Does SecTrustEvaluate() look for root certificates in the application keychain?

Question

The docs say: “If not all the certificates needed to verify the leaf certificate are included in the trust management object, then SecTrustEvaluate searches for certificates

Answer 1

Seems like it's been a while since you posted so I'm not sure if you still need the answer. If your use case is "I'm getting hit with connection:didReceiveAuthenticationChallenge:, and I'd like to make sure that exact certificate is being evaluated, then you can either use iOS built-in trust methods or do a bit more work via the Foundation APIs: (note that SecTrustEvaulate is not being called specifically here, but it could be added in quite easily)

#import 
#import 

From there, you can iterate the full array of certs, and compare it to something like a SHA1 of the challenge's server trust reference:

// way #1 - iOS built-in ================================================ //
SecTrustRef trust = challenge.protectionSpace.serverTrust;
CFIndex cnt = SecTrustGetCertificateCount(trust);

// way #2 - build it in yourself from a file ============================ //
OSErr err;
NSString *path = [[NSBundle mainBundle] pathForResource:@"my.cert" 
                                                 ofType:@"der"];
NSData *derData = [NSData dataWithContentsOfFile:path];

SecCertificateRef myCert = 
    SecCertificateCreateWithData(NULL, (CFDataRef)derData);

CFMutableArrayRef array = CFArrayCreateMutable(NULL, 1, NULL);
CFArrayInsertValueAtIndex(array, 0, myCert);

err = SecTrustSetAnchorCertificates(trust, array);
if (err != errSecSuccess) {
    // do something smarter here, obviously, logging would be a start
    abort();
}
CFArrayRef certs = NULL;
err = SecTrustCopyCustomAnchorCertificates(trust, &certs);
if (err != errSecSuccess) {
    // again, better choices needed
    abort();
}
CFIndex cnt = CFArrayGetCount(certs);

// loop and compare 'em
for (int i = 0; i < cnt; i++) {
    SecCertificateRef cert = SecTrustGetCertificateAtIndex(trust, i);

    CFDataRef cdata = SecCertificateCopyData(cert);
    NSData *data = [[NSData alloc] initWithData:(NSData *)cdata];

    unsigned char digest_result[CC_SHA1_DIGEST_LENGTH];

    CC_SHA1(data.bytes, data.length, digest_result);
    // compare each byte with your in-code SHA1 bytes
    if (allBytesMatch) {
        NSURLCredential *cred = [NSURLCredential credentialForTrust:trust];
        [challenge.sender useCredential:cred 
             forAuthenticationChallenge:challenge];
    }
}
// don't forget to release & CFRelease all the alloc'ed stuff from above