[openssl-users] Building an application with OpenSSL and FIPS support.

[Matthew Heimlich]

I'm on RHEL7. I've got a very simple encryption/decryption program that works fine without FIPS support enabled, but fails when it is:

#include <openssl/conf.h>
#include <openssl/evp.h>
#include <openssl/err.h>
#include <string.h>

void handleErrors(void)
{
    ERR_print_errors_fp(stderr);
    abort();
}

    int encrypt(unsigned char *plaintext, int plaintext_len, unsigned char *key,
    unsigned char *iv, unsigned char *ciphertext)
{
  EVP_CIPHER_CTX *ctx;

  int len;

  int ciphertext_len;

  /* Create and initialise the context */
  if(!(ctx = EVP_CIPHER_CTX_new())) handleErrors();

  /* Initialise the encryption operation. IMPORTANT - ensure you use a key
   * and IV size appropriate for your cipher
   * In this example we are using 256 bit AES (i.e. a 256 bit key). The
   * IV size for *most* modes is the same as the block size. For AES this
   * is 128 bits */
  if(1 != EVP_EncryptInit_ex(ctx, EVP_aes_256_cbc(), NULL, key, iv))
    handleErrors();

  /* Provide the message to be encrypted, and obtain the encrypted output.
   * EVP_EncryptUpdate can be called multiple times if necessary
   */
  if(1 != EVP_EncryptUpdate(ctx, ciphertext, &len, plaintext, plaintext_len))
    handleErrors();
  ciphertext_len = len;

  /* Finalise the encryption. Further ciphertext bytes may be written at
   * this stage.
   */
  if(1 != EVP_EncryptFinal_ex(ctx, ciphertext + len, &len)) handleErrors();
  ciphertext_len += len;

  /* Clean up */
  EVP_CIPHER_CTX_free(ctx);

  return ciphertext_len;
}

int decrypt(unsigned char *ciphertext, int ciphertext_len, unsigned char *key,
  unsigned char *iv, unsigned char *plaintext)
{
  EVP_CIPHER_CTX *ctx;

  int len;

  int plaintext_len;

  /* Create and initialise the context */
  if(!(ctx = EVP_CIPHER_CTX_new())) handleErrors();

  /* Initialise the decryption operation. IMPORTANT - ensure you use a key
   * and IV size appropriate for your cipher
   * In this example we are using 256 bit AES (i.e. a 256 bit key). The
   * IV size for *most* modes is the same as the block size. For AES this
   * is 128 bits */
  if(1 != EVP_DecryptInit_ex(ctx, EVP_aes_256_cbc(), NULL, key, iv))
    handleErrors();

  /* Provide the message to be decrypted, and obtain the plaintext output.
   * EVP_DecryptUpdate can be called multiple times if necessary
   */
  if(1 != EVP_DecryptUpdate(ctx, plaintext, &len, ciphertext, ciphertext_len))
    handleErrors();
  plaintext_len = len;

  /* Finalise the decryption. Further plaintext bytes may be written at
   * this stage.
   */
  if(1 != EVP_DecryptFinal_ex(ctx, plaintext + len, &len)) handleErrors();
  plaintext_len += len;

  /* Clean up */
  EVP_CIPHER_CTX_free(ctx);

  return plaintext_len;
}

int main (void)
{
  /* Force FIPS initialization */
  FIPS_mode_set(1);
  /* Set up the key and iv. Do I need to say to not hard code these in a
   * real application? :-)
   */

  /* A 256 bit key */
  unsigned char *key = (unsigned char *)"01234567890123456789012345678901";

  /* A 128 bit IV */
  unsigned char *iv = (unsigned char *)"01234567890123456";

  /* Message to be encrypted */
  unsigned char *plaintext =
                (unsigned char *)"The quick brown fox jumps over the lazy dog";

  /* Buffer for ciphertext. Ensure the buffer is long enough for the
   * ciphertext which may be longer than the plaintext, dependant on the
   * algorithm and mode
   */
  unsigned char ciphertext[128];

  /* Buffer for the decrypted text */
  unsigned char decryptedtext[128];

  int decryptedtext_len, ciphertext_len;

  /* Initialise the library */
  ERR_load_crypto_strings();
  OpenSSL_add_all_algorithms();
  OPENSSL_config(NULL);

  /* Encrypt the plaintext */
  ciphertext_len = encrypt (plaintext, strlen ((char *)plaintext), key, iv,
                            ciphertext);

  /* Do something useful with the ciphertext here */
  printf("Ciphertext is:\n");
  BIO_dump_fp (stdout, (const char *)ciphertext, ciphertext_len);

  /* Decrypt the ciphertext */
  decryptedtext_len = decrypt(ciphertext, ciphertext_len, key, iv,
    decryptedtext);

  /* Add a NULL terminator. We are expecting printable text */
  decryptedtext[decryptedtext_len] = '\0';

  /* Show the decrypted text */
  printf("Decrypted text is:\n");
  printf("%s\n", decryptedtext);

  /* Clean up */
  EVP_cleanup();
  ERR_free_strings();

  return 0;
}


As you can see, just the demo code with FIPS enabled. Without FIPS, my output is:

Ciphertext is:
0000 - e0 6f 63 a7 11 e8 b7 aa-9f 94 40 10 7d 46 80 a1   .oc....... at .}F..
0010 - 17 99 43 80 ea 31 d2 a2-99 b9 53 02 d4 39 b9 70   ..C..1....S..9.p
0020 - 2c 8e 65 a9 92 36 ec 92-07 04 91 5c f1 a9 8a 44   ,.e..6.....\...D
Decrypted text is:
The quick brown fox jumps over the lazy dog


With FIPS, compilation goes fine, but generates the following when run:

139686960322208:error:2D0A0086:FIPS routines:FIPS_cipher:selftest failed:fips_enc.c:336:
139686960322208:error:2D0A0086:FIPS routines:FIPS_cipher:selftest failed:fips_enc.c:336:


I've tried both as a C project, and as a C++ project, pointing the CC env variable at both the fipsld script, and the modified fipsld++ from the wiki script as appropriate. My FIPSLD_CC variable points to gcc as noted in the FIPS documentation.

What am I missing here??



Thanks,

Matt Heimlich ?
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