crypto: hmac - require that the underlying hash algorithm is unkeyed (CVE-2017-17806)
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Salvatore Bonaccorso
parent
4f056ca2c6
commit
196596c560
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@ -507,6 +507,8 @@ linux (4.14.7-1) UNRELEASED; urgency=medium
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* xen/time: do not decrease steal time after live migration on xen
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(Closes: #871608)
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* crypto: salsa20 - fix blkcipher_walk API usage (CVE-2017-17805)
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* crypto: hmac - require that the underlying hash algorithm is unkeyed
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(CVE-2017-17806)
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[ Vagrant Cascadian ]
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* [armhf, arm64] Backport patches from 4.15.x to support dwmac-sun8i.
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151
debian/patches/bugfix/all/crypto-hmac-require-that-the-underlying-hash-algorit.patch
vendored
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151
debian/patches/bugfix/all/crypto-hmac-require-that-the-underlying-hash-algorit.patch
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@ -0,0 +1,151 @@
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From: Eric Biggers <ebiggers@google.com>
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Date: Tue, 28 Nov 2017 18:01:38 -0800
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Subject: crypto: hmac - require that the underlying hash algorithm is unkeyed
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Origin: https://git.kernel.org/linus/af3ff8045bbf3e32f1a448542e73abb4c8ceb6f1
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Bug-Debian-Security: https://security-tracker.debian.org/tracker/CVE-2017-17806
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Because the HMAC template didn't check that its underlying hash
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algorithm is unkeyed, trying to use "hmac(hmac(sha3-512-generic))"
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through AF_ALG or through KEYCTL_DH_COMPUTE resulted in the inner HMAC
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being used without having been keyed, resulting in sha3_update() being
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called without sha3_init(), causing a stack buffer overflow.
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This is a very old bug, but it seems to have only started causing real
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problems when SHA-3 support was added (requires CONFIG_CRYPTO_SHA3)
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because the innermost hash's state is ->import()ed from a zeroed buffer,
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and it just so happens that other hash algorithms are fine with that,
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but SHA-3 is not. However, there could be arch or hardware-dependent
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hash algorithms also affected; I couldn't test everything.
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Fix the bug by introducing a function crypto_shash_alg_has_setkey()
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which tests whether a shash algorithm is keyed. Then update the HMAC
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template to require that its underlying hash algorithm is unkeyed.
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Here is a reproducer:
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#include <linux/if_alg.h>
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#include <sys/socket.h>
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int main()
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{
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int algfd;
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struct sockaddr_alg addr = {
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.salg_type = "hash",
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.salg_name = "hmac(hmac(sha3-512-generic))",
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};
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char key[4096] = { 0 };
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algfd = socket(AF_ALG, SOCK_SEQPACKET, 0);
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bind(algfd, (const struct sockaddr *)&addr, sizeof(addr));
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setsockopt(algfd, SOL_ALG, ALG_SET_KEY, key, sizeof(key));
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}
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Here was the KASAN report from syzbot:
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BUG: KASAN: stack-out-of-bounds in memcpy include/linux/string.h:341 [inline]
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BUG: KASAN: stack-out-of-bounds in sha3_update+0xdf/0x2e0 crypto/sha3_generic.c:161
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Write of size 4096 at addr ffff8801cca07c40 by task syzkaller076574/3044
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CPU: 1 PID: 3044 Comm: syzkaller076574 Not tainted 4.14.0-mm1+ #25
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Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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Call Trace:
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__dump_stack lib/dump_stack.c:17 [inline]
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dump_stack+0x194/0x257 lib/dump_stack.c:53
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print_address_description+0x73/0x250 mm/kasan/report.c:252
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kasan_report_error mm/kasan/report.c:351 [inline]
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kasan_report+0x25b/0x340 mm/kasan/report.c:409
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check_memory_region_inline mm/kasan/kasan.c:260 [inline]
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check_memory_region+0x137/0x190 mm/kasan/kasan.c:267
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memcpy+0x37/0x50 mm/kasan/kasan.c:303
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memcpy include/linux/string.h:341 [inline]
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sha3_update+0xdf/0x2e0 crypto/sha3_generic.c:161
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crypto_shash_update+0xcb/0x220 crypto/shash.c:109
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shash_finup_unaligned+0x2a/0x60 crypto/shash.c:151
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crypto_shash_finup+0xc4/0x120 crypto/shash.c:165
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hmac_finup+0x182/0x330 crypto/hmac.c:152
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crypto_shash_finup+0xc4/0x120 crypto/shash.c:165
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shash_digest_unaligned+0x9e/0xd0 crypto/shash.c:172
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crypto_shash_digest+0xc4/0x120 crypto/shash.c:186
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hmac_setkey+0x36a/0x690 crypto/hmac.c:66
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crypto_shash_setkey+0xad/0x190 crypto/shash.c:64
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shash_async_setkey+0x47/0x60 crypto/shash.c:207
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crypto_ahash_setkey+0xaf/0x180 crypto/ahash.c:200
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hash_setkey+0x40/0x90 crypto/algif_hash.c:446
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alg_setkey crypto/af_alg.c:221 [inline]
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alg_setsockopt+0x2a1/0x350 crypto/af_alg.c:254
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SYSC_setsockopt net/socket.c:1851 [inline]
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SyS_setsockopt+0x189/0x360 net/socket.c:1830
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entry_SYSCALL_64_fastpath+0x1f/0x96
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Reported-by: syzbot <syzkaller@googlegroups.com>
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Cc: <stable@vger.kernel.org>
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Signed-off-by: Eric Biggers <ebiggers@google.com>
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Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
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---
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crypto/hmac.c | 6 +++++-
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crypto/shash.c | 5 +++--
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include/crypto/internal/hash.h | 8 ++++++++
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3 files changed, 16 insertions(+), 3 deletions(-)
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diff --git a/crypto/hmac.c b/crypto/hmac.c
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index 92871dc2a63e..e74730224f0a 100644
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--- a/crypto/hmac.c
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+++ b/crypto/hmac.c
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@@ -195,11 +195,15 @@ static int hmac_create(struct crypto_template *tmpl, struct rtattr **tb)
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salg = shash_attr_alg(tb[1], 0, 0);
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if (IS_ERR(salg))
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return PTR_ERR(salg);
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+ alg = &salg->base;
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+ /* The underlying hash algorithm must be unkeyed */
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err = -EINVAL;
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+ if (crypto_shash_alg_has_setkey(salg))
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+ goto out_put_alg;
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+
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ds = salg->digestsize;
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ss = salg->statesize;
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- alg = &salg->base;
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if (ds > alg->cra_blocksize ||
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ss < alg->cra_blocksize)
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goto out_put_alg;
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diff --git a/crypto/shash.c b/crypto/shash.c
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index 325a14da5827..e849d3ee2e27 100644
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--- a/crypto/shash.c
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+++ b/crypto/shash.c
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@@ -25,11 +25,12 @@
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static const struct crypto_type crypto_shash_type;
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-static int shash_no_setkey(struct crypto_shash *tfm, const u8 *key,
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- unsigned int keylen)
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+int shash_no_setkey(struct crypto_shash *tfm, const u8 *key,
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+ unsigned int keylen)
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{
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return -ENOSYS;
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}
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+EXPORT_SYMBOL_GPL(shash_no_setkey);
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static int shash_setkey_unaligned(struct crypto_shash *tfm, const u8 *key,
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unsigned int keylen)
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diff --git a/include/crypto/internal/hash.h b/include/crypto/internal/hash.h
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index f0b44c16e88f..c2bae8da642c 100644
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--- a/include/crypto/internal/hash.h
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+++ b/include/crypto/internal/hash.h
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@@ -82,6 +82,14 @@ int ahash_register_instance(struct crypto_template *tmpl,
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struct ahash_instance *inst);
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void ahash_free_instance(struct crypto_instance *inst);
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+int shash_no_setkey(struct crypto_shash *tfm, const u8 *key,
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+ unsigned int keylen);
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+
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+static inline bool crypto_shash_alg_has_setkey(struct shash_alg *alg)
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+{
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+ return alg->setkey != shash_no_setkey;
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+}
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+
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int crypto_init_ahash_spawn(struct crypto_ahash_spawn *spawn,
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struct hash_alg_common *alg,
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struct crypto_instance *inst);
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--
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2.11.0
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@ -128,6 +128,7 @@ bugfix/all/media-hdpvr-fix-an-error-handling-path-in-hdpvr_prob.patch
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bugfix/all/kvm-fix-stack-out-of-bounds-read-in-write_mmio.patch
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bugfix/all/bluetooth-prevent-stack-info-leak-from-the-efs-element.patch
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bugfix/all/crypto-salsa20-fix-blkcipher_walk-API-usage.patch
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bugfix/all/crypto-hmac-require-that-the-underlying-hash-algorit.patch
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# Fix exported symbol versions
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bugfix/all/module-disable-matching-missing-version-crc.patch
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