Importing a PKCS12 Using SecItemImport

Question

Apple's documentation for OS X talks about using SecItemImport to obtain a SecKeyRef. The function signature looks like this:

OSStatus SecItemImport (
   CFDataRef importedData,
   CFStringRef fileNameOrExtension,
   SecExternalFormat *inputFormat,
   SecExternalItemType *itemType,
   SecItemImportExportFlags flags,
   const SecItemImportExportKeyParameters *keyParams,
   SecKeychainRef importKeychain,
   CFArrayRef *outItems
);

The following code will attempt to load a PKCS12 byte array that contains a single RSA key:

#include <Security/Security.h>
#include <Security/SecKey.h>
#include <CoreFoundation/CoreFoundation.h>

int main(void) {
    CFArrayRef array = NULL;
    SecItemImportExportKeyParameters params;
    SecExternalItemType itemType = kSecItemTypeUnknown;
    SecExternalFormat format = kSecFormatUnknown;
    params.flags = kSecKeyNoAccessControl;
    UInt8 bytes[] = {
        0x30, 0x82, 0x2, 0x1e, 0x2, 0x1, 0x3, 0x30, 0x82, 0x1, 0xe8, 0x6, 0x9, 0x2a, 0x86, 0x48, 0x86, 0xf7,
        0xd, 0x1, 0x7, 0x1, 0xa0, 0x82, 0x1, 0xd9, 0x4, 0x82, 0x1, 0xd5, 0x30, 0x82, 0x1, 0xd1, 0x30, 0x82,
        0x1, 0xcd, 0x6, 0x9, 0x2a, 0x86, 0x48, 0x86, 0xf7, 0xd, 0x1, 0x7, 0x1, 0xa0, 0x82, 0x1, 0xbe, 0x4,
        0x82, 0x1, 0xba, 0x30, 0x82, 0x1, 0xb6, 0x30, 0x82, 0x1, 0xb2, 0x6, 0xb, 0x2a, 0x86, 0x48, 0x86,
        0xf7, 0xd, 0x1, 0xc, 0xa, 0x1, 0x2, 0xa0, 0x82, 0x1, 0x86, 0x30, 0x82, 0x1, 0x82, 0x30, 0x1c, 0x6,
        0xa, 0x2a, 0x86, 0x48, 0x86, 0xf7, 0xd, 0x1, 0xc, 0x1, 0x3, 0x30, 0xe, 0x4, 0x8, 0x8f, 0x14, 0x15,
        0x85, 0x8e, 0x1c, 0x64, 0x6c, 0x2, 0x2, 0x8, 0x0, 0x4, 0x82, 0x1, 0x60, 0x86, 0x44, 0x55, 0x7e, 0xa3,
        0xce, 0x63, 0xb0, 0x83, 0xf6, 0x34, 0xb8, 0x88, 0xe3, 0x6e, 0xbf, 0x7e, 0xcb, 0xe7, 0x4f, 0x57, 0xde,
        0xaa, 0x4f, 0x28, 0xaa, 0x38, 0x6f, 0xc0, 0xd2, 0xcc, 0xc9, 0x95, 0x1b, 0x69, 0x2c, 0x7b, 0x78, 0xdf,
        0x77, 0xd7, 0xb3, 0x30, 0xe6, 0x3f, 0x6f, 0xaa, 0xe2, 0x68, 0x2e, 0x50, 0x28, 0x97, 0x16, 0x1d, 0xb8,
        0x7a, 0x26, 0x80, 0x57, 0x15, 0xf5, 0xe5, 0xce, 0x45, 0xed, 0x99, 0x68, 0x4f, 0x87, 0x97, 0x7c, 0xa0,
        0x19, 0xaf, 0x41, 0xf4, 0xcb, 0xdb, 0x2b, 0xd5, 0x42, 0xac, 0x9c, 0x50, 0x63, 0xd5, 0x1f, 0x5c, 0x1b,
        0x32, 0x1d, 0x3a, 0x77, 0x14, 0x78, 0x97, 0xe4, 0x38, 0xc2, 0x18, 0x9b, 0x5f, 0xa4, 0xf1, 0xec, 0xe0,
        0xd3, 0xc4, 0x7d, 0xcb, 0x25, 0x7, 0xd4, 0x68, 0x8b, 0x6d, 0x1d, 0x68, 0xa6, 0x8d, 0xf7, 0xf3, 0x63,
        0xf6, 0x6f, 0x5c, 0x8e, 0xed, 0x13, 0xdd, 0x11, 0xd7, 0x9, 0xe8, 0x6b, 0xda, 0x12, 0x44, 0x75, 0x15,
        0x82, 0xfa, 0xf6, 0xa1, 0x92, 0x54, 0x81, 0x9a, 0xa8, 0x4b, 0x21, 0x69, 0x8c, 0xc7, 0xba, 0x3e, 0x59,
        0xb6, 0x5b, 0x3, 0x50, 0xad, 0xd5, 0x6e, 0x9e, 0x11, 0x85, 0x12, 0x28, 0x6b, 0xf6, 0x4e, 0xbe, 0xaf,
        0xac, 0x9b, 0xee, 0x41, 0xf1, 0x3c, 0x36, 0xd9, 0xed, 0x4b, 0x68, 0x5e, 0x17, 0x88, 0xe5, 0xc2, 0x51,
        0x25, 0x19, 0xa4, 0xda, 0x1b, 0xb8, 0xec, 0xe2, 0x16, 0x42, 0xb1, 0x43, 0x32, 0x83, 0x89, 0x7a, 0xf3,
        0x3e, 0xee, 0x45, 0x18, 0x98, 0xb7, 0xe0, 0x23, 0xe4, 0x59, 0x58, 0x89, 0xa7, 0xf3, 0x50, 0x43, 0x3e,
        0xa7, 0xf9, 0xf, 0x89, 0x6c, 0xd1, 0xb3, 0xd7, 0xc7, 0x61, 0xa9, 0x75, 0x72, 0x52, 0x8a, 0xc0, 0x17,
        0x60, 0xbc, 0x26, 0x51, 0xec, 0x0, 0x46, 0xdb, 0x98, 0x41, 0xa0, 0x18, 0x7b, 0x2f, 0x11, 0xde, 0xb5,
        0xdc, 0xa4, 0x63, 0xbc, 0x93, 0x93, 0xcc, 0x98, 0x90, 0x74, 0xcb, 0xf6, 0xa, 0xe5, 0x99, 0x66, 0xd6,
        0x40, 0x81, 0x3, 0x7a, 0x40, 0x8, 0xa9, 0x42, 0x6, 0x53, 0xbe, 0x2c, 0x3a, 0x82, 0xe2, 0x9a, 0x62, 0x5a,
        0x1b, 0xb6, 0x3f, 0xd7, 0x10, 0x7f, 0x57, 0x0, 0xdb, 0x29, 0x8d, 0x4d, 0xe8, 0x9c, 0x70, 0x86, 0x66,
        0x78, 0x7b, 0x96, 0xba, 0xef, 0xb4, 0x4c, 0x30, 0x20, 0x97, 0x25, 0x5d, 0xf6, 0xff, 0x9d, 0x97, 0x60,
        0x34, 0x58, 0x2e, 0x6a, 0xf7, 0x12, 0x9f, 0x3b, 0x77, 0x2e, 0x3e, 0x43, 0x75, 0x97, 0x73, 0xf6, 0x53,
        0x0, 0x9b, 0x74, 0x34, 0xf4, 0xec, 0x31, 0x19, 0x30, 0x17, 0x6, 0x9, 0x2a, 0x86, 0x48, 0x86, 0xf7,
        0xd, 0x1, 0x9, 0x14, 0x31, 0xa, 0x1e, 0x8, 0x0, 0x6e, 0x0, 0x61, 0x0, 0x6d, 0x0, 0x65, 0x30, 0x2d,
        0x30, 0x21, 0x30, 0x9, 0x6, 0x5, 0x2b, 0xe, 0x3, 0x2, 0x1a, 0x5, 0x0, 0x4, 0x14, 0x95, 0x9, 0x91,
        0xf7, 0x6c, 0x7f, 0x35, 0x99, 0x64, 0xfc, 0x3e, 0x5e, 0xcf, 0xb6, 0x24, 0x8a, 0xc, 0x54, 0x44, 0xc6,
        0x4, 0x8, 0xfe, 0xe0, 0xe7, 0xbb, 0x72, 0xe1, 0xc9, 0x97
    };
    FILE* file = fopen( "test.p12", "wb" );
    fwrite( bytes, sizeof(UInt8), sizeof(bytes)/sizeof(UInt8), file );

    params.passphrase = CFStringCreateWithCString(kCFAllocatorDefault, "pass", kCFStringEncodingASCII);

    CFDataRef dataref = CFDataCreate(kCFAllocatorDefault, bytes, sizeof(bytes)/sizeof(bytes[0]));

    OSStatus res = SecItemImport(dataref, CFSTR(".p12"), &format, &itemType, 0, &params, NULL, &array);
    printf("response: %d\n", res);
    printf("format: %d\n", format);
    printf("itemType: %d\n", itemType);
    printf("count: %ld\n", CFArrayGetCount(array));
}

To compile the above you can use clang filename.c -framework Security -framework CoreFoundation.

This code returns no error (OSStatus 0) but fails to populate the array with a parsed SecKeyRef. I've tried quite a few different flags but haven't been able to get it to return the data needed. Does anyone know what I'm doing wrong?

Mini

Don't you need to flush/close the file after writing to it? Was the file created correctly? – Dungaree

The file isn't relevant. It's just for testing. Note how it isn't read later? The file also seems correct (in that openssl can read it fine). – Aecium

@RobNapier OK, I can see that now, unfortunately my Octational tool is at work. Paul, have you tried kSecFormatPKCS12 as format? I cannot easily check the validity of the P12 right now, the hex is in a bit of a tricky format. – Dungaree

Looks like PKCS#7 (CMS) instead of PKCS#12 to me. Sheesh, wrote a hex decoder just to see that :) It contains a PKCS#12 though. – Dungaree

Oops, indeed that FILE * existed only for test. I intended to strip it out for the example, but failed. @owlstead, I will take a look at that. The PKCS12 was generated via OpenSSL using the export flags, but I'll try your alternate hex. – Mini

Answer 1

This really looks like a Keychain bug. That isn't shocking; Keychain has lots of little corner cases that aren't well handled. I'd open a radar (bugreport.apple.com). Some additional notes:

PKCS12 is usually used to store a certificate along with a private key. You're just importing a bare private key. I'm betting that's not well tested, although it claims to be supported:

Note: When importing a PKCS12 blob, typically one SecIdentityRef object and zero or more additional SecCertificateRef objects are returned in outItems. No SecKeyRef objects are returned unless a key is found in the incoming blob that does not have a matching certificate.

I'd be curious if this would work if there were a certificate involved.

I've tried this code with a keychain (created with SecKeychainCreate). The resulting keychain is readable by Keychain Access and contains the private key, so the import is working.

I've tried using all the same code as SecPKCS12Import, but it returns the same result. For instance, I made sure to memset() the parameters structure, which your code should, but doesn't.

As an irrelevant point, you're leaking the passphrase. You should use CFSTR() here to pass the constant string.

Aecium

If I import a key+cert pair then I do get an element in the CFArray so it looks like that is a potential workaround. Ultimately the goal here is to import an RSA/DSA/EC key for use with Apple's signing APIs directly so I may experiment with some other import formats (PKCS1/PKCS8 would be ideal). Thanks! – Mini

@PaulKehrer Did you have any luck? I stuck in a similar problem… Thank you! – Shawntashawwal

Answer 2

SecItemImport() is broken in macOS and cannot import anything other than certificates from PKCS#12. Even if you have stored an identity there and provide the correct password, you end up with just a certificate and not an identity. The code does seem to decrypt the content, since if you provide the wrong password, you get nothing at all but I never was able to obtain an identity.

The only way to import correctly from PKCS#12 is using SecPKCS12Import(), however this function has another bug. On macOS it always import into the default keychain, even if no keychain import was requested. You will get references of the imported items in an array but they are also now permanently stored in keychain. On iOS this function does not import into keychain, unless you explicitly request that (just as documented).

All issue mentioned above are known to Apple for ages but they have no interest in fixing any of them. SecItemImport() is macOS only and they won't ever touch it again, they rather would prefer to deprecate it and they don't want to change the behavior of SecPKCS12Import(), as they fear breaking code that relies on the old (incorrect) behavior.

Gley

Additional bit of trivia: SecItemImport() does return a SecIdentity from importing PKCS#12 if an importKeychain was specified. – Foreboding