crypto: hash - Zap unaligned buffers

Some unaligned buffers on the stack weren't zapped properly which
may cause secret data to be leaked.  This patch fixes them by doing
a zero memset.

It is also possible for us to place random kernel stack contents
in the digest buffer if a digest operation fails.  This is fixed
by only copying if the operation succeeded.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

2 files changed, 12 insertions, 5 deletions

diff --git a/crypto/ahash.c b/crypto/ahash.c
index cc824ef25830..1576f95f9afe 100644
--- a/crypto/ahash.c
+++ b/crypto/ahash.c
@@ -152,8 +152,7 @@ static int ahash_setkey_unaligned(struct crypto_ahash *tfm, const u8 *key,
         alignbuffer = (u8 *)ALIGN((unsigned long)buffer, alignmask + 1);
         memcpy(alignbuffer, key, keylen);
         ret = ahash->setkey(tfm, alignbuffer, keylen);
-        memset(alignbuffer, 0, keylen);
-        kfree(buffer);
+        kzfree(buffer);
         return ret;
 }
 
diff --git a/crypto/shash.c b/crypto/shash.c
index fd92c03b38fc..e54328364a85 100644
--- a/crypto/shash.c
+++ b/crypto/shash.c
@@ -45,8 +45,7 @@ static int shash_setkey_unaligned(struct crypto_shash *tfm, const u8 *key,
         alignbuffer = (u8 *)ALIGN((unsigned long)buffer, alignmask + 1);
         memcpy(alignbuffer, key, keylen);
         err = shash->setkey(tfm, alignbuffer, keylen);
-        memset(alignbuffer, 0, keylen);
-        kfree(buffer);
+        kzfree(buffer);
         return err;
 }
 
@@ -79,13 +78,16 @@ static int shash_update_unaligned(struct shash_desc *desc, const u8 *data,
                                      ((unsigned long)data & alignmask);
         u8 buf[shash_align_buffer_size(unaligned_len, alignmask)]
                 __attribute__ ((aligned));
+        int err;
 
         if (unaligned_len > len)
                 unaligned_len = len;
 
         memcpy(buf, data, unaligned_len);
+        err = shash->update(desc, buf, unaligned_len);
+        memset(buf, 0, unaligned_len);
 
-        return shash->update(desc, buf, unaligned_len) ?:
+        return err ?:
                shash->update(desc, data + unaligned_len, len - unaligned_len);
 }
 
@@ -114,7 +116,13 @@ static int shash_final_unaligned(struct shash_desc *desc, u8 *out)
         int err;
 
         err = shash->final(desc, buf);
+        if (err)
+                goto out;
+
         memcpy(out, buf, ds);
+
+out:
+        memset(buf, 0, ds);
         return err;
 }