crypto: memzero_explicit - make sure to clear out sensitive data

Recently, in commit 13aa93c70e71 ("random: add and use memzero_explicit()
for clearing data"), we have found that GCC may optimize some memset()
cases away when it detects a stack variable is not being used anymore
and going out of scope. This can happen, for example, in cases when we
are clearing out sensitive information such as keying material or any
e.g. intermediate results from crypto computations, etc.

With the help of Coccinelle, we can figure out and fix such occurences
in the crypto subsytem as well. Julia Lawall provided the following
Coccinelle program:

  @@
  type T;
  identifier x;
  @@

  T x;
  ... when exists
      when any
  -memset
  +memzero_explicit
     (&x,
  -0,
     ...)
  ... when != x
      when strict

  @@
  type T;
  identifier x;
  @@

  T x[...];
  ... when exists
      when any
  -memset
  +memzero_explicit
     (x,
  -0,
     ...)
  ... when != x
      when strict

Therefore, make use of the drop-in replacement memzero_explicit() for
exactly such cases instead of using memset().

Signed-off-by: Daniel Borkmann <dborkman@redhat.com>
Cc: Julia Lawall <julia.lawall@lip6.fr>
Cc: Herbert Xu <herbert@gondor.apana.org.au>
Cc: Theodore Ts'o <tytso@mit.edu>
Cc: Hannes Frederic Sowa <hannes@stressinduktion.org>
Acked-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
Acked-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

7 files changed, 13 insertions, 13 deletions

diff --git a/crypto/cts.c b/crypto/cts.c
index 042223f8e733..133f0874c95e 100644
--- a/crypto/cts.c
+++ b/crypto/cts.c
@@ -202,7 +202,8 @@ static int cts_cbc_decrypt(struct crypto_cts_ctx *ctx,
         /* 5. Append the tail (BB - Ln) bytes of Xn (tmp) to Cn to create En */
         memcpy(s + bsize + lastn, tmp + lastn, bsize - lastn);
         /* 6. Decrypt En to create Pn-1 */
-        memset(iv, 0, sizeof(iv));
+        memzero_explicit(iv, sizeof(iv));
+
         sg_set_buf(&sgsrc[0], s + bsize, bsize);
         sg_set_buf(&sgdst[0], d, bsize);
         err = crypto_blkcipher_decrypt_iv(&lcldesc, sgdst, sgsrc, bsize);
diff --git a/crypto/sha1_generic.c b/crypto/sha1_generic.c
index 42794803c480..7bb047432782 100644
--- a/crypto/sha1_generic.c
+++ b/crypto/sha1_generic.c
@@ -64,7 +64,7 @@ int crypto_sha1_update(struct shash_desc *desc, const u8 *data,
                         src = data + done;
                 } while (done + SHA1_BLOCK_SIZE <= len);
 
-                memset(temp, 0, sizeof(temp));
+                memzero_explicit(temp, sizeof(temp));
                 partial = 0;
         }
         memcpy(sctx->buffer + partial, src, len - done);
diff --git a/crypto/sha256_generic.c b/crypto/sha256_generic.c
index 543366779524..32c5e5ea205a 100644
--- a/crypto/sha256_generic.c
+++ b/crypto/sha256_generic.c
@@ -210,10 +210,9 @@ static void sha256_transform(u32 *state, const u8 *input)
 
         /* clear any sensitive info... */
         a = b = c = d = e = f = g = h = t1 = t2 = 0;
-        memset(W, 0, 64 * sizeof(u32));
+        memzero_explicit(W, 64 * sizeof(u32));
 }
 
-
 static int sha224_init(struct shash_desc *desc)
 {
         struct sha256_state *sctx = shash_desc_ctx(desc);
@@ -316,7 +315,7 @@ static int sha224_final(struct shash_desc *desc, u8 *hash)
         sha256_final(desc, D);
 
         memcpy(hash, D, SHA224_DIGEST_SIZE);
-        memset(D, 0, SHA256_DIGEST_SIZE);
+        memzero_explicit(D, SHA256_DIGEST_SIZE);
 
         return 0;
 }
diff --git a/crypto/sha512_generic.c b/crypto/sha512_generic.c
index 6ed124f3ea0f..04d295a8bc08 100644
--- a/crypto/sha512_generic.c
+++ b/crypto/sha512_generic.c
@@ -238,7 +238,7 @@ static int sha384_final(struct shash_desc *desc, u8 *hash)
         sha512_final(desc, D);
 
         memcpy(hash, D, 48);
-        memset(D, 0, 64);
+        memzero_explicit(D, 64);
 
         return 0;
 }
diff --git a/crypto/tgr192.c b/crypto/tgr192.c
index 87403556fd0b..3c7af0d1ff7a 100644
--- a/crypto/tgr192.c
+++ b/crypto/tgr192.c
@@ -612,7 +612,7 @@ static int tgr160_final(struct shash_desc *desc, u8 * out)
 
         tgr192_final(desc, D);
         memcpy(out, D, TGR160_DIGEST_SIZE);
-        memset(D, 0, TGR192_DIGEST_SIZE);
+        memzero_explicit(D, TGR192_DIGEST_SIZE);
 
         return 0;
 }
@@ -623,7 +623,7 @@ static int tgr128_final(struct shash_desc *desc, u8 * out)
 
         tgr192_final(desc, D);
         memcpy(out, D, TGR128_DIGEST_SIZE);
-        memset(D, 0, TGR192_DIGEST_SIZE);
+        memzero_explicit(D, TGR192_DIGEST_SIZE);
 
         return 0;
 }
diff --git a/crypto/vmac.c b/crypto/vmac.c
index 2eb11a30c29c..d84c24bd7ff7 100644
--- a/crypto/vmac.c
+++ b/crypto/vmac.c
@@ -613,7 +613,7 @@ static int vmac_final(struct shash_desc *pdesc, u8 *out)
         }
         mac = vmac(ctx->partial, ctx->partial_size, nonce, NULL, ctx);
         memcpy(out, &mac, sizeof(vmac_t));
-        memset(&mac, 0, sizeof(vmac_t));
+        memzero_explicit(&mac, sizeof(vmac_t));
         memset(&ctx->__vmac_ctx, 0, sizeof(struct vmac_ctx));
         ctx->partial_size = 0;
         return 0;
diff --git a/crypto/wp512.c b/crypto/wp512.c
index 180f1d6e03f4..ec64e7762fbb 100644
--- a/crypto/wp512.c
+++ b/crypto/wp512.c
@@ -1102,8 +1102,8 @@ static int wp384_final(struct shash_desc *desc, u8 *out)
         u8 D[64];
 
         wp512_final(desc, D);
-        memcpy (out, D, WP384_DIGEST_SIZE);
-        memset (D, 0, WP512_DIGEST_SIZE);
+        memcpy(out, D, WP384_DIGEST_SIZE);
+        memzero_explicit(D, WP512_DIGEST_SIZE);
 
         return 0;
 }
@@ -1113,8 +1113,8 @@ static int wp256_final(struct shash_desc *desc, u8 *out)
         u8 D[64];
 
         wp512_final(desc, D);
-        memcpy (out, D, WP256_DIGEST_SIZE);
-        memset (D, 0, WP512_DIGEST_SIZE);
+        memcpy(out, D, WP256_DIGEST_SIZE);
+        memzero_explicit(D, WP512_DIGEST_SIZE);
 
         return 0;
 }