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crypto: vmac - separate tfm and request context

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syzbot reported a crash in vmac_final() when multiple threads
concurrently use the same "vmac(aes)" transform through AF_ALG.  The bug
is pretty fundamental: the VMAC template doesn't separate per-request
state from per-tfm (per-key) state like the other hash algorithms do,
but rather stores it all in the tfm context.  That's wrong.

Also, vmac_final() incorrectly zeroes most of the state including the
derived keys and cached pseudorandom pad.  Therefore, only the first
VMAC invocation with a given key calculates the correct digest.

Fix these bugs by splitting the per-tfm state from the per-request state
and using the proper init/update/final sequencing for requests.

Reproducer for the crash:

    #include <linux/if_alg.h>
    #include <sys/socket.h>
    #include <unistd.h>

    int main()
    {
            int fd;
            struct sockaddr_alg addr = {
                    .salg_type = "hash",
                    .salg_name = "vmac(aes)",
            };
            char buf[256] = { 0 };

            fd = socket(AF_ALG, SOCK_SEQPACKET, 0);
            bind(fd, (void *)&addr, sizeof(addr));
            setsockopt(fd, SOL_ALG, ALG_SET_KEY, buf, 16);
            fork();
            fd = accept(fd, NULL, NULL);
            for (;;)
                    write(fd, buf, 256);
    }

The immediate cause of the crash is that vmac_ctx_t.partial_size exceeds
VMAC_NHBYTES, causing vmac_final() to memset() a negative length.

Reported-by: syzbot+264bca3a6e8d645550d3@syzkaller.appspotmail.com
Fixes: f1939f7c56 ("crypto: vmac - New hash algorithm for intel_txt support")
Cc: <stable@vger.kernel.org> # v2.6.32+
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
This commit is contained in:
Eric Biggers 2018-06-18 10:22:38 -07:00 committed by Herbert Xu
parent 73bf20ef3d
commit bb29648102
2 changed files with 191 additions and 300 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

428
crypto/vmac.c
View File

@ -1,6 +1,10 @@
/*
* Modified to interface to the Linux kernel
* VMAC: Message Authentication Code using Universal Hashing
*
* Reference: https://tools.ietf.org/html/draft-krovetz-vmac-01
*
* Copyright (c) 2009, Intel Corporation.
* Copyright (c) 2018, Google Inc.
*
* This program is free software; you can redistribute it and/or modify it
* under the terms and conditions of the GNU General Public License,
@ -16,14 +20,15 @@
* Place - Suite 330, Boston, MA 02111-1307 USA.
*/
/* --------------------------------------------------------------------------
* VMAC and VHASH Implementation by Ted Krovetz (tdk@acm.org) and Wei Dai.
* This implementation is herby placed in the public domain.
* The authors offers no warranty. Use at your own risk.
* Please send bug reports to the authors.
* Last modified: 17 APR 08, 1700 PDT
* ----------------------------------------------------------------------- */
/*
* Derived from:
* VMAC and VHASH Implementation by Ted Krovetz (tdk@acm.org) and Wei Dai.
* This implementation is herby placed in the public domain.
* The authors offers no warranty. Use at your own risk.
* Last modified: 17 APR 08, 1700 PDT
*/
#include <asm/unaligned.h>
#include <linux/init.h>
#include <linux/types.h>
#include <linux/crypto.h>
@ -31,9 +36,35 @@
#include <linux/scatterlist.h>
#include <asm/byteorder.h>
#include <crypto/scatterwalk.h>
#include <crypto/vmac.h>
#include <crypto/internal/hash.h>
/*
* User definable settings.
*/
#define VMAC_TAG_LEN 64
#define VMAC_KEY_SIZE 128/* Must be 128, 192 or 256 */
#define VMAC_KEY_LEN (VMAC_KEY_SIZE/8)
#define VMAC_NHBYTES 128/* Must 2^i for any 3 < i < 13 Standard = 128*/
/* per-transform (per-key) context */
struct vmac_tfm_ctx {
struct crypto_cipher *cipher;
u64 nhkey[(VMAC_NHBYTES/8)+2*(VMAC_TAG_LEN/64-1)];
u64 polykey[2*VMAC_TAG_LEN/64];
u64 l3key[2*VMAC_TAG_LEN/64];
};
/* per-request context */
struct vmac_desc_ctx {
union {
u8 partial[VMAC_NHBYTES]; /* partial block */
__le64 partial_words[VMAC_NHBYTES / 8];
};
unsigned int partial_size; /* size of the partial block */
bool first_block_processed;
u64 polytmp[2*VMAC_TAG_LEN/64]; /* running total of L2-hash */
};
/*
* Constants and masks
*/
@ -318,13 +349,6 @@ static void poly_step_func(u64 *ahi, u64 *alo,
} while (0)
#endif
static void vhash_abort(struct vmac_ctx *ctx)
{
ctx->polytmp[0] = ctx->polykey[0] ;
ctx->polytmp[1] = ctx->polykey[1] ;
ctx->first_block_processed = 0;
}
static u64 l3hash(u64 p1, u64 p2, u64 k1, u64 k2, u64 len)
{
u64 rh, rl, t, z = 0;
@ -364,280 +388,209 @@ static u64 l3hash(u64 p1, u64 p2, u64 k1, u64 k2, u64 len)
return rl;
}
static void vhash_update(const unsigned char *m,
unsigned int mbytes, /* Pos multiple of VMAC_NHBYTES */
struct vmac_ctx *ctx)
/* L1 and L2-hash one or more VMAC_NHBYTES-byte blocks */
static void vhash_blocks(const struct vmac_tfm_ctx *tctx,
struct vmac_desc_ctx *dctx,
const __le64 *mptr, unsigned int blocks)
{
u64 rh, rl, *mptr;
const u64 *kptr = (u64 *)ctx->nhkey;
int i;
u64 ch, cl;
u64 pkh = ctx->polykey[0];
u64 pkl = ctx->polykey[1];
const u64 *kptr = tctx->nhkey;
const u64 pkh = tctx->polykey[0];
const u64 pkl = tctx->polykey[1];
u64 ch = dctx->polytmp[0];
u64 cl = dctx->polytmp[1];
u64 rh, rl;
if (!mbytes)
return;
BUG_ON(mbytes % VMAC_NHBYTES);
mptr = (u64 *)m;
i = mbytes / VMAC_NHBYTES; /* Must be non-zero */
ch = ctx->polytmp[0];
cl = ctx->polytmp[1];
if (!ctx->first_block_processed) {
ctx->first_block_processed = 1;
if (!dctx->first_block_processed) {
dctx->first_block_processed = true;
nh_vmac_nhbytes(mptr, kptr, VMAC_NHBYTES/8, rh, rl);
rh &= m62;
ADD128(ch, cl, rh, rl);
mptr += (VMAC_NHBYTES/sizeof(u64));
i--;
blocks--;
}
while (i--) {
while (blocks--) {
nh_vmac_nhbytes(mptr, kptr, VMAC_NHBYTES/8, rh, rl);
rh &= m62;
poly_step(ch, cl, pkh, pkl, rh, rl);
mptr += (VMAC_NHBYTES/sizeof(u64));
}
ctx->polytmp[0] = ch;
ctx->polytmp[1] = cl;
dctx->polytmp[0] = ch;
dctx->polytmp[1] = cl;
}
static u64 vhash(unsigned char m[], unsigned int mbytes,
u64 *tagl, struct vmac_ctx *ctx)
static int vmac_setkey(struct crypto_shash *tfm,
const u8 *key, unsigned int keylen)
{
u64 rh, rl, *mptr;
const u64 *kptr = (u64 *)ctx->nhkey;
int i, remaining;
u64 ch, cl;
u64 pkh = ctx->polykey[0];
u64 pkl = ctx->polykey[1];
struct vmac_tfm_ctx *tctx = crypto_shash_ctx(tfm);
__be64 out[2];
u8 in[16] = { 0 };
unsigned int i;
int err;
mptr = (u64 *)m;
i = mbytes / VMAC_NHBYTES;
remaining = mbytes % VMAC_NHBYTES;
if (ctx->first_block_processed) {
ch = ctx->polytmp[0];
cl = ctx->polytmp[1];
} else if (i) {
nh_vmac_nhbytes(mptr, kptr, VMAC_NHBYTES/8, ch, cl);
ch &= m62;
ADD128(ch, cl, pkh, pkl);
mptr += (VMAC_NHBYTES/sizeof(u64));
i--;
} else if (remaining) {
nh_16(mptr, kptr, 2*((remaining+15)/16), ch, cl);
ch &= m62;
ADD128(ch, cl, pkh, pkl);
mptr += (VMAC_NHBYTES/sizeof(u64));
goto do_l3;
} else {/* Empty String */
ch = pkh; cl = pkl;
goto do_l3;
if (keylen != VMAC_KEY_LEN) {
crypto_shash_set_flags(tfm, CRYPTO_TFM_RES_BAD_KEY_LEN);
return -EINVAL;
}
while (i--) {
nh_vmac_nhbytes(mptr, kptr, VMAC_NHBYTES/8, rh, rl);
rh &= m62;
poly_step(ch, cl, pkh, pkl, rh, rl);
mptr += (VMAC_NHBYTES/sizeof(u64));
}
if (remaining) {
nh_16(mptr, kptr, 2*((remaining+15)/16), rh, rl);
rh &= m62;
poly_step(ch, cl, pkh, pkl, rh, rl);
}
do_l3:
vhash_abort(ctx);
remaining *= 8;
return l3hash(ch, cl, ctx->l3key[0], ctx->l3key[1], remaining);
}
static u64 vmac(unsigned char m[], unsigned int mbytes,
const unsigned char n[16], u64 *tagl,
struct vmac_ctx_t *ctx)
{
u64 *in_n, *out_p;
u64 p, h;
int i;
in_n = ctx->__vmac_ctx.cached_nonce;
out_p = ctx->__vmac_ctx.cached_aes;
i = n[15] & 1;
if ((*(u64 *)(n+8) != in_n[1]) || (*(u64 *)(n) != in_n[0])) {
in_n[0] = *(u64 *)(n);
in_n[1] = *(u64 *)(n+8);
((unsigned char *)in_n)[15] &= 0xFE;
crypto_cipher_encrypt_one(ctx->child,
(unsigned char *)out_p, (unsigned char *)in_n);
((unsigned char *)in_n)[15] |= (unsigned char)(1-i);
}
p = be64_to_cpup(out_p + i);
h = vhash(m, mbytes, (u64 *)0, &ctx->__vmac_ctx);
return le64_to_cpu(p + h);
}
static int vmac_set_key(unsigned char user_key[], struct vmac_ctx_t *ctx)
{
u64 in[2] = {0}, out[2];
unsigned i;
int err = 0;
err = crypto_cipher_setkey(ctx->child, user_key, VMAC_KEY_LEN);
err = crypto_cipher_setkey(tctx->cipher, key, keylen);
if (err)
return err;
/* Fill nh key */
((unsigned char *)in)[0] = 0x80;
for (i = 0; i < sizeof(ctx->__vmac_ctx.nhkey)/8; i += 2) {
crypto_cipher_encrypt_one(ctx->child,
(unsigned char *)out, (unsigned char *)in);
ctx->__vmac_ctx.nhkey[i] = be64_to_cpup(out);
ctx->__vmac_ctx.nhkey[i+1] = be64_to_cpup(out+1);
((unsigned char *)in)[15] += 1;
in[0] = 0x80;
for (i = 0; i < ARRAY_SIZE(tctx->nhkey); i += 2) {
crypto_cipher_encrypt_one(tctx->cipher, (u8 *)out, in);
tctx->nhkey[i] = be64_to_cpu(out[0]);
tctx->nhkey[i+1] = be64_to_cpu(out[1]);
in[15]++;
}
/* Fill poly key */
((unsigned char *)in)[0] = 0xC0;
in[1] = 0;
for (i = 0; i < sizeof(ctx->__vmac_ctx.polykey)/8; i += 2) {
crypto_cipher_encrypt_one(ctx->child,
(unsigned char *)out, (unsigned char *)in);
ctx->__vmac_ctx.polytmp[i] =
ctx->__vmac_ctx.polykey[i] =
be64_to_cpup(out) & mpoly;
ctx->__vmac_ctx.polytmp[i+1] =
ctx->__vmac_ctx.polykey[i+1] =
be64_to_cpup(out+1) & mpoly;
((unsigned char *)in)[15] += 1;
in[0] = 0xC0;
in[15] = 0;
for (i = 0; i < ARRAY_SIZE(tctx->polykey); i += 2) {
crypto_cipher_encrypt_one(tctx->cipher, (u8 *)out, in);
tctx->polykey[i] = be64_to_cpu(out[0]) & mpoly;
tctx->polykey[i+1] = be64_to_cpu(out[1]) & mpoly;
in[15]++;
}
/* Fill ip key */
((unsigned char *)in)[0] = 0xE0;
in[1] = 0;
for (i = 0; i < sizeof(ctx->__vmac_ctx.l3key)/8; i += 2) {
in[0] = 0xE0;
in[15] = 0;
for (i = 0; i < ARRAY_SIZE(tctx->l3key); i += 2) {
do {
crypto_cipher_encrypt_one(ctx->child,
(unsigned char *)out, (unsigned char *)in);
ctx->__vmac_ctx.l3key[i] = be64_to_cpup(out);
ctx->__vmac_ctx.l3key[i+1] = be64_to_cpup(out+1);
((unsigned char *)in)[15] += 1;
} while (ctx->__vmac_ctx.l3key[i] >= p64
|| ctx->__vmac_ctx.l3key[i+1] >= p64);
crypto_cipher_encrypt_one(tctx->cipher, (u8 *)out, in);
tctx->l3key[i] = be64_to_cpu(out[0]);
tctx->l3key[i+1] = be64_to_cpu(out[1]);
in[15]++;
} while (tctx->l3key[i] >= p64 || tctx->l3key[i+1] >= p64);
}
/* Invalidate nonce/aes cache and reset other elements */
ctx->__vmac_ctx.cached_nonce[0] = (u64)-1; /* Ensure illegal nonce */
ctx->__vmac_ctx.cached_nonce[1] = (u64)0; /* Ensure illegal nonce */
ctx->__vmac_ctx.first_block_processed = 0;
return err;
}
static int vmac_setkey(struct crypto_shash *parent,
const u8 *key, unsigned int keylen)
{
struct vmac_ctx_t *ctx = crypto_shash_ctx(parent);
if (keylen != VMAC_KEY_LEN) {
crypto_shash_set_flags(parent, CRYPTO_TFM_RES_BAD_KEY_LEN);
return -EINVAL;
}
return vmac_set_key((u8 *)key, ctx);
}
static int vmac_init(struct shash_desc *pdesc)
{
return 0;
}
static int vmac_update(struct shash_desc *pdesc, const u8 *p,
unsigned int len)
{
struct crypto_shash *parent = pdesc->tfm;
struct vmac_ctx_t *ctx = crypto_shash_ctx(parent);
int expand;
int min;
expand = VMAC_NHBYTES - ctx->partial_size > 0 ?
VMAC_NHBYTES - ctx->partial_size : 0;
min = len < expand ? len : expand;
memcpy(ctx->partial + ctx->partial_size, p, min);
ctx->partial_size += min;
if (len < expand)
return 0;
vhash_update(ctx->partial, VMAC_NHBYTES, &ctx->__vmac_ctx);
ctx->partial_size = 0;
len -= expand;
p += expand;
if (len % VMAC_NHBYTES) {
memcpy(ctx->partial, p + len - (len % VMAC_NHBYTES),
len % VMAC_NHBYTES);
ctx->partial_size = len % VMAC_NHBYTES;
}
vhash_update(p, len - len % VMAC_NHBYTES, &ctx->__vmac_ctx);
return 0;
}
static int vmac_final(struct shash_desc *pdesc, u8 *out)
static int vmac_init(struct shash_desc *desc)
{
struct crypto_shash *parent = pdesc->tfm;
struct vmac_ctx_t *ctx = crypto_shash_ctx(parent);
vmac_t mac;
u8 nonce[16] = {};
const struct vmac_tfm_ctx *tctx = crypto_shash_ctx(desc->tfm);
struct vmac_desc_ctx *dctx = shash_desc_ctx(desc);
/* vmac() ends up accessing outside the array bounds that
* we specify. In appears to access up to the next 2-word
* boundary. We'll just be uber cautious and zero the
* unwritten bytes in the buffer.
*/
if (ctx->partial_size) {
memset(ctx->partial + ctx->partial_size, 0,
VMAC_NHBYTES - ctx->partial_size);
dctx->partial_size = 0;
dctx->first_block_processed = false;
memcpy(dctx->polytmp, tctx->polykey, sizeof(dctx->polytmp));
return 0;
}
static int vmac_update(struct shash_desc *desc, const u8 *p, unsigned int len)
{
const struct vmac_tfm_ctx *tctx = crypto_shash_ctx(desc->tfm);
struct vmac_desc_ctx *dctx = shash_desc_ctx(desc);
unsigned int n;
if (dctx->partial_size) {
n = min(len, VMAC_NHBYTES - dctx->partial_size);
memcpy(&dctx->partial[dctx->partial_size], p, n);
dctx->partial_size += n;
p += n;
len -= n;
if (dctx->partial_size == VMAC_NHBYTES) {
vhash_blocks(tctx, dctx, dctx->partial_words, 1);
dctx->partial_size = 0;
}
}
mac = vmac(ctx->partial, ctx->partial_size, nonce, NULL, ctx);
memcpy(out, &mac, sizeof(vmac_t));
memzero_explicit(&mac, sizeof(vmac_t));
memset(&ctx->__vmac_ctx, 0, sizeof(struct vmac_ctx));
ctx->partial_size = 0;
if (len >= VMAC_NHBYTES) {
n = round_down(len, VMAC_NHBYTES);
/* TODO: 'p' may be misaligned here */
vhash_blocks(tctx, dctx, (const __le64 *)p, n / VMAC_NHBYTES);
p += n;
len -= n;
}
if (len) {
memcpy(dctx->partial, p, len);
dctx->partial_size = len;
}
return 0;
}
static u64 vhash_final(const struct vmac_tfm_ctx *tctx,
struct vmac_desc_ctx *dctx)
{
unsigned int partial = dctx->partial_size;
u64 ch = dctx->polytmp[0];
u64 cl = dctx->polytmp[1];
/* L1 and L2-hash the final block if needed */
if (partial) {
/* Zero-pad to next 128-bit boundary */
unsigned int n = round_up(partial, 16);
u64 rh, rl;
memset(&dctx->partial[partial], 0, n - partial);
nh_16(dctx->partial_words, tctx->nhkey, n / 8, rh, rl);
rh &= m62;
if (dctx->first_block_processed)
poly_step(ch, cl, tctx->polykey[0], tctx->polykey[1],
rh, rl);
else
ADD128(ch, cl, rh, rl);
}
/* L3-hash the 128-bit output of L2-hash */
return l3hash(ch, cl, tctx->l3key[0], tctx->l3key[1], partial * 8);
}
static int vmac_final(struct shash_desc *desc, u8 *out)
{
const struct vmac_tfm_ctx *tctx = crypto_shash_ctx(desc->tfm);
struct vmac_desc_ctx *dctx = shash_desc_ctx(desc);
static const u8 nonce[16] = {}; /* TODO: this is insecure */
union {
u8 bytes[16];
__be64 pads[2];
} block;
int index;
u64 hash, pad;
/* Finish calculating the VHASH of the message */
hash = vhash_final(tctx, dctx);
/* Generate pseudorandom pad by encrypting the nonce */
memcpy(&block, nonce, 16);
index = block.bytes[15] & 1;
block.bytes[15] &= ~1;
crypto_cipher_encrypt_one(tctx->cipher, block.bytes, block.bytes);
pad = be64_to_cpu(block.pads[index]);
/* The VMAC is the sum of VHASH and the pseudorandom pad */
put_unaligned_le64(hash + pad, out);
return 0;
}
static int vmac_init_tfm(struct crypto_tfm *tfm)
{
struct crypto_cipher *cipher;
struct crypto_instance *inst = (void *)tfm->__crt_alg;
struct crypto_instance *inst = crypto_tfm_alg_instance(tfm);
struct crypto_spawn *spawn = crypto_instance_ctx(inst);
struct vmac_ctx_t *ctx = crypto_tfm_ctx(tfm);
struct vmac_tfm_ctx *tctx = crypto_tfm_ctx(tfm);
struct crypto_cipher *cipher;
cipher = crypto_spawn_cipher(spawn);
if (IS_ERR(cipher))
return PTR_ERR(cipher);
ctx->child = cipher;
tctx->cipher = cipher;
return 0;
}
static void vmac_exit_tfm(struct crypto_tfm *tfm)
{
struct vmac_ctx_t *ctx = crypto_tfm_ctx(tfm);
crypto_free_cipher(ctx->child);
struct vmac_tfm_ctx *tctx = crypto_tfm_ctx(tfm);
crypto_free_cipher(tctx->cipher);
}
static int vmac_create(struct crypto_template *tmpl, struct rtattr **tb)
@ -674,11 +627,12 @@ static int vmac_create(struct crypto_template *tmpl, struct rtattr **tb)
inst->alg.base.cra_blocksize = alg->cra_blocksize;
inst->alg.base.cra_alignmask = alg->cra_alignmask;
inst->alg.digestsize = sizeof(vmac_t);
inst->alg.base.cra_ctxsize = sizeof(struct vmac_ctx_t);
inst->alg.base.cra_ctxsize = sizeof(struct vmac_tfm_ctx);
inst->alg.base.cra_init = vmac_init_tfm;
inst->alg.base.cra_exit = vmac_exit_tfm;
inst->alg.descsize = sizeof(struct vmac_desc_ctx);
inst->alg.digestsize = VMAC_TAG_LEN / 8;
inst->alg.init = vmac_init;
inst->alg.update = vmac_update;
inst->alg.final = vmac_final;

63
include/crypto/vmac.h
View File

@ -1,63 +0,0 @@
/*
* Modified to interface to the Linux kernel
* Copyright (c) 2009, Intel Corporation.
*
* This program is free software; you can redistribute it and/or modify it
* under the terms and conditions of the GNU General Public License,
* version 2, as published by the Free Software Foundation.
*
* This program is distributed in the hope it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
* more details.
*
* You should have received a copy of the GNU General Public License along with
* this program; if not, write to the Free Software Foundation, Inc., 59 Temple
* Place - Suite 330, Boston, MA 02111-1307 USA.
*/
#ifndef __CRYPTO_VMAC_H
#define __CRYPTO_VMAC_H
/* --------------------------------------------------------------------------
* VMAC and VHASH Implementation by Ted Krovetz (tdk@acm.org) and Wei Dai.
* This implementation is herby placed in the public domain.
* The authors offers no warranty. Use at your own risk.
* Please send bug reports to the authors.
* Last modified: 17 APR 08, 1700 PDT
* ----------------------------------------------------------------------- */
/*
* User definable settings.
*/
#define VMAC_TAG_LEN 64
#define VMAC_KEY_SIZE 128/* Must be 128, 192 or 256 */
#define VMAC_KEY_LEN (VMAC_KEY_SIZE/8)
#define VMAC_NHBYTES 128/* Must 2^i for any 3 < i < 13 Standard = 128*/
/*
* This implementation uses u32 and u64 as names for unsigned 32-
* and 64-bit integer types. These are defined in C99 stdint.h. The
* following may need adaptation if you are not running a C99 or
* Microsoft C environment.
*/
struct vmac_ctx {
u64 nhkey[(VMAC_NHBYTES/8)+2*(VMAC_TAG_LEN/64-1)];
u64 polykey[2*VMAC_TAG_LEN/64];
u64 l3key[2*VMAC_TAG_LEN/64];
u64 polytmp[2*VMAC_TAG_LEN/64];
u64 cached_nonce[2];
u64 cached_aes[2];
int first_block_processed;
};
typedef u64 vmac_t;
struct vmac_ctx_t {
struct crypto_cipher *child;
struct vmac_ctx __vmac_ctx;
u8 partial[VMAC_NHBYTES]; /* partial block */
int partial_size; /* size of the partial block */
};
#endif /* __CRYPTO_VMAC_H */