libkmod/libkmod-signature.c

   1 /*
   2  * libkmod - module signature display
   3  *
   4  * Copyright (C) 2013 Michal Marek, SUSE
   5  *
   6  * This library is free software; you can redistribute it and/or
   7  * modify it under the terms of the GNU Lesser General Public
   8  * License as published by the Free Software Foundation; either
   9  * version 2.1 of the License, or (at your option) any later version.
  10  *
  11  * This library is distributed in the hope that it will be useful,
  12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14  * Lesser General Public License for more details.
  15  *
  16  * You should have received a copy of the GNU Lesser General Public
  17  * License along with this library; if not, see <http://www.gnu.org/licenses/>.
  18  */
  19
  20 #include <endian.h>
  21 #include <inttypes.h>
  22 #ifdef ENABLE_OPENSSL
  23 #include <openssl/pkcs7.h>
  24 #include <openssl/ssl.h>
  25 #endif
  26 #include <stdio.h>
  27 #include <stdlib.h>
  28 #include <string.h>
  29
  30 #include <shared/missing.h>
  31 #include <shared/util.h>
  32
  33 #include "libkmod-internal.h"
  34
  35 /* These types and tables were copied from the 3.7 kernel sources.
  36  * As this is just description of the signature format, it should not be
  37  * considered derived work (so libkmod can use the LGPL license).
  38  */
  39 enum pkey_algo {
  40         PKEY_ALGO_DSA,
  41         PKEY_ALGO_RSA,
  42         PKEY_ALGO__LAST
  43 };
  44
  45 static const char *const pkey_algo[PKEY_ALGO__LAST] = {
  46         [PKEY_ALGO_DSA]         = "DSA",
  47         [PKEY_ALGO_RSA]         = "RSA",
  48 };
  49
  50 enum pkey_hash_algo {
  51         PKEY_HASH_MD4,
  52         PKEY_HASH_MD5,
  53         PKEY_HASH_SHA1,
  54         PKEY_HASH_RIPE_MD_160,
  55         PKEY_HASH_SHA256,
  56         PKEY_HASH_SHA384,
  57         PKEY_HASH_SHA512,
  58         PKEY_HASH_SHA224,
  59         PKEY_HASH_SM3,
  60         PKEY_HASH__LAST
  61 };
  62
  63 const char *const pkey_hash_algo[PKEY_HASH__LAST] = {
  64         [PKEY_HASH_MD4]         = "md4",
  65         [PKEY_HASH_MD5]         = "md5",
  66         [PKEY_HASH_SHA1]        = "sha1",
  67         [PKEY_HASH_RIPE_MD_160] = "rmd160",
  68         [PKEY_HASH_SHA256]      = "sha256",
  69         [PKEY_HASH_SHA384]      = "sha384",
  70         [PKEY_HASH_SHA512]      = "sha512",
  71         [PKEY_HASH_SHA224]      = "sha224",
  72         [PKEY_HASH_SM3]         = "sm3",
  73 };
  74
  75 enum pkey_id_type {
  76         PKEY_ID_PGP,            /* OpenPGP generated key ID */
  77         PKEY_ID_X509,           /* X.509 arbitrary subjectKeyIdentifier */
  78         PKEY_ID_PKCS7,          /* Signature in PKCS#7 message */
  79         PKEY_ID_TYPE__LAST
  80 };
  81
  82 const char *const pkey_id_type[PKEY_ID_TYPE__LAST] = {
  83         [PKEY_ID_PGP]           = "PGP",
  84         [PKEY_ID_X509]          = "X509",
  85         [PKEY_ID_PKCS7]         = "PKCS#7",
  86 };
  87
  88 /*
  89  * Module signature information block.
  90  */
  91 struct module_signature {
  92         uint8_t algo;        /* Public-key crypto algorithm [enum pkey_algo] */
  93         uint8_t hash;        /* Digest algorithm [enum pkey_hash_algo] */
  94         uint8_t id_type;     /* Key identifier type [enum pkey_id_type] */
  95         uint8_t signer_len;  /* Length of signer's name */
  96         uint8_t key_id_len;  /* Length of key identifier */
  97         uint8_t __pad[3];
  98         uint32_t sig_len;    /* Length of signature data (big endian) */
  99 };
 100
 101 static bool fill_default(const char *mem, off_t size,
 102                          const struct module_signature *modsig, size_t sig_len,
 103                          struct kmod_signature_info *sig_info)
 104 {
 105         size -= sig_len;
 106         sig_info->sig = mem + size;
 107         sig_info->sig_len = sig_len;
 108
 109         size -= modsig->key_id_len;
 110         sig_info->key_id = mem + size;
 111         sig_info->key_id_len = modsig->key_id_len;
 112
 113         size -= modsig->signer_len;
 114         sig_info->signer = mem + size;
 115         sig_info->signer_len = modsig->signer_len;
 116
 117         sig_info->algo = pkey_algo[modsig->algo];
 118         sig_info->hash_algo = pkey_hash_algo[modsig->hash];
 119         sig_info->id_type = pkey_id_type[modsig->id_type];
 120
 121         return true;
 122 }
 123
 124 #ifdef ENABLE_OPENSSL
 125
 126 struct pkcs7_private {
 127         PKCS7 *pkcs7;
 128         unsigned char *key_id;
 129         BIGNUM *sno;
 130         char *hash_algo;
 131 };
 132
 133 static void pkcs7_free(void *s)
 134 {
 135         struct kmod_signature_info *si = s;
 136         struct pkcs7_private *pvt = si->private;
 137
 138         PKCS7_free(pvt->pkcs7);
 139         BN_free(pvt->sno);
 140         free(pvt->key_id);
 141         free(pvt->hash_algo);
 142         free(pvt);
 143         si->private = NULL;
 144 }
 145
 146 static const char *x509_name_to_str(X509_NAME *name)
 147 {
 148         int i;
 149         X509_NAME_ENTRY *e;
 150         ASN1_STRING *d;
 151         ASN1_OBJECT *o;
 152         int nid = -1;
 153         const char *str;
 154
 155         for (i = 0; i < X509_NAME_entry_count(name); i++) {
 156                 e = X509_NAME_get_entry(name, i);
 157                 o = X509_NAME_ENTRY_get_object(e);
 158                 nid = OBJ_obj2nid(o);
 159                 if (nid == NID_commonName)
 160                         break;
 161         }
 162         if (nid == -1)
 163                 return NULL;
 164
 165         d = X509_NAME_ENTRY_get_data(e);
 166         str = (const char *)ASN1_STRING_get0_data(d);
 167
 168         return str;
 169 }
 170
 171 static bool fill_pkcs7(const char *mem, off_t size,
 172                        const struct module_signature *modsig, size_t sig_len,
 173                        struct kmod_signature_info *sig_info)
 174 {
 175         const char *pkcs7_raw;
 176         PKCS7 *pkcs7;
 177         STACK_OF(PKCS7_SIGNER_INFO) *sis;
 178         PKCS7_SIGNER_INFO *si;
 179         PKCS7_ISSUER_AND_SERIAL *is;
 180         X509_NAME *issuer;
 181         ASN1_INTEGER *sno;
 182         ASN1_OCTET_STRING *sig;
 183         BIGNUM *sno_bn;
 184         X509_ALGOR *dig_alg;
 185         X509_ALGOR *sig_alg;
 186         const ASN1_OBJECT *o;
 187         BIO *in;
 188         int len;
 189         unsigned char *key_id_str;
 190         struct pkcs7_private *pvt;
 191         const char *issuer_str;
 192         char *hash_algo;
 193         int hash_algo_len;
 194
 195         size -= sig_len;
 196         pkcs7_raw = mem + size;
 197
 198         in = BIO_new_mem_buf(pkcs7_raw, sig_len);
 199
 200         pkcs7 = d2i_PKCS7_bio(in, NULL);
 201         if (pkcs7 == NULL) {
 202                 BIO_free(in);
 203                 return false;
 204         }
 205
 206         BIO_free(in);
 207
 208         sis = PKCS7_get_signer_info(pkcs7);
 209         if (sis == NULL)
 210                 goto err;
 211
 212         si = sk_PKCS7_SIGNER_INFO_value(sis, 0);
 213         if (si == NULL)
 214                 goto err;
 215
 216         is = si->issuer_and_serial;
 217         if (is == NULL)
 218                 goto err;
 219         issuer = is->issuer;
 220         sno = is->serial;
 221
 222         sig = si->enc_digest;
 223         if (sig == NULL)
 224                 goto err;
 225
 226         PKCS7_SIGNER_INFO_get0_algs(si, NULL, &dig_alg, &sig_alg);
 227
 228         sig_info->sig = (const char *)ASN1_STRING_get0_data(sig);
 229         sig_info->sig_len = ASN1_STRING_length(sig);
 230
 231         sno_bn = ASN1_INTEGER_to_BN(sno, NULL);
 232         if (sno_bn == NULL)
 233                 goto err;
 234
 235         len = BN_num_bytes(sno_bn);
 236         key_id_str = malloc(len);
 237         if (key_id_str == NULL)
 238                 goto err2;
 239         BN_bn2bin(sno_bn, key_id_str);
 240
 241         sig_info->key_id = (const char *)key_id_str;
 242         sig_info->key_id_len = len;
 243
 244         issuer_str = x509_name_to_str(issuer);
 245         if (issuer_str != NULL) {
 246                 sig_info->signer = issuer_str;
 247                 sig_info->signer_len = strlen(issuer_str);
 248         }
 249
 250         X509_ALGOR_get0(&o, NULL, NULL, dig_alg);
 251
 252         // Use OBJ_obj2txt to calculate string length
 253         hash_algo_len = OBJ_obj2txt(NULL, 0, o, 0);
 254         if (hash_algo_len < 0)
 255                 goto err3;
 256         hash_algo = malloc(hash_algo_len + 1);
 257         if (hash_algo == NULL)
 258                 goto err3;
 259         hash_algo_len = OBJ_obj2txt(hash_algo, hash_algo_len + 1, o, 0);
 260         if (hash_algo_len < 0)
 261                 goto err4;
 262
 263         // Assign libcrypto hash algo string or number
 264         sig_info->hash_algo = hash_algo;
 265
 266         sig_info->id_type = pkey_id_type[modsig->id_type];
 267
 268         pvt = malloc(sizeof(*pvt));
 269         if (pvt == NULL)
 270                 goto err4;
 271
 272         pvt->pkcs7 = pkcs7;
 273         pvt->key_id = key_id_str;
 274         pvt->sno = sno_bn;
 275         pvt->hash_algo = hash_algo;
 276         sig_info->private = pvt;
 277
 278         sig_info->free = pkcs7_free;
 279
 280         return true;
 281 err4:
 282         free(hash_algo);
 283 err3:
 284         free(key_id_str);
 285 err2:
 286         BN_free(sno_bn);
 287 err:
 288         PKCS7_free(pkcs7);
 289         return false;
 290 }
 291
 292 #else /* ENABLE OPENSSL */
 293
 294 static bool fill_pkcs7(const char *mem, off_t size,
 295                        const struct module_signature *modsig, size_t sig_len,
 296                        struct kmod_signature_info *sig_info)
 297 {
 298         sig_info->hash_algo = "unknown";
 299         sig_info->id_type = pkey_id_type[modsig->id_type];
 300         return true;
 301 }
 302
 303 #endif /* ENABLE OPENSSL */
 304
 305 #define SIG_MAGIC "~Module signature appended~\n"
 306
 307 /*
 308  * A signed module has the following layout:
 309  *
 310  * [ module                  ]
 311  * [ signer's name           ]
 312  * [ key identifier          ]
 313  * [ signature data          ]
 314  * [ struct module_signature ]
 315  * [ SIG_MAGIC               ]
 316  */
 317
 318 bool kmod_module_signature_info(const struct kmod_file *file, struct kmod_signature_info *sig_info)
 319 {
 320         const char *mem;
 321         off_t size;
 322         const struct module_signature *modsig;
 323         size_t sig_len;
 324
 325         size = kmod_file_get_size(file);
 326         mem = kmod_file_get_contents(file);
 327         if (size < (off_t)strlen(SIG_MAGIC))
 328                 return false;
 329         size -= strlen(SIG_MAGIC);
 330         if (memcmp(SIG_MAGIC, mem + size, strlen(SIG_MAGIC)) != 0)
 331                 return false;
 332
 333         if (size < (off_t)sizeof(struct module_signature))
 334                 return false;
 335         size -= sizeof(struct module_signature);
 336         modsig = (struct module_signature *)(mem + size);
 337         if (modsig->algo >= PKEY_ALGO__LAST ||
 338                         modsig->hash >= PKEY_HASH__LAST ||
 339                         modsig->id_type >= PKEY_ID_TYPE__LAST)
 340                 return false;
 341         sig_len = be32toh(get_unaligned(&modsig->sig_len));
 342         if (sig_len == 0 ||
 343             size < (int64_t)(modsig->signer_len + modsig->key_id_len + sig_len))
 344                 return false;
 345
 346         switch (modsig->id_type) {
 347         case PKEY_ID_PKCS7:
 348                 return fill_pkcs7(mem, size, modsig, sig_len, sig_info);
 349         default:
 350                 return fill_default(mem, size, modsig, sig_len, sig_info);
 351         }
 352 }
 353
 354 void kmod_module_signature_info_free(struct kmod_signature_info *sig_info)
 355 {
 356         if (sig_info->free)
 357                 sig_info->free(sig_info);
 358 }