CK_RV aes_cbc_sample()

in src/encrypt/aes_cbc.c [199:307]
75 lines of code
12 McCabe index (conditional complexity)

CK_RV aes_cbc_sample(CK_SESSION_HANDLE session) {
    CK_RV rv;
    CK_BYTE_PTR decrypted_ciphertext = NULL;

    // Generate a 256 bit AES key.
    CK_OBJECT_HANDLE aes_key;
    rv = generate_aes_key(session, 32, &aes_key);
    if (CKR_OK != rv) {
        printf("AES key generation failed: %lu\n", rv);
        return rv;
    }

    CK_BYTE_PTR plaintext = "plaintext payload to encrypt";
    CK_ULONG plaintext_length = (CK_ULONG) strlen(plaintext);

    printf("Plaintext: %s\n", plaintext);
    printf("Plaintext length: %lu\n", plaintext_length);

    // Prepare the mechanism 
    // The IV is hardcoded to all 0x01 bytes for this example.
    CK_BYTE iv[16] = {0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01,
                      0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01};
    CK_MECHANISM mech = {CKM_AES_CBC_PAD, iv, 16};

    //**********************************************************************************************
    // Encrypt
    //**********************************************************************************************    

    rv = funcs->C_EncryptInit(session, &mech, aes_key);
    if (CKR_OK != rv) {
        printf("Encryption Init failed: %lu\n", rv);
        return rv;
    }

    // Determine how much memory will be required to hold the ciphertext.
    CK_ULONG ciphertext_length = 0;
    rv = funcs->C_Encrypt(session, plaintext, plaintext_length, NULL, &ciphertext_length);
    if (CKR_OK != rv) {
        printf("Encryption failed: %lu\n", rv);
        return rv;
    }

    // Allocate the required memory.
    CK_BYTE_PTR ciphertext = malloc(ciphertext_length);
    if (NULL == ciphertext) {
        printf("Could not allocate memory for ciphertext\n");
        return rv;
    }
    memset(ciphertext, 0, ciphertext_length);

    // Encrypt the data.
    rv = funcs->C_Encrypt(session, plaintext, plaintext_length, ciphertext, &ciphertext_length);
    if (CKR_OK != rv) {
        printf("Encryption failed: %lu\n", rv);
        goto done;
    }

    // Print just the ciphertext in hex format
    printf("Ciphertext: ");
    print_bytes_as_hex(ciphertext, ciphertext_length);
    printf("Ciphertext length: %lu\n", ciphertext_length);

    //**********************************************************************************************
    // Decrypt
    //**********************************************************************************************    

    rv = funcs->C_DecryptInit(session, &mech, aes_key);
    if (CKR_OK != rv) {
        printf("Decryption Init failed: %lu\n", rv);
        return rv;
    }

    // Determine how much memory is required to hold the decrypted text.
    CK_ULONG decrypted_ciphertext_length = 0;
    rv = funcs->C_Decrypt(session, ciphertext, ciphertext_length, NULL, &decrypted_ciphertext_length);
    if (CKR_OK != rv) {
        printf("Decryption failed: %lu\n", rv);
        goto done;
    }

    // Allocate memory for the decrypted ciphertext.
    decrypted_ciphertext = malloc(decrypted_ciphertext_length + 1); //We want to null terminate the raw chars later
    if (NULL == decrypted_ciphertext) {
        rv = 1;
        printf("Could not allocate memory for decrypted ciphertext\n");
        goto done;
    }

    // Decrypt the ciphertext.
    rv = funcs->C_Decrypt(session, ciphertext, ciphertext_length, decrypted_ciphertext, &decrypted_ciphertext_length);
    if (CKR_OK != rv) {
        printf("Decryption failed: %lu\n", rv);
        goto done;
    }
    decrypted_ciphertext[decrypted_ciphertext_length] = 0; // Turn the chars into a C-String via null termination

    printf("Decrypted ciphertext: %s\n", decrypted_ciphertext);
    printf("Decrypted ciphertext length: %lu\n", decrypted_ciphertext_length);

done:
    if (NULL != decrypted_ciphertext) {
        free(decrypted_ciphertext);
    }

    if (NULL != ciphertext) {
        free(ciphertext);
    }
    return rv;
}