OSStatus -9809 when verifying on iOS

Question

I have a key pair created like this:

openssl req -x509 -out public_key.der -outform der -new -newkey rsa:1024 -keyout private_key.pem -days 3650

Next I sign a text file using the foll. commands:

openssl dgst -sha256 some_text.txt > hash256
openssl rsautl -sign -inkey private_key.pem -keyform PEM -in hash256 > signature256.txt

Now, I want to verify it on iOS:

    + (BOOL)verifySignature {
         NSData* publicKeyData = [NSData dataWithContentsOfURL:[[NSBundle mainBundle] URLForResource:@"public_key" withExtension:@"der"]];

         SecCertificateRef pubCertificate = SecCertificateCreateWithData(kCFAllocatorDefault, ( __bridge CFDataRef) publicKeyData);
         if (pubCertificate == nil) {
              NSLog(@"Can not read certificate from data");
              return NO;
         }

         SecTrustRef trust;
         SecPolicyRef policy = SecPolicyCreateBasicX509();
         OSStatus returnCode = SecTrustCreateWithCertificates(pubCertificate, policy, &trust);
         if (returnCode != errSecSuccess) {
               NSLog(@"SecTrustCreateWithCertificates fail. Error Code: %d", (int)returnCode);
               return NO;
         }

         SecTrustResultType trustResultType;
         returnCode = SecTrustEvaluate(trust, &trustResultType);
         if (returnCode != errSecSuccess) {
                 return NO;
         }

         SecKeyRef publicKey = SecTrustCopyPublicKey(trust);

         NSURL* textFileUrl = [[NSBundle mainBundle] URLForResource:@"some_text" withExtension:@"txt"];

         NSData* signedData = [NSData dataWithContentsOfURL:textFileUrl];
         size_t signedDataLen = [signedData length];
         void *signedDataBuffer = malloc(signedDataLen);
         [signedData getBytes:signedDataBuffer length:signedDataLen];

         void* hashBuffer = malloc(CC_SHA256_DIGEST_LENGTH);
         CC_SHA256(signedDataBuffer, (CC_LONG)signedDataLen, hashBuffer);

         NSURL* signatureFileUrl = [[NSBundle mainBundle]     URLForResource:@"signature256" withExtension:@"txt"];
         NSData* signatureData = [NSData dataWithContentsOfURL:signatureFileUrl];
         size_t signatureLen = [signatureData length];
         void* signatureBuffer = malloc(signatureLen);
         [signatureData getBytes:signatureBuffer length:signatureLen];

          returnCode = SecKeyRawVerify(publicKey, kSecPaddingPKCS1SHA256, hashBuffer, CC_SHA256_DIGEST_LENGTH, signatureBuffer, signatureLen);
          if (returnCode != errSecSuccess) {
                 NSLog(@"SecKeyRawVerify fail. Error Code: %d", (int)returnCode);
          }

          free(signedDataBuffer);
          free(signatureBuffer);
          free(hashBuffer);

          CFRelease(pubCertificate);
          CFRelease(policy);
          CFRelease(trust);
          CFRelease(publicKey);

Everything looks OK until the point where I call SecKeyRawVerify, which returns error code -9809.

What am I doing wrong?