {
        match self.inner {
            ClientCert::Pkcs12(id) | ClientCert::Pkcs8(id) => {
                tls.identity(id);
                Ok(())
            }
            #[cfg(feature = "__rustls")]
            ClientCert::Pem { .. } => Err(crate::error::builder("incompatible TLS identity type")),
        }
    }

    #[cfg(feature = "__rustls")]
    pub(crate) fn add_to_rustls(
        self,
        config_builder: rustls::ConfigBuilder<
            rustls::ClientConfig,
            rustls::client::WantsTransparencyPolicyOrClientCert,
        >,
    ) -> crate::Result<rustls::ClientConfig> {
        match self.inner {
            ClientCert::Pem { key, certs } => config_builder
                .with_single_cert(certs, key)
                .map_err(crate::error::builder),
            #[cfg(feature = "native-tls")]
            ClientCert::Pkcs12(..) | ClientCert::Pkcs8(..) => {
                Err(crate::error::builder("incompatible TLS identity type"))
            }
        }
    }
}

impl fmt::Debug for Certificate {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        f.debug_struct("Certificate").finish()
    }
}

impl fmt::Debug for Identity {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        f.debug_struct("Identity").finish()
    }
}

/// A TLS protocol version.
#[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord)]
pub struct Version(InnerVersion);

#[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord)]
#[non_exhaustive]
enum InnerVersion {
    Tls1_0,
    Tls1_1,
    Tls1_2,
    Tls1_3,
}

// These could perhaps be From/TryFrom implementations, but those would be
// part of the public API so let's be careful
impl Version {
    /// Version 1.0 of the TLS protocol.
    pub const TLS_1_0: Version = Version(InnerVersion::Tls1_0);
    /// Version 1.1 of the TLS protocol.
    pub const TLS_1_1: Version = Version(InnerVersion::Tls1_1);
    /// Version 1.2 of the TLS protocol.
    pub const TLS_1_2: Version = Version(InnerVersion::Tls1_2);
    /// Version 1.3 of the TLS protocol.
    pub const TLS_1_3: Version = Version(InnerVersion::Tls1_3);

    #[cfg(feature = "default-tls")]
    pub(crate) fn to_native_tls(self) -> Option<native_tls_crate::Protocol> {
        match self.0 {
            InnerVersion::Tls1_0 => Some(native_tls_crate::Protocol::Tlsv10),
            InnerVersion::Tls1_1 => Some(native_tls_crate::Protocol::Tlsv11),
            InnerVersion::Tls1_2 => Some(native_tls_crate::Protocol::Tlsv12),
            InnerVersion::Tls1_3 => None,
        }
    }

    #[cfg(feature = "__rustls")]
    pub(crate) fn from_rustls(version: rustls::ProtocolVersion) -> Option<Self> {
        match version {
            rustls::ProtocolVersion::SSLv2 => None,
            rustls::ProtocolVersion::SSLv3 => None,
            rustls::ProtocolVersion::TLSv1_0 => Some(Self(InnerVersion::Tls1_0)),
            rustls::ProtocolVersion::TLSv1_1 => Some(Self(InnerVersion::Tls1_1)),
            rustls::ProtocolVersion::TLSv1_2 => Some(Self(InnerVersion::Tls1_2)),
            rustls::ProtocolVersion::TLSv1_3 => Some(Self(InnerVersion::Tls1_3)),
            _ => None,
        }
    }
}

pub(crate) enum TlsBackend {
    #[cfg(feature = "default-tls")]
    Default,
    #[cfg(feature = "native-tls")]
    BuiltNativeTls(native_tls_crate::TlsConnector),
    #[cfg(feature = "__rustls")]
    Rustls,
    #[cfg(feature = "__rustls")]
    BuiltRustls(rustls::ClientConfig),
    #[cfg(any(feature = "native-tls", feature = "__rustls",))]
    UnknownPreconfigured,
}

impl fmt::Debug for TlsBackend {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        match self {
            #[cfg(feature = "default-tls")]
            TlsBackend::Default => write!(f, "Default"),
            #[cfg(feature = "native-tls")]
            TlsBackend::BuiltNativeTls(_) => write!(f, "BuiltNativeTls"),
            #[cfg(feature = "__rustls")]
            TlsBackend::Rustls => write!(f, "Rustls"),
            #[cfg(feature = "__rustls")]
            TlsBackend::BuiltRustls(_) => write!(f, "BuiltRustls"),
            #[cfg(any(feature = "native-tls", feature = "__rustls",))]
            TlsBackend::UnknownPreconfigured => write!(f, "UnknownPreconfigured"),
        }
    }
}

impl Default for TlsBackend {
    fn default() -> TlsBackend {
        #[cfg(feature = "default-tls")]
        {
            TlsBackend::Default
        }

        #[cfg(all(feature = "__rustls", not(feature = "default-tls")))]
        {
            TlsBackend::Rustls
        }
    }
}

#[cfg(feature = "__rustls")]
pub(crate) struct NoVerifier;

#[cfg(feature = "__rustls")]
impl ServerCertVerifier for NoVerifier {
    fn verify_server_cert(
        &self,
        _end_entity: &rustls::Certificate,
        _intermediates: &[rustls::Certificate],
        _server_name: &ServerName,
        _scts: &mut dyn Iterator<Item = &[u8]>,
        _ocsp_response: &[u8],
        _now: std::time::SystemTime,
    ) -> Result<ServerCertVerified, TLSError> {
        Ok(ServerCertVerified::assertion())
    }

    fn verify_tls12_signature(
        &self,
        _message: &[u8],
        _cert: &rustls::Certificate,
        _dss: &DigitallySignedStruct,
    ) -> Result<HandshakeSignatureValid, TLSError> {
        Ok(HandshakeSignatureValid::assertion())
    }

    fn verify_tls13_signature(
        &self,
        _message: &[u8],
        _cert: &rustls::Certificate,
        _dss: &DigitallySignedStruct,
    ) -> Result<HandshakeSignatureValid, TLSError> {
        Ok(HandshakeSignatureValid::assertion())
    }
}

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

    #[cfg(feature = "default-tls")]
    #[test]
    fn certificate_from_der_invalid() {
        Certificate::from_der(b"not der").unwrap_err();
    }

    #[cfg(feature = "default-tls")]
    #[test]
    fn certificate_from_pem_invalid() {
        Certificate::from_pem(b"not pem").unwrap_err();
    }

    #[cfg(feature = "native-tls")]
    #[test]
    fn identity_from_pkcs12_der_invalid() {
        Identity::from_pkcs12_der(b"not der", "nope").unwrap_err();
    }

    #[cfg(feature = "native-tls")]
    #[test]
    fn identity_from_pkcs8_pem_invalid() {
        Identity::from_pkcs8_pem(b"not pem", b"not key").unwrap_err();
    }

    #[cfg(feature = "__rustls")]
    #[test]
    fn identity_from_pem_invalid() {
        Identity::from_pem(b"not pem").unwrap_err();
    }

    #[cfg(feature = "__rustls")]
    #[test]
    fn identity_from_pem_pkcs1_key() {
        let pem = b"-----BEGIN CERTIFICATE-----\n\
            -----END CERTIFICATE-----\n\
            -----BEGIN RSA PRIVATE KEY-----\n\
            -----END RSA PRIVATE KEY-----\n";

        Identity::from_pem(pem).unwrap();
    }
}