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/export.h>
  15 #include <linux/slab.h>
  16 #include <linux/err.h>
  17 #include <linux/oid_registry.h>
  18 #include <crypto/public_key.h>
  19 #include "x509_parser.h"
  20 #include "x509-asn1.h"
  21 #include "x509_akid-asn1.h"
  22
  23 struct x509_parse_context {
  24         struct x509_certificate *cert;          /* Certificate being constructed */
  25         unsigned long   data;                   /* Start of data */
  26         const void      *cert_start;            /* Start of cert content */
  27         const void      *key;                   /* Key data */
  28         size_t          key_size;               /* Size of key data */
  29         enum OID        last_oid;               /* Last OID encountered */
  30         enum OID        algo_oid;               /* Algorithm OID */
  31         unsigned char   nr_mpi;                 /* Number of MPIs stored */
  32         u8              o_size;                 /* Size of organizationName (O) */
  33         u8              cn_size;                /* Size of commonName (CN) */
  34         u8              email_size;             /* Size of emailAddress */
  35         u16             o_offset;               /* Offset of organizationName (O) */
  36         u16             cn_offset;              /* Offset of commonName (CN) */
  37         u16             email_offset;           /* Offset of emailAddress */
  38         unsigned        raw_akid_size;
  39         const void      *raw_akid;              /* Raw authorityKeyId in ASN.1 */
  40         const void      *akid_raw_issuer;       /* Raw directoryName in authorityKeyId */
  41         unsigned        akid_raw_issuer_size;
  42 };
  43
  44 /*
  45  * Free an X.509 certificate
  46  */
  47 void x509_free_certificate(struct x509_certificate *cert)
  48 {
  49         if (cert) {
  50                 public_key_free(cert->pub);
  51                 public_key_signature_free(cert->sig);
  52                 kfree(cert->issuer);
  53                 kfree(cert->subject);
  54                 kfree(cert->id);
  55                 kfree(cert->skid);
  56                 kfree(cert);
  57         }
  58 }
  59 EXPORT_SYMBOL_GPL(x509_free_certificate);
  60
  61 /*
  62  * Parse an X.509 certificate
  63  */
  64 struct x509_certificate *x509_cert_parse(const void *data, size_t datalen)
  65 {
  66         struct x509_certificate *cert;
  67         struct x509_parse_context *ctx;
  68         struct asymmetric_key_id *kid;
  69         long ret;
  70
  71         ret = -ENOMEM;
  72         cert = kzalloc(sizeof(struct x509_certificate), GFP_KERNEL);
  73         if (!cert)
  74                 goto error_no_cert;
  75         cert->pub = kzalloc(sizeof(struct public_key), GFP_KERNEL);
  76         if (!cert->pub)
  77                 goto error_no_ctx;
  78         cert->sig = kzalloc(sizeof(struct public_key_signature), GFP_KERNEL);
  79         if (!cert->sig)
  80                 goto error_no_ctx;
  81         ctx = kzalloc(sizeof(struct x509_parse_context), GFP_KERNEL);
  82         if (!ctx)
  83                 goto error_no_ctx;
  84
  85         ctx->cert = cert;
  86         ctx->data = (unsigned long)data;
  87
  88         /* Attempt to decode the certificate */
  89         ret = asn1_ber_decoder(&x509_decoder, ctx, data, datalen);
  90         if (ret < 0)
  91                 goto error_decode;
  92
  93         /* Decode the AuthorityKeyIdentifier */
  94         if (ctx->raw_akid) {
  95                 pr_devel("AKID: %u %*phN\n",
  96                          ctx->raw_akid_size, ctx->raw_akid_size, ctx->raw_akid);
  97                 ret = asn1_ber_decoder(&x509_akid_decoder, ctx,
  98                                        ctx->raw_akid, ctx->raw_akid_size);
  99                 if (ret < 0) {
 100                         pr_warn("Couldn't decode AuthKeyIdentifier\n");
 101                         goto error_decode;
 102                 }
 103         }
 104
 105         ret = -ENOMEM;
 106         cert->pub->key = kmemdup(ctx->key, ctx->key_size, GFP_KERNEL);
 107         if (!cert->pub->key)
 108                 goto error_decode;
 109
 110         cert->pub->keylen = ctx->key_size;
 111
 112         /* Grab the signature bits */
 113         ret = x509_get_sig_params(cert);
 114         if (ret < 0)
 115                 goto error_decode;
 116
 117         /* Generate cert issuer + serial number key ID */
 118         kid = asymmetric_key_generate_id(cert->raw_serial,
 119                                          cert->raw_serial_size,
 120                                          cert->raw_issuer,
 121                                          cert->raw_issuer_size);
 122         if (IS_ERR(kid)) {
 123                 ret = PTR_ERR(kid);
 124                 goto error_decode;
 125         }
 126         cert->id = kid;
 127
 128         /* Detect self-signed certificates */
 129         ret = x509_check_for_self_signed(cert);
 130         if (ret < 0)
 131                 goto error_decode;
 132
 133         kfree(ctx);
 134         return cert;
 135
 136 error_decode:
 137         kfree(ctx);
 138 error_no_ctx:
 139         x509_free_certificate(cert);
 140 error_no_cert:
 141         return ERR_PTR(ret);
 142 }
 143 EXPORT_SYMBOL_GPL(x509_cert_parse);
 144
 145 /*
 146  * Note an OID when we find one for later processing when we know how
 147  * to interpret it.
 148  */
 149 int x509_note_OID(void *context, size_t hdrlen,
 150              unsigned char tag,
 151              const void *value, size_t vlen)
 152 {
 153         struct x509_parse_context *ctx = context;
 154
 155         ctx->last_oid = look_up_OID(value, vlen);
 156         if (ctx->last_oid == OID__NR) {
 157                 char buffer[50];
 158                 sprint_oid(value, vlen, buffer, sizeof(buffer));
 159                 pr_debug("Unknown OID: [%lu] %s\n",
 160                          (unsigned long)value - ctx->data, buffer);
 161         }
 162         return 0;
 163 }
 164
 165 /*
 166  * Save the position of the TBS data so that we can check the signature over it
 167  * later.
 168  */
 169 int x509_note_tbs_certificate(void *context, size_t hdrlen,
 170                               unsigned char tag,
 171                               const void *value, size_t vlen)
 172 {
 173         struct x509_parse_context *ctx = context;
 174
 175         pr_debug("x509_note_tbs_certificate(,%zu,%02x,%ld,%zu)!\n",
 176                  hdrlen, tag, (unsigned long)value - ctx->data, vlen);
 177
 178         ctx->cert->tbs = value - hdrlen;
 179         ctx->cert->tbs_size = vlen + hdrlen;
 180         return 0;
 181 }
 182
 183 /*
 184  * Record the public key algorithm
 185  */
 186 int x509_note_pkey_algo(void *context, size_t hdrlen,
 187                         unsigned char tag,
 188                         const void *value, size_t vlen)
 189 {
 190         struct x509_parse_context *ctx = context;
 191
 192         pr_debug("PubKey Algo: %u\n", ctx->last_oid);
 193
 194         switch (ctx->last_oid) {
 195         case OID_md2WithRSAEncryption:
 196         case OID_md3WithRSAEncryption:
 197         default:
 198                 return -ENOPKG; /* Unsupported combination */
 199
 200         case OID_md4WithRSAEncryption:
 201                 ctx->cert->sig->hash_algo = "md4";
 202                 ctx->cert->sig->pkey_algo = "rsa";
 203                 break;
 204
 205         case OID_sha1WithRSAEncryption:
 206                 ctx->cert->sig->hash_algo = "sha1";
 207                 ctx->cert->sig->pkey_algo = "rsa";
 208                 break;
 209
 210         case OID_sha256WithRSAEncryption:
 211                 ctx->cert->sig->hash_algo = "sha256";
 212                 ctx->cert->sig->pkey_algo = "rsa";
 213                 break;
 214
 215         case OID_sha384WithRSAEncryption:
 216                 ctx->cert->sig->hash_algo = "sha384";
 217                 ctx->cert->sig->pkey_algo = "rsa";
 218                 break;
 219
 220         case OID_sha512WithRSAEncryption:
 221                 ctx->cert->sig->hash_algo = "sha512";
 222                 ctx->cert->sig->pkey_algo = "rsa";
 223                 break;
 224
 225         case OID_sha224WithRSAEncryption:
 226                 ctx->cert->sig->hash_algo = "sha224";
 227                 ctx->cert->sig->pkey_algo = "rsa";
 228                 break;
 229         }
 230
 231         ctx->algo_oid = ctx->last_oid;
 232         return 0;
 233 }
 234
 235 /*
 236  * Note the whereabouts and type of the signature.
 237  */
 238 int x509_note_signature(void *context, size_t hdrlen,
 239                         unsigned char tag,
 240                         const void *value, size_t vlen)
 241 {
 242         struct x509_parse_context *ctx = context;
 243
 244         pr_debug("Signature type: %u size %zu\n", ctx->last_oid, vlen);
 245
 246         if (ctx->last_oid != ctx->algo_oid) {
 247                 pr_warn("Got cert with pkey (%u) and sig (%u) algorithm OIDs\n",
 248                         ctx->algo_oid, ctx->last_oid);
 249                 return -EINVAL;
 250         }
 251
 252         ctx->cert->raw_sig = value;
 253         ctx->cert->raw_sig_size = vlen;
 254         return 0;
 255 }
 256
 257 /*
 258  * Note the certificate serial number
 259  */
 260 int x509_note_serial(void *context, size_t hdrlen,
 261                      unsigned char tag,
 262                      const void *value, size_t vlen)
 263 {
 264         struct x509_parse_context *ctx = context;
 265         ctx->cert->raw_serial = value;
 266         ctx->cert->raw_serial_size = vlen;
 267         return 0;
 268 }
 269
 270 /*
 271  * Note some of the name segments from which we'll fabricate a name.
 272  */
 273 int x509_extract_name_segment(void *context, size_t hdrlen,
 274                               unsigned char tag,
 275                               const void *value, size_t vlen)
 276 {
 277         struct x509_parse_context *ctx = context;
 278
 279         switch (ctx->last_oid) {
 280         case OID_commonName:
 281                 ctx->cn_size = vlen;
 282                 ctx->cn_offset = (unsigned long)value - ctx->data;
 283                 break;
 284         case OID_organizationName:
 285                 ctx->o_size = vlen;
 286                 ctx->o_offset = (unsigned long)value - ctx->data;
 287                 break;
 288         case OID_email_address:
 289                 ctx->email_size = vlen;
 290                 ctx->email_offset = (unsigned long)value - ctx->data;
 291                 break;
 292         default:
 293                 break;
 294         }
 295
 296         return 0;
 297 }
 298
 299 /*
 300  * Fabricate and save the issuer and subject names
 301  */
 302 static int x509_fabricate_name(struct x509_parse_context *ctx, size_t hdrlen,
 303                                unsigned char tag,
 304                                char **_name, size_t vlen)
 305 {
 306         const void *name, *data = (const void *)ctx->data;
 307         size_t namesize;
 308         char *buffer;
 309
 310         if (*_name)
 311                 return -EINVAL;
 312
 313         /* Empty name string if no material */
 314         if (!ctx->cn_size && !ctx->o_size && !ctx->email_size) {
 315                 buffer = kmalloc(1, GFP_KERNEL);
 316                 if (!buffer)
 317                         return -ENOMEM;
 318                 buffer[0] = 0;
 319                 goto done;
 320         }
 321
 322         if (ctx->cn_size && ctx->o_size) {
 323                 /* Consider combining O and CN, but use only the CN if it is
 324                  * prefixed by the O, or a significant portion thereof.
 325                  */
 326                 namesize = ctx->cn_size;
 327                 name = data + ctx->cn_offset;
 328                 if (ctx->cn_size >= ctx->o_size &&
 329                     memcmp(data + ctx->cn_offset, data + ctx->o_offset,
 330                            ctx->o_size) == 0)
 331                         goto single_component;
 332                 if (ctx->cn_size >= 7 &&
 333                     ctx->o_size >= 7 &&
 334                     memcmp(data + ctx->cn_offset, data + ctx->o_offset, 7) == 0)
 335                         goto single_component;
 336
 337                 buffer = kmalloc(ctx->o_size + 2 + ctx->cn_size + 1,
 338                                  GFP_KERNEL);
 339                 if (!buffer)
 340                         return -ENOMEM;
 341
 342                 memcpy(buffer,
 343                        data + ctx->o_offset, ctx->o_size);
 344                 buffer[ctx->o_size + 0] = ':';
 345                 buffer[ctx->o_size + 1] = ' ';
 346                 memcpy(buffer + ctx->o_size + 2,
 347                        data + ctx->cn_offset, ctx->cn_size);
 348                 buffer[ctx->o_size + 2 + ctx->cn_size] = 0;
 349                 goto done;
 350
 351         } else if (ctx->cn_size) {
 352                 namesize = ctx->cn_size;
 353                 name = data + ctx->cn_offset;
 354         } else if (ctx->o_size) {
 355                 namesize = ctx->o_size;
 356                 name = data + ctx->o_offset;
 357         } else {
 358                 namesize = ctx->email_size;
 359                 name = data + ctx->email_offset;
 360         }
 361
 362 single_component:
 363         buffer = kmalloc(namesize + 1, GFP_KERNEL);
 364         if (!buffer)
 365                 return -ENOMEM;
 366         memcpy(buffer, name, namesize);
 367         buffer[namesize] = 0;
 368
 369 done:
 370         *_name = buffer;
 371         ctx->cn_size = 0;
 372         ctx->o_size = 0;
 373         ctx->email_size = 0;
 374         return 0;
 375 }
 376
 377 int x509_note_issuer(void *context, size_t hdrlen,
 378                      unsigned char tag,
 379                      const void *value, size_t vlen)
 380 {
 381         struct x509_parse_context *ctx = context;
 382         ctx->cert->raw_issuer = value;
 383         ctx->cert->raw_issuer_size = vlen;
 384         return x509_fabricate_name(ctx, hdrlen, tag, &ctx->cert->issuer, vlen);
 385 }
 386
 387 int x509_note_subject(void *context, size_t hdrlen,
 388                       unsigned char tag,
 389                       const void *value, size_t vlen)
 390 {
 391         struct x509_parse_context *ctx = context;
 392         ctx->cert->raw_subject = value;
 393         ctx->cert->raw_subject_size = vlen;
 394         return x509_fabricate_name(ctx, hdrlen, tag, &ctx->cert->subject, vlen);
 395 }
 396
 397 /*
 398  * Extract the data for the public key algorithm
 399  */
 400 int x509_extract_key_data(void *context, size_t hdrlen,
 401                           unsigned char tag,
 402                           const void *value, size_t vlen)
 403 {
 404         struct x509_parse_context *ctx = context;
 405
 406         if (ctx->last_oid != OID_rsaEncryption)
 407                 return -ENOPKG;
 408
 409         ctx->cert->pub->pkey_algo = "rsa";
 410
 411         /* Discard the BIT STRING metadata */
 412         ctx->key = value + 1;
 413         ctx->key_size = vlen - 1;
 414         return 0;
 415 }
 416
 417 /* The keyIdentifier in AuthorityKeyIdentifier SEQUENCE is tag(CONT,PRIM,0) */
 418 #define SEQ_TAG_KEYID (ASN1_CONT << 6)
 419
 420 /*
 421  * Process certificate extensions that are used to qualify the certificate.
 422  */
 423 int x509_process_extension(void *context, size_t hdrlen,
 424                            unsigned char tag,
 425                            const void *value, size_t vlen)
 426 {
 427         struct x509_parse_context *ctx = context;
 428         struct asymmetric_key_id *kid;
 429         const unsigned char *v = value;
 430
 431         pr_debug("Extension: %u\n", ctx->last_oid);
 432
 433         if (ctx->last_oid == OID_subjectKeyIdentifier) {
 434                 /* Get hold of the key fingerprint */
 435                 if (ctx->cert->skid || vlen < 3)
 436                         return -EBADMSG;
 437                 if (v[0] != ASN1_OTS || v[1] != vlen - 2)
 438                         return -EBADMSG;
 439                 v += 2;
 440                 vlen -= 2;
 441
 442                 ctx->cert->raw_skid_size = vlen;
 443                 ctx->cert->raw_skid = v;
 444                 kid = asymmetric_key_generate_id(v, vlen, "", 0);
 445                 if (IS_ERR(kid))
 446                         return PTR_ERR(kid);
 447                 ctx->cert->skid = kid;
 448                 pr_debug("subjkeyid %*phN\n", kid->len, kid->data);
 449                 return 0;
 450         }
 451
 452         if (ctx->last_oid == OID_authorityKeyIdentifier) {
 453                 /* Get hold of the CA key fingerprint */
 454                 ctx->raw_akid = v;
 455                 ctx->raw_akid_size = vlen;
 456                 return 0;
 457         }
 458
 459         return 0;
 460 }
 461
 462 /**
 463  * x509_decode_time - Decode an X.509 time ASN.1 object
 464  * @_t: The time to fill in
 465  * @hdrlen: The length of the object header
 466  * @tag: The object tag
 467  * @value: The object value
 468  * @vlen: The size of the object value
 469  *
 470  * Decode an ASN.1 universal time or generalised time field into a struct the
 471  * kernel can handle and check it for validity.  The time is decoded thus:
 472  *
 473  *      [RFC5280 §4.1.2.5]
 474  *      CAs conforming to this profile MUST always encode certificate validity
 475  *      dates through the year 2049 as UTCTime; certificate validity dates in
 476  *      2050 or later MUST be encoded as GeneralizedTime.  Conforming
 477  *      applications MUST be able to process validity dates that are encoded in
 478  *      either UTCTime or GeneralizedTime.
 479  */
 480 int x509_decode_time(time64_t *_t,  size_t hdrlen,
 481                      unsigned char tag,
 482                      const unsigned char *value, size_t vlen)
 483 {
 484         static const unsigned char month_lengths[] = { 31, 28, 31, 30, 31, 30,
 485                                                        31, 31, 30, 31, 30, 31 };
 486         const unsigned char *p = value;
 487         unsigned year, mon, day, hour, min, sec, mon_len;
 488
 489 #define dec2bin(X) ({ unsigned char x = (X) - '0'; if (x > 9) goto invalid_time; x; })
 490 #define DD2bin(P) ({ unsigned x = dec2bin(P[0]) * 10 + dec2bin(P[1]); P += 2; x; })
 491
 492         if (tag == ASN1_UNITIM) {
 493                 /* UTCTime: YYMMDDHHMMSSZ */
 494                 if (vlen != 13)
 495                         goto unsupported_time;
 496                 year = DD2bin(p);
 497                 if (year >= 50)
 498                         year += 1900;
 499                 else
 500                         year += 2000;
 501         } else if (tag == ASN1_GENTIM) {
 502                 /* GenTime: YYYYMMDDHHMMSSZ */
 503                 if (vlen != 15)
 504                         goto unsupported_time;
 505                 year = DD2bin(p) * 100 + DD2bin(p);
 506                 if (year >= 1950 && year <= 2049)
 507                         goto invalid_time;
 508         } else {
 509                 goto unsupported_time;
 510         }
 511
 512         mon  = DD2bin(p);
 513         day = DD2bin(p);
 514         hour = DD2bin(p);
 515         min  = DD2bin(p);
 516         sec  = DD2bin(p);
 517
 518         if (*p != 'Z')
 519                 goto unsupported_time;
 520
 521         if (year < 1970 ||
 522             mon < 1 || mon > 12)
 523                 goto invalid_time;
 524
 525         mon_len = month_lengths[mon - 1];
 526         if (mon == 2) {
 527                 if (year % 4 == 0) {
 528                         mon_len = 29;
 529                         if (year % 100 == 0) {
 530                                 mon_len = 28;
 531                                 if (year % 400 == 0)
 532                                         mon_len = 29;
 533                         }
 534                 }
 535         }
 536
 537         if (day < 1 || day > mon_len ||
 538             hour > 24 || /* ISO 8601 permits 24:00:00 as midnight tomorrow */
 539             min > 59 ||
 540             sec > 60) /* ISO 8601 permits leap seconds [X.680 46.3] */
 541                 goto invalid_time;
 542
 543         *_t = mktime64(year, mon, day, hour, min, sec);
 544         return 0;
 545
 546 unsupported_time:
 547         pr_debug("Got unsupported time [tag %02x]: '%*phN'\n",
 548                  tag, (int)vlen, value);
 549         return -EBADMSG;
 550 invalid_time:
 551         pr_debug("Got invalid time [tag %02x]: '%*phN'\n",
 552                  tag, (int)vlen, value);
 553         return -EBADMSG;
 554 }
 555 EXPORT_SYMBOL_GPL(x509_decode_time);
 556
 557 int x509_note_not_before(void *context, size_t hdrlen,
 558                          unsigned char tag,
 559                          const void *value, size_t vlen)
 560 {
 561         struct x509_parse_context *ctx = context;
 562         return x509_decode_time(&ctx->cert->valid_from, hdrlen, tag, value, vlen);
 563 }
 564
 565 int x509_note_not_after(void *context, size_t hdrlen,
 566                         unsigned char tag,
 567                         const void *value, size_t vlen)
 568 {
 569         struct x509_parse_context *ctx = context;
 570         return x509_decode_time(&ctx->cert->valid_to, hdrlen, tag, value, vlen);
 571 }
 572
 573 /*
 574  * Note a key identifier-based AuthorityKeyIdentifier
 575  */
 576 int x509_akid_note_kid(void *context, size_t hdrlen,
 577                        unsigned char tag,
 578                        const void *value, size_t vlen)
 579 {
 580         struct x509_parse_context *ctx = context;
 581         struct asymmetric_key_id *kid;
 582
 583         pr_debug("AKID: keyid: %*phN\n", (int)vlen, value);
 584
 585         if (ctx->cert->sig->auth_ids[1])
 586                 return 0;
 587
 588         kid = asymmetric_key_generate_id(value, vlen, "", 0);
 589         if (IS_ERR(kid))
 590                 return PTR_ERR(kid);
 591         pr_debug("authkeyid %*phN\n", kid->len, kid->data);
 592         ctx->cert->sig->auth_ids[1] = kid;
 593         return 0;
 594 }
 595
 596 /*
 597  * Note a directoryName in an AuthorityKeyIdentifier
 598  */
 599 int x509_akid_note_name(void *context, size_t hdrlen,
 600                         unsigned char tag,
 601                         const void *value, size_t vlen)
 602 {
 603         struct x509_parse_context *ctx = context;
 604
 605         pr_debug("AKID: name: %*phN\n", (int)vlen, value);
 606
 607         ctx->akid_raw_issuer = value;
 608         ctx->akid_raw_issuer_size = vlen;
 609         return 0;
 610 }
 611
 612 /*
 613  * Note a serial number in an AuthorityKeyIdentifier
 614  */
 615 int x509_akid_note_serial(void *context, size_t hdrlen,
 616                           unsigned char tag,
 617                           const void *value, size_t vlen)
 618 {
 619         struct x509_parse_context *ctx = context;
 620         struct asymmetric_key_id *kid;
 621
 622         pr_debug("AKID: serial: %*phN\n", (int)vlen, value);
 623
 624         if (!ctx->akid_raw_issuer || ctx->cert->sig->auth_ids[0])
 625                 return 0;
 626
 627         kid = asymmetric_key_generate_id(value,
 628                                          vlen,
 629                                          ctx->akid_raw_issuer,
 630                                          ctx->akid_raw_issuer_size);
 631         if (IS_ERR(kid))
 632                 return PTR_ERR(kid);
 633
 634         pr_debug("authkeyid %*phN\n", kid->len, kid->data);
 635         ctx->cert->sig->auth_ids[0] = kid;
 636         return 0;
 637 }