crypto: CVE-2017-17806

crypto: hmac - require that the underlying hash algorithm is unkeyed

References:
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?h=linux-4.1.y&id=bd7f57da8fff9b75204d6dd2b3ac6a30a6430a5c

Change-Id: I26546d4145e6190cada911545ad939c9aed8d891
Signed-off-by: Andreas Wellving <andreas.wellving@enea.com>

2 files changed, 159 insertions, 0 deletions

diff --git a/patches/cve/4.1.x.scc b/patches/cve/4.1.x.scc
index 97f8d60..7901020 100644
--- a/patches/cve/4.1.x.scc
+++ b/patches/cve/4.1.x.scc
@@ -27,4 +27,5 @@ patch CVE-2018-10675-mm-mempolicy-fix-use-after-free-when-calling-get_mem.patch
 
 #fixed in 4.1.49
 patch CVE-2017-17805-crypto-salsa20-fix-blkcipher_walk-API-usage.patch
+patch CVE-2017-17806-crypto-hmac-require-that-the-underlying-hash-algorit.patch
 
diff --git a/patches/cve/CVE-2017-17806-crypto-hmac-require-that-the-underlying-hash-algorit.patch b/patches/cve/CVE-2017-17806-crypto-hmac-require-that-the-underlying-hash-algorit.patch
new file mode 100644
index 0000000..4b21af2
--- /dev/null
+++ b/patches/cve/CVE-2017-17806-crypto-hmac-require-that-the-underlying-hash-algorit.patch
@@ -0,0 +1,158 @@
+From bd7f57da8fff9b75204d6dd2b3ac6a30a6430a5c Mon Sep 17 00:00:00 2001
+From: Eric Biggers <ebiggers@google.com>
+Date: Tue, 28 Nov 2017 18:01:38 -0800
+Subject: [PATCH] crypto: hmac - require that the underlying hash algorithm is
+ unkeyed
+
+[ Upstream commit af3ff8045bbf3e32f1a448542e73abb4c8ceb6f1 ]
+
+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
+
+CVE: CVE-2017-17806 
+Upstream-Status: Backport  
+
+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>
+Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
+Signed-off-by: Andreas Wellving <andreas.wellving@enea.com>
+---
+ crypto/hmac.c                  | 6 +++++-
+ crypto/shash.c                 | 5 +++--
+ include/crypto/internal/hash.h | 8 ++++++++
+ 3 files changed, 16 insertions(+), 3 deletions(-)
+
+diff --git a/crypto/hmac.c b/crypto/hmac.c
+index 72e38c0..ba07fb6 100644
+--- a/crypto/hmac.c
++++ b/crypto/hmac.c
+@@ -194,11 +194,15 @@ static int hmac_create(struct crypto_template *tmpl, struct rtattr **tb)
+        salg = shash_attr_alg(tb[1], 0, 0);
+        if (IS_ERR(salg))
+                return PTR_ERR(salg);
++       alg = &salg->base;
+ 
++       /* The underlying hash algorithm must be unkeyed */
+        err = -EINVAL;
++       if (crypto_shash_alg_has_setkey(salg))
++               goto out_put_alg;
++
+        ds = salg->digestsize;
+        ss = salg->statesize;
+-       alg = &salg->base;
+        if (ds > alg->cra_blocksize ||
+            ss < alg->cra_blocksize)
+                goto out_put_alg;
+diff --git a/crypto/shash.c b/crypto/shash.c
+index 17510ea..73c0653 100644
+--- a/crypto/shash.c
++++ b/crypto/shash.c
+@@ -24,11 +24,12 @@
+ 
+ static const struct crypto_type crypto_shash_type;
+ 
+-static int shash_no_setkey(struct crypto_shash *tfm, const u8 *key,
+-                          unsigned int keylen)
++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)
+diff --git a/include/crypto/internal/hash.h b/include/crypto/internal/hash.h
+index a25414c..9779c35 100644
+--- a/include/crypto/internal/hash.h
++++ b/include/crypto/internal/hash.h
+@@ -83,6 +83,14 @@ int ahash_register_instance(struct crypto_template *tmpl,
+                            struct ahash_instance *inst);
+ void ahash_free_instance(struct crypto_instance *inst);
+ 
++int shash_no_setkey(struct crypto_shash *tfm, const u8 *key,
++                   unsigned int keylen);
++
++static inline bool crypto_shash_alg_has_setkey(struct shash_alg *alg)
++{
++       return alg->setkey != shash_no_setkey;
++}
++
+ int crypto_init_ahash_spawn(struct crypto_ahash_spawn *spawn,
+                            struct hash_alg_common *alg,
+                            struct crypto_instance *inst);
+-- 
+2.7.4
+