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Patch "KEYS: encrypted: avoid encrypting/decrypting stack buffers" has been added to the 4.9-stable tree

PATCH [email protected] 1 participant 1 message Jun 12, 2017

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Stable branch Security (LSM) Keys/keyrings Keys-encrypted
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This is a note to let you know that I've just added the patch titled

KEYS: encrypted: avoid encrypting/decrypting stack buffers

to the 4.9-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
keys-encrypted-avoid-encrypting-decrypting-stack-buffers.patch
and it can be found in the queue-4.9 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

Quoted 1 line

From e9ff56ac352446f55141aaef1553cee662b2e310 Mon Sep 17 00:00:00 2001

From: Eric Biggers <[email protected]>
Date: Thu, 8 Jun 2017 14:48:10 +0100
Subject: KEYS: encrypted: avoid encrypting/decrypting stack buffers

From: Eric Biggers <[email protected]>

commit e9ff56ac352446f55141aaef1553cee662b2e310 upstream.

Since v4.9, the crypto API cannot (normally) be used to encrypt/decrypt stack buffers because the stack may be virtually mapped. Fix this for the padding buffers in encrypted-keys by using ZERO_PAGE for the encryption padding and by allocating a temporary heap buffer for the decryption padding.

Tested with CONFIG_DEBUG_SG=y:

	keyctl new_session
	keyctl add user master "abcdefghijklmnop" @s
	keyid=$(keyctl add encrypted desc "new user:master 25" @s)
	datablob="$(keyctl pipe $keyid)"
	keyctl unlink $keyid
	keyid=$(keyctl add encrypted desc "load $datablob" @s)
	datablob2="$(keyctl pipe $keyid)"
	[ "$datablob" = "$datablob2" ] && echo "Success!"
Cc Andy Lutomirski <[email protected]>
Cc Herbert Xu <[email protected]>
Cc Mimi Zohar <[email protected]>
Signed-off-by Eric Biggers <[email protected]>
Signed-off-by David Howells <[email protected]>
Signed-off-by James Morris <[email protected]>
Signed-off-by Greg Kroah-Hartman <[email protected]>
---
 security/keys/encrypted-keys/encrypted.c |   17 +++++++++--------
 1 file changed, 9 insertions(+), 8 deletions(-)
security/keys/encrypted-keys/encrypted.c +9 -8
@@ -480,12 +480,9 @@ static int derived_key_encrypt(struct en
 	struct skcipher_request *req;
 	unsigned int encrypted_datalen;
 	u8 iv[AES_BLOCK_SIZE];
-	unsigned int padlen;
-	char pad[16];
 	int ret;
 
 	encrypted_datalen = roundup(epayload->decrypted_datalen, blksize);
-	padlen = encrypted_datalen - epayload->decrypted_datalen;
 
 	req = init_skcipher_req(derived_key, derived_keylen);
 	ret = PTR_ERR(req);

@@ -493,11 +490,10 @@ static int derived_key_encrypt(struct en
 		goto out;
 	dump_decrypted_data(epayload);
 
-	memset(pad, 0, sizeof pad);
 	sg_init_table(sg_in, 2);
 	sg_set_buf(&sg_in[0], epayload->decrypted_data,
 		   epayload->decrypted_datalen);
-	sg_set_buf(&sg_in[1], pad, padlen);
+	sg_set_page(&sg_in[1], ZERO_PAGE(0), AES_BLOCK_SIZE, 0);
 
 	sg_init_table(sg_out, 1);
 	sg_set_buf(sg_out, epayload->encrypted_data, encrypted_datalen);

@@ -584,9 +580,14 @@ static int derived_key_decrypt(struct en
 	struct skcipher_request *req;
 	unsigned int encrypted_datalen;
 	u8 iv[AES_BLOCK_SIZE];
-	char pad[16];
+	u8 *pad;
 	int ret;
 
+	/* Throwaway buffer to hold the unused zero padding at the end */
+	pad = kmalloc(AES_BLOCK_SIZE, GFP_KERNEL);
+	if (!pad)
+		return -ENOMEM;
+
 	encrypted_datalen = roundup(epayload->decrypted_datalen, blksize);
 	req = init_skcipher_req(derived_key, derived_keylen);
 	ret = PTR_ERR(req);

@@ -594,13 +595,12 @@ static int derived_key_decrypt(struct en
 		goto out;
 	dump_encrypted_data(epayload, encrypted_datalen);
 
-	memset(pad, 0, sizeof pad);
 	sg_init_table(sg_in, 1);
 	sg_init_table(sg_out, 2);
 	sg_set_buf(sg_in, epayload->encrypted_data, encrypted_datalen);
 	sg_set_buf(&sg_out[0], epayload->decrypted_data,
 		   epayload->decrypted_datalen);
-	sg_set_buf(&sg_out[1], pad, sizeof pad);
+	sg_set_buf(&sg_out[1], pad, AES_BLOCK_SIZE);
 
 	memcpy(iv, epayload->iv, sizeof(iv));
 	skcipher_request_set_crypt(req, sg_in, sg_out, encrypted_datalen, iv);

@@ -612,6 +612,7 @@ static int derived_key_decrypt(struct en
 		goto out;
 	dump_decrypted_data(epayload);
 out:
+	kfree(pad);
 	return ret;
 }

Patches currently in stable-queue which might be from [email protected] are

queue-4.9/keys-encrypted-avoid-encrypting-decrypting-stack-buffers.patch queue-4.9/keys-fix-freeing-uninitialized-memory-in-key_update.patch queue-4.9/keys-fix-dereferencing-null-payload-with-nonzero-length.patch