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//===----------------------------------------------------------------------===//
//
// This source file is part of the SwiftCertificates open source project
//
// Copyright (c) 2023 Apple Inc. and the SwiftCertificates project authors
// Licensed under Apache License v2.0
//
// See LICENSE.txt for license information
// See CONTRIBUTORS.txt for the list of SwiftCertificates project authors
//
// SPDX-License-Identifier: Apache-2.0
//
//===----------------------------------------------------------------------===//
import Foundation
import SwiftASN1
import Crypto
/// An ECDSA signature is laid out as follows:
///
/// ECDSASignature ::= SEQUENCE {
/// r INTEGER,
/// s INTEGER
/// }
///
/// We define this type here because an X.509 certificate may have an ECDSA signature
/// in it without reference to what key created it. We need to be able to store it
/// abstractly, and then turn it into the signature type we need on request.
@usableFromInline
struct ECDSASignature: DERImplicitlyTaggable, Hashable, Sendable {
@inlinable
static var defaultIdentifier: ASN1Identifier {
.sequence
}
@usableFromInline
var r: ArraySlice<UInt8>
@usableFromInline
var s: ArraySlice<UInt8>
@inlinable
init(r: ArraySlice<UInt8>, s: ArraySlice<UInt8>) {
self.r = r
self.s = s
}
@inlinable
init(derEncoded rootNode: ASN1Node, withIdentifier identifier: ASN1Identifier) throws {
self = try DER.sequence(rootNode, identifier: identifier) { nodes in
let r = try ArraySlice<UInt8>(derEncoded: &nodes)
let s = try ArraySlice<UInt8>(derEncoded: &nodes)
return ECDSASignature(r: r, s: s)
}
}
@inlinable
func serialize(into coder: inout DER.Serializer, withIdentifier identifier: ASN1Identifier) throws {
try coder.appendConstructedNode(identifier: identifier) { coder in
try coder.serialize(self.r)
try coder.serialize(self.s)
}
}
@inlinable
init(rawSignatureBytes raw: Data) {
let half = raw.count / 2
let r = ArraySlice(normalisingToASN1IntegerForm: raw.prefix(upTo: half))
let s = ArraySlice(normalisingToASN1IntegerForm: raw.suffix(from: half))
self = ECDSASignature(r: r, s: s)
}
@inlinable
init(_ sig: P256.Signing.ECDSASignature) {
self = .init(rawSignatureBytes: sig.rawRepresentation)
}
@inlinable
init(_ sig: P384.Signing.ECDSASignature) {
self = .init(rawSignatureBytes: sig.rawRepresentation)
}
@inlinable
init(_ sig: P521.Signing.ECDSASignature) {
self = .init(rawSignatureBytes: sig.rawRepresentation)
}
}
extension P256.Signing.ECDSASignature {
@inlinable
init?(_ signature: ECDSASignature) {
let coordinateByteCount = 32
guard signature.r.count <= coordinateByteCount && signature.s.count <= coordinateByteCount else {
return nil
}
// r and s must be padded out to the coordinate byte count.
// We use Data here because Crypto wants that type anyway.
var raw = Data()
raw.reserveCapacity(2 * coordinateByteCount)
raw.append(contentsOf: repeatElement(0, count: coordinateByteCount - signature.r.count))
raw.append(contentsOf: signature.r)
raw.append(contentsOf: repeatElement(0, count: coordinateByteCount - signature.s.count))
raw.append(contentsOf: signature.s)
do {
self = try .init(rawRepresentation: raw)
} catch {
return nil
}
}
}
extension P384.Signing.ECDSASignature {
@inlinable
init?(_ signature: ECDSASignature) {
let coordinateByteCount = 48
guard signature.r.count <= coordinateByteCount && signature.s.count <= coordinateByteCount else {
return nil
}
// r and s must be padded out to the coordinate byte count.
// We use Data here because Crypto wants that type anyway.
var raw = Data()
raw.reserveCapacity(2 * coordinateByteCount)
raw.append(contentsOf: repeatElement(0, count: coordinateByteCount - signature.r.count))
raw.append(contentsOf: signature.r)
raw.append(contentsOf: repeatElement(0, count: coordinateByteCount - signature.s.count))
raw.append(contentsOf: signature.s)
do {
self = try .init(rawRepresentation: raw)
} catch {
return nil
}
}
}
extension P521.Signing.ECDSASignature {
@inlinable
init?(_ signature: ECDSASignature) {
let coordinateByteCount = 66
guard signature.r.count <= coordinateByteCount && signature.s.count <= coordinateByteCount else {
return nil
}
// r and s must be padded out to the coordinate byte count.
// We use Data here because Crypto wants that type anyway.
var raw = Data()
raw.reserveCapacity(2 * coordinateByteCount)
raw.append(contentsOf: repeatElement(0, count: coordinateByteCount - signature.r.count))
raw.append(contentsOf: signature.r)
raw.append(contentsOf: repeatElement(0, count: coordinateByteCount - signature.s.count))
raw.append(contentsOf: signature.s)
do {
self = try .init(rawRepresentation: raw)
} catch {
return nil
}
}
}
extension ArraySlice where Element == UInt8 {
/// Normalizes a sequence of bytes that represent an unsigned big endian raw integer into the
/// form we'd get from decoding an ASN1 integer.
///
/// This means we strip leading zero bytes.
@inlinable
init<Bytes: Collection>(normalisingToASN1IntegerForm bigEndianRawInteger: Bytes) where Bytes.Element == UInt8 {
let realBytes = bigEndianRawInteger.drop(while: { $0 == 0 })
self = ArraySlice(realBytes)
}
@inlinable
init(normalisingToASN1IntegerForm bigEndianRawInteger: ArraySlice<UInt8>) {
self = bigEndianRawInteger.drop(while: { $0 == 0 })
}
@inlinable
init(normalisingToASN1IntegerForm bigEndianRawInteger: [UInt8]) {
self.init(normalisingToASN1IntegerForm: bigEndianRawInteger[...])
}
}
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