(Objective-C) Decrypt MIME using RSAES-OAEP with SHA256 and AES-128 content encryption

Demonstrates how to decrypt MIME what was encrypted with RSAES-OAEP with SHA256 and AES-128 content encryption.

In actuality, we don't really need to know in advance the various algorithms used to encrypt the MIME. When decrypting, the information about the algorithms required are embedded in the PCKS7 message itself, and this tells a decryptor what it should use.

Note: This example requires Chilkat v9.5.0.67 or greater.

Chilkat Objective-C Library Downloads MAC OS X (Cocoa) Libs iOS Libs

#import <CkoStringBuilder.h>
#import <CkoMime.h>
#import <CkoCert.h>
#import <CkoPrivateKey.h>

// This requires the Chilkat API to have been previously unlocked.
// See Global Unlock Sample for sample code.

// We begin with this encrypted MIME:

// Content-Type: application/x-pkcs7-mime; name="smime.p7m"; smime-type="enveloped-data"
// someHeader1: Some value 1
// someHeader2: Some value 2
// Content-Disposition: attachment; filename="smime.p7m"
// Content-Transfer-Encoding: base64
// 
// MIIDvAYJKoZIhvcNAQcDoIIDrTCCA6kCAQAxggGgMIIBnAIBADB1MGgxCzAJBgNVBAYTAlVTMQsw
// CQYDVQQIDAJJTDEQMA4GA1UEBwwHV2hlYXRvbjEhMB8GA1UECgwYSW50ZXJuZXQgV2lkZ2l0cyBQ
// dHkgTHRkMRcwFQYDVQQDDA5DaGlsa2F0V2lkZ2V0cwIJAMRwugDmvniwMBwGCSqGSIb3DQEBBzAP
// oA0wCwYJYIZIAWUDBAIBBIIBAFaUL1ga1bOrdqYKcMm+FHUacBvzfBxk0fnPA0AMBdN8BvTWT3CN
// YuqBhjOGyq0FpYD9pVZybUuFMCVsVyIW2O62HnsOK58YaPEUUcdH2sI+yjqX9UAn0P0nVDSsVdeK
// W8x9kMfZg+3UP+y1q+lu7VRJO3f2C9oLQpTkc4VW4n7UOcUI0waykLCjCTL8lFDb7/J3GeuMKyhH
// 5riNz50kpbzqn7m2Ks9yA+QmcTdXclclGFr2vwEUFzSdT2pxh/vaUrogCxkYWbQ2eV7vZg6O4kV0
// aqHBqySkPTAzHKiHH8K8GVdlTuJ8350CpICa4T8w7/Ht5I7dyOPPKy4C+rVtrvcwggH+BgkqhkiG
// 9w0BBwEwHQYJYIZIAWUDBAECBBDTC2WNBN+z2I47/4Feu9YqgIIB0MZvl3nC/q/Wzil6HtfQTr12
// Q5moHY+ORzAa1P9XvX2ZUFhW530mV395mQw/A4o4ekmX9eRPEZquYzZPLT8hNeZIuNdhpcSQUmad
// rKnKkR0wKJ3jJ3LhOIohVBQSYs8kVDZKq6lJBIznlsurFelZoNEhyRschhteDZx5rb7fCe8c2+/O
// DHxaqaHCAzm/Bd7kcg6FFfuTZy3tu0PgP5IsXN4OFA3kkvwjAs4XsVS8jdIcmDNBkYieE8WmJOIm
// Mz7mh/CHWLgWfGKa0Dkb9RcbFgLwYNT3GzuXFw9XPbKkEZjEAtJajWbN6P0WQl96YYd9qZxUpGxZ
// zjTHEYzViUdUXolfpLufttrRXyxN1RFWhNFMFbv66xYqklMSgpdM/Mbk+EuvX6eXayDPvDBpfYMw
// NoRAzv1Ony2c0ez9rBemJICicxAzpuvHbRxdjYs63Dnv+TYgpBK12AxWWpPIjXvw0WQKgTC3Tg8s
// EnuGhpENqso/clJBEBSn4+2WhYtYbdI5sVme67lvqQl1Xxy3r18SWaQbyDOwgYi1E+54lMDOxMy0
// y0FPHk5pP45DnXWj+XORPp5LhuZr5mf62YOXSSUwR5P0cXy4Rc+pN5lhRQPCf5z2

BOOL success;
CkoStringBuilder *sb = [[CkoStringBuilder alloc] init];
BOOL bCrlf = YES;
[sb AppendLine: @"Content-Type: application/x-pkcs7-mime; name=\"smime.p7m\"; smime-type=\"enveloped-data\"" crlf: bCrlf];
[sb AppendLine: @"someHeader1: Some value 1" crlf: bCrlf];
[sb AppendLine: @"someHeader2: Some value 2" crlf: bCrlf];
[sb AppendLine: @"Content-Disposition: attachment; filename=\"smime.p7m\"" crlf: bCrlf];
[sb AppendLine: @"Content-Transfer-Encoding: base64" crlf: bCrlf];
[sb AppendLine: @"" crlf: bCrlf];
[sb AppendLine: @"MIIDvAYJKoZIhvcNAQcDoIIDrTCCA6kCAQAxggGgMIIBnAIBADB1MGgxCzAJBgNVBAYTAlVTMQsw" crlf: bCrlf];
[sb AppendLine: @"CQYDVQQIDAJJTDEQMA4GA1UEBwwHV2hlYXRvbjEhMB8GA1UECgwYSW50ZXJuZXQgV2lkZ2l0cyBQ" crlf: bCrlf];
[sb AppendLine: @"dHkgTHRkMRcwFQYDVQQDDA5DaGlsa2F0V2lkZ2V0cwIJAMRwugDmvniwMBwGCSqGSIb3DQEBBzAP" crlf: bCrlf];
[sb AppendLine: @"oA0wCwYJYIZIAWUDBAIBBIIBAFaUL1ga1bOrdqYKcMm+FHUacBvzfBxk0fnPA0AMBdN8BvTWT3CN" crlf: bCrlf];
[sb AppendLine: @"YuqBhjOGyq0FpYD9pVZybUuFMCVsVyIW2O62HnsOK58YaPEUUcdH2sI+yjqX9UAn0P0nVDSsVdeK" crlf: bCrlf];
[sb AppendLine: @"W8x9kMfZg+3UP+y1q+lu7VRJO3f2C9oLQpTkc4VW4n7UOcUI0waykLCjCTL8lFDb7/J3GeuMKyhH" crlf: bCrlf];
[sb AppendLine: @"5riNz50kpbzqn7m2Ks9yA+QmcTdXclclGFr2vwEUFzSdT2pxh/vaUrogCxkYWbQ2eV7vZg6O4kV0" crlf: bCrlf];
[sb AppendLine: @"aqHBqySkPTAzHKiHH8K8GVdlTuJ8350CpICa4T8w7/Ht5I7dyOPPKy4C+rVtrvcwggH+BgkqhkiG" crlf: bCrlf];
[sb AppendLine: @"9w0BBwEwHQYJYIZIAWUDBAECBBDTC2WNBN+z2I47/4Feu9YqgIIB0MZvl3nC/q/Wzil6HtfQTr12" crlf: bCrlf];
[sb AppendLine: @"Q5moHY+ORzAa1P9XvX2ZUFhW530mV395mQw/A4o4ekmX9eRPEZquYzZPLT8hNeZIuNdhpcSQUmad" crlf: bCrlf];
[sb AppendLine: @"rKnKkR0wKJ3jJ3LhOIohVBQSYs8kVDZKq6lJBIznlsurFelZoNEhyRschhteDZx5rb7fCe8c2+/O" crlf: bCrlf];
[sb AppendLine: @"DHxaqaHCAzm/Bd7kcg6FFfuTZy3tu0PgP5IsXN4OFA3kkvwjAs4XsVS8jdIcmDNBkYieE8WmJOIm" crlf: bCrlf];
[sb AppendLine: @"Mz7mh/CHWLgWfGKa0Dkb9RcbFgLwYNT3GzuXFw9XPbKkEZjEAtJajWbN6P0WQl96YYd9qZxUpGxZ" crlf: bCrlf];
[sb AppendLine: @"zjTHEYzViUdUXolfpLufttrRXyxN1RFWhNFMFbv66xYqklMSgpdM/Mbk+EuvX6eXayDPvDBpfYMw" crlf: bCrlf];
[sb AppendLine: @"NoRAzv1Ony2c0ez9rBemJICicxAzpuvHbRxdjYs63Dnv+TYgpBK12AxWWpPIjXvw0WQKgTC3Tg8s" crlf: bCrlf];
[sb AppendLine: @"EnuGhpENqso/clJBEBSn4+2WhYtYbdI5sVme67lvqQl1Xxy3r18SWaQbyDOwgYi1E+54lMDOxMy0" crlf: bCrlf];
[sb AppendLine: @"y0FPHk5pP45DnXWj+XORPp5LhuZr5mf62YOXSSUwR5P0cXy4Rc+pN5lhRQPCf5z2" crlf: bCrlf];

// Load the encrypted MIME into the MIME object.
CkoMime *mime = [[CkoMime alloc] init];
[mime LoadMimeSb: sb];

// Provide the required cert + private key from a PFX (.pfx/.p12) file.
success = [mime AddPfxSourceFile: @"qa_data/rsaes-oaep/cert_plus_privatekey.pfx" password: @"PFX_PASSWORD"];
if (success != YES) {
    NSLog(@"%@",mime.LastErrorText);
    return;
}

// Decrypt.
success = [mime Decrypt];
if (success != YES) {
    NSLog(@"%@",mime.LastErrorText);
    return;
}

// Examine the decrypted MIME.
NSLog(@"%@",[mime GetMime]);
NSLog(@"%@",@"Decrypt test 1 succeeded.");

// -----------------------------------------------------------
// Now let's decrypt another way..
// We have the same cert and private key in PEM files..

CkoCert *cert = [[CkoCert alloc] init];
success = [cert LoadFromFile: @"qa_data/rsaes-oaep/cert.pem"];

CkoPrivateKey *privKey = [[CkoPrivateKey alloc] init];
success = [privKey LoadPemFile: @"qa_data/rsaes-oaep/privatekey.pem"];

// Decrypt using the cert + private key
CkoMime *mime2 = [[CkoMime alloc] init];
[mime2 LoadMimeSb: sb];

success = [mime2 Decrypt2: cert privateKey: privKey];
if (success != YES) {
    NSLog(@"%@",mime2.LastErrorText);
    return;
}

// Examine the decrypted MIME.
NSLog(@"%@",[mime2 GetMime]);
NSLog(@"%@",@"Decrypt test 2 succeeded.");