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/*
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* Copyright (C) 2011 Nokia Corporation
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* Copyright (C) 2011 Intel Corporation
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*
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* Author:
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* Dmitry Kasatkin <dmitry.kasatkin@nokia.com>
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* <dmitry.kasatkin@intel.com>
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation, version 2 of the License.
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*
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* File: sign.c
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* implements signature (RSA) verification
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* pkcs decoding is based on LibTomCrypt code
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*/
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#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
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#include <linux/err.h>
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#include <linux/module.h>
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#include <linux/slab.h>
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#include <linux/key.h>
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#include <linux/crypto.h>
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#include <crypto/hash.h>
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#include <crypto/sha.h>
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#include <keys/user-type.h>
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#include <linux/mpi.h>
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#include <linux/digsig.h>
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static struct crypto_shash *shash;
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static const char *pkcs_1_v1_5_decode_emsa(const unsigned char *msg,
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unsigned long msglen,
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unsigned long modulus_bitlen,
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unsigned long *outlen)
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{
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unsigned long modulus_len, ps_len, i;
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modulus_len = (modulus_bitlen >> 3) + (modulus_bitlen & 7 ? 1 : 0);
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/* test message size */
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if ((msglen > modulus_len) || (modulus_len < 11))
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return NULL;
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/* separate encoded message */
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if (msg[0] != 0x00 || msg[1] != 0x01)
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return NULL;
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for (i = 2; i < modulus_len - 1; i++)
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if (msg[i] != 0xFF)
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break;
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/* separator check */
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if (msg[i] != 0)
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/* There was no octet with hexadecimal value 0x00
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to separate ps from m. */
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return NULL;
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ps_len = i - 2;
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*outlen = (msglen - (2 + ps_len + 1));
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return msg + 2 + ps_len + 1;
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}
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/*
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* RSA Signature verification with public key
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*/
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static int digsig_verify_rsa(struct key *key,
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const char *sig, int siglen,
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const char *h, int hlen)
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{
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int err = -EINVAL;
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unsigned long len;
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unsigned long mlen, mblen;
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unsigned nret, l;
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int head, i;
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unsigned char *out1 = NULL;
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const char *m;
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MPI in = NULL, res = NULL, pkey[2];
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uint8_t *p, *datap;
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const uint8_t *endp;
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const struct user_key_payload *ukp;
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struct pubkey_hdr *pkh;
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down_read(&key->sem);
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ukp = user_key_payload_locked(key);
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if (!ukp) {
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/* key was revoked before we acquired its semaphore */
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err = -EKEYREVOKED;
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goto err1;
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}
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if (ukp->datalen < sizeof(*pkh))
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goto err1;
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pkh = (struct pubkey_hdr *)ukp->data;
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if (pkh->version != 1)
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goto err1;
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if (pkh->algo != PUBKEY_ALGO_RSA)
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goto err1;
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if (pkh->nmpi != 2)
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goto err1;
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datap = pkh->mpi;
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endp = ukp->data + ukp->datalen;
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for (i = 0; i < pkh->nmpi; i++) {
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unsigned int remaining = endp - datap;
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pkey[i] = mpi_read_from_buffer(datap, &remaining);
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lib/mpi: mpi_read_from_buffer(): return error code
mpi_read_from_buffer() reads a MPI from a buffer into a newly allocated
MPI instance. It expects the buffer's leading two bytes to contain the
number of bits, followed by the actual payload.
On failure, it returns NULL and updates the in/out argument ret_nread
somewhat inconsistently:
- If the given buffer is too short to contain the leading two bytes
encoding the number of bits or their value is unsupported, then
ret_nread will be cleared.
- If the allocation of the resulting MPI instance fails, ret_nread is left
as is.
The only user of mpi_read_from_buffer(), digsig_verify_rsa(), simply checks
for a return value of NULL and returns -ENOMEM if that happens.
While this is all of cosmetic nature only, there is another error condition
which currently isn't detectable by the caller of mpi_read_from_buffer():
if the given buffer is too small to hold the number of bits as encoded in
its first two bytes, the return value will be non-NULL and *ret_nread > 0.
In preparation of communicating this condition to the caller, let
mpi_read_from_buffer() return error values by means of the ERR_PTR()
mechanism.
Make the sole caller of mpi_read_from_buffer(), digsig_verify_rsa(),
check the return value for IS_ERR() rather than == NULL. If IS_ERR() is
true, return the associated error value rather than the fixed -ENOMEM.
Signed-off-by: Nicolai Stange <nicstange@gmail.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
9 years ago
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if (IS_ERR(pkey[i])) {
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err = PTR_ERR(pkey[i]);
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goto err;
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lib/mpi: mpi_read_from_buffer(): return error code
mpi_read_from_buffer() reads a MPI from a buffer into a newly allocated
MPI instance. It expects the buffer's leading two bytes to contain the
number of bits, followed by the actual payload.
On failure, it returns NULL and updates the in/out argument ret_nread
somewhat inconsistently:
- If the given buffer is too short to contain the leading two bytes
encoding the number of bits or their value is unsupported, then
ret_nread will be cleared.
- If the allocation of the resulting MPI instance fails, ret_nread is left
as is.
The only user of mpi_read_from_buffer(), digsig_verify_rsa(), simply checks
for a return value of NULL and returns -ENOMEM if that happens.
While this is all of cosmetic nature only, there is another error condition
which currently isn't detectable by the caller of mpi_read_from_buffer():
if the given buffer is too small to hold the number of bits as encoded in
its first two bytes, the return value will be non-NULL and *ret_nread > 0.
In preparation of communicating this condition to the caller, let
mpi_read_from_buffer() return error values by means of the ERR_PTR()
mechanism.
Make the sole caller of mpi_read_from_buffer(), digsig_verify_rsa(),
check the return value for IS_ERR() rather than == NULL. If IS_ERR() is
true, return the associated error value rather than the fixed -ENOMEM.
Signed-off-by: Nicolai Stange <nicstange@gmail.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
9 years ago
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}
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datap += remaining;
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}
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mblen = mpi_get_nbits(pkey[0]);
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mlen = DIV_ROUND_UP(mblen, 8);
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if (mlen == 0) {
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err = -EINVAL;
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goto err;
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}
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err = -ENOMEM;
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out1 = kzalloc(mlen, GFP_KERNEL);
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if (!out1)
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goto err;
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nret = siglen;
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in = mpi_read_from_buffer(sig, &nret);
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lib/mpi: mpi_read_from_buffer(): return error code
mpi_read_from_buffer() reads a MPI from a buffer into a newly allocated
MPI instance. It expects the buffer's leading two bytes to contain the
number of bits, followed by the actual payload.
On failure, it returns NULL and updates the in/out argument ret_nread
somewhat inconsistently:
- If the given buffer is too short to contain the leading two bytes
encoding the number of bits or their value is unsupported, then
ret_nread will be cleared.
- If the allocation of the resulting MPI instance fails, ret_nread is left
as is.
The only user of mpi_read_from_buffer(), digsig_verify_rsa(), simply checks
for a return value of NULL and returns -ENOMEM if that happens.
While this is all of cosmetic nature only, there is another error condition
which currently isn't detectable by the caller of mpi_read_from_buffer():
if the given buffer is too small to hold the number of bits as encoded in
its first two bytes, the return value will be non-NULL and *ret_nread > 0.
In preparation of communicating this condition to the caller, let
mpi_read_from_buffer() return error values by means of the ERR_PTR()
mechanism.
Make the sole caller of mpi_read_from_buffer(), digsig_verify_rsa(),
check the return value for IS_ERR() rather than == NULL. If IS_ERR() is
true, return the associated error value rather than the fixed -ENOMEM.
Signed-off-by: Nicolai Stange <nicstange@gmail.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
9 years ago
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if (IS_ERR(in)) {
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err = PTR_ERR(in);
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goto err;
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lib/mpi: mpi_read_from_buffer(): return error code
mpi_read_from_buffer() reads a MPI from a buffer into a newly allocated
MPI instance. It expects the buffer's leading two bytes to contain the
number of bits, followed by the actual payload.
On failure, it returns NULL and updates the in/out argument ret_nread
somewhat inconsistently:
- If the given buffer is too short to contain the leading two bytes
encoding the number of bits or their value is unsupported, then
ret_nread will be cleared.
- If the allocation of the resulting MPI instance fails, ret_nread is left
as is.
The only user of mpi_read_from_buffer(), digsig_verify_rsa(), simply checks
for a return value of NULL and returns -ENOMEM if that happens.
While this is all of cosmetic nature only, there is another error condition
which currently isn't detectable by the caller of mpi_read_from_buffer():
if the given buffer is too small to hold the number of bits as encoded in
its first two bytes, the return value will be non-NULL and *ret_nread > 0.
In preparation of communicating this condition to the caller, let
mpi_read_from_buffer() return error values by means of the ERR_PTR()
mechanism.
Make the sole caller of mpi_read_from_buffer(), digsig_verify_rsa(),
check the return value for IS_ERR() rather than == NULL. If IS_ERR() is
true, return the associated error value rather than the fixed -ENOMEM.
Signed-off-by: Nicolai Stange <nicstange@gmail.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
9 years ago
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}
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res = mpi_alloc(mpi_get_nlimbs(in) * 2);
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if (!res)
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goto err;
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err = mpi_powm(res, in, pkey[1], pkey[0]);
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if (err)
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goto err;
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if (mpi_get_nlimbs(res) * BYTES_PER_MPI_LIMB > mlen) {
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err = -EINVAL;
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goto err;
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}
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p = mpi_get_buffer(res, &l, NULL);
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if (!p) {
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err = -EINVAL;
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goto err;
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}
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len = mlen;
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head = len - l;
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memset(out1, 0, head);
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memcpy(out1 + head, p, l);
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kfree(p);
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m = pkcs_1_v1_5_decode_emsa(out1, len, mblen, &len);
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if (!m || len != hlen || memcmp(m, h, hlen))
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err = -EINVAL;
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err:
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mpi_free(in);
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mpi_free(res);
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kfree(out1);
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while (--i >= 0)
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mpi_free(pkey[i]);
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err1:
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up_read(&key->sem);
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return err;
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}
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/**
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* digsig_verify() - digital signature verification with public key
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* @keyring: keyring to search key in
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* @sig: digital signature
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* @siglen: length of the signature
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* @data: data
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* @datalen: length of the data
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*
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* Returns 0 on success, -EINVAL otherwise
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*
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* Verifies data integrity against digital signature.
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* Currently only RSA is supported.
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* Normally hash of the content is used as a data for this function.
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*
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*/
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int digsig_verify(struct key *keyring, const char *sig, int siglen,
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const char *data, int datalen)
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{
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int err = -ENOMEM;
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struct signature_hdr *sh = (struct signature_hdr *)sig;
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struct shash_desc *desc = NULL;
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unsigned char hash[SHA1_DIGEST_SIZE];
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struct key *key;
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char name[20];
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if (siglen < sizeof(*sh) + 2)
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return -EINVAL;
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if (sh->algo != PUBKEY_ALGO_RSA)
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return -ENOTSUPP;
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sprintf(name, "%llX", __be64_to_cpup((uint64_t *)sh->keyid));
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if (keyring) {
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/* search in specific keyring */
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key_ref_t kref;
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kref = keyring_search(make_key_ref(keyring, 1UL),
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&key_type_user, name);
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if (IS_ERR(kref))
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key = ERR_CAST(kref);
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else
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key = key_ref_to_ptr(kref);
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} else {
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key = request_key(&key_type_user, name, NULL);
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}
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if (IS_ERR(key)) {
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pr_err("key not found, id: %s\n", name);
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return PTR_ERR(key);
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}
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desc = kzalloc(sizeof(*desc) + crypto_shash_descsize(shash),
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GFP_KERNEL);
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if (!desc)
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goto err;
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desc->tfm = shash;
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desc->flags = CRYPTO_TFM_REQ_MAY_SLEEP;
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crypto_shash_init(desc);
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crypto_shash_update(desc, data, datalen);
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crypto_shash_update(desc, sig, sizeof(*sh));
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crypto_shash_final(desc, hash);
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kfree(desc);
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/* pass signature mpis address */
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err = digsig_verify_rsa(key, sig + sizeof(*sh), siglen - sizeof(*sh),
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hash, sizeof(hash));
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err:
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key_put(key);
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return err ? -EINVAL : 0;
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}
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EXPORT_SYMBOL_GPL(digsig_verify);
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static int __init digsig_init(void)
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{
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shash = crypto_alloc_shash("sha1", 0, 0);
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if (IS_ERR(shash)) {
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pr_err("shash allocation failed\n");
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return PTR_ERR(shash);
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}
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return 0;
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}
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static void __exit digsig_cleanup(void)
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{
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|
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crypto_free_shash(shash);
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}
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module_init(digsig_init);
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module_exit(digsig_cleanup);
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MODULE_LICENSE("GPL");
|