Add the AES-GCM AEAD mode to the gnutls backend so it is available when QEMU is built with gnutls (neither gcrypt nor nettle). GCM uses the incremental gnutls_cipher_* API with the GNUTLS_CIPHER_AES_*_GCM algorithms: gnutls_cipher_set_iv() sets the nonce, gnutls_cipher_add_auth() feeds the associated data, gnutls_cipher_encrypt2()/decrypt2() process the message, and gnutls_cipher_tag() reads back the authentication tag.
Signed-off-by: Jamin Lin <[email protected]> --- crypto/cipher-gnutls.c.inc | 154 +++++++++++++++++++++++++++++++++++++ 1 file changed, 154 insertions(+) diff --git a/crypto/cipher-gnutls.c.inc b/crypto/cipher-gnutls.c.inc index a8263fff6d..963b328fa1 100644 --- a/crypto/cipher-gnutls.c.inc +++ b/crypto/cipher-gnutls.c.inc @@ -48,6 +48,15 @@ bool qcrypto_cipher_supports(QCryptoCipherAlgo alg, default: return false; } + case QCRYPTO_CIPHER_MODE_GCM: + switch (alg) { + case QCRYPTO_CIPHER_ALGO_AES_128: + case QCRYPTO_CIPHER_ALGO_AES_192: + case QCRYPTO_CIPHER_ALGO_AES_256: + return true; + default: + return false; + } default: return false; } @@ -223,6 +232,147 @@ static struct QCryptoCipherDriver gnutls_driver = { .cipher_free = qcrypto_gnutls_cipher_free, }; +/* + * GCM is an AEAD stream mode: the nonce need not match the block size, the + * message length need not be a multiple of the block size, associated data is + * fed with gnutls_cipher_add_auth() and the authentication tag is read back + * with gnutls_cipher_tag(). + */ +static int +qcrypto_gnutls_cipher_encrypt_gcm(QCryptoCipher *cipher, + const void *in, void *out, + size_t len, Error **errp) +{ + QCryptoCipherGnutls *ctx = container_of(cipher, QCryptoCipherGnutls, base); + int err; + + err = gnutls_cipher_encrypt2(ctx->handle, in, len, out, len); + if (err != 0) { + error_setg(errp, "Cannot encrypt data: %s", gnutls_strerror(err)); + return -1; + } + + return 0; +} + +static int +qcrypto_gnutls_cipher_decrypt_gcm(QCryptoCipher *cipher, + const void *in, void *out, + size_t len, Error **errp) +{ + QCryptoCipherGnutls *ctx = container_of(cipher, QCryptoCipherGnutls, base); + int err; + + err = gnutls_cipher_decrypt2(ctx->handle, in, len, out, len); + if (err != 0) { + error_setg(errp, "Cannot decrypt data: %s", gnutls_strerror(err)); + return -1; + } + + return 0; +} + +static int +qcrypto_gnutls_cipher_setiv_gcm(QCryptoCipher *cipher, + const uint8_t *iv, size_t niv, + Error **errp) +{ + QCryptoCipherGnutls *ctx = container_of(cipher, QCryptoCipherGnutls, base); + + gnutls_cipher_set_iv(ctx->handle, (void *)iv, niv); + + return 0; +} + +static int +qcrypto_gnutls_cipher_setaad_gcm(QCryptoCipher *cipher, + const uint8_t *aad, size_t len, + Error **errp) +{ + QCryptoCipherGnutls *ctx = container_of(cipher, QCryptoCipherGnutls, base); + int err; + + err = gnutls_cipher_add_auth(ctx->handle, aad, len); + if (err != 0) { + error_setg(errp, "Cannot add associated data: %s", + gnutls_strerror(err)); + return -1; + } + + return 0; +} + +static int +qcrypto_gnutls_cipher_gettag_gcm(QCryptoCipher *cipher, + uint8_t *tag, size_t len, + Error **errp) +{ + QCryptoCipherGnutls *ctx = container_of(cipher, QCryptoCipherGnutls, base); + int err; + + err = gnutls_cipher_tag(ctx->handle, tag, len); + if (err != 0) { + error_setg(errp, "Cannot get authentication tag: %s", + gnutls_strerror(err)); + return -1; + } + + return 0; +} + +static struct QCryptoCipherDriver gnutls_gcm_driver = { + .cipher_encrypt = qcrypto_gnutls_cipher_encrypt_gcm, + .cipher_decrypt = qcrypto_gnutls_cipher_decrypt_gcm, + .cipher_setiv = qcrypto_gnutls_cipher_setiv_gcm, + .cipher_setaad = qcrypto_gnutls_cipher_setaad_gcm, + .cipher_gettag = qcrypto_gnutls_cipher_gettag_gcm, + .cipher_free = qcrypto_gnutls_cipher_free, +}; + +static QCryptoCipher * +qcrypto_gnutls_aes_gcm_ctx_new(QCryptoCipherAlgo alg, const uint8_t *key, + size_t nkey, Error **errp) +{ + gnutls_datum_t gkey = { (unsigned char *)key, nkey }; + gnutls_cipher_algorithm_t galg = GNUTLS_CIPHER_UNKNOWN; + QCryptoCipherGnutls *ctx; + int err; + + switch (alg) { + case QCRYPTO_CIPHER_ALGO_AES_128: + galg = GNUTLS_CIPHER_AES_128_GCM; + break; + case QCRYPTO_CIPHER_ALGO_AES_192: + galg = GNUTLS_CIPHER_AES_192_GCM; + break; + case QCRYPTO_CIPHER_ALGO_AES_256: + galg = GNUTLS_CIPHER_AES_256_GCM; + break; + default: + error_setg(errp, "Unsupported cipher algorithm %s with GCM mode", + QCryptoCipherAlgo_str(alg)); + return NULL; + } + + if (!qcrypto_cipher_validate_key_length(alg, QCRYPTO_CIPHER_MODE_GCM, + nkey, errp)) { + return NULL; + } + + ctx = g_new0(QCryptoCipherGnutls, 1); + ctx->base.driver = &gnutls_gcm_driver; + ctx->blocksize = 16; + + err = gnutls_cipher_init(&ctx->handle, galg, &gkey, NULL); + if (err != 0) { + error_setg(errp, "Cannot initialize cipher: %s", gnutls_strerror(err)); + g_free(ctx); + return NULL; + } + + return &ctx->base; +} + static QCryptoCipher *qcrypto_cipher_ctx_new(QCryptoCipherAlgo alg, QCryptoCipherMode mode, const uint8_t *key, @@ -234,6 +384,10 @@ static QCryptoCipher *qcrypto_cipher_ctx_new(QCryptoCipherAlgo alg, gnutls_cipher_algorithm_t galg = GNUTLS_CIPHER_UNKNOWN; int err; + if (mode == QCRYPTO_CIPHER_MODE_GCM) { + return qcrypto_gnutls_aes_gcm_ctx_new(alg, key, nkey, errp); + } + switch (mode) { case QCRYPTO_CIPHER_MODE_XTS: switch (alg) { -- 2.43.0
