/*
* aes_gcm_nss.c
*
* AES Galois Counter Mode
*
* Richard L. Barnes
* Cisco Systems, Inc.
*
*/
/*
*
* Copyright (c) 2013-2017, Cisco Systems, Inc.
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
*
* Redistributions in binary form must reproduce the above
* copyright notice, this list of conditions and the following
* disclaimer in the documentation and/or other materials provided
* with the distribution.
*
* Neither the name of the Cisco Systems, Inc. nor the names of its
* contributors may be used to endorse or promote products derived
* from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
* COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
* INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
* (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
* SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
* STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
* OF THE POSSIBILITY OF SUCH DAMAGE.
*
*/
#ifdef HAVE_CONFIG_H
#include <config.h>
#endif
#include "aes_gcm.h"
#include "alloc.h"
#include "err.h" /* for srtp_debug */
#include "crypto_types.h"
#include "cipher_types.h"
#include "cipher_test_cases.h"
#include <secerr.h>
#include <nspr.h>
srtp_debug_module_t srtp_mod_aes_gcm = {
0, /* debugging is off by default */
"aes gcm nss" /* printable module name */
};
/*
* For now we only support 8 and 16 octet tags. The spec allows for
* optional 12 byte tag, which may be supported in the future.
*/
#define GCM_IV_LEN 12
#define GCM_AUTH_TAG_LEN 16
#define GCM_AUTH_TAG_LEN_8 8
/*
* This function allocates a new instance of this crypto engine.
* The key_len parameter should be one of 28 or 44 for
* AES-128-GCM or AES-256-GCM respectively. Note that the
* key length includes the 14 byte salt value that is used when
* initializing the KDF.
*/
static srtp_err_status_t srtp_aes_gcm_nss_alloc(srtp_cipher_t **c,
int key_len,
int tlen)
{
srtp_aes_gcm_ctx_t *gcm;
NSSInitContext *nss;
debug_print(srtp_mod_aes_gcm, "allocating cipher with key length %d",
key_len);
debug_print(srtp_mod_aes_gcm, "allocating cipher with tag length %d", tlen);
/*
* Verify the key_len is valid for one of: AES-128/256
*/
if (key_len != SRTP_AES_GCM_128_KEY_LEN_WSALT &&
key_len != SRTP_AES_GCM_256_KEY_LEN_WSALT) {
return (srtp_err_status_bad_param);
}
if (tlen != GCM_AUTH_TAG_LEN && tlen != GCM_AUTH_TAG_LEN_8) {
return (srtp_err_status_bad_param);
}
/* Initialize NSS equiv of NSS_NoDB_Init(NULL) */
nss = NSS_InitContext("", "", "", "", NULL,
NSS_INIT_READONLY | NSS_INIT_NOCERTDB |
NSS_INIT_NOMODDB | NSS_INIT_FORCEOPEN |
NSS_INIT_OPTIMIZESPACE);
if (!nss) {
return (srtp_err_status_cipher_fail);
}
/* allocate memory a cipher of type aes_gcm */
*c = (srtp_cipher_t *)srtp_crypto_alloc(sizeof(srtp_cipher_t));
if (*c == NULL) {
NSS_ShutdownContext(nss);
return (srtp_err_status_alloc_fail);
}
gcm = (srtp_aes_gcm_ctx_t *)srtp_crypto_alloc(sizeof(srtp_aes_gcm_ctx_t));
if (gcm == NULL) {
NSS_ShutdownContext(nss);
srtp_crypto_free(*c);
*c = NULL;
return (srtp_err_status_alloc_fail);
}
gcm->nss = nss;
/* set pointers */
(*c)->state = gcm;
/* setup cipher attributes */
switch (key_len) {
case SRTP_AES_GCM_128_KEY_LEN_WSALT:
(*c)->type = &srtp_aes_gcm_128;
(*c)->algorithm = SRTP_AES_GCM_128;
gcm->key_size = SRTP_AES_128_KEY_LEN;
gcm->tag_size = tlen;
gcm->params.ulTagBits = 8 * tlen;
break;
case SRTP_AES_GCM_256_KEY_LEN_WSALT:
(*c)->type = &srtp_aes_gcm_256;
(*c)->algorithm = SRTP_AES_GCM_256;
gcm->key_size = SRTP_AES_256_KEY_LEN;
gcm->tag_size = tlen;
gcm->params.ulTagBits = 8 * tlen;
break;
default:
/* this should never hit, but to be sure... */
return (srtp_err_status_bad_param);
}
/* set key size and tag size*/
(*c)->key_len = key_len;
return (srtp_err_status_ok);
}
/*
* This function deallocates a GCM session
*/
static srtp_err_status_t srtp_aes_gcm_nss_dealloc(srtp_cipher_t *c)
{
srtp_aes_gcm_ctx_t *ctx;
ctx = (srtp_aes_gcm_ctx_t *)c->state;
if (ctx) {
/* release NSS resources */
if (ctx->key) {
PK11_FreeSymKey(ctx->key);
}
if (ctx->nss) {
NSS_ShutdownContext(ctx->nss);
ctx->nss = NULL;
}
/* zeroize the key material */
octet_string_set_to_zero(ctx, sizeof(srtp_aes_gcm_ctx_t));
srtp_crypto_free(ctx);
}
/* free memory */
srtp_crypto_free(c);
return (srtp_err_status_ok);
}
/*
* aes_gcm_nss_context_init(...) initializes the aes_gcm_context
* using the value in key[].
*
* the key is the secret key
*/
static srtp_err_status_t srtp_aes_gcm_nss_context_init(void *cv,
const uint8_t *key)
{
srtp_aes_gcm_ctx_t *c = (srtp_aes_gcm_ctx_t *)cv;
c->dir = srtp_direction_any;
debug_print(srtp_mod_aes_gcm, "key: %s",
srtp_octet_string_hex_string(key, c->key_size));
if (c->key) {
PK11_FreeSymKey(c->key);
c->key = NULL;
}
PK11SlotInfo *slot = PK11_GetBestSlot(CKM_AES_GCM, NULL);
if (!slot) {
return (srtp_err_status_cipher_fail);
}
SECItem key_item = { siBuffer, (unsigned char *)key, c->key_size };
c->key = PK11_ImportSymKey(slot, CKM_AES_GCM, PK11_OriginUnwrap,
CKA_ENCRYPT, &key_item, NULL);
PK11_FreeSlot(slot);
if (!c->key) {
return (srtp_err_status_cipher_fail);
}
return (srtp_err_status_ok);
}
/*
* aes_gcm_nss_set_iv(c, iv) sets the counter value to the exor of iv with
* the offset
*/
static srtp_err_status_t srtp_aes_gcm_nss_set_iv(
void *cv,
uint8_t *iv,
srtp_cipher_direction_t direction)
{
srtp_aes_gcm_ctx_t *c = (srtp_aes_gcm_ctx_t *)cv;
if (direction != srtp_direction_encrypt &&
direction != srtp_direction_decrypt) {
return (srtp_err_status_bad_param);
}
c->dir = direction;
debug_print(srtp_mod_aes_gcm, "setting iv: %s",
srtp_octet_string_hex_string(iv, GCM_IV_LEN));
memcpy(c->iv, iv, GCM_IV_LEN);
return (srtp_err_status_ok);
}
/*
* This function processes the AAD
*
* Parameters:
* c Crypto context
* aad Additional data to process for AEAD cipher suites
* aad_len length of aad buffer
*/
static srtp_err_status_t srtp_aes_gcm_nss_set_aad(void *cv,
const uint8_t *aad,
uint32_t aad_len)
{
srtp_aes_gcm_ctx_t *c = (srtp_aes_gcm_ctx_t *)cv;
debug_print(srtp_mod_aes_gcm, "setting AAD: %s",
srtp_octet_string_hex_string(aad, aad_len));
if (aad_len + c->aad_size > MAX_AD_SIZE) {
return srtp_err_status_bad_param;
}
memcpy(c->aad + c->aad_size, aad, aad_len);
c->aad_size += aad_len;
return (srtp_err_status_ok);
}
static srtp_err_status_t srtp_aes_gcm_nss_do_crypto(void *cv,
int encrypt,
unsigned char *buf,
unsigned int *enc_len)
{
srtp_aes_gcm_ctx_t *c = (srtp_aes_gcm_ctx_t *)cv;
c->params.pIv = c->iv;
c->params.ulIvLen = GCM_IV_LEN;
c->params.pAAD = c->aad;
c->params.ulAADLen = c->aad_size;
// Reset AAD
c->aad_size = 0;
int rv;
SECItem param = { siBuffer, (unsigned char *)&c->params,
sizeof(CK_GCM_PARAMS) };
if (encrypt) {
rv = PK11_Encrypt(c->key, CKM_AES_GCM, ¶m, buf, enc_len,
*enc_len + 16, buf, *enc_len);
} else {
rv = PK11_Decrypt(c->key, CKM_AES_GCM, ¶m, buf, enc_len, *enc_len,
buf, *enc_len);
}
srtp_err_status_t status = (srtp_err_status_ok);
if (rv != SECSuccess) {
status = (srtp_err_status_cipher_fail);
}
return status;
}
/*
* This function encrypts a buffer using AES GCM mode
*
* XXX(rlb@ipv.sx): We're required to break off and cache the tag
* here, because the get_tag() method is separate and the tests expect
* encrypt() not to change the size of the plaintext. It might be
* good to update the calling API so that this is cleaner.
*
* Parameters:
* c Crypto context
* buf data to encrypt
* enc_len length of encrypt buffer
*/
static srtp_err_status_t srtp_aes_gcm_nss_encrypt(void *cv,
unsigned char *buf,
unsigned int *enc_len)
{
srtp_aes_gcm_ctx_t *c = (srtp_aes_gcm_ctx_t *)cv;
// When we get a non-NULL buffer, we know that the caller is
// prepared to also take the tag. When we get a NULL buffer,
// even though there's no data, we need to give NSS a buffer
// where it can write the tag. We can't just use c->tag because
// memcpy has undefined behavior on overlapping ranges.
unsigned char tagbuf[16];
unsigned char *non_null_buf = buf;
if (!non_null_buf && (*enc_len == 0)) {
non_null_buf = tagbuf;
} else if (!non_null_buf) {
return srtp_err_status_bad_param;
}
srtp_err_status_t status =
srtp_aes_gcm_nss_do_crypto(cv, 1, non_null_buf, enc_len);
if (status != srtp_err_status_ok) {
return status;
}
memcpy(c->tag, non_null_buf + (*enc_len - c->tag_size), c->tag_size);
*enc_len -= c->tag_size;
return srtp_err_status_ok;
}
/*
* This function calculates and returns the GCM tag for a given context.
* This should be called after encrypting the data. The *len value
* is increased by the tag size. The caller must ensure that *buf has
* enough room to accept the appended tag.
*
* Parameters:
* c Crypto context
* buf data to encrypt
* len length of encrypt buffer
*/
static srtp_err_status_t srtp_aes_gcm_nss_get_tag(void *cv,
uint8_t *buf,
uint32_t *len)
{
srtp_aes_gcm_ctx_t *c = (srtp_aes_gcm_ctx_t *)cv;
*len = c->tag_size;
memcpy(buf, c->tag, c->tag_size);
return (srtp_err_status_ok);
}
/*
* This function decrypts a buffer using AES GCM mode
*
* Parameters:
* c Crypto context
* buf data to encrypt
* enc_len length of encrypt buffer
*/
static srtp_err_status_t srtp_aes_gcm_nss_decrypt(void *cv,
unsigned char *buf,
unsigned int *enc_len)
{
srtp_err_status_t status = srtp_aes_gcm_nss_do_crypto(cv, 0, buf, enc_len);
if (status != srtp_err_status_ok) {
int err = PR_GetError();
if (err == SEC_ERROR_BAD_DATA) {
status = srtp_err_status_auth_fail;
}
}
return status;
}
/*
* Name of this crypto engine
*/
static const char srtp_aes_gcm_128_nss_description[] = "AES-128 GCM using NSS";
static const char srtp_aes_gcm_256_nss_description[] = "AES-256 GCM using NSS";
/*
* This is the vector function table for this crypto engine.
*/
/* clang-format off */
const srtp_cipher_type_t srtp_aes_gcm_128 = {
srtp_aes_gcm_nss_alloc,
srtp_aes_gcm_nss_dealloc,
srtp_aes_gcm_nss_context_init,
srtp_aes_gcm_nss_set_aad,
srtp_aes_gcm_nss_encrypt,
srtp_aes_gcm_nss_decrypt,
srtp_aes_gcm_nss_set_iv,
srtp_aes_gcm_nss_get_tag,
srtp_aes_gcm_128_nss_description,
&srtp_aes_gcm_128_test_case_0,
SRTP_AES_GCM_128
};
/* clang-format on */
/*
* This is the vector function table for this crypto engine.
*/
/* clang-format off */
const srtp_cipher_type_t srtp_aes_gcm_256 = {
srtp_aes_gcm_nss_alloc,
srtp_aes_gcm_nss_dealloc,
srtp_aes_gcm_nss_context_init,
srtp_aes_gcm_nss_set_aad,
srtp_aes_gcm_nss_encrypt,
srtp_aes_gcm_nss_decrypt,
srtp_aes_gcm_nss_set_iv,
srtp_aes_gcm_nss_get_tag,
srtp_aes_gcm_256_nss_description,
&srtp_aes_gcm_256_test_case_0,
SRTP_AES_GCM_256
};
/* clang-format on */