Hash each certificate's SPKI as encoded instead of rebuilding it

Package.swift

@@ -1,4 +1,4 @@
-// swift-tools-version:5.9
+// swift-tools-version:6.0
 import PackageDescription
 
 let package = Package(
@@ -22,10 +22,16 @@ let package = Package(
     targets: [
         .target(
             name: "TrustKit",
+            dependencies: ["TrustKitSwift"],
             path: "TrustKit",   
+            exclude: ["Swift"],
             resources: [.process("PrivacyInfo.xcprivacy")],
             publicHeadersPath: "public",
             cSettings: [.define("NS_BLOCK_ASSERTIONS", to: "1", .when(configuration: .release))]
         ),
+        .target(
+            name: "TrustKitSwift",
+            path: "TrustKit/Swift"
+        ),
     ]
 )

TrustKit/Pinning/TSKSPKIHashCache.h

@@ -25,7 +25,8 @@ NS_ASSUME_NONNULL_BEGIN
 
 // The identifier used for the default shared hash cache. Use this identifier
 // in the TSKSPKIHashCache constructor to use the shared cache.
-static NSString * const kTSKSPKISharedHashCacheIdentifier = @"spki-hash.cache";
+// Versioned so that hashes cached by TrustKit 3.x, which rebuilt the SPKI from the key, are not reused.
+static NSString * const kTSKSPKISharedHashCacheIdentifier = @"spki-hash-v2.cache";
 
 // Each key is a raw certificate data (for easy lookup) and each value is the certificate's raw SPKI data
 typedef NSMutableDictionary<NSData *, NSData *> SPKICacheDictionnary;

TrustKit/Pinning/TSKSPKIHashCache.m

@@ -13,122 +13,11 @@
 #import "TSKSPKIHashCache.h"
 #import "../TSKLog.h"
 #import <CommonCrypto/CommonDigest.h>
-#import "pinning_utils.h"
-
-#pragma mark Missing ASN1 SPKI Headers
-
-// These are the ASN1 headers for the Subject Public Key Info section of a certificate
-// TODO(AD): Are they returned by the new iOS API https://developer.apple.com/documentation/security/2963103-seccertificatecopykey ?
-static const unsigned char rsa2048Asn1Header[] =
-{
-    0x30, 0x82, 0x01, 0x22, 0x30, 0x0d, 0x06, 0x09, 0x2a, 0x86, 0x48, 0x86,
-    0xf7, 0x0d, 0x01, 0x01, 0x01, 0x05, 0x00, 0x03, 0x82, 0x01, 0x0f, 0x00
-};
-
-static const unsigned char rsa3072Asn1Header[] =
-{
-    0x30, 0x82, 0x01, 0xA2, 0x30, 0x0D, 0x06, 0x09, 0x2A, 0x86, 0x48, 0x86,
-    0xF7, 0x0D, 0x01, 0x01, 0x01, 0x05, 0x00, 0x03, 0x82, 0x01, 0x8F, 0x00
-};
-
-static const unsigned char rsa4096Asn1Header[] =
-{
-    0x30, 0x82, 0x02, 0x22, 0x30, 0x0d, 0x06, 0x09, 0x2a, 0x86, 0x48, 0x86,
-    0xf7, 0x0d, 0x01, 0x01, 0x01, 0x05, 0x00, 0x03, 0x82, 0x02, 0x0f, 0x00
-};
-
-static const unsigned char ecDsaSecp256r1Asn1Header[] =
-{
-    0x30, 0x59, 0x30, 0x13, 0x06, 0x07, 0x2a, 0x86, 0x48, 0xce, 0x3d, 0x02,
-    0x01, 0x06, 0x08, 0x2a, 0x86, 0x48, 0xce, 0x3d, 0x03, 0x01, 0x07, 0x03,
-    0x42, 0x00
-};
-
-static const unsigned char ecDsaSecp384r1Asn1Header[] =
-{
-    0x30, 0x76, 0x30, 0x10, 0x06, 0x07, 0x2a, 0x86, 0x48, 0xce, 0x3d, 0x02,
-    0x01, 0x06, 0x05, 0x2b, 0x81, 0x04, 0x00, 0x22, 0x03, 0x62, 0x00
-};
-
-
-static BOOL isKeySupported(NSString *publicKeyType, NSNumber *publicKeySize)
-{
-    if (([publicKeyType isEqualToString:(NSString *)kSecAttrKeyTypeRSA]) && ([publicKeySize integerValue] == 2048))
-    {
-        return YES;
-    }
-    else if (([publicKeyType isEqualToString:(NSString *)kSecAttrKeyTypeRSA]) && ([publicKeySize integerValue] == 3072))
-    {
-        return YES;
-    }
-    else if (([publicKeyType isEqualToString:(NSString *)kSecAttrKeyTypeRSA]) && ([publicKeySize integerValue] == 4096))
-    {
-        return YES;
-    }
-    else if (([publicKeyType isEqualToString:(NSString *)kSecAttrKeyTypeECSECPrimeRandom]) && ([publicKeySize integerValue] == 256))
-    {
-        return YES;
-    }
-    else if (([publicKeyType isEqualToString:(NSString *)kSecAttrKeyTypeECSECPrimeRandom]) && ([publicKeySize integerValue] == 384))
-    {
-        return YES;
-    }
-    return NO;
-}
-
-
-static char *getAsn1HeaderBytes(NSString *publicKeyType, NSNumber *publicKeySize)
-{
-    if (([publicKeyType isEqualToString:(NSString *)kSecAttrKeyTypeRSA]) && ([publicKeySize integerValue] == 2048))
-    {
-        return (char *)rsa2048Asn1Header;
-    }
-    else if (([publicKeyType isEqualToString:(NSString *)kSecAttrKeyTypeRSA]) && ([publicKeySize integerValue] == 3072))
-    {
-        return (char *)rsa3072Asn1Header;
-    }
-    else if (([publicKeyType isEqualToString:(NSString *)kSecAttrKeyTypeRSA]) && ([publicKeySize integerValue] == 4096))
-    {
-        return (char *)rsa4096Asn1Header;
-    }
-    else if (([publicKeyType isEqualToString:(NSString *)kSecAttrKeyTypeECSECPrimeRandom]) && ([publicKeySize integerValue] == 256))
-    {
-        return (char *)ecDsaSecp256r1Asn1Header;
-    }
-    else if (([publicKeyType isEqualToString:(NSString *)kSecAttrKeyTypeECSECPrimeRandom]) && ([publicKeySize integerValue] == 384))
-    {
-        return (char *)ecDsaSecp384r1Asn1Header;
-    }
-
-    @throw([NSException exceptionWithName:@"Unsupported public key algorithm" reason:@"Tried to generate the SPKI hash for an unsupported key algorithm" userInfo:nil]);
-}
-
-static unsigned int getAsn1HeaderSize(NSString *publicKeyType, NSNumber *publicKeySize)
-{
-    if (([publicKeyType isEqualToString:(NSString *)kSecAttrKeyTypeRSA]) && ([publicKeySize integerValue] == 2048))
-    {
-        return sizeof(rsa2048Asn1Header);
-    }
-    else if (([publicKeyType isEqualToString:(NSString *)kSecAttrKeyTypeRSA]) && ([publicKeySize integerValue] == 3072))
-    {
-        return sizeof(rsa3072Asn1Header);
-    }
-    else if (([publicKeyType isEqualToString:(NSString *)kSecAttrKeyTypeRSA]) && ([publicKeySize integerValue] == 4096))
-    {
-        return sizeof(rsa4096Asn1Header);
-    }
-    else if (([publicKeyType isEqualToString:(NSString *)kSecAttrKeyTypeECSECPrimeRandom]) && ([publicKeySize integerValue] == 256))
-    {
-        return sizeof(ecDsaSecp256r1Asn1Header);
-    }
-    else if (([publicKeyType isEqualToString:(NSString *)kSecAttrKeyTypeECSECPrimeRandom]) && ([publicKeySize integerValue] == 384))
-    {
-        return sizeof(ecDsaSecp384r1Asn1Header);
-    }
-
-    @throw([NSException exceptionWithName:@"Unsupported public key algorithm" reason:@"Tried to generate the SPKI hash for an unsupported key algorithm" userInfo:nil]);
-}
-
+#if SWIFT_PACKAGE
+@import TrustKitSwift;
+#else
+#import <TrustKit/TrustKit-Swift.h>
+#endif
 
 @interface TSKSPKIHashCache ()
 
@@ -234,54 +123,15 @@ - (NSData *)_hashSubjectPublicKeyInfoFromCertificate:(SecCertificateRef)certific
     // We didn't this certificate in the cache so we need to generate its SPKI hash
     os_log_debug(TSKLogHandle(), "Generating Subject Public Key Info hash...");
 
-    // First extract the public key
-    SecKeyRef publicKey = [self copyPublicKeyFromCertificate:certificate];
-    if (publicKey == nil)
-    {
-        os_log_error(TSKLogHandle(), "Could not copy the public key from the certificate");
-        return nil;
-    }
-
-    // Obtain the public key bytes from the key reference
-    NSData *publicKeyData = (__bridge_transfer NSData *)SecKeyCopyExternalRepresentation(publicKey, NULL);
-    if (publicKeyData == nil)
+    NSData *subjectPublicKeyInfo = [TSKSubjectPublicKeyInfo dataFromCertificate:certificateData];
+    if (subjectPublicKeyInfo == nil)
     {
-        os_log_error(TSKLogHandle(), "Could not extract the public key bytes");
-        CFRelease(publicKey);
+        os_log_error(TSKLogHandle(), "Could not read the Subject Public Key Info from the certificate");
         return nil;
     }
 
-    // Obtain the SPKI header based on the key's algorithm
-    CFDictionaryRef publicKeyAttributes = SecKeyCopyAttributes(publicKey);
-    NSString *publicKeyType = CFDictionaryGetValue(publicKeyAttributes, kSecAttrKeyType);
-    NSNumber *publicKeysize = CFDictionaryGetValue(publicKeyAttributes, kSecAttrKeySizeInBits);
-    CFRelease(publicKeyAttributes);
-
-    if (!isKeySupported(publicKeyType, publicKeysize))
-    {
-        os_log_error(TSKLogHandle(), "Public key algorithm or length is not supported");
-        CFRelease(publicKey);
-        return nil;
-    }
-
-    char *asn1HeaderBytes = getAsn1HeaderBytes(publicKeyType, publicKeysize);
-    unsigned int asn1HeaderSize = getAsn1HeaderSize(publicKeyType, publicKeysize);
-
-    CFRelease(publicKey);
-
-    // Generate a hash of the subject public key info
     NSMutableData *subjectPublicKeyInfoHash = [NSMutableData dataWithLength:CC_SHA256_DIGEST_LENGTH];
-    CC_SHA256_CTX shaCtx;
-    CC_SHA256_Init(&shaCtx);
-
-    // Add the missing ASN1 header for public keys to re-create the subject public key info
-    CC_SHA256_Update(&shaCtx, asn1HeaderBytes, asn1HeaderSize);
-
-
-    // Add the public key
-    CC_SHA256_Update(&shaCtx, [publicKeyData bytes], (unsigned int)[publicKeyData length]);
-    CC_SHA256_Final((unsigned char *)[subjectPublicKeyInfoHash bytes], &shaCtx);
-
+    CC_SHA256([subjectPublicKeyInfo bytes], (CC_LONG)[subjectPublicKeyInfo length], [subjectPublicKeyInfoHash mutableBytes]);
 
     // Store the hash in our memory cache
     self->_spkiCache[certificateData] = subjectPublicKeyInfoHash;
@@ -339,41 +189,6 @@ - (SPKICacheDictionnary *)loadSPKICacheFromFileSystem
     return spkiCache;
 }
 
-- (SecKeyRef)copyPublicKeyFromCertificate:(SecCertificateRef)certificate
-{
-    OSStatus status;
-
-    // Create an X509 trust using the using the certificate
-    SecTrustRef trust;
-    SecPolicyRef policy = SecPolicyCreateBasicX509();
-    status = SecTrustCreateWithCertificates(certificate, policy, &trust);
-    CFRelease(policy);
-
-    if (status != errSecSuccess)
-    {
-        os_log_error(TSKLogHandle(), "Could not create trust from certificate, got status %d", (int)status);
-        return nil;
-    }
-
-    // Get a public key reference for the certificate from the trust
-    // The certificate chain must be evaluated first in order to be able
-    // to determine which is the leaf certificate of the chain, and only
-    // then SecTrustCopyKey can be called
-    NSError *error = NULL;
-    SecTrustResultType trustResult = 0;
-    evaluateCertificateChainTrust(trust, &trustResult, &error);
-    if ((error != NULL) && (trustResult != kSecTrustResultRecoverableTrustFailure))
-    {
-        os_log_error(TSKLogHandle(), "Could not evaluate trust for the certificate: %{public}@", [error localizedDescription]);
-        CFRelease(trust);
-        return nil;
-    }
-
-    SecKeyRef publicKey = copyKey(trust);
-    CFRelease(trust);
-    return publicKey;
-}
-
 - (NSURL *)SPKICachePath
 {
     NSURL *cachesDirUrl = [NSFileManager.defaultManager URLsForDirectory:NSCachesDirectory

TrustKit/Pinning/pinning_utils.h

@@ -44,12 +44,4 @@ void evaluateCertificateChainTrust(SecTrustRef serverTrust, SecTrustResultType *
  */
 SecCertificateRef getCertificateAtIndex(SecTrustRef serverTrust, CFIndex index);
 
-/**
- Returns the public key for a leaf certificate after it has been evaluated.
-
- @param serverTrust The trust management object to evaluate
- @return The leaf certificate's public key, or nil if the public key could not be extracted
- */
-SecKeyRef copyKey(SecTrustRef serverTrust);
-
 #endif

TrustKit/Pinning/pinning_utils.m

@@ -34,7 +34,3 @@ SecCertificateRef getCertificateAtIndex(SecTrustRef serverTrust, CFIndex index)
     CFRelease(certs);
     return certificate;
 }
-
-SecKeyRef copyKey(SecTrustRef serverTrust) {
-    return SecTrustCopyKey(serverTrust);
-}

TrustKit/Swift/SubjectPublicKeyInfo.swift

@@ -0,0 +1,80 @@
+/*
+
+ SubjectPublicKeyInfo.swift
+ TrustKit
+
+ Copyright 2026 The TrustKit Project Authors
+ Licensed under the MIT license, see associated LICENSE file for terms.
+ See AUTHORS file for the list of project authors.
+
+ */
+
+import Foundation
+
+@objc(TSKSubjectPublicKeyInfo)
+public final class SubjectPublicKeyInfo: NSObject {
+    /// Returns the DER-encoded Subject Public Key Info of a DER-encoded certificate, exactly as it
+    /// is encoded in the certificate, or nil if the certificate could not be read.
+    @objc public static func data(fromCertificate certificate: Data) -> Data? {
+        // An Array keeps every read below bounds-checked, including in release builds
+        let der = [UInt8](certificate)
+        guard let subjectPublicKeyInfo = subjectPublicKeyInfoRange(in: der) else {
+            return nil
+        }
+        return Data(der[subjectPublicKeyInfo])
+    }
+}
+
+private struct DERElement {
+    let tag: UInt8
+    let content: Range<Int>
+    let element: Range<Int>
+}
+
+private func subjectPublicKeyInfoRange(in der: [UInt8]) -> Range<Int>? {
+    guard let certificate = readElement(der, in: der.indices), certificate.tag == 0x30,
+          let tbsCertificate = readElement(der, in: certificate.content), tbsCertificate.tag == 0x30 else {
+        return nil
+    }
+
+    // RFC 5280 4.1: an optional [0] version, then serialNumber, signature, issuer, validity and subject
+    var remaining = tbsCertificate.content
+    if let version = readElement(der, in: remaining), version.tag == 0xa0 {
+        remaining = version.element.upperBound..<remaining.upperBound
+    }
+    for expectedTag: UInt8 in [0x02, 0x30, 0x30, 0x30, 0x30] {
+        guard let field = readElement(der, in: remaining), field.tag == expectedTag else {
+            return nil
+        }
+        remaining = field.element.upperBound..<remaining.upperBound
+    }
+
+    guard let subjectPublicKeyInfo = readElement(der, in: remaining), subjectPublicKeyInfo.tag == 0x30 else {
+        return nil
+    }
+    return subjectPublicKeyInfo.element
+}
+
+private func readElement(_ der: [UInt8], in range: Range<Int>) -> DERElement? {
+    guard range.count >= 2 else {
+        return nil
+    }
+    let tag = der[range.lowerBound]
+    var contentStart = range.lowerBound + 2
+    var length = Int(der[range.lowerBound + 1])
+    if length & 0x80 != 0 {
+        // DER has no indefinite length (0x80), and no certificate needs more than 3 length bytes
+        let lengthBytes = length & 0x7f
+        guard (1...3).contains(lengthBytes), range.upperBound - contentStart >= lengthBytes else {
+            return nil
+        }
+        length = der[contentStart..<contentStart + lengthBytes].reduce(0) { $0 << 8 | Int($1) }
+        contentStart += lengthBytes
+    }
+    guard range.upperBound - contentStart >= length else {
+        return nil
+    }
+    return DERElement(tag: tag,
+                      content: contentStart..<contentStart + length,
+                      element: range.lowerBound..<contentStart + length)
+}