linux/crypto/hmac.c

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// SPDX-License-Identifier: GPL-2.0-or-later
/*
* Cryptographic API.
*
* HMAC: Keyed-Hashing for Message Authentication (RFC2104).
*
* Copyright (c) 2002 James Morris <jmorris@intercode.com.au>
* Copyright (c) 2006 Herbert Xu <herbert@gondor.apana.org.au>
*
* The HMAC implementation is derived from USAGI.
* Copyright (c) 2002 Kazunori Miyazawa <miyazawa@linux-ipv6.org> / USAGI
*/
#include <crypto/hmac.h>
#include <crypto/internal/hash.h>
#include <crypto/scatterwalk.h>
#include <linux/err.h>
#include <linux/fips.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/scatterlist.h>
#include <linux/string.h>
struct hmac_ctx {
struct crypto_shash *hash;
/* Contains 'u8 ipad[statesize];', then 'u8 opad[statesize];' */
u8 pads[];
};
static int hmac_setkey(struct crypto_shash *parent,
const u8 *inkey, unsigned int keylen)
{
int bs = crypto_shash_blocksize(parent);
int ds = crypto_shash_digestsize(parent);
int ss = crypto_shash_statesize(parent);
struct hmac_ctx *tctx = crypto_shash_ctx(parent);
struct crypto_shash *hash = tctx->hash;
u8 *ipad = &tctx->pads[0];
u8 *opad = &tctx->pads[ss];
SHASH_DESC_ON_STACK(shash, hash);
unsigned int i;
if (fips_enabled && (keylen < 112 / 8))
return -EINVAL;
shash->tfm = hash;
if (keylen > bs) {
int err;
err = crypto_shash_digest(shash, inkey, keylen, ipad);
if (err)
return err;
keylen = ds;
} else
memcpy(ipad, inkey, keylen);
memset(ipad + keylen, 0, bs - keylen);
memcpy(opad, ipad, bs);
for (i = 0; i < bs; i++) {
ipad[i] ^= HMAC_IPAD_VALUE;
opad[i] ^= HMAC_OPAD_VALUE;
}
return crypto_shash_init(shash) ?:
crypto_shash_update(shash, ipad, bs) ?:
crypto_shash_export(shash, ipad) ?:
crypto_shash_init(shash) ?:
crypto_shash_update(shash, opad, bs) ?:
crypto_shash_export(shash, opad);
}
static int hmac_export(struct shash_desc *pdesc, void *out)
{
struct shash_desc *desc = shash_desc_ctx(pdesc);
return crypto_shash_export(desc, out);
}
static int hmac_import(struct shash_desc *pdesc, const void *in)
{
struct shash_desc *desc = shash_desc_ctx(pdesc);
const struct hmac_ctx *tctx = crypto_shash_ctx(pdesc->tfm);
desc->tfm = tctx->hash;
return crypto_shash_import(desc, in);
}
static int hmac_init(struct shash_desc *pdesc)
{
const struct hmac_ctx *tctx = crypto_shash_ctx(pdesc->tfm);
return hmac_import(pdesc, &tctx->pads[0]);
}
static int hmac_update(struct shash_desc *pdesc,
const u8 *data, unsigned int nbytes)
{
struct shash_desc *desc = shash_desc_ctx(pdesc);
return crypto_shash_update(desc, data, nbytes);
}
static int hmac_final(struct shash_desc *pdesc, u8 *out)
{
struct crypto_shash *parent = pdesc->tfm;
int ds = crypto_shash_digestsize(parent);
int ss = crypto_shash_statesize(parent);
const struct hmac_ctx *tctx = crypto_shash_ctx(parent);
const u8 *opad = &tctx->pads[ss];
struct shash_desc *desc = shash_desc_ctx(pdesc);
return crypto_shash_final(desc, out) ?:
crypto_shash_import(desc, opad) ?:
crypto_shash_finup(desc, out, ds, out);
}
static int hmac_finup(struct shash_desc *pdesc, const u8 *data,
unsigned int nbytes, u8 *out)
{
struct crypto_shash *parent = pdesc->tfm;
int ds = crypto_shash_digestsize(parent);
int ss = crypto_shash_statesize(parent);
const struct hmac_ctx *tctx = crypto_shash_ctx(parent);
const u8 *opad = &tctx->pads[ss];
struct shash_desc *desc = shash_desc_ctx(pdesc);
return crypto_shash_finup(desc, data, nbytes, out) ?:
crypto_shash_import(desc, opad) ?:
crypto_shash_finup(desc, out, ds, out);
}
static int hmac_init_tfm(struct crypto_shash *parent)
{
struct crypto_shash *hash;
struct shash_instance *inst = shash_alg_instance(parent);
struct crypto_shash_spawn *spawn = shash_instance_ctx(inst);
struct hmac_ctx *tctx = crypto_shash_ctx(parent);
hash = crypto_spawn_shash(spawn);
if (IS_ERR(hash))
return PTR_ERR(hash);
parent->descsize = sizeof(struct shash_desc) +
crypto_shash_descsize(hash);
tctx->hash = hash;
return 0;
}
static int hmac_clone_tfm(struct crypto_shash *dst, struct crypto_shash *src)
{
struct hmac_ctx *sctx = crypto_shash_ctx(src);
struct hmac_ctx *dctx = crypto_shash_ctx(dst);
struct crypto_shash *hash;
hash = crypto_clone_shash(sctx->hash);
if (IS_ERR(hash))
return PTR_ERR(hash);
dctx->hash = hash;
return 0;
}
static void hmac_exit_tfm(struct crypto_shash *parent)
{
struct hmac_ctx *tctx = crypto_shash_ctx(parent);
crypto_free_shash(tctx->hash);
}
static int hmac_create(struct crypto_template *tmpl, struct rtattr **tb)
{
struct shash_instance *inst;
struct crypto_shash_spawn *spawn;
struct crypto_alg *alg;
struct shash_alg *salg;
u32 mask;
int err;
int ds;
int ss;
err = crypto_check_attr_type(tb, CRYPTO_ALG_TYPE_SHASH, &mask);
if (err)
return err;
inst = kzalloc(sizeof(*inst) + sizeof(*spawn), GFP_KERNEL);
if (!inst)
return -ENOMEM;
spawn = shash_instance_ctx(inst);
err = crypto_grab_shash(spawn, shash_crypto_instance(inst),
crypto_attr_alg_name(tb[1]), 0, mask);
if (err)
goto err_free_inst;
salg = crypto_spawn_shash_alg(spawn);
crypto: hmac - require that the underlying hash algorithm is unkeyed Because the HMAC template didn't check that its underlying hash algorithm is unkeyed, trying to use "hmac(hmac(sha3-512-generic))" through AF_ALG or through KEYCTL_DH_COMPUTE resulted in the inner HMAC being used without having been keyed, resulting in sha3_update() being called without sha3_init(), causing a stack buffer overflow. This is a very old bug, but it seems to have only started causing real problems when SHA-3 support was added (requires CONFIG_CRYPTO_SHA3) because the innermost hash's state is ->import()ed from a zeroed buffer, and it just so happens that other hash algorithms are fine with that, but SHA-3 is not. However, there could be arch or hardware-dependent hash algorithms also affected; I couldn't test everything. Fix the bug by introducing a function crypto_shash_alg_has_setkey() which tests whether a shash algorithm is keyed. Then update the HMAC template to require that its underlying hash algorithm is unkeyed. Here is a reproducer: #include <linux/if_alg.h> #include <sys/socket.h> int main() { int algfd; struct sockaddr_alg addr = { .salg_type = "hash", .salg_name = "hmac(hmac(sha3-512-generic))", }; char key[4096] = { 0 }; algfd = socket(AF_ALG, SOCK_SEQPACKET, 0); bind(algfd, (const struct sockaddr *)&addr, sizeof(addr)); setsockopt(algfd, SOL_ALG, ALG_SET_KEY, key, sizeof(key)); } Here was the KASAN report from syzbot: BUG: KASAN: stack-out-of-bounds in memcpy include/linux/string.h:341 [inline] BUG: KASAN: stack-out-of-bounds in sha3_update+0xdf/0x2e0 crypto/sha3_generic.c:161 Write of size 4096 at addr ffff8801cca07c40 by task syzkaller076574/3044 CPU: 1 PID: 3044 Comm: syzkaller076574 Not tainted 4.14.0-mm1+ #25 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Call Trace: __dump_stack lib/dump_stack.c:17 [inline] dump_stack+0x194/0x257 lib/dump_stack.c:53 print_address_description+0x73/0x250 mm/kasan/report.c:252 kasan_report_error mm/kasan/report.c:351 [inline] kasan_report+0x25b/0x340 mm/kasan/report.c:409 check_memory_region_inline mm/kasan/kasan.c:260 [inline] check_memory_region+0x137/0x190 mm/kasan/kasan.c:267 memcpy+0x37/0x50 mm/kasan/kasan.c:303 memcpy include/linux/string.h:341 [inline] sha3_update+0xdf/0x2e0 crypto/sha3_generic.c:161 crypto_shash_update+0xcb/0x220 crypto/shash.c:109 shash_finup_unaligned+0x2a/0x60 crypto/shash.c:151 crypto_shash_finup+0xc4/0x120 crypto/shash.c:165 hmac_finup+0x182/0x330 crypto/hmac.c:152 crypto_shash_finup+0xc4/0x120 crypto/shash.c:165 shash_digest_unaligned+0x9e/0xd0 crypto/shash.c:172 crypto_shash_digest+0xc4/0x120 crypto/shash.c:186 hmac_setkey+0x36a/0x690 crypto/hmac.c:66 crypto_shash_setkey+0xad/0x190 crypto/shash.c:64 shash_async_setkey+0x47/0x60 crypto/shash.c:207 crypto_ahash_setkey+0xaf/0x180 crypto/ahash.c:200 hash_setkey+0x40/0x90 crypto/algif_hash.c:446 alg_setkey crypto/af_alg.c:221 [inline] alg_setsockopt+0x2a1/0x350 crypto/af_alg.c:254 SYSC_setsockopt net/socket.c:1851 [inline] SyS_setsockopt+0x189/0x360 net/socket.c:1830 entry_SYSCALL_64_fastpath+0x1f/0x96 Reported-by: syzbot <syzkaller@googlegroups.com> Cc: <stable@vger.kernel.org> Signed-off-by: Eric Biggers <ebiggers@google.com> Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
2017-11-29 02:01:38 +00:00
alg = &salg->base;
/* The underlying hash algorithm must not require a key */
err = -EINVAL;
if (crypto_shash_alg_needs_key(salg))
goto err_free_inst;
crypto: hmac - require that the underlying hash algorithm is unkeyed Because the HMAC template didn't check that its underlying hash algorithm is unkeyed, trying to use "hmac(hmac(sha3-512-generic))" through AF_ALG or through KEYCTL_DH_COMPUTE resulted in the inner HMAC being used without having been keyed, resulting in sha3_update() being called without sha3_init(), causing a stack buffer overflow. This is a very old bug, but it seems to have only started causing real problems when SHA-3 support was added (requires CONFIG_CRYPTO_SHA3) because the innermost hash's state is ->import()ed from a zeroed buffer, and it just so happens that other hash algorithms are fine with that, but SHA-3 is not. However, there could be arch or hardware-dependent hash algorithms also affected; I couldn't test everything. Fix the bug by introducing a function crypto_shash_alg_has_setkey() which tests whether a shash algorithm is keyed. Then update the HMAC template to require that its underlying hash algorithm is unkeyed. Here is a reproducer: #include <linux/if_alg.h> #include <sys/socket.h> int main() { int algfd; struct sockaddr_alg addr = { .salg_type = "hash", .salg_name = "hmac(hmac(sha3-512-generic))", }; char key[4096] = { 0 }; algfd = socket(AF_ALG, SOCK_SEQPACKET, 0); bind(algfd, (const struct sockaddr *)&addr, sizeof(addr)); setsockopt(algfd, SOL_ALG, ALG_SET_KEY, key, sizeof(key)); } Here was the KASAN report from syzbot: BUG: KASAN: stack-out-of-bounds in memcpy include/linux/string.h:341 [inline] BUG: KASAN: stack-out-of-bounds in sha3_update+0xdf/0x2e0 crypto/sha3_generic.c:161 Write of size 4096 at addr ffff8801cca07c40 by task syzkaller076574/3044 CPU: 1 PID: 3044 Comm: syzkaller076574 Not tainted 4.14.0-mm1+ #25 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Call Trace: __dump_stack lib/dump_stack.c:17 [inline] dump_stack+0x194/0x257 lib/dump_stack.c:53 print_address_description+0x73/0x250 mm/kasan/report.c:252 kasan_report_error mm/kasan/report.c:351 [inline] kasan_report+0x25b/0x340 mm/kasan/report.c:409 check_memory_region_inline mm/kasan/kasan.c:260 [inline] check_memory_region+0x137/0x190 mm/kasan/kasan.c:267 memcpy+0x37/0x50 mm/kasan/kasan.c:303 memcpy include/linux/string.h:341 [inline] sha3_update+0xdf/0x2e0 crypto/sha3_generic.c:161 crypto_shash_update+0xcb/0x220 crypto/shash.c:109 shash_finup_unaligned+0x2a/0x60 crypto/shash.c:151 crypto_shash_finup+0xc4/0x120 crypto/shash.c:165 hmac_finup+0x182/0x330 crypto/hmac.c:152 crypto_shash_finup+0xc4/0x120 crypto/shash.c:165 shash_digest_unaligned+0x9e/0xd0 crypto/shash.c:172 crypto_shash_digest+0xc4/0x120 crypto/shash.c:186 hmac_setkey+0x36a/0x690 crypto/hmac.c:66 crypto_shash_setkey+0xad/0x190 crypto/shash.c:64 shash_async_setkey+0x47/0x60 crypto/shash.c:207 crypto_ahash_setkey+0xaf/0x180 crypto/ahash.c:200 hash_setkey+0x40/0x90 crypto/algif_hash.c:446 alg_setkey crypto/af_alg.c:221 [inline] alg_setsockopt+0x2a1/0x350 crypto/af_alg.c:254 SYSC_setsockopt net/socket.c:1851 [inline] SyS_setsockopt+0x189/0x360 net/socket.c:1830 entry_SYSCALL_64_fastpath+0x1f/0x96 Reported-by: syzbot <syzkaller@googlegroups.com> Cc: <stable@vger.kernel.org> Signed-off-by: Eric Biggers <ebiggers@google.com> Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
2017-11-29 02:01:38 +00:00
ds = salg->digestsize;
ss = salg->statesize;
if (ds > alg->cra_blocksize ||
ss < alg->cra_blocksize)
goto err_free_inst;
err = crypto_inst_setname(shash_crypto_instance(inst), tmpl->name, alg);
if (err)
goto err_free_inst;
inst->alg.base.cra_priority = alg->cra_priority;
inst->alg.base.cra_blocksize = alg->cra_blocksize;
inst->alg.base.cra_ctxsize = sizeof(struct hmac_ctx) + (ss * 2);
inst->alg.digestsize = ds;
inst->alg.statesize = ss;
inst->alg.init = hmac_init;
inst->alg.update = hmac_update;
inst->alg.final = hmac_final;
inst->alg.finup = hmac_finup;
inst->alg.export = hmac_export;
inst->alg.import = hmac_import;
inst->alg.setkey = hmac_setkey;
inst->alg.init_tfm = hmac_init_tfm;
inst->alg.clone_tfm = hmac_clone_tfm;
inst->alg.exit_tfm = hmac_exit_tfm;
inst->free = shash_free_singlespawn_instance;
err = shash_register_instance(tmpl, inst);
if (err) {
err_free_inst:
shash_free_singlespawn_instance(inst);
}
return err;
}
static struct crypto_template hmac_tmpl = {
.name = "hmac",
.create = hmac_create,
.module = THIS_MODULE,
};
static int __init hmac_module_init(void)
{
return crypto_register_template(&hmac_tmpl);
}
static void __exit hmac_module_exit(void)
{
crypto_unregister_template(&hmac_tmpl);
}
subsys_initcall(hmac_module_init);
module_exit(hmac_module_exit);
MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("HMAC hash algorithm");
MODULE_ALIAS_CRYPTO("hmac");