[libvirt] [PATCH v5 2/6] util: Introduce encryption APIs
Peter Krempa
pkrempa at redhat.com
Fri May 20 12:56:25 UTC 2016
On Thu, May 19, 2016 at 16:29:01 -0400, John Ferlan wrote:
> Introduce virCryptoHaveCipher and virCryptoEncryptData to handle
> performing encryption.
>
> virCryptoHaveCipher:
> Boolean function to determine whether the requested cipher algorithm
> is available. It's expected this API will be called prior to
> virCryptoEncryptdata. It will return true/false.
>
> virCryptoEncryptData:
> Based on the requested cipher type, call the specific encryption
> API to encrypt the data.
>
> Currently the only algorithm support is the AES 256 CBC encryption.
>
> Adjust tests for the API's
>
> Signed-off-by: John Ferlan <jferlan at redhat.com>
> ---
> configure.ac | 1 +
> src/libvirt_private.syms | 2 +
> src/util/vircrypto.c | 192 ++++++++++++++++++++++++++++++++++++++++++++++-
> src/util/vircrypto.h | 20 ++++-
> tests/vircryptotest.c | 100 +++++++++++++++++++++++-
> 5 files changed, 312 insertions(+), 3 deletions(-)
[...]
> diff --git a/src/util/vircrypto.c b/src/util/vircrypto.c
> index 39a479a..b8f5554 100644
> --- a/src/util/vircrypto.c
> +++ b/src/util/vircrypto.c
[...]
> @@ -76,3 +85,184 @@ virCryptoHashString(virCryptoHash hash,
>
> return 0;
> }
> +
> +
> +/* virCryptoHaveCipher:
> + * @algorithm: Specific cipher algorithm desired
> + *
> + * Expected to be called prior to virCryptoEncryptData in order
> + * to determine whether the requested encryption option is available,
> + * so that "other" alternatives can be taken if the algorithm is
> + * not available.
> + *
> + * Returns true if we can support the encryption.
> + */
> +bool
> +virCryptoHaveCipher(virCryptoCipher algorithm)
> +{
> + switch (algorithm) {
> +
> + case VIR_CRYPTO_CIPHER_AES256CBC:
> +#ifdef HAVE_GNUTLS_CIPHER_ENCRYPT
> + return true;
> +#else
> + return false;
> +#endif
> +
> + case VIR_CRYPTO_CIPHER_NONE:
> + case VIR_CRYPTO_CIPHER_LAST:
> + break;
> + };
> +
> + return false;
> +}
> +
> +
> +#ifdef HAVE_GNUTLS_CIPHER_ENCRYPT
> +/* virCryptoEncryptDataAESgntuls:
> + *
> + * Performs the AES gnutls encryption
> + *
> + * Same input as virCryptoEncryptData, except the algoritm is replaced
> + * by the specific gnutls algorithm.
> + *
> + * Encrypts the @data buffer using the @enckey and if available the @iv
> + *
> + * Returns 0 on success with the ciphertext being filled. It is the
> + * caller's responsibility to clear and free it. Returns -1 on failure
> + * w/ error set.
> + */
> +static int
> +virCryptoEncryptDataAESgnutls(gnutls_cipher_algorithm_t gnutls_enc_alg,
> + uint8_t *enckey,
> + size_t enckeylen,
> + uint8_t *iv,
> + size_t ivlen,
> + uint8_t *data,
> + size_t datalen,
> + uint8_t **ciphertextret,
> + size_t *ciphertextlenret)
> +{
> + int rc;
> + size_t i;
> + gnutls_cipher_hd_t handle = NULL;
> + gnutls_datum_t enc_key;
> + gnutls_datum_t iv_buf;
> + uint8_t *ciphertext;
> + size_t ciphertextlen;
> +
> + /* Allocate a padded buffer, copy in the data */
> + ciphertextlen = VIR_ROUND_UP(datalen, 16);
> + if (VIR_ALLOC_N(ciphertext, ciphertextlen) < 0)
> + return -1;
> + memcpy(ciphertext, data, datalen);
> +
> + /* Fill in the padding of the buffer with the size of the padding
> + * which is required for decryption. */
> + for (i = datalen; i < ciphertextlen; i++)
> + ciphertext[i] = ciphertextlen - datalen;
> +
> + /* Initialize the gnutls cipher */
> + enc_key.size = enckeylen;
> + enc_key.data = enckey;
> + if (iv) {
> + iv_buf.size = ivlen;
> + iv_buf.data = iv;
> + }
> + if ((rc = gnutls_cipher_init(&handle, gnutls_enc_alg,
> + &enc_key, &iv_buf)) < 0) {
> + virReportError(VIR_ERR_INTERNAL_ERROR,
> + _("failed to initialize cipher: '%s'"),
> + gnutls_strerror(rc));
> + goto error;
> + }
> +
> + /* Encrypt the data and free the memory for cipher operations */
> + rc = gnutls_cipher_encrypt(handle, ciphertext, ciphertextlen);
> + gnutls_cipher_deinit(handle);
> + if (rc < 0) {
> + virReportError(VIR_ERR_INTERNAL_ERROR,
> + _("failed to encrypt the data: '%s'"),
> + gnutls_strerror(rc));
> + goto error;
> + }
> +
> + *ciphertextret = ciphertext;
> + *ciphertextlenret = ciphertextlen;
> + return 0;
> +
> + error:
> + VIR_DISPOSE_N(ciphertext, ciphertextlen);
> + return -1;
In both cases you should clear the stack'd copy of the encryption key.
> +}
> +#endif
> +
> +
> +/* virCryptoEncryptData:
> + * @algorithm: algoritm desired for encryption
> + * @enckey: encryption key
> + * @enckeylen: encription key length
> + * @iv: initialization vector
> + * @ivlen: length of initialization vector
> + * @data: data to encrypt
> + * @datalen: length of data
> + * @ciphertext: stream of bytes allocated to store ciphertext
> + * @ciphertextlen: size of the stream of bytes
> + *
> + * If available, attempt and return the requested encryption type
> + * using the parameters passed.
> + *
> + * Returns 0 on success, -1 on failure with error set
> + */
> +int
> +virCryptoEncryptData(virCryptoCipher algorithm,
> + uint8_t *enckey,
> + size_t enckeylen,
> + uint8_t *iv,
> + size_t ivlen,
> + uint8_t *data,
> + size_t datalen,
> + uint8_t **ciphertext,
> + size_t *ciphertextlen)
> +{
> + switch (algorithm) {
> + case VIR_CRYPTO_CIPHER_AES256CBC:
> + if (enckeylen != 32) {
> + virReportError(VIR_ERR_INVALID_ARG,
> + _("AES256CBC encryption invalid keylen=%zu"),
> + enckeylen);
> + return -1;
> + }
> +
> + if (ivlen != 16) {
> + virReportError(VIR_ERR_INVALID_ARG,
> + _("AES256CBC initialization vector invalid len=%zu"),
> + ivlen);
> + return -1;
> + }
> +
> +#ifdef HAVE_GNUTLS_CIPHER_ENCRYPT
> + /*
> + * Encrypt the data buffer using an encryption key and
> + * initialization vector via the gnutls_cipher_encrypt API
> + * for GNUTLS_CIPHER_AES_256_CBC.
> + */
> + return virCryptoEncryptDataAESgnutls(GNUTLS_CIPHER_AES_256_CBC,
> + enckey, enckeylen, iv, ivlen,
> + data, datalen,
> + ciphertext, ciphertextlen);
> +#else
> + virReportError(VIR_ERR_OPERATION_UNSUPPORTED, "%s",
> + _("no encryption algorithm exists"));
That is quite a strong message. I'd say that the chosen algorithm is not
supported.
> + return -1;
> +#endif
> +
> + case VIR_CRYPTO_CIPHER_NONE:
> + case VIR_CRYPTO_CIPHER_LAST:
> + break;
> + }
> +
> + virReportError(VIR_ERR_INVALID_ARG,
> + _("algorithm=%d is not supported"), algorithm);
e.g. as you do here.
[...]
> --- a/src/util/vircrypto.h
> +++ b/src/util/vircrypto.h
[...]
> @@ -37,4 +45,14 @@ virCryptoHashString(virCryptoHash hash,
> ATTRIBUTE_NONNULL(2) ATTRIBUTE_NONNULL(3)
> ATTRIBUTE_RETURN_CHECK;
>
> +bool virCryptoHaveCipher(virCryptoCipher algorithm);
> +
> +int virCryptoEncryptData(virCryptoCipher algorithm,
> + uint8_t *enckey, size_t enckeylen,
> + uint8_t *iv, size_t ivlen,
> + uint8_t *data, size_t datalen,
> + uint8_t **ciphertext, size_t *ciphertextlen)
> + ATTRIBUTE_NONNULL(2) ATTRIBUTE_NONNULL(6)
> + ATTRIBUTE_NONNULL(8) ATTRIBUTE_RETURN_CHECK;
ciphertext and ciphertextlen must be nonnull too.
> +
> #endif /* __VIR_CRYPTO_H__ */
> diff --git a/tests/vircryptotest.c b/tests/vircryptotest.c
> index bfc47db..1d719d9 100644
> --- a/tests/vircryptotest.c
> +++ b/tests/vircryptotest.c
[...]
> @@ -56,10 +58,82 @@ testCryptoHash(const void *opaque)
> }
>
>
> +struct testCryptoEncryptData {
> + virCryptoCipher algorithm;
> + uint8_t *input;
> + size_t inputlen;
> + uint8_t *ciphertext;
> + size_t ciphertextlen;
> +};
> +
> +static int
> +testCryptoEncrypt(const void *opaque)
> +{
> + const struct testCryptoEncryptData *data = opaque;
> + size_t i;
> + uint8_t *enckey = NULL;
> + size_t enckeylen = 32;
> + uint8_t *iv = NULL;
> + size_t ivlen = 16;
> + uint8_t *ciphertext = NULL;
> + size_t ciphertextlen = 0;
> + int ret = -1;
> +
> + if (!virCryptoHaveCipher(data->algorithm)) {
> + fprintf(stderr, "Invalid cipher algorithm=%d\n", data->algorithm);
> + return -1;
> + }
> +
> + if (VIR_ALLOC_N(enckey, enckeylen) < 0 ||
> + VIR_ALLOC_N(iv, ivlen) < 0)
> + goto cleanup;
> +
> + if (virRandomBytes(enckey, enckeylen) < 0 ||
> + virRandomBytes(iv, ivlen) < 0)
> + goto cleanup;
> +
> + if (virCryptoEncryptData(data->algorithm, enckey, enckeylen, iv, ivlen,
> + data->input, data->inputlen,
> + &ciphertext, &ciphertextlen) < 0)
> + goto cleanup;
> +
> + if (data->ciphertextlen != ciphertextlen) {
> + fprintf(stderr, "Expected ciphertextlen(%zu) doesn't match (%zu)\n",
> + data->ciphertextlen, ciphertextlen);
> + goto cleanup;
> + }
> +
> + if (memcmp(data->ciphertext, ciphertext, ciphertextlen)) {
> + fprintf(stderr, "Expected ciphertext doesn't match\n");
> + for (i = 0; i < ciphertextlen; i++) {
> + if (data->ciphertext[i] != ciphertext[i]) {
> + fprintf(stderr, "expected[%zu]=%x ciphertext[%zu]=%x\n",
> + i, data->ciphertext[i],
> + i, ciphertext[i]);
Last time I was pointing out that it doesn't make much sense to output
the difference whether encoded to base64 or not.
[...]
> @@ -84,7 +158,31 @@ mymain(void)
> VIR_CRYPTO_HASH(VIR_CRYPTO_HASH_MD5, "The quick brown fox", "a2004f37730b9445670a738fa0fc9ee5");
> VIR_CRYPTO_HASH(VIR_CRYPTO_HASH_SHA256, "The quick brown fox", "5cac4f980fedc3d3f1f99b4be3472c9b30d56523e632d151237ec9309048bda9");
>
> +#undef VIR_CRYPTO_HASH
> +
> +#define VIR_CRYPTO_ENCRYPT(a, n, i, il, c, cl) \
> + do { \
> + struct testCryptoEncryptData data = { \
> + .algorithm = a, \
> + .input = i, \
> + .inputlen = il, \
> + .ciphertext = c, \
> + .ciphertextlen = cl, \
> + }; \
> + if (virtTestRun("Encrypt " n, testCryptoEncrypt, &data) < 0) \
> + ret = -1; \
> + } while (0)
> +
> + memset(&secretdata, 0, 8);
> + memcpy(&secretdata, "letmein", 7);
> +
> + VIR_CRYPTO_ENCRYPT(VIR_CRYPTO_CIPHER_AES256CBC, "aes265cbc",
> + secretdata, 7, expected_ciphertext, 16);
> +
This test will fail on builds without gnutls.
ACK with the nits fixed.
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