x509_public_key.c 6.6 KB

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  1. // SPDX-License-Identifier: GPL-2.0-or-later
  2. /* Instantiate a public key crypto key from an X.509 Certificate
  3. *
  4. * Copyright (C) 2012 Red Hat, Inc. All Rights Reserved.
  5. * Written by David Howells (dhowells@redhat.com)
  6. */
  7. #define pr_fmt(fmt) "X.509: "fmt
  8. #ifdef __UBOOT__
  9. #include <common.h>
  10. #include <linux/compat.h>
  11. #include <linux/errno.h>
  12. #else
  13. #include <linux/module.h>
  14. #endif
  15. #include <linux/kernel.h>
  16. #ifndef __UBOOT__
  17. #include <linux/slab.h>
  18. #include <keys/asymmetric-subtype.h>
  19. #include <keys/asymmetric-parser.h>
  20. #include <keys/system_keyring.h>
  21. #include <crypto/hash.h>
  22. #include "asymmetric_keys.h"
  23. #endif
  24. #include "x509_parser.h"
  25. /*
  26. * Set up the signature parameters in an X.509 certificate. This involves
  27. * digesting the signed data and extracting the signature.
  28. */
  29. int x509_get_sig_params(struct x509_certificate *cert)
  30. {
  31. struct public_key_signature *sig = cert->sig;
  32. #ifndef __UBOOT__
  33. struct crypto_shash *tfm;
  34. struct shash_desc *desc;
  35. size_t desc_size;
  36. #endif
  37. int ret;
  38. pr_devel("==>%s()\n", __func__);
  39. if (!cert->pub->pkey_algo)
  40. cert->unsupported_key = true;
  41. if (!sig->pkey_algo)
  42. cert->unsupported_sig = true;
  43. /* We check the hash if we can - even if we can't then verify it */
  44. if (!sig->hash_algo) {
  45. cert->unsupported_sig = true;
  46. return 0;
  47. }
  48. sig->s = kmemdup(cert->raw_sig, cert->raw_sig_size, GFP_KERNEL);
  49. if (!sig->s)
  50. return -ENOMEM;
  51. sig->s_size = cert->raw_sig_size;
  52. #ifdef __UBOOT__
  53. /*
  54. * Note:
  55. * This part (filling sig->digest) should be implemented if
  56. * x509_check_for_self_signed() is enabled x509_cert_parse().
  57. * Currently, this check won't affect UEFI secure boot.
  58. */
  59. ret = 0;
  60. #else
  61. /* Allocate the hashing algorithm we're going to need and find out how
  62. * big the hash operational data will be.
  63. */
  64. tfm = crypto_alloc_shash(sig->hash_algo, 0, 0);
  65. if (IS_ERR(tfm)) {
  66. if (PTR_ERR(tfm) == -ENOENT) {
  67. cert->unsupported_sig = true;
  68. return 0;
  69. }
  70. return PTR_ERR(tfm);
  71. }
  72. desc_size = crypto_shash_descsize(tfm) + sizeof(*desc);
  73. sig->digest_size = crypto_shash_digestsize(tfm);
  74. ret = -ENOMEM;
  75. sig->digest = kmalloc(sig->digest_size, GFP_KERNEL);
  76. if (!sig->digest)
  77. goto error;
  78. desc = kzalloc(desc_size, GFP_KERNEL);
  79. if (!desc)
  80. goto error;
  81. desc->tfm = tfm;
  82. ret = crypto_shash_digest(desc, cert->tbs, cert->tbs_size, sig->digest);
  83. if (ret < 0)
  84. goto error_2;
  85. ret = is_hash_blacklisted(sig->digest, sig->digest_size, "tbs");
  86. if (ret == -EKEYREJECTED) {
  87. pr_err("Cert %*phN is blacklisted\n",
  88. sig->digest_size, sig->digest);
  89. cert->blacklisted = true;
  90. ret = 0;
  91. }
  92. error_2:
  93. kfree(desc);
  94. error:
  95. crypto_free_shash(tfm);
  96. #endif /* __UBOOT__ */
  97. pr_devel("<==%s() = %d\n", __func__, ret);
  98. return ret;
  99. }
  100. #ifndef __UBOOT__
  101. /*
  102. * Check for self-signedness in an X.509 cert and if found, check the signature
  103. * immediately if we can.
  104. */
  105. int x509_check_for_self_signed(struct x509_certificate *cert)
  106. {
  107. int ret = 0;
  108. pr_devel("==>%s()\n", __func__);
  109. if (cert->raw_subject_size != cert->raw_issuer_size ||
  110. memcmp(cert->raw_subject, cert->raw_issuer,
  111. cert->raw_issuer_size) != 0)
  112. goto not_self_signed;
  113. if (cert->sig->auth_ids[0] || cert->sig->auth_ids[1]) {
  114. /* If the AKID is present it may have one or two parts. If
  115. * both are supplied, both must match.
  116. */
  117. bool a = asymmetric_key_id_same(cert->skid, cert->sig->auth_ids[1]);
  118. bool b = asymmetric_key_id_same(cert->id, cert->sig->auth_ids[0]);
  119. if (!a && !b)
  120. goto not_self_signed;
  121. ret = -EKEYREJECTED;
  122. if (((a && !b) || (b && !a)) &&
  123. cert->sig->auth_ids[0] && cert->sig->auth_ids[1])
  124. goto out;
  125. }
  126. ret = -EKEYREJECTED;
  127. if (strcmp(cert->pub->pkey_algo, cert->sig->pkey_algo) != 0)
  128. goto out;
  129. ret = public_key_verify_signature(cert->pub, cert->sig);
  130. if (ret < 0) {
  131. if (ret == -ENOPKG) {
  132. cert->unsupported_sig = true;
  133. ret = 0;
  134. }
  135. goto out;
  136. }
  137. pr_devel("Cert Self-signature verified");
  138. cert->self_signed = true;
  139. out:
  140. pr_devel("<==%s() = %d\n", __func__, ret);
  141. return ret;
  142. not_self_signed:
  143. pr_devel("<==%s() = 0 [not]\n", __func__);
  144. return 0;
  145. }
  146. /*
  147. * Attempt to parse a data blob for a key as an X509 certificate.
  148. */
  149. static int x509_key_preparse(struct key_preparsed_payload *prep)
  150. {
  151. struct asymmetric_key_ids *kids;
  152. struct x509_certificate *cert;
  153. const char *q;
  154. size_t srlen, sulen;
  155. char *desc = NULL, *p;
  156. int ret;
  157. cert = x509_cert_parse(prep->data, prep->datalen);
  158. if (IS_ERR(cert))
  159. return PTR_ERR(cert);
  160. pr_devel("Cert Issuer: %s\n", cert->issuer);
  161. pr_devel("Cert Subject: %s\n", cert->subject);
  162. if (cert->unsupported_key) {
  163. ret = -ENOPKG;
  164. goto error_free_cert;
  165. }
  166. pr_devel("Cert Key Algo: %s\n", cert->pub->pkey_algo);
  167. pr_devel("Cert Valid period: %lld-%lld\n", cert->valid_from, cert->valid_to);
  168. cert->pub->id_type = "X509";
  169. if (cert->unsupported_sig) {
  170. public_key_signature_free(cert->sig);
  171. cert->sig = NULL;
  172. } else {
  173. pr_devel("Cert Signature: %s + %s\n",
  174. cert->sig->pkey_algo, cert->sig->hash_algo);
  175. }
  176. /* Don't permit addition of blacklisted keys */
  177. ret = -EKEYREJECTED;
  178. if (cert->blacklisted)
  179. goto error_free_cert;
  180. /* Propose a description */
  181. sulen = strlen(cert->subject);
  182. if (cert->raw_skid) {
  183. srlen = cert->raw_skid_size;
  184. q = cert->raw_skid;
  185. } else {
  186. srlen = cert->raw_serial_size;
  187. q = cert->raw_serial;
  188. }
  189. ret = -ENOMEM;
  190. desc = kmalloc(sulen + 2 + srlen * 2 + 1, GFP_KERNEL);
  191. if (!desc)
  192. goto error_free_cert;
  193. p = memcpy(desc, cert->subject, sulen);
  194. p += sulen;
  195. *p++ = ':';
  196. *p++ = ' ';
  197. p = bin2hex(p, q, srlen);
  198. *p = 0;
  199. kids = kmalloc(sizeof(struct asymmetric_key_ids), GFP_KERNEL);
  200. if (!kids)
  201. goto error_free_desc;
  202. kids->id[0] = cert->id;
  203. kids->id[1] = cert->skid;
  204. /* We're pinning the module by being linked against it */
  205. __module_get(public_key_subtype.owner);
  206. prep->payload.data[asym_subtype] = &public_key_subtype;
  207. prep->payload.data[asym_key_ids] = kids;
  208. prep->payload.data[asym_crypto] = cert->pub;
  209. prep->payload.data[asym_auth] = cert->sig;
  210. prep->description = desc;
  211. prep->quotalen = 100;
  212. /* We've finished with the certificate */
  213. cert->pub = NULL;
  214. cert->id = NULL;
  215. cert->skid = NULL;
  216. cert->sig = NULL;
  217. desc = NULL;
  218. ret = 0;
  219. error_free_desc:
  220. kfree(desc);
  221. error_free_cert:
  222. x509_free_certificate(cert);
  223. return ret;
  224. }
  225. static struct asymmetric_key_parser x509_key_parser = {
  226. .owner = THIS_MODULE,
  227. .name = "x509",
  228. .parse = x509_key_preparse,
  229. };
  230. /*
  231. * Module stuff
  232. */
  233. static int __init x509_key_init(void)
  234. {
  235. return register_asymmetric_key_parser(&x509_key_parser);
  236. }
  237. static void __exit x509_key_exit(void)
  238. {
  239. unregister_asymmetric_key_parser(&x509_key_parser);
  240. }
  241. module_init(x509_key_init);
  242. module_exit(x509_key_exit);
  243. #endif /* !__UBOOT__ */
  244. MODULE_DESCRIPTION("X.509 certificate parser");
  245. MODULE_AUTHOR("Red Hat, Inc.");
  246. MODULE_LICENSE("GPL");