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This allows implementing signing and verification with more than openssl PKey(Ref), like a TPM or AWS KMS keys (#5). It implements the abstracted methods for PKeyRef, and PKey calls out to PKeyRef. Signed-off-by: Patrick Uiterwijk <patrick@puiterwijk.org>
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//! (Signing) cryptography abstraction | ||
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use openssl::{hash::MessageDigest, nid::Nid}; | ||
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use crate::{error::COSEError, sign::SignatureAlgorithm}; | ||
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#[cfg(feature = "key_openssl_pkey")] | ||
mod openssl_pkey; | ||
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/// A public key that can verify an existing signature | ||
pub trait SigningPublicKey { | ||
/// This returns the signature algorithm and message digest to be used for this | ||
/// public key. | ||
fn get_parameters(&self) -> Result<(SignatureAlgorithm, MessageDigest), COSEError>; | ||
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/// Given a vector of data and a signature, returns a boolean whether the signature | ||
/// was valid. | ||
fn verify(&self, data: &[u8], signature: &[u8]) -> Result<bool, COSEError>; | ||
} | ||
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/// Follows the recommandations put in place by the RFC and doesn't deal with potential | ||
/// mismatches: https://tools.ietf.org/html/rfc8152#section-8.1. | ||
pub fn ec_curve_to_parameters( | ||
curve_name: Nid, | ||
) -> Result<(SignatureAlgorithm, MessageDigest, usize), COSEError> { | ||
match curve_name { | ||
// Recommended to use with SHA256 | ||
Nid::X9_62_PRIME256V1 => Ok((SignatureAlgorithm::ES256, MessageDigest::sha256(), 32)), | ||
// Recommended to use with SHA384 | ||
Nid::SECP384R1 => Ok((SignatureAlgorithm::ES384, MessageDigest::sha384(), 48)), | ||
// Recommended to use with SHA512 | ||
Nid::SECP521R1 => Ok(( | ||
SignatureAlgorithm::ES512, | ||
MessageDigest::sha512(), | ||
66, /* Not a typo */ | ||
)), | ||
_ => Err(COSEError::UnsupportedError(format!( | ||
"Curve name {:?} is not supported", | ||
curve_name | ||
))), | ||
} | ||
} | ||
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/// A private key that can produce new signatures | ||
pub trait SigningPrivateKey: SigningPublicKey { | ||
/// Given a slice of data, returns a signature | ||
fn sign(&self, data: &[u8]) -> Result<Vec<u8>, COSEError>; | ||
} |
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//! OpenSSL PKey(Ref) implementation for cryptography | ||
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use openssl::{ | ||
bn::BigNum, | ||
ecdsa::EcdsaSig, | ||
hash::MessageDigest, | ||
pkey::{HasPrivate, HasPublic, PKey, PKeyRef}, | ||
}; | ||
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use crate::{ | ||
crypto::{ec_curve_to_parameters, SigningPrivateKey, SigningPublicKey}, | ||
error::COSEError, | ||
sign::SignatureAlgorithm, | ||
}; | ||
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impl<T> SigningPublicKey for PKey<T> | ||
where | ||
T: HasPublic, | ||
{ | ||
fn get_parameters(&self) -> Result<(SignatureAlgorithm, MessageDigest), COSEError> { | ||
self.as_ref().get_parameters() | ||
} | ||
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fn verify(&self, data: &[u8], signature: &[u8]) -> Result<bool, COSEError> { | ||
self.as_ref().verify(data, signature) | ||
} | ||
} | ||
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impl<T> SigningPublicKey for PKeyRef<T> | ||
where | ||
T: HasPublic, | ||
{ | ||
fn get_parameters(&self) -> Result<(SignatureAlgorithm, MessageDigest), COSEError> { | ||
let curve_name = self | ||
.ec_key() | ||
.map_err(|_| COSEError::UnsupportedError("Non-EC keys are not supported".to_string()))? | ||
.group() | ||
.curve_name() | ||
.ok_or_else(|| { | ||
COSEError::UnsupportedError("Anonymous EC keys are not supported".to_string()) | ||
})?; | ||
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let curve_parameters = ec_curve_to_parameters(curve_name)?; | ||
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Ok((curve_parameters.0, curve_parameters.1)) | ||
} | ||
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fn verify(&self, data: &[u8], signature: &[u8]) -> Result<bool, COSEError> { | ||
let key = self.ec_key().map_err(|_| { | ||
COSEError::UnsupportedError("Non-EC keys are not yet supported".to_string()) | ||
})?; | ||
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let curve_name = key.group().curve_name().ok_or_else(|| { | ||
COSEError::UnsupportedError("Anonymous EC keys are not supported".to_string()) | ||
})?; | ||
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let (_, _, key_length) = ec_curve_to_parameters(curve_name)?; | ||
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// Recover the R and S factors from the signature contained in the object | ||
let (bytes_r, bytes_s) = signature.split_at(key_length); | ||
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let r = BigNum::from_slice(&bytes_r).map_err(COSEError::SignatureError)?; | ||
let s = BigNum::from_slice(&bytes_s).map_err(COSEError::SignatureError)?; | ||
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let sig = EcdsaSig::from_private_components(r, s).map_err(COSEError::SignatureError)?; | ||
sig.verify(data, &key).map_err(COSEError::SignatureError) | ||
} | ||
} | ||
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impl<T> SigningPrivateKey for PKey<T> | ||
where | ||
T: HasPrivate, | ||
{ | ||
fn sign(&self, data: &[u8]) -> Result<Vec<u8>, COSEError> { | ||
self.as_ref().sign(data) | ||
} | ||
} | ||
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impl<T> SigningPrivateKey for PKeyRef<T> | ||
where | ||
T: HasPrivate, | ||
{ | ||
fn sign(&self, data: &[u8]) -> Result<Vec<u8>, COSEError> { | ||
let key = self.ec_key().map_err(|_| { | ||
COSEError::UnsupportedError("Non-EC keys are not yet supported".to_string()) | ||
})?; | ||
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let curve_name = key.group().curve_name().ok_or_else(|| { | ||
COSEError::UnsupportedError("Anonymous EC keys are not supported".to_string()) | ||
})?; | ||
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let (_, _, key_length) = ec_curve_to_parameters(curve_name)?; | ||
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// The spec defines the signature as: | ||
// Signature = I2OSP(R, n) | I2OSP(S, n), where n = ceiling(key_length / 8) | ||
// The Signer interface doesn't provide this, so this will use EcdsaSig interface instead | ||
// and concatenate R and S. | ||
// See https://tools.ietf.org/html/rfc8017#section-4.1 for details. | ||
let signature = EcdsaSig::sign(data, &key).map_err(COSEError::SignatureError)?; | ||
let bytes_r = signature.r().to_vec(); | ||
let bytes_s = signature.s().to_vec(); | ||
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// These should *never* exceed ceiling(key_length / 8) | ||
assert!(bytes_r.len() <= key_length); | ||
assert!(bytes_s.len() <= key_length); | ||
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let mut signature_bytes = vec![0u8; key_length * 2]; | ||
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// This is big-endian encoding so padding might be added at the start if the factor is | ||
// too short. | ||
let offset_copy = key_length - bytes_r.len(); | ||
signature_bytes[offset_copy..offset_copy + bytes_r.len()].copy_from_slice(&bytes_r); | ||
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// This is big-endian encoding so padding might be added at the start if the factor is | ||
// too short. | ||
let offset_copy = key_length - bytes_s.len() + key_length; | ||
signature_bytes[offset_copy..offset_copy + bytes_s.len()].copy_from_slice(&bytes_s); | ||
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Ok(signature_bytes) | ||
} | ||
} |
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