crypto/asymmetric_keys/x509_cert_parser.c

   1 /* X.509 certificate parser
   2  *
   3  * Copyright (C) 2012 Red Hat, Inc. All Rights Reserved.
   4  * Written by David Howells (dhowells@redhat.com)
   5  *
   6  * This program is free software; you can redistribute it and/or
   7  * modify it under the terms of the GNU General Public Licence
   8  * as published by the Free Software Foundation; either version
   9  * 2 of the Licence, or (at your option) any later version.
  10  */
  11
  12 #define pr_fmt(fmt) "X.509: "fmt
  13 #include <linux/kernel.h>
  14 #include <linux/slab.h>
  15 #include <linux/err.h>
  16 #include <linux/oid_registry.h>
  17 #include "public_key.h"
  18 #include "x509_parser.h"
  19 #include "x509-asn1.h"
  20 #include "x509_rsakey-asn1.h"
  21
  22 struct x509_parse_context {
  23         struct x509_certificate *cert;          /* Certificate being constructed */
  24         unsigned long   data;                   /* Start of data */
  25         const void      *cert_start;            /* Start of cert content */
  26         const void      *key;                   /* Key data */
  27         size_t          key_size;               /* Size of key data */
  28         enum OID        last_oid;               /* Last OID encountered */
  29         enum OID        algo_oid;               /* Algorithm OID */
  30         unsigned char   nr_mpi;                 /* Number of MPIs stored */
  31         u8              o_size;                 /* Size of organizationName (O) */
  32         u8              cn_size;                /* Size of commonName (CN) */
  33         u8              email_size;             /* Size of emailAddress */
  34         u16             o_offset;               /* Offset of organizationName (O) */
  35         u16             cn_offset;              /* Offset of commonName (CN) */
  36         u16             email_offset;           /* Offset of emailAddress */
  37 };
  38
  39 /*
  40  * Free an X.509 certificate
  41  */
  42 void x509_free_certificate(struct x509_certificate *cert)
  43 {
  44         if (cert) {
  45                 public_key_destroy(cert->pub);
  46                 kfree(cert->issuer);
  47                 kfree(cert->subject);
  48                 kfree(cert->fingerprint);
  49                 kfree(cert->authority);
  50                 kfree(cert);
  51         }
  52 }
  53
  54 /*
  55  * Parse an X.509 certificate
  56  */
  57 struct x509_certificate *x509_cert_parse(const void *data, size_t datalen)
  58 {
  59         struct x509_certificate *cert;
  60         struct x509_parse_context *ctx;
  61         long ret;
  62
  63         ret = -ENOMEM;
  64         cert = kzalloc(sizeof(struct x509_certificate), GFP_KERNEL);
  65         if (!cert)
  66                 goto error_no_cert;
  67         cert->pub = kzalloc(sizeof(struct public_key), GFP_KERNEL);
  68         if (!cert->pub)
  69                 goto error_no_ctx;
  70         ctx = kzalloc(sizeof(struct x509_parse_context), GFP_KERNEL);
  71         if (!ctx)
  72                 goto error_no_ctx;
  73
  74         ctx->cert = cert;
  75         ctx->data = (unsigned long)data;
  76
  77         /* Attempt to decode the certificate */
  78         ret = asn1_ber_decoder(&x509_decoder, ctx, data, datalen);
  79         if (ret < 0)
  80                 goto error_decode;
  81
  82         /* Decode the public key */
  83         ret = asn1_ber_decoder(&x509_rsakey_decoder, ctx,
  84                                ctx->key, ctx->key_size);
  85         if (ret < 0)
  86                 goto error_decode;
  87
  88         kfree(ctx);
  89         return cert;
  90
  91 error_decode:
  92         kfree(ctx);
  93 error_no_ctx:
  94         x509_free_certificate(cert);
  95 error_no_cert:
  96         return ERR_PTR(ret);
  97 }
  98
  99 /*
 100  * Note an OID when we find one for later processing when we know how
 101  * to interpret it.
 102  */
 103 int x509_note_OID(void *context, size_t hdrlen,
 104              unsigned char tag,
 105              const void *value, size_t vlen)
 106 {
 107         struct x509_parse_context *ctx = context;
 108
 109         ctx->last_oid = look_up_OID(value, vlen);
 110         if (ctx->last_oid == OID__NR) {
 111                 char buffer[50];
 112                 sprint_oid(value, vlen, buffer, sizeof(buffer));
 113                 pr_debug("Unknown OID: [%lu] %s\n",
 114                          (unsigned long)value - ctx->data, buffer);
 115         }
 116         return 0;
 117 }
 118
 119 /*
 120  * Save the position of the TBS data so that we can check the signature over it
 121  * later.
 122  */
 123 int x509_note_tbs_certificate(void *context, size_t hdrlen,
 124                               unsigned char tag,
 125                               const void *value, size_t vlen)
 126 {
 127         struct x509_parse_context *ctx = context;
 128
 129         pr_debug("x509_note_tbs_certificate(,%zu,%02x,%ld,%zu)!\n",
 130                  hdrlen, tag, (unsigned long)value - ctx->data, vlen);
 131
 132         ctx->cert->tbs = value - hdrlen;
 133         ctx->cert->tbs_size = vlen + hdrlen;
 134         return 0;
 135 }
 136
 137 /*
 138  * Record the public key algorithm
 139  */
 140 int x509_note_pkey_algo(void *context, size_t hdrlen,
 141                         unsigned char tag,
 142                         const void *value, size_t vlen)
 143 {
 144         struct x509_parse_context *ctx = context;
 145
 146         pr_debug("PubKey Algo: %u\n", ctx->last_oid);
 147
 148         switch (ctx->last_oid) {
 149         case OID_md2WithRSAEncryption:
 150         case OID_md3WithRSAEncryption:
 151         default:
 152                 return -ENOPKG; /* Unsupported combination */
 153
 154         case OID_md4WithRSAEncryption:
 155                 ctx->cert->sig_hash_algo = PKEY_HASH_MD5;
 156                 ctx->cert->sig_pkey_algo = PKEY_ALGO_RSA;
 157                 break;
 158
 159         case OID_sha1WithRSAEncryption:
 160                 ctx->cert->sig_hash_algo = PKEY_HASH_SHA1;
 161                 ctx->cert->sig_pkey_algo = PKEY_ALGO_RSA;
 162                 break;
 163
 164         case OID_sha256WithRSAEncryption:
 165                 ctx->cert->sig_hash_algo = PKEY_HASH_SHA256;
 166                 ctx->cert->sig_pkey_algo = PKEY_ALGO_RSA;
 167                 break;
 168
 169         case OID_sha384WithRSAEncryption:
 170                 ctx->cert->sig_hash_algo = PKEY_HASH_SHA384;
 171                 ctx->cert->sig_pkey_algo = PKEY_ALGO_RSA;
 172                 break;
 173
 174         case OID_sha512WithRSAEncryption:
 175                 ctx->cert->sig_hash_algo = PKEY_HASH_SHA512;
 176                 ctx->cert->sig_pkey_algo = PKEY_ALGO_RSA;
 177                 break;
 178
 179         case OID_sha224WithRSAEncryption:
 180                 ctx->cert->sig_hash_algo = PKEY_HASH_SHA224;
 181                 ctx->cert->sig_pkey_algo = PKEY_ALGO_RSA;
 182                 break;
 183         }
 184
 185         ctx->algo_oid = ctx->last_oid;
 186         return 0;
 187 }
 188
 189 /*
 190  * Note the whereabouts and type of the signature.
 191  */
 192 int x509_note_signature(void *context, size_t hdrlen,
 193                         unsigned char tag,
 194                         const void *value, size_t vlen)
 195 {
 196         struct x509_parse_context *ctx = context;
 197
 198         pr_debug("Signature type: %u size %zu\n", ctx->last_oid, vlen);
 199
 200         if (ctx->last_oid != ctx->algo_oid) {
 201                 pr_warn("Got cert with pkey (%u) and sig (%u) algorithm OIDs\n",
 202                         ctx->algo_oid, ctx->last_oid);
 203                 return -EINVAL;
 204         }
 205
 206         ctx->cert->sig = value;
 207         ctx->cert->sig_size = vlen;
 208         return 0;
 209 }
 210
 211 /*
 212  * Note some of the name segments from which we'll fabricate a name.
 213  */
 214 int x509_extract_name_segment(void *context, size_t hdrlen,
 215                               unsigned char tag,
 216                               const void *value, size_t vlen)
 217 {
 218         struct x509_parse_context *ctx = context;
 219
 220         switch (ctx->last_oid) {
 221         case OID_commonName:
 222                 ctx->cn_size = vlen;
 223                 ctx->cn_offset = (unsigned long)value - ctx->data;
 224                 break;
 225         case OID_organizationName:
 226                 ctx->o_size = vlen;
 227                 ctx->o_offset = (unsigned long)value - ctx->data;
 228                 break;
 229         case OID_email_address:
 230                 ctx->email_size = vlen;
 231                 ctx->email_offset = (unsigned long)value - ctx->data;
 232                 break;
 233         default:
 234                 break;
 235         }
 236
 237         return 0;
 238 }
 239
 240 /*
 241  * Fabricate and save the issuer and subject names
 242  */
 243 static int x509_fabricate_name(struct x509_parse_context *ctx, size_t hdrlen,
 244                                unsigned char tag,
 245                                char **_name, size_t vlen)
 246 {
 247         const void *name, *data = (const void *)ctx->data;
 248         size_t namesize;
 249         char *buffer;
 250
 251         if (*_name)
 252                 return -EINVAL;
 253
 254         /* Empty name string if no material */
 255         if (!ctx->cn_size && !ctx->o_size && !ctx->email_size) {
 256                 buffer = kmalloc(1, GFP_KERNEL);
 257                 if (!buffer)
 258                         return -ENOMEM;
 259                 buffer[0] = 0;
 260                 goto done;
 261         }
 262
 263         if (ctx->cn_size && ctx->o_size) {
 264                 /* Consider combining O and CN, but use only the CN if it is
 265                  * prefixed by the O, or a significant portion thereof.
 266                  */
 267                 namesize = ctx->cn_size;
 268                 name = data + ctx->cn_offset;
 269                 if (ctx->cn_size >= ctx->o_size &&
 270                     memcmp(data + ctx->cn_offset, data + ctx->o_offset,
 271                            ctx->o_size) == 0)
 272                         goto single_component;
 273                 if (ctx->cn_size >= 7 &&
 274                     ctx->o_size >= 7 &&
 275                     memcmp(data + ctx->cn_offset, data + ctx->o_offset, 7) == 0)
 276                         goto single_component;
 277
 278                 buffer = kmalloc(ctx->o_size + 2 + ctx->cn_size + 1,
 279                                  GFP_KERNEL);
 280                 if (!buffer)
 281                         return -ENOMEM;
 282
 283                 memcpy(buffer,
 284                        data + ctx->o_offset, ctx->o_size);
 285                 buffer[ctx->o_size + 0] = ':';
 286                 buffer[ctx->o_size + 1] = ' ';
 287                 memcpy(buffer + ctx->o_size + 2,
 288                        data + ctx->cn_offset, ctx->cn_size);
 289                 buffer[ctx->o_size + 2 + ctx->cn_size] = 0;
 290                 goto done;
 291
 292         } else if (ctx->cn_size) {
 293                 namesize = ctx->cn_size;
 294                 name = data + ctx->cn_offset;
 295         } else if (ctx->o_size) {
 296                 namesize = ctx->o_size;
 297                 name = data + ctx->o_offset;
 298         } else {
 299                 namesize = ctx->email_size;
 300                 name = data + ctx->email_offset;
 301         }
 302
 303 single_component:
 304         buffer = kmalloc(namesize + 1, GFP_KERNEL);
 305         if (!buffer)
 306                 return -ENOMEM;
 307         memcpy(buffer, name, namesize);
 308         buffer[namesize] = 0;
 309
 310 done:
 311         *_name = buffer;
 312         ctx->cn_size = 0;
 313         ctx->o_size = 0;
 314         ctx->email_size = 0;
 315         return 0;
 316 }
 317
 318 int x509_note_issuer(void *context, size_t hdrlen,
 319                      unsigned char tag,
 320                      const void *value, size_t vlen)
 321 {
 322         struct x509_parse_context *ctx = context;
 323         return x509_fabricate_name(ctx, hdrlen, tag, &ctx->cert->issuer, vlen);
 324 }
 325
 326 int x509_note_subject(void *context, size_t hdrlen,
 327                       unsigned char tag,
 328                       const void *value, size_t vlen)
 329 {
 330         struct x509_parse_context *ctx = context;
 331         return x509_fabricate_name(ctx, hdrlen, tag, &ctx->cert->subject, vlen);
 332 }
 333
 334 /*
 335  * Extract the data for the public key algorithm
 336  */
 337 int x509_extract_key_data(void *context, size_t hdrlen,
 338                           unsigned char tag,
 339                           const void *value, size_t vlen)
 340 {
 341         struct x509_parse_context *ctx = context;
 342
 343         if (ctx->last_oid != OID_rsaEncryption)
 344                 return -ENOPKG;
 345
 346         /* There seems to be an extraneous 0 byte on the front of the data */
 347         ctx->cert->pkey_algo = PKEY_ALGO_RSA;
 348         ctx->key = value + 1;
 349         ctx->key_size = vlen - 1;
 350         return 0;
 351 }
 352
 353 /*
 354  * Extract a RSA public key value
 355  */
 356 int rsa_extract_mpi(void *context, size_t hdrlen,
 357                     unsigned char tag,
 358                     const void *value, size_t vlen)
 359 {
 360         struct x509_parse_context *ctx = context;
 361         MPI mpi;
 362
 363         if (ctx->nr_mpi >= ARRAY_SIZE(ctx->cert->pub->mpi)) {
 364                 pr_err("Too many public key MPIs in certificate\n");
 365                 return -EBADMSG;
 366         }
 367
 368         mpi = mpi_read_raw_data(value, vlen);
 369         if (!mpi)
 370                 return -ENOMEM;
 371
 372         ctx->cert->pub->mpi[ctx->nr_mpi++] = mpi;
 373         return 0;
 374 }
 375
 376 /*
 377  * Process certificate extensions that are used to qualify the certificate.
 378  */
 379 int x509_process_extension(void *context, size_t hdrlen,
 380                            unsigned char tag,
 381                            const void *value, size_t vlen)
 382 {
 383         struct x509_parse_context *ctx = context;
 384         const unsigned char *v = value;
 385         char *f;
 386         int i;
 387
 388         pr_debug("Extension: %u\n", ctx->last_oid);
 389
 390         if (ctx->last_oid == OID_subjectKeyIdentifier) {
 391                 /* Get hold of the key fingerprint */
 392                 if (vlen < 3)
 393                         return -EBADMSG;
 394                 if (v[0] != ASN1_OTS || v[1] != vlen - 2)
 395                         return -EBADMSG;
 396                 v += 2;
 397                 vlen -= 2;
 398
 399                 f = kmalloc(vlen * 2 + 1, GFP_KERNEL);
 400                 if (!f)
 401                         return -ENOMEM;
 402                 for (i = 0; i < vlen; i++)
 403                         sprintf(f + i * 2, "%02x", v[i]);
 404                 pr_debug("fingerprint %s\n", f);
 405                 ctx->cert->fingerprint = f;
 406                 return 0;
 407         }
 408
 409         if (ctx->last_oid == OID_authorityKeyIdentifier) {
 410                 /* Get hold of the CA key fingerprint */
 411                 if (vlen < 5)
 412                         return -EBADMSG;
 413                 if (v[0] != (ASN1_SEQ | (ASN1_CONS << 5)) ||
 414                     v[1] != vlen - 2 ||
 415                     v[2] != (ASN1_CONT << 6) ||
 416                     v[3] != vlen - 4)
 417                         return -EBADMSG;
 418                 v += 4;
 419                 vlen -= 4;
 420
 421                 f = kmalloc(vlen * 2 + 1, GFP_KERNEL);
 422                 if (!f)
 423                         return -ENOMEM;
 424                 for (i = 0; i < vlen; i++)
 425                         sprintf(f + i * 2, "%02x", v[i]);
 426                 pr_debug("authority   %s\n", f);
 427                 ctx->cert->authority = f;
 428                 return 0;
 429         }
 430
 431         return 0;
 432 }
 433
 434 /*
 435  * Record a certificate time.
 436  */
 437 static int x509_note_time(struct tm *tm,  size_t hdrlen,
 438                           unsigned char tag,
 439                           const unsigned char *value, size_t vlen)
 440 {
 441         const unsigned char *p = value;
 442
 443 #define dec2bin(X) ((X) - '0')
 444 #define DD2bin(P) ({ unsigned x = dec2bin(P[0]) * 10 + dec2bin(P[1]); P += 2; x; })
 445
 446         if (tag == ASN1_UNITIM) {
 447                 /* UTCTime: YYMMDDHHMMSSZ */
 448                 if (vlen != 13)
 449                         goto unsupported_time;
 450                 tm->tm_year = DD2bin(p);
 451                 if (tm->tm_year >= 50)
 452                         tm->tm_year += 1900;
 453                 else
 454                         tm->tm_year += 2000;
 455         } else if (tag == ASN1_GENTIM) {
 456                 /* GenTime: YYYYMMDDHHMMSSZ */
 457                 if (vlen != 15)
 458                         goto unsupported_time;
 459                 tm->tm_year = DD2bin(p) * 100 + DD2bin(p);
 460         } else {
 461                 goto unsupported_time;
 462         }
 463
 464         tm->tm_year -= 1900;
 465         tm->tm_mon  = DD2bin(p) - 1;
 466         tm->tm_mday = DD2bin(p);
 467         tm->tm_hour = DD2bin(p);
 468         tm->tm_min  = DD2bin(p);
 469         tm->tm_sec  = DD2bin(p);
 470
 471         if (*p != 'Z')
 472                 goto unsupported_time;
 473
 474         return 0;
 475
 476 unsupported_time:
 477         pr_debug("Got unsupported time [tag %02x]: '%*.*s'\n",
 478                  tag, (int)vlen, (int)vlen, value);
 479         return -EBADMSG;
 480 }
 481
 482 int x509_note_not_before(void *context, size_t hdrlen,
 483                          unsigned char tag,
 484                          const void *value, size_t vlen)
 485 {
 486         struct x509_parse_context *ctx = context;
 487         return x509_note_time(&ctx->cert->valid_from, hdrlen, tag, value, vlen);
 488 }
 489
 490 int x509_note_not_after(void *context, size_t hdrlen,
 491                         unsigned char tag,
 492                         const void *value, size_t vlen)
 493 {
 494         struct x509_parse_context *ctx = context;
 495         return x509_note_time(&ctx->cert->valid_to, hdrlen, tag, value, vlen);
 496 }