3.16.62-rc1 review patch. If anyone has any objections, please let me know.
------------------
From: Eric Biggers ebiggers@google.com
commit bb29648102335586e9a66289a1d98a0cb392b6e5 upstream.
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: f1939f7c5645 ("crypto: vmac - New hash algorithm for intel_txt support") Signed-off-by: Eric Biggers ebiggers@google.com Signed-off-by: Herbert Xu herbert@gondor.apana.org.au Signed-off-by: Ben Hutchings ben@decadent.org.uk --- crypto/vmac.c | 408 +++++++++++++++++++----------------------- include/crypto/vmac.h | 63 ------- 2 files changed, 181 insertions(+), 290 deletions(-) delete mode 100644 include/crypto/vmac.h
--- a/crypto/vmac.c +++ b/crypto/vmac.c @@ -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> @@ -31,10 +36,36 @@ #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 */ #define UINT64_C(x) x##ULL @@ -318,13 +349,6 @@ static void poly_step_func(u64 *ahi, u64 } 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 return rl; }
-static void vhash_update(const unsigned char *m, - unsigned int mbytes, /* Pos multiple of VMAC_NHBYTES */ - struct vmac_ctx *ctx) -{ - 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]; - - if (!mbytes) - return; - - BUG_ON(mbytes % VMAC_NHBYTES); +/* 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) +{ + 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;
- 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]; - - 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; - } - - 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); + struct vmac_tfm_ctx *tctx = crypto_shash_ctx(tfm); + __be64 out[2]; + u8 in[16] = { 0 }; + unsigned int i; + int err;
- ((unsigned char *)in_n)[15] |= (unsigned char)(1-i); + if (keylen != VMAC_KEY_LEN) { + crypto_shash_set_flags(tfm, CRYPTO_TFM_RES_BAD_KEY_LEN); + return -EINVAL; } - 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; + return 0; }
-static int vmac_setkey(struct crypto_shash *parent, - const u8 *key, unsigned int keylen) +static int vmac_init(struct shash_desc *desc) { - struct vmac_ctx_t *ctx = crypto_shash_ctx(parent); + const struct vmac_tfm_ctx *tctx = crypto_shash_ctx(desc->tfm); + struct vmac_desc_ctx *dctx = shash_desc_ctx(desc);
- 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) -{ + 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 *pdesc, const u8 *p, - unsigned int len) +static int vmac_update(struct shash_desc *desc, 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; + 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; + } + } + + 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; }
- vhash_update(p, len - len % VMAC_NHBYTES, &ctx->__vmac_ctx); - return 0; }
-static int vmac_final(struct shash_desc *pdesc, u8 *out) +static u64 vhash_final(const struct vmac_tfm_ctx *tctx, + struct vmac_desc_ctx *dctx) { - struct crypto_shash *parent = pdesc->tfm; - struct vmac_ctx_t *ctx = crypto_shash_ctx(parent); - vmac_t mac; - u8 nonce[16] = {}; - - /* 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); - } - 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; + 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_tem 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; --- a/include/crypto/vmac.h +++ /dev/null @@ -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 */