Expose cryptography backends via CryptoProvider

Author: arckoor

README.md

@@ -15,7 +15,8 @@ jsonwebtoken = { version = "10", features = ["aws_lc_rs"] }
 serde = {version = "1.0", features = ["derive"] }
 ```
 
-Two crypto backends are available via features, `aws_lc_rs` and `rust_crypto`, exactly one of which must be enabled.
+Two crypto backends are available via features, `aws_lc_rs` and `rust_crypto`, at most one of which must be enabled. If you select neither feature, you need to provide your own `CryptoProvider`.
+See e.g. [arckoor/jsonwebtoken-botan](https://github.com/arckoor/jsonwebtoken-botan) for an example of how to implement a `CryptoProvider`.
 
 The minimum required Rust version (MSRV) is specified in the `rust-version` field in this project's [Cargo.toml](Cargo.toml).
 

src/algorithms.rs

@@ -5,10 +5,15 @@ use serde::{Deserialize, Serialize};
 use crate::errors::{Error, ErrorKind, Result};
 
 #[derive(Debug, Eq, PartialEq, Copy, Clone, Serialize, Deserialize)]
+/// Supported families of algorithms.
 pub enum AlgorithmFamily {
+    /// HMAC shared secret family.
     Hmac,
+    /// RSA-based public key family.
     Rsa,
+    /// Edwards curve public key family.
     Ec,
+    /// Elliptic curve public key family.
     Ed,
 }
 
@@ -34,6 +39,7 @@ impl AlgorithmFamily {
 /// The algorithms supported for signing/verifying JWTs
 #[allow(clippy::upper_case_acronyms)]
 #[derive(Debug, Default, PartialEq, Eq, Hash, Copy, Clone, Serialize, Deserialize)]
+#[non_exhaustive]
 pub enum Algorithm {
     /// HMAC using SHA-256
     #[default]

src/crypto/aws_lc/ecdsa.rs

@@ -18,7 +18,7 @@ macro_rules! define_ecdsa_signer {
 
         impl $name {
             pub(crate) fn new(encoding_key: &EncodingKey) -> Result<Self> {
-                if encoding_key.family != AlgorithmFamily::Ec {
+                if encoding_key.family() != AlgorithmFamily::Ec {
                     return Err(new_error(ErrorKind::InvalidKeyFormat));
                 }
 
@@ -51,7 +51,7 @@ macro_rules! define_ecdsa_verifier {
 
         impl $name {
             pub(crate) fn new(decoding_key: &DecodingKey) -> Result<Self> {
-                if decoding_key.family != AlgorithmFamily::Ec {
+                if decoding_key.family() != AlgorithmFamily::Ec {
                     return Err(new_error(ErrorKind::InvalidKeyFormat));
                 }
 

src/crypto/aws_lc/eddsa.rs

@@ -11,7 +11,7 @@ pub struct EdDSASigner(Ed25519KeyPair);
 
 impl EdDSASigner {
     pub(crate) fn new(encoding_key: &EncodingKey) -> Result<Self> {
-        if encoding_key.family != AlgorithmFamily::Ed {
+        if encoding_key.family() != AlgorithmFamily::Ed {
             return Err(new_error(ErrorKind::InvalidKeyFormat));
         }
 
@@ -38,7 +38,7 @@ pub struct EdDSAVerifier(DecodingKey);
 
 impl EdDSAVerifier {
     pub(crate) fn new(decoding_key: &DecodingKey) -> Result<Self> {
-        if decoding_key.family != AlgorithmFamily::Ed {
+        if decoding_key.family() != AlgorithmFamily::Ed {
             return Err(new_error(ErrorKind::InvalidKeyFormat));
         }
 

src/crypto/aws_lc/mod.rs

@@ -1,4 +1,111 @@
-pub(crate) mod ecdsa;
-pub(crate) mod eddsa;
-pub(crate) mod hmac;
-pub(crate) mod rsa;
+use aws_lc_rs::{
+    digest,
+    signature::{self as aws_sig, KeyPair},
+};
+
+use crate::{
+    Algorithm, DecodingKey, EncodingKey,
+    crypto::{CryptoProvider, JwkUtils, JwtSigner, JwtVerifier},
+    errors::{self, Error, ErrorKind},
+    jwk::{EllipticCurve, ThumbprintHash},
+};
+
+mod ecdsa;
+mod eddsa;
+mod hmac;
+mod rsa;
+
+fn extract_rsa_public_key_components(key_content: &[u8]) -> errors::Result<(Vec<u8>, Vec<u8>)> {
+    let key_pair = aws_sig::RsaKeyPair::from_der(key_content)
+        .map_err(|e| ErrorKind::InvalidRsaKey(e.to_string()))?;
+    let public = key_pair.public_key();
+    let components = aws_sig::RsaPublicKeyComponents::<Vec<u8>>::from(public);
+    Ok((components.n, components.e))
+}
+
+fn extract_ec_public_key_coordinates(
+    key_content: &[u8],
+    alg: Algorithm,
+) -> errors::Result<(EllipticCurve, Vec<u8>, Vec<u8>)> {
+    use aws_lc_rs::signature::{
+        ECDSA_P256_SHA256_FIXED_SIGNING, ECDSA_P384_SHA384_FIXED_SIGNING, EcdsaKeyPair,
+    };
+
+    let (signing_alg, curve, pub_elem_bytes) = match alg {
+        Algorithm::ES256 => (&ECDSA_P256_SHA256_FIXED_SIGNING, EllipticCurve::P256, 32),
+        Algorithm::ES384 => (&ECDSA_P384_SHA384_FIXED_SIGNING, EllipticCurve::P384, 48),
+        _ => return Err(ErrorKind::InvalidEcdsaKey.into()),
+    };
+
+    let key_pair = EcdsaKeyPair::from_pkcs8(signing_alg, key_content)
+        .map_err(|_| ErrorKind::InvalidEcdsaKey)?;
+
+    let pub_bytes = key_pair.public_key().as_ref();
+    if pub_bytes[0] != 4 {
+        return Err(ErrorKind::InvalidEcdsaKey.into());
+    }
+
+    let (x, y) = pub_bytes[1..].split_at(pub_elem_bytes);
+    Ok((curve, x.to_vec(), y.to_vec()))
+}
+
+fn compute_digest(data: &[u8], hash_function: ThumbprintHash) -> Vec<u8> {
+    let algorithm = match hash_function {
+        ThumbprintHash::SHA256 => &digest::SHA256,
+        ThumbprintHash::SHA384 => &digest::SHA384,
+        ThumbprintHash::SHA512 => &digest::SHA512,
+    };
+    digest::digest(algorithm, data).as_ref().to_vec()
+}
+
+fn new_signer(algorithm: &Algorithm, key: &EncodingKey) -> Result<Box<dyn JwtSigner>, Error> {
+    let jwt_signer = match algorithm {
+        Algorithm::HS256 => Box::new(hmac::Hs256Signer::new(key)?) as Box<dyn JwtSigner>,
+        Algorithm::HS384 => Box::new(hmac::Hs384Signer::new(key)?) as Box<dyn JwtSigner>,
+        Algorithm::HS512 => Box::new(hmac::Hs512Signer::new(key)?) as Box<dyn JwtSigner>,
+        Algorithm::ES256 => Box::new(ecdsa::Es256Signer::new(key)?) as Box<dyn JwtSigner>,
+        Algorithm::ES384 => Box::new(ecdsa::Es384Signer::new(key)?) as Box<dyn JwtSigner>,
+        Algorithm::RS256 => Box::new(rsa::Rsa256Signer::new(key)?) as Box<dyn JwtSigner>,
+        Algorithm::RS384 => Box::new(rsa::Rsa384Signer::new(key)?) as Box<dyn JwtSigner>,
+        Algorithm::RS512 => Box::new(rsa::Rsa512Signer::new(key)?) as Box<dyn JwtSigner>,
+        Algorithm::PS256 => Box::new(rsa::RsaPss256Signer::new(key)?) as Box<dyn JwtSigner>,
+        Algorithm::PS384 => Box::new(rsa::RsaPss384Signer::new(key)?) as Box<dyn JwtSigner>,
+        Algorithm::PS512 => Box::new(rsa::RsaPss512Signer::new(key)?) as Box<dyn JwtSigner>,
+        Algorithm::EdDSA => Box::new(eddsa::EdDSASigner::new(key)?) as Box<dyn JwtSigner>,
+    };
+
+    Ok(jwt_signer)
+}
+
+fn new_verifier(
+    algorithm: &Algorithm,
+    key: &DecodingKey,
+) -> Result<Box<dyn super::JwtVerifier>, Error> {
+    let jwt_verifier = match algorithm {
+        Algorithm::HS256 => Box::new(hmac::Hs256Verifier::new(key)?) as Box<dyn JwtVerifier>,
+        Algorithm::HS384 => Box::new(hmac::Hs384Verifier::new(key)?) as Box<dyn JwtVerifier>,
+        Algorithm::HS512 => Box::new(hmac::Hs512Verifier::new(key)?) as Box<dyn JwtVerifier>,
+        Algorithm::ES256 => Box::new(ecdsa::Es256Verifier::new(key)?) as Box<dyn JwtVerifier>,
+        Algorithm::ES384 => Box::new(ecdsa::Es384Verifier::new(key)?) as Box<dyn JwtVerifier>,
+        Algorithm::RS256 => Box::new(rsa::Rsa256Verifier::new(key)?) as Box<dyn JwtVerifier>,
+        Algorithm::RS384 => Box::new(rsa::Rsa384Verifier::new(key)?) as Box<dyn JwtVerifier>,
+        Algorithm::RS512 => Box::new(rsa::Rsa512Verifier::new(key)?) as Box<dyn JwtVerifier>,
+        Algorithm::PS256 => Box::new(rsa::RsaPss256Verifier::new(key)?) as Box<dyn JwtVerifier>,
+        Algorithm::PS384 => Box::new(rsa::RsaPss384Verifier::new(key)?) as Box<dyn JwtVerifier>,
+        Algorithm::PS512 => Box::new(rsa::RsaPss512Verifier::new(key)?) as Box<dyn JwtVerifier>,
+        Algorithm::EdDSA => Box::new(eddsa::EdDSAVerifier::new(key)?) as Box<dyn JwtVerifier>,
+    };
+
+    Ok(jwt_verifier)
+}
+
+/// The default [`CryptoProvider`] backed by [`aws_lc_rs`].
+pub const DEFAULT_PROVIDER: CryptoProvider = CryptoProvider {
+    signer_factory: new_signer,
+    verifier_factory: new_verifier,
+    jwk_utils: JwkUtils {
+        extract_rsa_public_key_components,
+        extract_ec_public_key_coordinates,
+        compute_digest,
+    },
+};

src/crypto/aws_lc/rsa.rs

@@ -37,7 +37,7 @@ fn verify_rsa(
     msg: &[u8],
     signature: &[u8],
 ) -> std::result::Result<(), signature::Error> {
-    match &decoding_key.kind {
+    match decoding_key.kind() {
         DecodingKeyKind::SecretOrDer(bytes) => {
             let public_key = crypto_sig::UnparsedPublicKey::new(algorithm, bytes);
             public_key.verify(msg, signature).map_err(signature::Error::from_source)?;
@@ -57,7 +57,7 @@ macro_rules! define_rsa_signer {
 
         impl $name {
             pub(crate) fn new(encoding_key: &EncodingKey) -> Result<Self> {
-                if encoding_key.family != AlgorithmFamily::Rsa {
+                if encoding_key.family() != AlgorithmFamily::Rsa {
                     return Err(new_error(ErrorKind::InvalidKeyFormat));
                 }
 
@@ -85,7 +85,7 @@ macro_rules! define_rsa_verifier {
 
         impl $name {
             pub(crate) fn new(decoding_key: &DecodingKey) -> Result<Self> {
-                if decoding_key.family != AlgorithmFamily::Rsa {
+                if decoding_key.family() != AlgorithmFamily::Rsa {
                     return Err(new_error(ErrorKind::InvalidKeyFormat));
                 }
 

src/crypto/mod.rs

@@ -1,20 +1,28 @@
 //! The cryptography of the `jsonwebtoken` crate is decoupled behind
-//! [`JwtSigner`] and [`JwtVerifier`] traits. These make use of `RustCrypto`'s
+//! [`JwtSigner`] and [`JwtVerifier`] traits. These make use of `signature`'s
 //! [`Signer`] and [`Verifier`] traits respectively.
+//! Crypto provider selection is handled by [`CryptoProvider`].
 //!
 //! [`JwtSigner`]: crate::crypto::JwtSigner
 //! [`JwtVerifier`]: crate::crypto::JwtVerifier
 //! [`Signer`]: signature::Signer
 //! [`Verifier`]: signature::Verifier
+//! [`CryptoProvider`]: crate::crypto::CryptoProvider
+
+use std::sync::Arc;
 
 use crate::algorithms::Algorithm;
 use crate::errors::Result;
+use crate::jwk::{EllipticCurve, ThumbprintHash};
 use crate::{DecodingKey, EncodingKey};
 
+/// `aws_lc_rs` based CryptoProvider.
 #[cfg(feature = "aws_lc_rs")]
-pub(crate) mod aws_lc;
+pub mod aws_lc;
+
+/// `RustCrypto` based CryptoProvider.
 #[cfg(feature = "rust_crypto")]
-pub(crate) mod rust_crypto;
+pub mod rust_crypto;
 
 use crate::serialization::{b64_decode, b64_encode};
 use signature::{Signer, Verifier};
@@ -40,7 +48,9 @@ pub trait JwtVerifier: Verifier<Vec<u8>> {
 ///
 /// If you just want to encode a JWT, use `encode` instead.
 pub fn sign(message: &[u8], key: &EncodingKey, algorithm: Algorithm) -> Result<String> {
-    let provider = crate::encoding::jwt_signer_factory(&algorithm, key)?;
+    let provider = (CryptoProvider::get_default_or_install_from_crate_features().signer_factory)(
+        &algorithm, key,
+    )?;
     Ok(b64_encode(provider.sign(message)))
 }
 
@@ -58,6 +68,121 @@ pub fn verify(
     key: &DecodingKey,
     algorithm: Algorithm,
 ) -> Result<bool> {
-    let provider = crate::decoding::jwt_verifier_factory(&algorithm, key)?;
+    let provider = (CryptoProvider::get_default_or_install_from_crate_features().verifier_factory)(
+        &algorithm, key,
+    )?;
     Ok(provider.verify(message, &b64_decode(signature)?).is_ok())
 }
+
+/// Controls the cryptography used by jsonwebtoken.
+///
+/// You can either install one of the built-in options:
+/// - [`crypto::aws_lc::DEFAULT_PROVIDER`]: (behind the `aws_lc_rs` crate feature).
+///   This provider uses the [aws-lc-rs](https://github.com/aws/aws-lc-rs) crate.
+/// - [`crypto::rust_crypto::DEFAULT_PROVIDER`]: (behind the `rust_crypto` crate feature)
+///   This provider uses crates from the [Rust Crypto](https://github.com/RustCrypto) project.
+///
+/// or provide your own custom custom implementation of `CryptoProvider`.
+// This implementation appropriates a good chunk of code from the `rustls` CryptoProvider,
+// and is very much inspired by it.
+#[derive(Clone, Debug)]
+pub struct CryptoProvider {
+    /// A function that produces a [`JwtSigner`] for a given [`Algorithm`]
+    pub signer_factory: fn(&Algorithm, &EncodingKey) -> Result<Box<dyn JwtSigner>>,
+    /// A function that produces a [`JwtVerifier`] for a given [`Algorithm`]
+    pub verifier_factory: fn(&Algorithm, &DecodingKey) -> Result<Box<dyn JwtVerifier>>,
+    /// Struct with utility functions for JWK processing.
+    pub jwk_utils: JwkUtils,
+}
+
+impl CryptoProvider {
+    /// Set this `CryptoProvider` as the default for this process.
+    ///
+    /// This can be called successfully at most once in any process execution.
+    pub fn install_default(self) -> std::result::Result<(), Arc<Self>> {
+        static_default::install_default(self)
+    }
+
+    /// Get the default `CryptoProvider` for this process.
+    ///
+    /// This will be `None` if no default has been set yet.
+    pub fn get_default() -> Option<&'static Arc<Self>> {
+        static_default::get_default()
+    }
+
+    /// Get the default if it has been set yet, or determine one from the crate features if possible.
+    pub(crate) fn get_default_or_install_from_crate_features() -> &'static Arc<Self> {
+        if let Some(provider) = Self::get_default() {
+            return provider;
+        }
+
+        let provider = Self::from_crate_features()
+            .expect(r###"
+Could not automatically determine the process-level CryptoProvider from jsonwebtoken crate features.
+Call CryptoProvider::install_default() before this point to select a provider manually, or make sure exactly one of the 'rust_crypto' and 'aws_lc_rs' features is enabled.
+See the documentation of the CryptoProvider type for more information.
+            "###);
+        let _ = provider.install_default();
+        Self::get_default().unwrap()
+    }
+
+    /// Determine a `CryptoProvider` based on crate features.
+    pub fn from_crate_features() -> Option<Self> {
+        #[cfg(all(feature = "rust_crypto", not(feature = "aws_lc_rs")))]
+        {
+            return Some(rust_crypto::DEFAULT_PROVIDER);
+        }
+
+        #[cfg(all(feature = "aws_lc_rs", not(feature = "rust_crypto")))]
+        {
+            return Some(aws_lc::DEFAULT_PROVIDER);
+        }
+
+        #[allow(unreachable_code)]
+        None
+    }
+}
+
+/// Holds utility functions required for JWK processing.
+/// The `Default` implementation initializes all functions to `unimplemented!()`.
+#[derive(Clone, Debug)]
+pub struct JwkUtils {
+    /// Given a DER encoded private key, extract the RSA public key components (n, e)
+    #[allow(clippy::type_complexity)]
+    pub extract_rsa_public_key_components: fn(&[u8]) -> Result<(Vec<u8>, Vec<u8>)>,
+    /// Given a DER encoded private key and an algorithm, extract the associated curve
+    /// and the EC public key components (x, y)
+    #[allow(clippy::type_complexity)]
+    pub extract_ec_public_key_coordinates:
+        fn(&[u8], Algorithm) -> Result<(EllipticCurve, Vec<u8>, Vec<u8>)>,
+    /// Given some data and a name of a hash function, compute hash_function(data)
+    pub compute_digest: fn(&[u8], ThumbprintHash) -> Vec<u8>,
+}
+
+impl Default for JwkUtils {
+    fn default() -> Self {
+        Self {
+            extract_rsa_public_key_components: |_| unimplemented!(),
+            extract_ec_public_key_coordinates: |_, _| unimplemented!(),
+            compute_digest: |_, _| unimplemented!(),
+        }
+    }
+}
+
+mod static_default {
+    use std::sync::{Arc, OnceLock};
+
+    use super::CryptoProvider;
+
+    static PROCESS_DEFAULT_PROVIDER: OnceLock<Arc<CryptoProvider>> = OnceLock::new();
+
+    pub(crate) fn install_default(
+        default_provider: CryptoProvider,
+    ) -> Result<(), Arc<CryptoProvider>> {
+        PROCESS_DEFAULT_PROVIDER.set(Arc::new(default_provider))
+    }
+
+    pub(crate) fn get_default() -> Option<&'static Arc<CryptoProvider>> {
+        PROCESS_DEFAULT_PROVIDER.get()
+    }
+}

src/crypto/rust_crypto/ecdsa.rs

@@ -20,7 +20,7 @@ macro_rules! define_ecdsa_signer {
 
         impl $name {
             pub(crate) fn new(encoding_key: &EncodingKey) -> Result<Self> {
-                if encoding_key.family != AlgorithmFamily::Ec {
+                if encoding_key.family() != AlgorithmFamily::Ec {
                     return Err(new_error(ErrorKind::InvalidKeyFormat));
                 }
 
@@ -52,7 +52,7 @@ macro_rules! define_ecdsa_verifier {
 
         impl $name {
             pub(crate) fn new(decoding_key: &DecodingKey) -> Result<Self> {
-                if decoding_key.family != AlgorithmFamily::Ec {
+                if decoding_key.family() != AlgorithmFamily::Ec {
                     return Err(new_error(ErrorKind::InvalidKeyFormat));
                 }