| // 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| /* key was revoked before we acquired its semaphore */ |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, 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"); |