Linux kernel for sysmoBTS v2
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  1. /*
  2. * Copyright (C) 2011 Nokia Corporation
  3. * Copyright (C) 2011 Intel Corporation
  4. *
  5. * Author:
  6. * Dmitry Kasatkin <dmitry.kasatkin@nokia.com>
  7. * <dmitry.kasatkin@intel.com>
  8. *
  9. * This program is free software; you can redistribute it and/or modify
  10. * it under the terms of the GNU General Public License as published by
  11. * the Free Software Foundation, version 2 of the License.
  12. *
  13. * File: sign.c
  14. * implements signature (RSA) verification
  15. * pkcs decoding is based on LibTomCrypt code
  16. */
  17. #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  18. #include <linux/err.h>
  19. #include <linux/module.h>
  20. #include <linux/slab.h>
  21. #include <linux/key.h>
  22. #include <linux/crypto.h>
  23. #include <crypto/hash.h>
  24. #include <crypto/sha.h>
  25. #include <keys/user-type.h>
  26. #include <linux/mpi.h>
  27. #include <linux/digsig.h>
  28. static struct crypto_shash *shash;
  29. static const char *pkcs_1_v1_5_decode_emsa(const unsigned char *msg,
  30. unsigned long msglen,
  31. unsigned long modulus_bitlen,
  32. unsigned long *outlen)
  33. {
  34. unsigned long modulus_len, ps_len, i;
  35. modulus_len = (modulus_bitlen >> 3) + (modulus_bitlen & 7 ? 1 : 0);
  36. /* test message size */
  37. if ((msglen > modulus_len) || (modulus_len < 11))
  38. return NULL;
  39. /* separate encoded message */
  40. if (msg[0] != 0x00 || msg[1] != 0x01)
  41. return NULL;
  42. for (i = 2; i < modulus_len - 1; i++)
  43. if (msg[i] != 0xFF)
  44. break;
  45. /* separator check */
  46. if (msg[i] != 0)
  47. /* There was no octet with hexadecimal value 0x00
  48. to separate ps from m. */
  49. return NULL;
  50. ps_len = i - 2;
  51. *outlen = (msglen - (2 + ps_len + 1));
  52. return msg + 2 + ps_len + 1;
  53. }
  54. /*
  55. * RSA Signature verification with public key
  56. */
  57. static int digsig_verify_rsa(struct key *key,
  58. const char *sig, int siglen,
  59. const char *h, int hlen)
  60. {
  61. int err = -EINVAL;
  62. unsigned long len;
  63. unsigned long mlen, mblen;
  64. unsigned nret, l;
  65. int head, i;
  66. unsigned char *out1 = NULL;
  67. const char *m;
  68. MPI in = NULL, res = NULL, pkey[2];
  69. uint8_t *p, *datap;
  70. const uint8_t *endp;
  71. const struct user_key_payload *ukp;
  72. struct pubkey_hdr *pkh;
  73. down_read(&key->sem);
  74. ukp = user_key_payload(key);
  75. if (!ukp) {
  76. /* key was revoked before we acquired its semaphore */
  77. err = -EKEYREVOKED;
  78. goto err1;
  79. }
  80. if (ukp->datalen < sizeof(*pkh))
  81. goto err1;
  82. pkh = (struct pubkey_hdr *)ukp->data;
  83. if (pkh->version != 1)
  84. goto err1;
  85. if (pkh->algo != PUBKEY_ALGO_RSA)
  86. goto err1;
  87. if (pkh->nmpi != 2)
  88. goto err1;
  89. datap = pkh->mpi;
  90. endp = ukp->data + ukp->datalen;
  91. for (i = 0; i < pkh->nmpi; i++) {
  92. unsigned int remaining = endp - datap;
  93. pkey[i] = mpi_read_from_buffer(datap, &remaining);
  94. if (IS_ERR(pkey[i])) {
  95. err = PTR_ERR(pkey[i]);
  96. goto err;
  97. }
  98. datap += remaining;
  99. }
  100. mblen = mpi_get_nbits(pkey[0]);
  101. mlen = DIV_ROUND_UP(mblen, 8);
  102. if (mlen == 0) {
  103. err = -EINVAL;
  104. goto err;
  105. }
  106. err = -ENOMEM;
  107. out1 = kzalloc(mlen, GFP_KERNEL);
  108. if (!out1)
  109. goto err;
  110. nret = siglen;
  111. in = mpi_read_from_buffer(sig, &nret);
  112. if (IS_ERR(in)) {
  113. err = PTR_ERR(in);
  114. goto err;
  115. }
  116. res = mpi_alloc(mpi_get_nlimbs(in) * 2);
  117. if (!res)
  118. goto err;
  119. err = mpi_powm(res, in, pkey[1], pkey[0]);
  120. if (err)
  121. goto err;
  122. if (mpi_get_nlimbs(res) * BYTES_PER_MPI_LIMB > mlen) {
  123. err = -EINVAL;
  124. goto err;
  125. }
  126. p = mpi_get_buffer(res, &l, NULL);
  127. if (!p) {
  128. err = -EINVAL;
  129. goto err;
  130. }
  131. len = mlen;
  132. head = len - l;
  133. memset(out1, 0, head);
  134. memcpy(out1 + head, p, l);
  135. kfree(p);
  136. m = pkcs_1_v1_5_decode_emsa(out1, len, mblen, &len);
  137. if (!m || len != hlen || memcmp(m, h, hlen))
  138. err = -EINVAL;
  139. err:
  140. mpi_free(in);
  141. mpi_free(res);
  142. kfree(out1);
  143. while (--i >= 0)
  144. mpi_free(pkey[i]);
  145. err1:
  146. up_read(&key->sem);
  147. return err;
  148. }
  149. /**
  150. * digsig_verify() - digital signature verification with public key
  151. * @keyring: keyring to search key in
  152. * @sig: digital signature
  153. * @siglen: length of the signature
  154. * @data: data
  155. * @datalen: length of the data
  156. *
  157. * Returns 0 on success, -EINVAL otherwise
  158. *
  159. * Verifies data integrity against digital signature.
  160. * Currently only RSA is supported.
  161. * Normally hash of the content is used as a data for this function.
  162. *
  163. */
  164. int digsig_verify(struct key *keyring, const char *sig, int siglen,
  165. const char *data, int datalen)
  166. {
  167. int err = -ENOMEM;
  168. struct signature_hdr *sh = (struct signature_hdr *)sig;
  169. struct shash_desc *desc = NULL;
  170. unsigned char hash[SHA1_DIGEST_SIZE];
  171. struct key *key;
  172. char name[20];
  173. if (siglen < sizeof(*sh) + 2)
  174. return -EINVAL;
  175. if (sh->algo != PUBKEY_ALGO_RSA)
  176. return -ENOTSUPP;
  177. sprintf(name, "%llX", __be64_to_cpup((uint64_t *)sh->keyid));
  178. if (keyring) {
  179. /* search in specific keyring */
  180. key_ref_t kref;
  181. kref = keyring_search(make_key_ref(keyring, 1UL),
  182. &key_type_user, name);
  183. if (IS_ERR(kref))
  184. key = ERR_CAST(kref);
  185. else
  186. key = key_ref_to_ptr(kref);
  187. } else {
  188. key = request_key(&key_type_user, name, NULL);
  189. }
  190. if (IS_ERR(key)) {
  191. pr_err("key not found, id: %s\n", name);
  192. return PTR_ERR(key);
  193. }
  194. desc = kzalloc(sizeof(*desc) + crypto_shash_descsize(shash),
  195. GFP_KERNEL);
  196. if (!desc)
  197. goto err;
  198. desc->tfm = shash;
  199. desc->flags = CRYPTO_TFM_REQ_MAY_SLEEP;
  200. crypto_shash_init(desc);
  201. crypto_shash_update(desc, data, datalen);
  202. crypto_shash_update(desc, sig, sizeof(*sh));
  203. crypto_shash_final(desc, hash);
  204. kfree(desc);
  205. /* pass signature mpis address */
  206. err = digsig_verify_rsa(key, sig + sizeof(*sh), siglen - sizeof(*sh),
  207. hash, sizeof(hash));
  208. err:
  209. key_put(key);
  210. return err ? -EINVAL : 0;
  211. }
  212. EXPORT_SYMBOL_GPL(digsig_verify);
  213. static int __init digsig_init(void)
  214. {
  215. shash = crypto_alloc_shash("sha1", 0, 0);
  216. if (IS_ERR(shash)) {
  217. pr_err("shash allocation failed\n");
  218. return PTR_ERR(shash);
  219. }
  220. return 0;
  221. }
  222. static void __exit digsig_cleanup(void)
  223. {
  224. crypto_free_shash(shash);
  225. }
  226. module_init(digsig_init);
  227. module_exit(digsig_cleanup);
  228. MODULE_LICENSE("GPL");