| Message ID | 20221209150633.1033556-1-roberto.sassu@huaweicloud.com (mailing list archive) |
|---|---|
| State | Not Applicable |
| Delegated to: | Herbert Xu |
| Headers | show |
| Series | [v2] KEYS: asymmetric: Copy sig and digest in public_key_verify_signature() | expand |
On Fri, Dec 09, 2022 at 04:06:33PM +0100, Roberto Sassu wrote: > + /* key is used to store the sig and digest too. */ > + key = kmalloc(key_max_len, GFP_KERNEL); > if (!key) > goto error_free_req; Maybe just call this 'buf', as the key is just one of the purposes the buffer is used for now. > + /* Cannot use one scatterlist. The first needs to be s->s_size long. */ > + sg_set_buf(&src_sg[0], key, sig->s_size); > + sg_set_buf(&src_sg[1], key + sig->s_size, sig->digest_size); > akcipher_request_set_crypt(req, src_sg, NULL, sig->s_size, > sig->digest_size); AFAIK, none of the crypto APIs that operate on 'scatterlist' are supposed to care how the data is divided up into scatterlist elements. So it sounds like there is another bug that needs to be fixed. It should be fixed, not worked around. - Eric
On Fri, 2022-12-09 at 11:04 -0800, Eric Biggers wrote: > On Fri, Dec 09, 2022 at 04:06:33PM +0100, Roberto Sassu wrote: > > + /* key is used to store the sig and digest too. */ > > + key = kmalloc(key_max_len, GFP_KERNEL); > > if (!key) > > goto error_free_req; > > Maybe just call this 'buf', as the key is just one of the purposes the buffer is > used for now. Yes, better. > > + /* Cannot use one scatterlist. The first needs to be s->s_size long. */ > > + sg_set_buf(&src_sg[0], key, sig->s_size); > > + sg_set_buf(&src_sg[1], key + sig->s_size, sig->digest_size); > > akcipher_request_set_crypt(req, src_sg, NULL, sig->s_size, > > sig->digest_size); > > AFAIK, none of the crypto APIs that operate on 'scatterlist' are supposed to > care how the data is divided up into scatterlist elements. So it sounds like > there is another bug that needs to be fixed. It should be fixed, not worked > around. The problem is a misalignment between req->src_len (set to sig->s_size by akcipher_request_set_crypt()) and the length of the scatterlist (if we set the latter to sig->s_size + sig->digest_size). When rsa_enc() calls mpi_read_raw_from_sgl(), it passes req->src_len as argument, and the latter allocates the MPI according to that. However, it does parsing depending on the length of the scatterlist. If there are two scatterlists, it is not a problem, there is no misalignment. mpi_read_raw_from_sgl() picks the first. If there is just one, mpi_read_raw_from_sgl() parses all data there. Roberto
On Mon, Dec 12, 2022 at 10:07:38AM +0100, Roberto Sassu wrote: > > The problem is a misalignment between req->src_len (set to sig->s_size > by akcipher_request_set_crypt()) and the length of the scatterlist (if > we set the latter to sig->s_size + sig->digest_size). > > When rsa_enc() calls mpi_read_raw_from_sgl(), it passes req->src_len as > argument, and the latter allocates the MPI according to that. However, > it does parsing depending on the length of the scatterlist. > > If there are two scatterlists, it is not a problem, there is no > misalignment. mpi_read_raw_from_sgl() picks the first. If there is just > one, mpi_read_raw_from_sgl() parses all data there. Thanks for the explanation. That's definitely a bug which should be fixed either in the RSA code or in MPI. I'll look into it. Cheers,
On Mon, 2022-12-12 at 17:15 +0800, Herbert Xu wrote: > On Mon, Dec 12, 2022 at 10:07:38AM +0100, Roberto Sassu wrote: > > The problem is a misalignment between req->src_len (set to sig->s_size > > by akcipher_request_set_crypt()) and the length of the scatterlist (if > > we set the latter to sig->s_size + sig->digest_size). > > > > When rsa_enc() calls mpi_read_raw_from_sgl(), it passes req->src_len as > > argument, and the latter allocates the MPI according to that. However, > > it does parsing depending on the length of the scatterlist. > > > > If there are two scatterlists, it is not a problem, there is no > > misalignment. mpi_read_raw_from_sgl() picks the first. If there is just > > one, mpi_read_raw_from_sgl() parses all data there. > > Thanks for the explanation. That's definitely a bug which should > be fixed either in the RSA code or in MPI. > > I'll look into it. Hi Herbert do you have any news on this bug? Thanks Roberto
diff --git a/crypto/asymmetric_keys/public_key.c b/crypto/asymmetric_keys/public_key.c index 2f8352e88860..ccc091119972 100644 --- a/crypto/asymmetric_keys/public_key.c +++ b/crypto/asymmetric_keys/public_key.c @@ -363,6 +363,7 @@ int public_key_verify_signature(const struct public_key *pkey, struct scatterlist src_sg[2]; char alg_name[CRYPTO_MAX_ALG_NAME]; char *key, *ptr; + u32 key_max_len; int ret; pr_devel("==>%s()\n", __func__); @@ -400,8 +401,12 @@ int public_key_verify_signature(const struct public_key *pkey, if (!req) goto error_free_tfm; - key = kmalloc(pkey->keylen + sizeof(u32) * 2 + pkey->paramlen, - GFP_KERNEL); + key_max_len = max_t(u32, + pkey->keylen + sizeof(u32) * 2 + pkey->paramlen, + sig->s_size + sig->digest_size); + + /* key is used to store the sig and digest too. */ + key = kmalloc(key_max_len, GFP_KERNEL); if (!key) goto error_free_req; @@ -424,9 +429,13 @@ int public_key_verify_signature(const struct public_key *pkey, goto error_free_key; } + memcpy(key, sig->s, sig->s_size); + memcpy(key + sig->s_size, sig->digest, sig->digest_size); + sg_init_table(src_sg, 2); - sg_set_buf(&src_sg[0], sig->s, sig->s_size); - sg_set_buf(&src_sg[1], sig->digest, sig->digest_size); + /* Cannot use one scatterlist. The first needs to be s->s_size long. */ + sg_set_buf(&src_sg[0], key, sig->s_size); + sg_set_buf(&src_sg[1], key + sig->s_size, sig->digest_size); akcipher_request_set_crypt(req, src_sg, NULL, sig->s_size, sig->digest_size); crypto_init_wait(&cwait);