On Tue, 2016-09-20 at 20:35 +0800, Herbert Xu wrote:
> On Tue, Sep 20, 2016 at 08:11:51AM -0400, Mimi Zohar wrote:
> > Hi Herbert,
> >
> > The initial random iv value, initialized in encrypted_init(), should
> > not be modified. Commit c3917fd "KEYS: Use skcipher", which replaced
> > the blkcipher with skcipher, modifies the iv in
> > crypto_skcipher_encrypt()/decrypt().
> >
> > The following example creates an encrypted key, writes the key to a
> > file, and then loads the key from the file. To illustrate the problem,
> > this patch provides crypto_skcipher_encrypt()/decrypt() with a copy of
> > the iv. With this change, the resulting test-key and test-key1 keys
> > are the same.
>
> Sorry, I missed the subtlety. This patch should fix the problem.
Thanks!
Mimi
>
> ---8<---
> Subject: KEYS: Fix skcipher IV clobbering
>
> The IV must not be modified by the skcipher operation so we need
> to duplicate it.
>
> Fixes: c3917fd9dfbc ("KEYS: Use skcipher")
> Cc: [email protected]
> Reported-by: Mimi Zohar <[email protected]>
> Signed-off-by: Herbert Xu <[email protected]>
>
> diff --git a/security/keys/encrypted-keys/encrypted.c
> b/security/keys/encrypted-keys/encrypted.c
> index 5adbfc3..17a0610 100644
> --- a/security/keys/encrypted-keys/encrypted.c
> +++ b/security/keys/encrypted-keys/encrypted.c
> @@ -29,6 +29,7 @@
> #include <linux/rcupdate.h>
> #include <linux/scatterlist.h>
> #include <linux/ctype.h>
> +#include <crypto/aes.h>
> #include <crypto/hash.h>
> #include <crypto/sha.h>
> #include <crypto/skcipher.h>
> @@ -478,6 +479,7 @@ static int derived_key_encrypt(struct
> encrypted_key_payload *epayload,
> struct crypto_skcipher *tfm;
> struct skcipher_request *req;
> unsigned int encrypted_datalen;
> + u8 iv[AES_BLOCK_SIZE];
> unsigned int padlen;
> char pad[16];
> int ret;
> @@ -500,8 +502,8 @@ static int derived_key_encrypt(struct
> encrypted_key_payload *epayload,
> sg_init_table(sg_out, 1);
> sg_set_buf(sg_out, epayload->encrypted_data, encrypted_datalen);
>
> - skcipher_request_set_crypt(req, sg_in, sg_out, encrypted_datalen,
> - epayload->iv);
> + memcpy(iv, epayload->iv, sizeof(iv));
> + skcipher_request_set_crypt(req, sg_in, sg_out, encrypted_datalen, iv);
> ret = crypto_skcipher_encrypt(req);
> tfm = crypto_skcipher_reqtfm(req);
> skcipher_request_free(req);
> @@ -581,6 +583,7 @@ static int derived_key_decrypt(struct
> encrypted_key_payload *epayload,
> struct crypto_skcipher *tfm;
> struct skcipher_request *req;
> unsigned int encrypted_datalen;
> + u8 iv[AES_BLOCK_SIZE];
> char pad[16];
> int ret;
>
> @@ -599,8 +602,8 @@ static int derived_key_decrypt(struct
> encrypted_key_payload *epayload,
> epayload->decrypted_datalen);
> sg_set_buf(&sg_out[1], pad, sizeof pad);
>
> - skcipher_request_set_crypt(req, sg_in, sg_out, encrypted_datalen,
> - epayload->iv);
> + memcpy(iv, epayload->iv, sizeof(iv));
> + skcipher_request_set_crypt(req, sg_in, sg_out, encrypted_datalen, iv);
> ret = crypto_skcipher_decrypt(req);
> tfm = crypto_skcipher_reqtfm(req);
> skcipher_request_free(req);
>
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