linux-stable/lib/digsig.c
Linus Torvalds 028db3e290 Revert "Merge tag 'keys-acl-20190703' of git://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs"
This reverts merge 0f75ef6a9c (and thus
effectively commits

   7a1ade8475 ("keys: Provide KEYCTL_GRANT_PERMISSION")
   2e12256b9a ("keys: Replace uid/gid/perm permissions checking with an ACL")

that the merge brought in).

It turns out that it breaks booting with an encrypted volume, and Eric
biggers reports that it also breaks the fscrypt tests [1] and loading of
in-kernel X.509 certificates [2].

The root cause of all the breakage is likely the same, but David Howells
is off email so rather than try to work it out it's getting reverted in
order to not impact the rest of the merge window.

 [1] https://lore.kernel.org/lkml/20190710011559.GA7973@sol.localdomain/
 [2] https://lore.kernel.org/lkml/20190710013225.GB7973@sol.localdomain/

Link: https://lore.kernel.org/lkml/CAHk-=wjxoeMJfeBahnWH=9zShKp2bsVy527vo3_y8HfOdhwAAw@mail.gmail.com/
Reported-by: Eric Biggers <ebiggers@kernel.org>
Cc: David Howells <dhowells@redhat.com>
Cc: James Morris <jmorris@namei.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2019-07-10 18:43:43 -07:00

279 lines
5.5 KiB
C

// SPDX-License-Identifier: GPL-2.0-only
/*
* Copyright (C) 2011 Nokia Corporation
* Copyright (C) 2011 Intel Corporation
*
* Author:
* Dmitry Kasatkin <dmitry.kasatkin@nokia.com>
* <dmitry.kasatkin@intel.com>
*
* File: sign.c
* implements signature (RSA) verification
* pkcs decoding is based on LibTomCrypt code
*/
#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
#include <linux/err.h>
#include <linux/module.h>
#include <linux/slab.h>
#include <linux/key.h>
#include <linux/crypto.h>
#include <crypto/hash.h>
#include <crypto/sha.h>
#include <keys/user-type.h>
#include <linux/mpi.h>
#include <linux/digsig.h>
static struct crypto_shash *shash;
static const char *pkcs_1_v1_5_decode_emsa(const unsigned char *msg,
unsigned long msglen,
unsigned long modulus_bitlen,
unsigned long *outlen)
{
unsigned long modulus_len, ps_len, i;
modulus_len = (modulus_bitlen >> 3) + (modulus_bitlen & 7 ? 1 : 0);
/* test message size */
if ((msglen > modulus_len) || (modulus_len < 11))
return NULL;
/* separate encoded message */
if (msg[0] != 0x00 || msg[1] != 0x01)
return NULL;
for (i = 2; i < modulus_len - 1; i++)
if (msg[i] != 0xFF)
break;
/* separator check */
if (msg[i] != 0)
/* There was no octet with hexadecimal value 0x00
to separate ps from m. */
return NULL;
ps_len = i - 2;
*outlen = (msglen - (2 + ps_len + 1));
return msg + 2 + ps_len + 1;
}
/*
* RSA Signature verification with public key
*/
static int digsig_verify_rsa(struct key *key,
const char *sig, int siglen,
const char *h, int hlen)
{
int err = -EINVAL;
unsigned long len;
unsigned long mlen, mblen;
unsigned nret, l;
int head, i;
unsigned char *out1 = NULL;
const char *m;
MPI in = NULL, res = NULL, pkey[2];
uint8_t *p, *datap;
const uint8_t *endp;
const struct user_key_payload *ukp;
struct pubkey_hdr *pkh;
down_read(&key->sem);
ukp = user_key_payload_locked(key);
if (!ukp) {
/* key was revoked before we acquired its semaphore */
err = -EKEYREVOKED;
goto err1;
}
if (ukp->datalen < sizeof(*pkh))
goto err1;
pkh = (struct pubkey_hdr *)ukp->data;
if (pkh->version != 1)
goto err1;
if (pkh->algo != PUBKEY_ALGO_RSA)
goto err1;
if (pkh->nmpi != 2)
goto err1;
datap = pkh->mpi;
endp = ukp->data + ukp->datalen;
for (i = 0; i < pkh->nmpi; i++) {
unsigned int remaining = endp - datap;
pkey[i] = mpi_read_from_buffer(datap, &remaining);
if (IS_ERR(pkey[i])) {
err = PTR_ERR(pkey[i]);
goto err;
}
datap += remaining;
}
mblen = mpi_get_nbits(pkey[0]);
mlen = DIV_ROUND_UP(mblen, 8);
if (mlen == 0) {
err = -EINVAL;
goto err;
}
err = -ENOMEM;
out1 = kzalloc(mlen, GFP_KERNEL);
if (!out1)
goto err;
nret = siglen;
in = mpi_read_from_buffer(sig, &nret);
if (IS_ERR(in)) {
err = PTR_ERR(in);
goto err;
}
res = mpi_alloc(mpi_get_nlimbs(in) * 2);
if (!res)
goto err;
err = mpi_powm(res, in, pkey[1], pkey[0]);
if (err)
goto err;
if (mpi_get_nlimbs(res) * BYTES_PER_MPI_LIMB > mlen) {
err = -EINVAL;
goto err;
}
p = mpi_get_buffer(res, &l, NULL);
if (!p) {
err = -EINVAL;
goto err;
}
len = mlen;
head = len - l;
memset(out1, 0, head);
memcpy(out1 + head, p, l);
kfree(p);
m = pkcs_1_v1_5_decode_emsa(out1, len, mblen, &len);
if (!m || len != hlen || memcmp(m, h, hlen))
err = -EINVAL;
err:
mpi_free(in);
mpi_free(res);
kfree(out1);
while (--i >= 0)
mpi_free(pkey[i]);
err1:
up_read(&key->sem);
return err;
}
/**
* digsig_verify() - digital signature verification with public key
* @keyring: keyring to search key in
* @sig: digital signature
* @siglen: length of the signature
* @data: data
* @datalen: length of the data
*
* Returns 0 on success, -EINVAL otherwise
*
* Verifies data integrity against digital signature.
* Currently only RSA is supported.
* Normally hash of the content is used as a data for this function.
*
*/
int digsig_verify(struct key *keyring, const char *sig, int siglen,
const char *data, int datalen)
{
int err = -ENOMEM;
struct signature_hdr *sh = (struct signature_hdr *)sig;
struct shash_desc *desc = NULL;
unsigned char hash[SHA1_DIGEST_SIZE];
struct key *key;
char name[20];
if (siglen < sizeof(*sh) + 2)
return -EINVAL;
if (sh->algo != PUBKEY_ALGO_RSA)
return -ENOTSUPP;
sprintf(name, "%llX", __be64_to_cpup((uint64_t *)sh->keyid));
if (keyring) {
/* search in specific keyring */
key_ref_t kref;
kref = keyring_search(make_key_ref(keyring, 1UL),
&key_type_user, name, true);
if (IS_ERR(kref))
key = ERR_CAST(kref);
else
key = key_ref_to_ptr(kref);
} else {
key = request_key(&key_type_user, name, NULL);
}
if (IS_ERR(key)) {
pr_err("key not found, id: %s\n", name);
return PTR_ERR(key);
}
desc = kzalloc(sizeof(*desc) + crypto_shash_descsize(shash),
GFP_KERNEL);
if (!desc)
goto err;
desc->tfm = shash;
crypto_shash_init(desc);
crypto_shash_update(desc, data, datalen);
crypto_shash_update(desc, sig, sizeof(*sh));
crypto_shash_final(desc, hash);
kfree(desc);
/* pass signature mpis address */
err = digsig_verify_rsa(key, sig + sizeof(*sh), siglen - sizeof(*sh),
hash, sizeof(hash));
err:
key_put(key);
return err ? -EINVAL : 0;
}
EXPORT_SYMBOL_GPL(digsig_verify);
static int __init digsig_init(void)
{
shash = crypto_alloc_shash("sha1", 0, 0);
if (IS_ERR(shash)) {
pr_err("shash allocation failed\n");
return PTR_ERR(shash);
}
return 0;
}
static void __exit digsig_cleanup(void)
{
crypto_free_shash(shash);
}
module_init(digsig_init);
module_exit(digsig_cleanup);
MODULE_LICENSE("GPL");