What is the reason of kSecTrustResultRecoverableTrustFailure?

It may be a server certificate problem….

Check here, I solved my kSecTrustResultRecoverableTrustFailure problem, adding subjectAltName = DNS:example.com into openssl config file, specifically in server key generation…

If you are not using openssl to generate it, I’m sorry but I can help you.. Anyway if you want to use openssl, here is a good tutorial to generate those keys and sign then with your own root certificate authority.

From this tutorial, I just changed my openssl server config file to:

    [ server ]
    basicConstraints = critical,CA:FALSE
    keyUsage = digitalSignature, keyEncipherment, dataEncipherment
    extendedKeyUsage = serverAuth
    nsCertType = server
    subjectAltName = IP:10.0.1.5,DNS:office.totendev.com
    

Hope it helps !

EDITED:

My Server evaluation code:

#pragma mark - SERVER Auth Helper
//Validate server certificate with challenge
+ (BOOL)validateServerWithChallenge:(NSURLAuthenticationChallenge *)challenge {
//Get server trust management object a set anchor objects to validate it
SecTrustSetAnchorCertificates([challenge.protectionSpace serverTrust], (__bridge CFArrayRef)[self allowedCAcertificates]);
//Set to server trust management object to JUST ALLOW those anchor objects assigned to it (ABOVE), and disable apple CA trusts 
SecTrustSetAnchorCertificatesOnly([challenge.protectionSpace serverTrust], YES);
//Try to evalute it
SecTrustResultType evaluateResult = kSecTrustResultInvalid; //evaluate result
OSStatus sanityCheck = SecTrustEvaluate([challenge.protectionSpace serverTrust], &evaluateResult);
//Check for no evaluate error
if (sanityCheck == noErr) {
    //Check for result
    if ([[self class] validateTrustResult:evaluateResult]) { return YES ; }
}
//deny!
return NO ;
}
//Validate SecTrustResulType
+ (BOOL)validateTrustResult:(SecTrustResultType)result {
switch (result) {
    case kSecTrustResultProceed: { TDLog(kLogLevelHandshake,nil,@"kSecTrustResultProceed"); return YES ; }
        break;
    case kSecTrustResultConfirm: { TDLog(kLogLevelHandshake,nil,@"kSecTrustResultConfirm"); return YES ; }
        break;
    case kSecTrustResultUnspecified: { TDLog(kLogLevelHandshake,nil,@"kSecTrustResultUnspecified"); return YES ; }
        break;
    case kSecTrustResultDeny: { TDLog(kLogLevelHandshake,nil,@"kSecTrustResultDeny"); return YES ; }
        break;
    case kSecTrustResultFatalTrustFailure: { TDLog(kLogLevelHandshake,nil,@"kSecTrustResultFatalTrustFailure"); return NO ; }
        break;
    case kSecTrustResultInvalid: { TDLog(kLogLevelHandshake,nil,@"kSecTrustResultInvalid"); return NO ; }
        break;
    case kSecTrustResultOtherError: { TDLog(kLogLevelHandshake,nil,@"kSecTrustResultOtherError"); return NO ; }
        break;
    case kSecTrustResultRecoverableTrustFailure: { TDLog(kLogLevelHandshake,nil,@"kSecTrustResultRecoverableTrustFailure"); return NO ; }
        break;
    default: { TDLog(kLogLevelHandshake,nil,@"unkown certificate evaluate result type! denying..."); return NO ; }
        break;
}

}

Hope now it helps 🙂 !