iOS: How to create PKCS12 (P12) keystore from private key and x509certificate in application programmatically?

Question

This question was apparently similar but had no answers of any kind: Programmatically create a x509 certificate for iPhone without using OpenSSL

In our application (

Answer 1

Thank you all very much for this nice solution!

I translated your code to Swift 3 and built the following function to create a P12 keystore using a signed X509 certificate and a RSA private key, both in PEM format:

func createP12(pemCertificate: String, pemPrivateKey: String) {
    // Read certificate
    let buffer = BIO_new(BIO_s_mem())
    pemCertificate.data(using: .utf8)!.withUnsafeBytes({ (bytes: UnsafePointer) -> Void in
        BIO_puts(buffer, bytes)
    })
    let certificate = PEM_read_bio_X509(buffer, nil, nil, nil)
    X509_print_fp(stdout, certificate)
    // Read private key
    let privateKeyBuffer = BIO_new(BIO_s_mem())
    pemPrivateKey.data(using: .utf8)!.withUnsafeBytes({ (bytes: UnsafePointer) -> Void in
        BIO_puts(privateKeyBuffer, bytes)
    })
    let privateKey = PEM_read_bio_PrivateKey(privateKeyBuffer, nil, nil, nil)
    PEM_write_PrivateKey(stdout, privateKey, nil, nil, 0, nil, nil)
    // Check if private key matches certificate
    guard X509_check_private_key(certificate, privateKey) == 1 else {
        NSLog("Private key does not match certificate")
        return
    }
    // Set OpenSSL parameters
    OPENSSL_add_all_algorithms_noconf()
    ERR_load_crypto_strings()
    // Create P12 keystore
    let passPhrase = UnsafeMutablePointer(mutating: ("" as NSString).utf8String)
    let name = UnsafeMutablePointer(mutating: ("SSL Certificate" as NSString).utf8String)
    guard let p12 = PKCS12_create(passPhrase, name, privateKey, certificate, nil, 0, 0, 0, 0, 0) else {
        NSLog("Cannot create P12 keystore:")
        ERR_print_errors_fp(stderr)
        return
    }
    // Save P12 keystore
    let fileManager = FileManager.default
    let tempDirectory = NSTemporaryDirectory() as NSString
    let path = tempDirectory.appendingPathComponent("ssl.p12")
    fileManager.createFile(atPath: path, contents: nil, attributes: nil)
    guard let fileHandle = FileHandle(forWritingAtPath: path) else {
        NSLog("Cannot open file handle: \(path)")
        return
    }
    let p12File = fdopen(fileHandle.fileDescriptor, "w")
    i2d_PKCS12_fp(p12File, p12)
    fclose(p12File)
    fileHandle.closeFile()
}

EDIT:

OpenSSL can be used in iOS with the OpenSSL-for-iPhone project:

1. Check out the repository
2. Build the static libraries with ./build-libssl.sh
3. Add $(YOUR_PATH)/OpenSSL-for-iPhone/include to header search paths
4. Add $(YOUR_PATH)/OpenSSL-for-iPhone/lib to library search paths
5. Add libcrypto.a and libssl.a to linked frameworks and libraries
6. Add the following headers to the bridging header:

Project-Bridging-Header.h:

#import 
#import 
#import 
#import