我在 NSData 类上实现了一个类别方法，该方法使用 SHA-1 哈希返回数据的签名，随后使用私钥进行加密，如下所示：
- (NSData *)signatureWithKey:(SecKeyRef)keyRef {
if (keyRef == NULL) {
return nil;
}
NSData *sha1Digest = [self dataWithSHA1Digest];
size_t maxLength = SecKeyGetBlockSize(keyRef) - 11;
if ([sha1Digest length] > maxLength) {
NSString *reason = [NSString stringWithFormat:@"Digest is too long to sign with this key, max length is %ld and actual length is %ld", maxLength, (unsigned long)[self length]];
NSException *ex = [NSException exceptionWithName:@"BMInvalidArgumentException" reason:reason userInfo:nil];
@throw ex;
}
#if TARGET_OS_IPHONE
OSStatus status = noErr;
uint8_t *plainBuffer = (uint8_t *)[sha1Digest bytes];
size_t plainBufferSize = [sha1Digest length];
size_t cipherBufferSize = SecKeyGetBlockSize(keyRef);
uint8_t *cipherBuffer = malloc(cipherBufferSize * sizeof(uint8_t));
status = SecKeyRawSign(keyRef,
kSecPaddingPKCS1SHA1,
plainBuffer,
plainBufferSize,
&cipherBuffer[0],
&cipherBufferSize
);
if (status == noErr) {
return [NSData dataWithBytesNoCopy:cipherBuffer length:cipherBufferSize freeWhenDone:YES];
}
free(cipherBuffer);
return nil;
#else
CFErrorRef error = NULL;
SecTransformRef signer = NULL;
CFTypeRef signature = NULL;
if ((signer = SecSignTransformCreate(keyRef, &error))) {
if (SecTransformSetAttribute(
signer,
kSecTransformInputAttributeName,
(CFDataRef)sha1Digest,
&error)) {
signature = SecTransformExecute(signer, &error);
}
}
if (error) {
LogWarn(@"Could not sign: %@", error);
CFRelease(error);
}
if (signer) {
CFRelease(signer);
}
if (signature) {
NSData *data = [NSData dataWithData:(NSData *)signature];
CFRelease(signature);
return data;
} else {
return nil;
}
#endif
}
现在奇怪的是，使用相同的私钥（从 p12 文件加载）在签署相同数据时，iOS 和 MacOSX 会得到两个不同的结果。我对此完全感到困惑。您可能会注意到，上面的方法使用安全转换为 MacOSX 使用了不同的实现，但即使我在 MacOSX 上使用 iOS 实现（它会发出编译警告但工作正常），我也会得到相同的结果。
从文件中加载私钥的方法如下：
+ (SecKeyRef)newPrivateKeyRefWithPassword:(NSString *)password fromData:(NSData *)data {
NSMutableDictionary * options = [[NSMutableDictionary alloc] init];
SecKeyRef privateKeyRef = NULL;
// Set the public key query dictionary
//change to your .pfx password here
[options setObject:password forKey:(id)kSecImportExportPassphrase];
CFArrayRef items = CFArrayCreate(NULL, 0, 0, NULL);
OSStatus securityError = SecPKCS12Import((CFDataRef)data,
(CFDictionaryRef)options, &items);
if (securityError == noErr && CFArrayGetCount(items) > 0) {
CFDictionaryRef identityDict = CFArrayGetValueAtIndex(items, 0);
SecIdentityRef identityApp =
(SecIdentityRef)CFDictionaryGetValue(identityDict,
kSecImportItemIdentity);
securityError = SecIdentityCopyPrivateKey(identityApp, &privateKeyRef);
if (securityError != noErr) {
privateKeyRef = NULL;
}
}
[options release];
if (items) CFRelease(items);
return privateKeyRef;
}
这是我使用的测试用例。请注意，在 iOS 和 MacOSX 上打印了两个不同的字符串：
NSString *test = @"bla";
NSData *testData = [test dataUsingEncoding:NSUTF8StringEncoding];
NSString *p12Path= [[NSBundle mainBundle] pathForResource:@"private_key" ofType:@"p12"];
NSData *p12Data = [NSData dataWithContentsOfFile:p12Path];
SecKeyRef keyRef = [BMSecurityHelper newPrivateKeyRefWithPassword:@"xxxxxxxx" fromData:p12Data];
NSData *signatureData = [testData signatureWithKey:keyRef];
NSString *signatureString = [BMEncodingHelper base64EncodedStringForData:signatureData withLineLength:0];
if (keyRef) CFRelease(keyRef);
NSLog(@"signatureString: %@", signatureString);