linux/crypto/shash.c
Eric Biggers 9fa68f6200 crypto: hash - prevent using keyed hashes without setting key
Currently, almost none of the keyed hash algorithms check whether a key
has been set before proceeding.  Some algorithms are okay with this and
will effectively just use a key of all 0's or some other bogus default.
However, others will severely break, as demonstrated using
"hmac(sha3-512-generic)", the unkeyed use of which causes a kernel crash
via a (potentially exploitable) stack buffer overflow.

A while ago, this problem was solved for AF_ALG by pairing each hash
transform with a 'has_key' bool.  However, there are still other places
in the kernel where userspace can specify an arbitrary hash algorithm by
name, and the kernel uses it as unkeyed hash without checking whether it
is really unkeyed.  Examples of this include:

    - KEYCTL_DH_COMPUTE, via the KDF extension
    - dm-verity
    - dm-crypt, via the ESSIV support
    - dm-integrity, via the "internal hash" mode with no key given
    - drbd (Distributed Replicated Block Device)

This bug is especially bad for KEYCTL_DH_COMPUTE as that requires no
privileges to call.

Fix the bug for all users by adding a flag CRYPTO_TFM_NEED_KEY to the
->crt_flags of each hash transform that indicates whether the transform
still needs to be keyed or not.  Then, make the hash init, import, and
digest functions return -ENOKEY if the key is still needed.

The new flag also replaces the 'has_key' bool which algif_hash was
previously using, thereby simplifying the algif_hash implementation.

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>
2018-01-12 23:03:37 +11:00

581 lines
15 KiB
C

/*
* Synchronous Cryptographic Hash operations.
*
* Copyright (c) 2008 Herbert Xu <herbert@gondor.apana.org.au>
*
* This program is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License as published by the Free
* Software Foundation; either version 2 of the License, or (at your option)
* any later version.
*
*/
#include <crypto/scatterwalk.h>
#include <crypto/internal/hash.h>
#include <linux/err.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/slab.h>
#include <linux/seq_file.h>
#include <linux/cryptouser.h>
#include <net/netlink.h>
#include <linux/compiler.h>
#include "internal.h"
static const struct crypto_type crypto_shash_type;
int shash_no_setkey(struct crypto_shash *tfm, const u8 *key,
unsigned int keylen)
{
return -ENOSYS;
}
EXPORT_SYMBOL_GPL(shash_no_setkey);
static int shash_setkey_unaligned(struct crypto_shash *tfm, const u8 *key,
unsigned int keylen)
{
struct shash_alg *shash = crypto_shash_alg(tfm);
unsigned long alignmask = crypto_shash_alignmask(tfm);
unsigned long absize;
u8 *buffer, *alignbuffer;
int err;
absize = keylen + (alignmask & ~(crypto_tfm_ctx_alignment() - 1));
buffer = kmalloc(absize, GFP_ATOMIC);
if (!buffer)
return -ENOMEM;
alignbuffer = (u8 *)ALIGN((unsigned long)buffer, alignmask + 1);
memcpy(alignbuffer, key, keylen);
err = shash->setkey(tfm, alignbuffer, keylen);
kzfree(buffer);
return err;
}
int crypto_shash_setkey(struct crypto_shash *tfm, const u8 *key,
unsigned int keylen)
{
struct shash_alg *shash = crypto_shash_alg(tfm);
unsigned long alignmask = crypto_shash_alignmask(tfm);
int err;
if ((unsigned long)key & alignmask)
err = shash_setkey_unaligned(tfm, key, keylen);
else
err = shash->setkey(tfm, key, keylen);
if (err)
return err;
crypto_shash_clear_flags(tfm, CRYPTO_TFM_NEED_KEY);
return 0;
}
EXPORT_SYMBOL_GPL(crypto_shash_setkey);
static inline unsigned int shash_align_buffer_size(unsigned len,
unsigned long mask)
{
typedef u8 __aligned_largest u8_aligned;
return len + (mask & ~(__alignof__(u8_aligned) - 1));
}
static int shash_update_unaligned(struct shash_desc *desc, const u8 *data,
unsigned int len)
{
struct crypto_shash *tfm = desc->tfm;
struct shash_alg *shash = crypto_shash_alg(tfm);
unsigned long alignmask = crypto_shash_alignmask(tfm);
unsigned int unaligned_len = alignmask + 1 -
((unsigned long)data & alignmask);
u8 ubuf[shash_align_buffer_size(unaligned_len, alignmask)]
__aligned_largest;
u8 *buf = PTR_ALIGN(&ubuf[0], alignmask + 1);
int err;
if (unaligned_len > len)
unaligned_len = len;
memcpy(buf, data, unaligned_len);
err = shash->update(desc, buf, unaligned_len);
memset(buf, 0, unaligned_len);
return err ?:
shash->update(desc, data + unaligned_len, len - unaligned_len);
}
int crypto_shash_update(struct shash_desc *desc, const u8 *data,
unsigned int len)
{
struct crypto_shash *tfm = desc->tfm;
struct shash_alg *shash = crypto_shash_alg(tfm);
unsigned long alignmask = crypto_shash_alignmask(tfm);
if ((unsigned long)data & alignmask)
return shash_update_unaligned(desc, data, len);
return shash->update(desc, data, len);
}
EXPORT_SYMBOL_GPL(crypto_shash_update);
static int shash_final_unaligned(struct shash_desc *desc, u8 *out)
{
struct crypto_shash *tfm = desc->tfm;
unsigned long alignmask = crypto_shash_alignmask(tfm);
struct shash_alg *shash = crypto_shash_alg(tfm);
unsigned int ds = crypto_shash_digestsize(tfm);
u8 ubuf[shash_align_buffer_size(ds, alignmask)]
__aligned_largest;
u8 *buf = PTR_ALIGN(&ubuf[0], alignmask + 1);
int err;
err = shash->final(desc, buf);
if (err)
goto out;
memcpy(out, buf, ds);
out:
memset(buf, 0, ds);
return err;
}
int crypto_shash_final(struct shash_desc *desc, u8 *out)
{
struct crypto_shash *tfm = desc->tfm;
struct shash_alg *shash = crypto_shash_alg(tfm);
unsigned long alignmask = crypto_shash_alignmask(tfm);
if ((unsigned long)out & alignmask)
return shash_final_unaligned(desc, out);
return shash->final(desc, out);
}
EXPORT_SYMBOL_GPL(crypto_shash_final);
static int shash_finup_unaligned(struct shash_desc *desc, const u8 *data,
unsigned int len, u8 *out)
{
return crypto_shash_update(desc, data, len) ?:
crypto_shash_final(desc, out);
}
int crypto_shash_finup(struct shash_desc *desc, const u8 *data,
unsigned int len, u8 *out)
{
struct crypto_shash *tfm = desc->tfm;
struct shash_alg *shash = crypto_shash_alg(tfm);
unsigned long alignmask = crypto_shash_alignmask(tfm);
if (((unsigned long)data | (unsigned long)out) & alignmask)
return shash_finup_unaligned(desc, data, len, out);
return shash->finup(desc, data, len, out);
}
EXPORT_SYMBOL_GPL(crypto_shash_finup);
static int shash_digest_unaligned(struct shash_desc *desc, const u8 *data,
unsigned int len, u8 *out)
{
return crypto_shash_init(desc) ?:
crypto_shash_finup(desc, data, len, out);
}
int crypto_shash_digest(struct shash_desc *desc, const u8 *data,
unsigned int len, u8 *out)
{
struct crypto_shash *tfm = desc->tfm;
struct shash_alg *shash = crypto_shash_alg(tfm);
unsigned long alignmask = crypto_shash_alignmask(tfm);
if (crypto_shash_get_flags(tfm) & CRYPTO_TFM_NEED_KEY)
return -ENOKEY;
if (((unsigned long)data | (unsigned long)out) & alignmask)
return shash_digest_unaligned(desc, data, len, out);
return shash->digest(desc, data, len, out);
}
EXPORT_SYMBOL_GPL(crypto_shash_digest);
static int shash_default_export(struct shash_desc *desc, void *out)
{
memcpy(out, shash_desc_ctx(desc), crypto_shash_descsize(desc->tfm));
return 0;
}
static int shash_default_import(struct shash_desc *desc, const void *in)
{
memcpy(shash_desc_ctx(desc), in, crypto_shash_descsize(desc->tfm));
return 0;
}
static int shash_async_setkey(struct crypto_ahash *tfm, const u8 *key,
unsigned int keylen)
{
struct crypto_shash **ctx = crypto_ahash_ctx(tfm);
return crypto_shash_setkey(*ctx, key, keylen);
}
static int shash_async_init(struct ahash_request *req)
{
struct crypto_shash **ctx = crypto_ahash_ctx(crypto_ahash_reqtfm(req));
struct shash_desc *desc = ahash_request_ctx(req);
desc->tfm = *ctx;
desc->flags = req->base.flags;
return crypto_shash_init(desc);
}
int shash_ahash_update(struct ahash_request *req, struct shash_desc *desc)
{
struct crypto_hash_walk walk;
int nbytes;
for (nbytes = crypto_hash_walk_first(req, &walk); nbytes > 0;
nbytes = crypto_hash_walk_done(&walk, nbytes))
nbytes = crypto_shash_update(desc, walk.data, nbytes);
return nbytes;
}
EXPORT_SYMBOL_GPL(shash_ahash_update);
static int shash_async_update(struct ahash_request *req)
{
return shash_ahash_update(req, ahash_request_ctx(req));
}
static int shash_async_final(struct ahash_request *req)
{
return crypto_shash_final(ahash_request_ctx(req), req->result);
}
int shash_ahash_finup(struct ahash_request *req, struct shash_desc *desc)
{
struct crypto_hash_walk walk;
int nbytes;
nbytes = crypto_hash_walk_first(req, &walk);
if (!nbytes)
return crypto_shash_final(desc, req->result);
do {
nbytes = crypto_hash_walk_last(&walk) ?
crypto_shash_finup(desc, walk.data, nbytes,
req->result) :
crypto_shash_update(desc, walk.data, nbytes);
nbytes = crypto_hash_walk_done(&walk, nbytes);
} while (nbytes > 0);
return nbytes;
}
EXPORT_SYMBOL_GPL(shash_ahash_finup);
static int shash_async_finup(struct ahash_request *req)
{
struct crypto_shash **ctx = crypto_ahash_ctx(crypto_ahash_reqtfm(req));
struct shash_desc *desc = ahash_request_ctx(req);
desc->tfm = *ctx;
desc->flags = req->base.flags;
return shash_ahash_finup(req, desc);
}
int shash_ahash_digest(struct ahash_request *req, struct shash_desc *desc)
{
unsigned int nbytes = req->nbytes;
struct scatterlist *sg;
unsigned int offset;
int err;
if (nbytes &&
(sg = req->src, offset = sg->offset,
nbytes < min(sg->length, ((unsigned int)(PAGE_SIZE)) - offset))) {
void *data;
data = kmap_atomic(sg_page(sg));
err = crypto_shash_digest(desc, data + offset, nbytes,
req->result);
kunmap_atomic(data);
crypto_yield(desc->flags);
} else
err = crypto_shash_init(desc) ?:
shash_ahash_finup(req, desc);
return err;
}
EXPORT_SYMBOL_GPL(shash_ahash_digest);
static int shash_async_digest(struct ahash_request *req)
{
struct crypto_shash **ctx = crypto_ahash_ctx(crypto_ahash_reqtfm(req));
struct shash_desc *desc = ahash_request_ctx(req);
desc->tfm = *ctx;
desc->flags = req->base.flags;
return shash_ahash_digest(req, desc);
}
static int shash_async_export(struct ahash_request *req, void *out)
{
return crypto_shash_export(ahash_request_ctx(req), out);
}
static int shash_async_import(struct ahash_request *req, const void *in)
{
struct crypto_shash **ctx = crypto_ahash_ctx(crypto_ahash_reqtfm(req));
struct shash_desc *desc = ahash_request_ctx(req);
desc->tfm = *ctx;
desc->flags = req->base.flags;
return crypto_shash_import(desc, in);
}
static void crypto_exit_shash_ops_async(struct crypto_tfm *tfm)
{
struct crypto_shash **ctx = crypto_tfm_ctx(tfm);
crypto_free_shash(*ctx);
}
int crypto_init_shash_ops_async(struct crypto_tfm *tfm)
{
struct crypto_alg *calg = tfm->__crt_alg;
struct shash_alg *alg = __crypto_shash_alg(calg);
struct crypto_ahash *crt = __crypto_ahash_cast(tfm);
struct crypto_shash **ctx = crypto_tfm_ctx(tfm);
struct crypto_shash *shash;
if (!crypto_mod_get(calg))
return -EAGAIN;
shash = crypto_create_tfm(calg, &crypto_shash_type);
if (IS_ERR(shash)) {
crypto_mod_put(calg);
return PTR_ERR(shash);
}
*ctx = shash;
tfm->exit = crypto_exit_shash_ops_async;
crt->init = shash_async_init;
crt->update = shash_async_update;
crt->final = shash_async_final;
crt->finup = shash_async_finup;
crt->digest = shash_async_digest;
crt->setkey = shash_async_setkey;
crypto_ahash_set_flags(crt, crypto_shash_get_flags(shash) &
CRYPTO_TFM_NEED_KEY);
if (alg->export)
crt->export = shash_async_export;
if (alg->import)
crt->import = shash_async_import;
crt->reqsize = sizeof(struct shash_desc) + crypto_shash_descsize(shash);
return 0;
}
static int crypto_shash_init_tfm(struct crypto_tfm *tfm)
{
struct crypto_shash *hash = __crypto_shash_cast(tfm);
struct shash_alg *alg = crypto_shash_alg(hash);
hash->descsize = alg->descsize;
if (crypto_shash_alg_has_setkey(alg) &&
!(alg->base.cra_flags & CRYPTO_ALG_OPTIONAL_KEY))
crypto_shash_set_flags(hash, CRYPTO_TFM_NEED_KEY);
return 0;
}
#ifdef CONFIG_NET
static int crypto_shash_report(struct sk_buff *skb, struct crypto_alg *alg)
{
struct crypto_report_hash rhash;
struct shash_alg *salg = __crypto_shash_alg(alg);
strncpy(rhash.type, "shash", sizeof(rhash.type));
rhash.blocksize = alg->cra_blocksize;
rhash.digestsize = salg->digestsize;
if (nla_put(skb, CRYPTOCFGA_REPORT_HASH,
sizeof(struct crypto_report_hash), &rhash))
goto nla_put_failure;
return 0;
nla_put_failure:
return -EMSGSIZE;
}
#else
static int crypto_shash_report(struct sk_buff *skb, struct crypto_alg *alg)
{
return -ENOSYS;
}
#endif
static void crypto_shash_show(struct seq_file *m, struct crypto_alg *alg)
__maybe_unused;
static void crypto_shash_show(struct seq_file *m, struct crypto_alg *alg)
{
struct shash_alg *salg = __crypto_shash_alg(alg);
seq_printf(m, "type : shash\n");
seq_printf(m, "blocksize : %u\n", alg->cra_blocksize);
seq_printf(m, "digestsize : %u\n", salg->digestsize);
}
static const struct crypto_type crypto_shash_type = {
.extsize = crypto_alg_extsize,
.init_tfm = crypto_shash_init_tfm,
#ifdef CONFIG_PROC_FS
.show = crypto_shash_show,
#endif
.report = crypto_shash_report,
.maskclear = ~CRYPTO_ALG_TYPE_MASK,
.maskset = CRYPTO_ALG_TYPE_MASK,
.type = CRYPTO_ALG_TYPE_SHASH,
.tfmsize = offsetof(struct crypto_shash, base),
};
struct crypto_shash *crypto_alloc_shash(const char *alg_name, u32 type,
u32 mask)
{
return crypto_alloc_tfm(alg_name, &crypto_shash_type, type, mask);
}
EXPORT_SYMBOL_GPL(crypto_alloc_shash);
static int shash_prepare_alg(struct shash_alg *alg)
{
struct crypto_alg *base = &alg->base;
if (alg->digestsize > PAGE_SIZE / 8 ||
alg->descsize > PAGE_SIZE / 8 ||
alg->statesize > PAGE_SIZE / 8)
return -EINVAL;
base->cra_type = &crypto_shash_type;
base->cra_flags &= ~CRYPTO_ALG_TYPE_MASK;
base->cra_flags |= CRYPTO_ALG_TYPE_SHASH;
if (!alg->finup)
alg->finup = shash_finup_unaligned;
if (!alg->digest)
alg->digest = shash_digest_unaligned;
if (!alg->export) {
alg->export = shash_default_export;
alg->import = shash_default_import;
alg->statesize = alg->descsize;
}
if (!alg->setkey)
alg->setkey = shash_no_setkey;
return 0;
}
int crypto_register_shash(struct shash_alg *alg)
{
struct crypto_alg *base = &alg->base;
int err;
err = shash_prepare_alg(alg);
if (err)
return err;
return crypto_register_alg(base);
}
EXPORT_SYMBOL_GPL(crypto_register_shash);
int crypto_unregister_shash(struct shash_alg *alg)
{
return crypto_unregister_alg(&alg->base);
}
EXPORT_SYMBOL_GPL(crypto_unregister_shash);
int crypto_register_shashes(struct shash_alg *algs, int count)
{
int i, ret;
for (i = 0; i < count; i++) {
ret = crypto_register_shash(&algs[i]);
if (ret)
goto err;
}
return 0;
err:
for (--i; i >= 0; --i)
crypto_unregister_shash(&algs[i]);
return ret;
}
EXPORT_SYMBOL_GPL(crypto_register_shashes);
int crypto_unregister_shashes(struct shash_alg *algs, int count)
{
int i, ret;
for (i = count - 1; i >= 0; --i) {
ret = crypto_unregister_shash(&algs[i]);
if (ret)
pr_err("Failed to unregister %s %s: %d\n",
algs[i].base.cra_driver_name,
algs[i].base.cra_name, ret);
}
return 0;
}
EXPORT_SYMBOL_GPL(crypto_unregister_shashes);
int shash_register_instance(struct crypto_template *tmpl,
struct shash_instance *inst)
{
int err;
err = shash_prepare_alg(&inst->alg);
if (err)
return err;
return crypto_register_instance(tmpl, shash_crypto_instance(inst));
}
EXPORT_SYMBOL_GPL(shash_register_instance);
void shash_free_instance(struct crypto_instance *inst)
{
crypto_drop_spawn(crypto_instance_ctx(inst));
kfree(shash_instance(inst));
}
EXPORT_SYMBOL_GPL(shash_free_instance);
int crypto_init_shash_spawn(struct crypto_shash_spawn *spawn,
struct shash_alg *alg,
struct crypto_instance *inst)
{
return crypto_init_spawn2(&spawn->base, &alg->base, inst,
&crypto_shash_type);
}
EXPORT_SYMBOL_GPL(crypto_init_shash_spawn);
struct shash_alg *shash_attr_alg(struct rtattr *rta, u32 type, u32 mask)
{
struct crypto_alg *alg;
alg = crypto_attr_alg2(rta, &crypto_shash_type, type, mask);
return IS_ERR(alg) ? ERR_CAST(alg) :
container_of(alg, struct shash_alg, base);
}
EXPORT_SYMBOL_GPL(shash_attr_alg);
MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("Synchronous cryptographic hash type");