[libvirt] [PATCH 3/3] util: Introduce encryption APIs
Peter Krempa
pkrempa at redhat.com
Thu May 19 09:00:06 UTC 2016
On Wed, May 18, 2016 at 19:52:32 -0400, John Ferlan wrote:
> Introduce virCryptoHaveEncrypt and virCryptoEncryptSecret to handle
> performing encryption.
>
> virCryptoHaveEncrypt:
> Boolean function to determine whether the requested encryption
> API is available. It's expected this API will be called prior to
> virCryptoEncryptSecret. It will return true/false.
>
> virCryptoEncryptSecret:
> Based on the requested encryption 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 | 189 ++++++++++++++++++++++++++++++++++++++++++++++-
> src/util/vircrypto.h | 20 ++++-
> tests/vircryptotest.c | 86 +++++++++++++++++++++
> 5 files changed, 296 insertions(+), 2 deletions(-)
>
[...]
> diff --git a/src/util/vircrypto.c b/src/util/vircrypto.c
> index 39a479a..05bd167 100644
> --- a/src/util/vircrypto.c
> +++ b/src/util/vircrypto.c
[...]
> @@ -76,3 +85,181 @@ virCryptoHashString(virCryptoHash hash,
>
> return 0;
> }
> +
> +
> +/* virCryptoHaveEncrypt:
> + * @algorithm: Specific encryption 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
> +virCryptoHaveEncrypt(virCryptoEncrypt algorithm)
Cipher rather than Encrypt
> +{
> + switch (algorithm) {
> +
> + case VIR_CRYPTO_ENCRYPT_AES256CBC:
> +#ifdef HAVE_GNUTLS_CIPHER_ENCRYPT
> + return true;
> +#else
> + return false;
> +#endif
> +
> + case VIR_CRYPTO_ENCRYPT_NONE:
> + case VIR_CRYPTO_ENCRYPT_LAST:
> + break;
> + };
> +
> + return false;
> +}
> +
> +
> +/* virCryptoEncryptDataAESgntuls:
> + *
> + * Performs the AES gnutls encryption - parameters essentially the
> + * same as virCryptoEncryptSecret, except the libvirt algorithm is
> + * converted to the gnutls_cipher_algorithm_t
> + *
> + * Same input as virCryptoEncryptData, but ensures encryption key and
> + * initialization vector lengths are correct.
> + *
> + * The data buffer will be cleared as soon as it has been prepared for
> + * encryption.
> + *
> + * 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_key;
As pointed out last time, even here it won't compile with gnutls.
> + uint8_t *ciphertext;
> + size_t ciphertextlen;
> +
> + /* Allocate a padded buffer, copy in the data, padding the buffer with
> + * the size of the padding size which is required for decryption, then
> + * clear the data buffer when we're done. */
> + ciphertextlen = VIR_ROUND_UP(datalen, 16);
> + if (VIR_ALLOC_N(ciphertext, ciphertextlen) < 0)
> + return -1;
> + memcpy(ciphertext, data, datalen);
> + for (i = datalen; i < ciphertextlen; i++)
And this still isn't documented.
> + ciphertext[i] = ciphertextlen - datalen;
> + memset(data, 0, datalen);
The caller should ensure sanitization. Especially sinc its _NOT_ done if
the above allocation fails. In such case the caller still needs to do
it.
> +
> + /* Initialize the gnutls cipher */
> + enc_key.size = enckeylen;
> + enc_key.data = enckey;
> + if (iv) {
> + iv_key.size = ivlen;
> + iv_key.data = iv;
> + }
> + if ((rc = gnutls_cipher_init(&handle, gnutls_enc_alg,
> + &enc_key, &iv_key)) < 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;
> +}
> +
> +
> +/* 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(virCryptoEncrypt 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_ENCRYPT_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,
> + _("AES246CBC initialization vector invalid len=%zu"),
AES256CBC
> + ivlen);
> + return -1;
> + }
> +
> + /*
> + * 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);
> +
> + case VIR_CRYPTO_ENCRYPT_NONE:
> + case VIR_CRYPTO_ENCRYPT_LAST:
> + break;
> + }
> +
> + virReportError(VIR_ERR_INVALID_ARG,
> + _("algorithm=%d is not supported"), algorithm);
> + return -1;
> +}
> diff --git a/src/util/vircrypto.h b/src/util/vircrypto.h
> index f67d49d..7d0829e 100644
> --- a/src/util/vircrypto.h
> +++ b/src/util/vircrypto.h
[...]
> @@ -30,6 +30,14 @@ typedef enum {
> VIR_CRYPTO_HASH_LAST
> } virCryptoHash;
>
> +
> +typedef enum {
> + VIR_CRYPTO_ENCRYPT_NONE = 0,
> + VIR_CRYPTO_ENCRYPT_AES256CBC,
> +
> + VIR_CRYPTO_ENCRYPT_LAST
> +} virCryptoEncrypt;
This can be used for decryption too. Thus virCryptoCipher.
> +
> int
> virCryptoHashString(virCryptoHash hash,
> const char *input,
[...]
> diff --git a/tests/vircryptotest.c b/tests/vircryptotest.c
> index bfc47db..038eb7a 100644
> --- a/tests/vircryptotest.c
> +++ b/tests/vircryptotest.c
[...]
> @@ -56,10 +57,74 @@ testCryptoHash(const void *opaque)
> }
>
>
> +struct testCryptoEncryptData {
> + virCryptoEncrypt algorithm;
> + uint8_t *input;
> + size_t inputlen;
> + const char *base64;
> +};
> +
> +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;
> + char *actual = NULL;
> + int ret = -1;
> +
> + if (!virCryptoHaveEncrypt(data->algorithm)) {
> + fprintf(stderr, "Invalid encryption algorithm=%d\n", data->algorithm);
> + return -1;
> + }
> +
> + if (VIR_ALLOC_N(enckey, enckeylen) < 0 ||
> + VIR_ALLOC_N(iv, ivlen) < 0)
> + goto cleanup;
> +
> + /* To be replaced by mock if I can get it to work */
Why not keep it this way? This is testing the encryption not the key
generation.
> + for (i = 0; i < enckeylen; i++)
> + enckey[i] = i;
> + for (i = 0; i < ivlen; i++)
> + iv[i] = i;
> +
> + if (virCryptoEncryptData(data->algorithm, enckey, enckeylen, iv, ivlen,
> + data->input, data->inputlen,
> + &ciphertext, &ciphertextlen) < 0)
> + goto cleanup;
> +
> + /* Comparing the encoded ciphertext would be what is desired in
> + * the long run and easier to read/format the expected ciphertext */
Read? nobody is going to read it if it doesn't match.
> + if (!(actual = virStringEncodeBase64(ciphertext, ciphertextlen)))
> + goto cleanup;
> +
> + if (STRNEQ(data->base64, actual)) {
> + fprintf(stderr, "Expected encoded encryption '%s' but got '%s'\n",
> + data->base64, NULLSTR(actual));
and it definitely doesn't make sense to print it. It's just binary
garbage.
> + goto cleanup;
> + }
> +
> + ret = 0;
> + cleanup:
> + VIR_DISPOSE_N(enckey, enckeylen);
> + VIR_DISPOSE_N(iv, ivlen);
> + VIR_DISPOSE_N(ciphertext, ciphertextlen);
This isn't really necessary for demo keys. You can also lose the lenght
variables.
> + VIR_FREE(actual);
> +
I won't review further versions until you fix the issue with compiling
without gnutls. I've pointed it out far too many times.
Peter
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