[PATCH 1/1] KEYS: encrypted: fix buffer overread in valid_master_desc()

[PATCH 1/1] KEYS: encrypted: fix buffer overread in valid_master_desc()

[Jin Qian]

From: Eric Biggers <ebiggers@google.com>

commit 794b4bc292f5d31739d89c0202c54e7dc9bc3add upstream

With the 'encrypted' key type it was possible for userspace to provide a
data blob ending with a master key description shorter than expected,
e.g. 'keyctl add encrypted desc "new x" @s'.  When validating such a
master key description, validate_master_desc() could read beyond the end
of the buffer.  Fix this by using strncmp() instead of memcmp().  [Also
clean up the code to deduplicate some logic.]

Cc: stable at vger.kernel.org
Cc: Mimi Zohar <zohar@linux.vnet.ibm.com>
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: James Morris <james.l.morris@oracle.com>
Signed-off-by: Jin Qian <jinqian@android.com>
---
 security/keys/encrypted-keys/encrypted.c | 31 +++++++++++++++----------------
 1 file changed, 15 insertions(+), 16 deletions(-)

diff --git a/security/keys/encrypted-keys/encrypted.c b/security/keys/encrypted-keys/encrypted.c
index a871159bf03c..ead2fd60244d 100644
--- a/security/keys/encrypted-keys/encrypted.c
+++ b/security/keys/encrypted-keys/encrypted.c
@@ -141,23 +141,22 @@ static int valid_ecryptfs_desc(const char *ecryptfs_desc)
  */
 static int valid_master_desc(const char *new_desc, const char *orig_desc)
 {
-	if (!memcmp(new_desc, KEY_TRUSTED_PREFIX, KEY_TRUSTED_PREFIX_LEN)) {
-		if (strlen(new_desc) == KEY_TRUSTED_PREFIX_LEN)
-			goto out;
-		if (orig_desc)
-			if (memcmp(new_desc, orig_desc, KEY_TRUSTED_PREFIX_LEN))
-				goto out;
-	} else if (!memcmp(new_desc, KEY_USER_PREFIX, KEY_USER_PREFIX_LEN)) {
-		if (strlen(new_desc) == KEY_USER_PREFIX_LEN)
-			goto out;
-		if (orig_desc)
-			if (memcmp(new_desc, orig_desc, KEY_USER_PREFIX_LEN))
-				goto out;
-	} else
-		goto out;
+	int prefix_len;
+
+	if (!strncmp(new_desc, KEY_TRUSTED_PREFIX, KEY_TRUSTED_PREFIX_LEN))
+		prefix_len = KEY_TRUSTED_PREFIX_LEN;
+	else if (!strncmp(new_desc, KEY_USER_PREFIX, KEY_USER_PREFIX_LEN))
+		prefix_len = KEY_USER_PREFIX_LEN;
+	else
+		return -EINVAL;
+
+	if (!new_desc[prefix_len])
+		return -EINVAL;
+
+	if (orig_desc && strncmp(new_desc, orig_desc, prefix_len))
+		return -EINVAL;
+
 	return 0;
-out:
-	return -EINVAL;
 }
 
 /*
-- 
2.16.0.rc1.238.g530d649a79-goog

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[PATCH 1/1] KEYS: encrypted: fix buffer overread in valid_master_desc()

[Eric Biggers]

On Mon, Feb 05, 2018 at 12:02:46PM -0800, Jin Qian wrote:
> From: Eric Biggers <ebiggers@google.com>
> 
> commit 794b4bc292f5d31739d89c0202c54e7dc9bc3add upstream
> 
> With the 'encrypted' key type it was possible for userspace to provide a
> data blob ending with a master key description shorter than expected,
> e.g. 'keyctl add encrypted desc "new x" @s'.  When validating such a
> master key description, validate_master_desc() could read beyond the end
> of the buffer.  Fix this by using strncmp() instead of memcmp().  [Also
> clean up the code to deduplicate some logic.]
> 
> Cc: stable at vger.kernel.org
> Cc: Mimi Zohar <zohar@linux.vnet.ibm.com>
> Signed-off-by: Eric Biggers <ebiggers@google.com>
> Signed-off-by: David Howells <dhowells@redhat.com>
> Signed-off-by: James Morris <james.l.morris@oracle.com>
> Signed-off-by: Jin Qian <jinqian@android.com>
> ---
>  security/keys/encrypted-keys/encrypted.c | 31 +++++++++++++++----------------
>  1 file changed, 15 insertions(+), 16 deletions(-)
> 

Hi Jin, see Documentation/stable_kernel_rules.txt -- patches for stable should
be sent To: stable at vger.kernel.org (and generally with a lighter Cc: list,
unless it's a complicated backport), and you need to say which kernel version(s)
it should be applied to.  Also for upstream commits that cherry-pick cleanly,
such as this one, you don't need to send an actual patch but rather just request
that it be applied.  The reason it should be applied is helpful too; in this
case the commit fixes a bug that caused a KASAN warning.

Thanks!

- Eric
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[PATCH 1/1] KEYS: encrypted: fix buffer overread in valid_master_desc()

[Jin Qian]

From: Eric Biggers <ebiggers@google.com>

commit 794b4bc292f5d31739d89c0202c54e7dc9bc3add upstream

With the 'encrypted' key type it was possible for userspace to provide a
data blob ending with a master key description shorter than expected,
e.g. 'keyctl add encrypted desc "new x" @s'.  When validating such a
master key description, validate_master_desc() could read beyond the end
of the buffer.  Fix this by using strncmp() instead of memcmp().  [Also
clean up the code to deduplicate some logic.]

Cc: linux-stable <stable@vger.kernel.org> # 3.18.y
Cc: Mimi Zohar <zohar@linux.vnet.ibm.com>
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: James Morris <james.l.morris@oracle.com>
Signed-off-by: Jin Qian <jinqian@google.com>
---
 security/keys/encrypted-keys/encrypted.c | 31 +++++++++++++++----------------
 1 file changed, 15 insertions(+), 16 deletions(-)

diff --git a/security/keys/encrypted-keys/encrypted.c b/security/keys/encrypted-keys/encrypted.c
index 89d5695c51cd..20251ee5c491 100644
--- a/security/keys/encrypted-keys/encrypted.c
+++ b/security/keys/encrypted-keys/encrypted.c
@@ -141,23 +141,22 @@ static int valid_ecryptfs_desc(const char *ecryptfs_desc)
  */
 static int valid_master_desc(const char *new_desc, const char *orig_desc)
 {
-	if (!memcmp(new_desc, KEY_TRUSTED_PREFIX, KEY_TRUSTED_PREFIX_LEN)) {
-		if (strlen(new_desc) == KEY_TRUSTED_PREFIX_LEN)
-			goto out;
-		if (orig_desc)
-			if (memcmp(new_desc, orig_desc, KEY_TRUSTED_PREFIX_LEN))
-				goto out;
-	} else if (!memcmp(new_desc, KEY_USER_PREFIX, KEY_USER_PREFIX_LEN)) {
-		if (strlen(new_desc) == KEY_USER_PREFIX_LEN)
-			goto out;
-		if (orig_desc)
-			if (memcmp(new_desc, orig_desc, KEY_USER_PREFIX_LEN))
-				goto out;
-	} else
-		goto out;
+	int prefix_len;
+
+	if (!strncmp(new_desc, KEY_TRUSTED_PREFIX, KEY_TRUSTED_PREFIX_LEN))
+		prefix_len = KEY_TRUSTED_PREFIX_LEN;
+	else if (!strncmp(new_desc, KEY_USER_PREFIX, KEY_USER_PREFIX_LEN))
+		prefix_len = KEY_USER_PREFIX_LEN;
+	else
+		return -EINVAL;
+
+	if (!new_desc[prefix_len])
+		return -EINVAL;
+
+	if (orig_desc && strncmp(new_desc, orig_desc, prefix_len))
+		return -EINVAL;
+
 	return 0;
-out:
-	return -EINVAL;
 }
 
 /*
-- 
2.16.0.rc1.238.g530d649a79-goog

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[PATCH 1/1] KEYS: encrypted: fix buffer overread in valid_master_desc()

[Jin Qian]

From: Eric Biggers <ebiggers@google.com>

commit 794b4bc292f5d31739d89c0202c54e7dc9bc3add upstream

With the 'encrypted' key type it was possible for userspace to provide a
data blob ending with a master key description shorter than expected,
e.g. 'keyctl add encrypted desc "new x" @s'.  When validating such a
master key description, validate_master_desc() could read beyond the end
of the buffer.  Fix this by using strncmp() instead of memcmp().  [Also
clean up the code to deduplicate some logic.]

Cc: linux-stable <stable@vger.kernel.org> # 4.4.y
Cc: Mimi Zohar <zohar@linux.vnet.ibm.com>
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: James Morris <james.l.morris@oracle.com>
Signed-off-by: Jin Qian <jinqian@google.com>
Signed-off-by: Jin Qian <jinqian@android.com>
---
 security/keys/encrypted-keys/encrypted.c | 31 +++++++++++++++----------------
 1 file changed, 15 insertions(+), 16 deletions(-)

diff --git a/security/keys/encrypted-keys/encrypted.c b/security/keys/encrypted-keys/encrypted.c
index ce295c0c1da0..e44e844c8ec4 100644
--- a/security/keys/encrypted-keys/encrypted.c
+++ b/security/keys/encrypted-keys/encrypted.c
@@ -141,23 +141,22 @@ static int valid_ecryptfs_desc(const char *ecryptfs_desc)
  */
 static int valid_master_desc(const char *new_desc, const char *orig_desc)
 {
-	if (!memcmp(new_desc, KEY_TRUSTED_PREFIX, KEY_TRUSTED_PREFIX_LEN)) {
-		if (strlen(new_desc) == KEY_TRUSTED_PREFIX_LEN)
-			goto out;
-		if (orig_desc)
-			if (memcmp(new_desc, orig_desc, KEY_TRUSTED_PREFIX_LEN))
-				goto out;
-	} else if (!memcmp(new_desc, KEY_USER_PREFIX, KEY_USER_PREFIX_LEN)) {
-		if (strlen(new_desc) == KEY_USER_PREFIX_LEN)
-			goto out;
-		if (orig_desc)
-			if (memcmp(new_desc, orig_desc, KEY_USER_PREFIX_LEN))
-				goto out;
-	} else
-		goto out;
+	int prefix_len;
+
+	if (!strncmp(new_desc, KEY_TRUSTED_PREFIX, KEY_TRUSTED_PREFIX_LEN))
+		prefix_len = KEY_TRUSTED_PREFIX_LEN;
+	else if (!strncmp(new_desc, KEY_USER_PREFIX, KEY_USER_PREFIX_LEN))
+		prefix_len = KEY_USER_PREFIX_LEN;
+	else
+		return -EINVAL;
+
+	if (!new_desc[prefix_len])
+		return -EINVAL;
+
+	if (orig_desc && strncmp(new_desc, orig_desc, prefix_len))
+		return -EINVAL;
+
 	return 0;
-out:
-	return -EINVAL;
 }
 
 /*
-- 
2.16.0.rc1.238.g530d649a79-goog

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