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         if (strcmp(ctx->cert->sig->pkey_algo, "rsa") == 0) {
 253                 /* Discard the BIT STRING metadata */
 254                 if (vlen < 1 || *(const u8 *)value != 0)
 255                         return -EBADMSG;
 256
 257                 value++;
 258                 vlen--;
 259         }
 260
 261         ctx->cert->raw_sig = value;
 262         ctx->cert->raw_sig_size = vlen;
 263         return 0;
 264 }
 265
 266 /*
 267  * Note the certificate serial number
 268  */
 269 int x509_note_serial(void *context, size_t hdrlen,
 270                      unsigned char tag,
 271                      const void *value, size_t vlen)
 272 {
 273         struct x509_parse_context *ctx = context;
 274         ctx->cert->raw_serial = value;
 275         ctx->cert->raw_serial_size = vlen;
 276         return 0;
 277 }
 278
 279 /*
 280  * Note some of the name segments from which we'll fabricate a name.
 281  */
 282 int x509_extract_name_segment(void *context, size_t hdrlen,
 283                               unsigned char tag,
 284                               const void *value, size_t vlen)
 285 {
 286         struct x509_parse_context *ctx = context;
 287
 288         switch (ctx->last_oid) {
 289         case OID_commonName:
 290                 ctx->cn_size = vlen;
 291                 ctx->cn_offset = (unsigned long)value - ctx->data;
 292                 break;
 293         case OID_organizationName:
 294                 ctx->o_size = vlen;
 295                 ctx->o_offset = (unsigned long)value - ctx->data;
 296                 break;
 297         case OID_email_address:
 298                 ctx->email_size = vlen;
 299                 ctx->email_offset = (unsigned long)value - ctx->data;
 300                 break;
 301         default:
 302                 break;
 303         }
 304
 305         return 0;
 306 }
 307
 308 /*
 309  * Fabricate and save the issuer and subject names
 310  */
 311 static int x509_fabricate_name(struct x509_parse_context *ctx, size_t hdrlen,
 312                                unsigned char tag,
 313                                char **_name, size_t vlen)
 314 {
 315         const void *name, *data = (const void *)ctx->data;
 316         size_t namesize;
 317         char *buffer;
 318
 319         if (*_name)
 320                 return -EINVAL;
 321
 322         /* Empty name string if no material */
 323         if (!ctx->cn_size && !ctx->o_size && !ctx->email_size) {
 324                 buffer = kmalloc(1, GFP_KERNEL);
 325                 if (!buffer)
 326                         return -ENOMEM;
 327                 buffer[0] = 0;
 328                 goto done;
 329         }
 330
 331         if (ctx->cn_size && ctx->o_size) {
 332                 /* Consider combining O and CN, but use only the CN if it is
 333                  * prefixed by the O, or a significant portion thereof.
 334                  */
 335                 namesize = ctx->cn_size;
 336                 name = data + ctx->cn_offset;
 337                 if (ctx->cn_size >= ctx->o_size &&
 338                     memcmp(data + ctx->cn_offset, data + ctx->o_offset,
 339                            ctx->o_size) == 0)
 340                         goto single_component;
 341                 if (ctx->cn_size >= 7 &&
 342                     ctx->o_size >= 7 &&
 343                     memcmp(data + ctx->cn_offset, data + ctx->o_offset, 7) == 0)
 344                         goto single_component;
 345
 346                 buffer = kmalloc(ctx->o_size + 2 + ctx->cn_size + 1,
 347                                  GFP_KERNEL);
 348                 if (!buffer)
 349                         return -ENOMEM;
 350
 351                 memcpy(buffer,
 352                        data + ctx->o_offset, ctx->o_size);
 353                 buffer[ctx->o_size + 0] = ':';
 354                 buffer[ctx->o_size + 1] = ' ';
 355                 memcpy(buffer + ctx->o_size + 2,
 356                        data + ctx->cn_offset, ctx->cn_size);
 357                 buffer[ctx->o_size + 2 + ctx->cn_size] = 0;
 358                 goto done;
 359
 360         } else if (ctx->cn_size) {
 361                 namesize = ctx->cn_size;
 362                 name = data + ctx->cn_offset;
 363         } else if (ctx->o_size) {
 364                 namesize = ctx->o_size;
 365                 name = data + ctx->o_offset;
 366         } else {
 367                 namesize = ctx->email_size;
 368                 name = data + ctx->email_offset;
 369         }
 370
 371 single_component:
 372         buffer = kmalloc(namesize + 1, GFP_KERNEL);
 373         if (!buffer)
 374                 return -ENOMEM;
 375         memcpy(buffer, name, namesize);
 376         buffer[namesize] = 0;
 377
 378 done:
 379         *_name = buffer;
 380         ctx->cn_size = 0;
 381         ctx->o_size = 0;
 382         ctx->email_size = 0;
 383         return 0;
 384 }
 385
 386 int x509_note_issuer(void *context, size_t hdrlen,
 387                      unsigned char tag,
 388                      const void *value, size_t vlen)
 389 {
 390         struct x509_parse_context *ctx = context;
 391         ctx->cert->raw_issuer = value;
 392         ctx->cert->raw_issuer_size = vlen;
 393         return x509_fabricate_name(ctx, hdrlen, tag, &ctx->cert->issuer, vlen);
 394 }
 395
 396 int x509_note_subject(void *context, size_t hdrlen,
 397                       unsigned char tag,
 398                       const void *value, size_t vlen)
 399 {
 400         struct x509_parse_context *ctx = context;
 401         ctx->cert->raw_subject = value;
 402         ctx->cert->raw_subject_size = vlen;
 403         return x509_fabricate_name(ctx, hdrlen, tag, &ctx->cert->subject, vlen);
 404 }
 405
 406 /*
 407  * Extract the data for the public key algorithm
 408  */
 409 int x509_extract_key_data(void *context, size_t hdrlen,
 410                           unsigned char tag,
 411                           const void *value, size_t vlen)
 412 {
 413         struct x509_parse_context *ctx = context;
 414
 415         if (ctx->last_oid != OID_rsaEncryption)
 416                 return -ENOPKG;
 417
 418         ctx->cert->pub->pkey_algo = "rsa";
 419
 420         /* Discard the BIT STRING metadata */
 421         if (vlen < 1 || *(const u8 *)value != 0)
 422                 return -EBADMSG;
 423         ctx->key = value + 1;
 424         ctx->key_size = vlen - 1;
 425         return 0;
 426 }
 427
 428 /* The keyIdentifier in AuthorityKeyIdentifier SEQUENCE is tag(CONT,PRIM,0) */
 429 #define SEQ_TAG_KEYID (ASN1_CONT << 6)
 430
 431 /*
 432  * Process certificate extensions that are used to qualify the certificate.
 433  */
 434 int x509_process_extension(void *context, size_t hdrlen,
 435                            unsigned char tag,
 436                            const void *value, size_t vlen)
 437 {
 438         struct x509_parse_context *ctx = context;
 439         struct asymmetric_key_id *kid;
 440         const unsigned char *v = value;
 441
 442         pr_debug("Extension: %u\n", ctx->last_oid);
 443
 444         if (ctx->last_oid == OID_subjectKeyIdentifier) {
 445                 /* Get hold of the key fingerprint */
 446                 if (ctx->cert->skid || vlen < 3)
 447                         return -EBADMSG;
 448                 if (v[0] != ASN1_OTS || v[1] != vlen - 2)
 449                         return -EBADMSG;
 450                 v += 2;
 451                 vlen -= 2;
 452
 453                 ctx->cert->raw_skid_size = vlen;
 454                 ctx->cert->raw_skid = v;
 455                 kid = asymmetric_key_generate_id(v, vlen, "", 0);
 456                 if (IS_ERR(kid))
 457                         return PTR_ERR(kid);
 458                 ctx->cert->skid = kid;
 459                 pr_debug("subjkeyid %*phN\n", kid->len, kid->data);
 460                 return 0;
 461         }
 462
 463         if (ctx->last_oid == OID_authorityKeyIdentifier) {
 464                 /* Get hold of the CA key fingerprint */
 465                 ctx->raw_akid = v;
 466                 ctx->raw_akid_size = vlen;
 467                 return 0;
 468         }
 469
 470         return 0;
 471 }
 472
 473 /**
 474  * x509_decode_time - Decode an X.509 time ASN.1 object
 475  * @_t: The time to fill in
 476  * @hdrlen: The length of the object header
 477  * @tag: The object tag
 478  * @value: The object value
 479  * @vlen: The size of the object value
 480  *
 481  * Decode an ASN.1 universal time or generalised time field into a struct the
 482  * kernel can handle and check it for validity.  The time is decoded thus:
 483  *
 484  *      [RFC5280 §4.1.2.5]
 485  *      CAs conforming to this profile MUST always encode certificate validity
 486  *      dates through the year 2049 as UTCTime; certificate validity dates in
 487  *      2050 or later MUST be encoded as GeneralizedTime.  Conforming
 488  *      applications MUST be able to process validity dates that are encoded in
 489  *      either UTCTime or GeneralizedTime.
 490  */
 491 int x509_decode_time(time64_t *_t,  size_t hdrlen,
 492                      unsigned char tag,
 493                      const unsigned char *value, size_t vlen)
 494 {
 495         static const unsigned char month_lengths[] = { 31, 28, 31, 30, 31, 30,
 496                                                        31, 31, 30, 31, 30, 31 };
 497         const unsigned char *p = value;
 498         unsigned year, mon, day, hour, min, sec, mon_len;
 499
 500 #define dec2bin(X) ({ unsigned char x = (X) - '0'; if (x > 9) goto invalid_time; x; })
 501 #define DD2bin(P) ({ unsigned x = dec2bin(P[0]) * 10 + dec2bin(P[1]); P += 2; x; })
 502
 503         if (tag == ASN1_UNITIM) {
 504                 /* UTCTime: YYMMDDHHMMSSZ */
 505                 if (vlen != 13)
 506                         goto unsupported_time;
 507                 year = DD2bin(p);
 508                 if (year >= 50)
 509                         year += 1900;
 510                 else
 511                         year += 2000;
 512         } else if (tag == ASN1_GENTIM) {
 513                 /* GenTime: YYYYMMDDHHMMSSZ */
 514                 if (vlen != 15)
 515                         goto unsupported_time;
 516                 year = DD2bin(p) * 100 + DD2bin(p);
 517                 if (year >= 1950 && year <= 2049)
 518                         goto invalid_time;
 519         } else {
 520                 goto unsupported_time;
 521         }
 522
 523         mon  = DD2bin(p);
 524         day = DD2bin(p);
 525         hour = DD2bin(p);
 526         min  = DD2bin(p);
 527         sec  = DD2bin(p);
 528
 529         if (*p != 'Z')
 530                 goto unsupported_time;
 531
 532         if (year < 1970 ||
 533             mon < 1 || mon > 12)
 534                 goto invalid_time;
 535
 536         mon_len = month_lengths[mon - 1];
 537         if (mon == 2) {
 538                 if (year % 4 == 0) {
 539                         mon_len = 29;
 540                         if (year % 100 == 0) {
 541                                 mon_len = 28;
 542                                 if (year % 400 == 0)
 543                                         mon_len = 29;
 544                         }
 545                 }
 546         }
 547
 548         if (day < 1 || day > mon_len ||
 549             hour > 24 || /* ISO 8601 permits 24:00:00 as midnight tomorrow */
 550             min > 59 ||
 551             sec > 60) /* ISO 8601 permits leap seconds [X.680 46.3] */
 552                 goto invalid_time;
 553
 554         *_t = mktime64(year, mon, day, hour, min, sec);
 555         return 0;
 556
 557 unsupported_time:
 558         pr_debug("Got unsupported time [tag %02x]: '%*phN'\n",
 559                  tag, (int)vlen, value);
 560         return -EBADMSG;
 561 invalid_time:
 562         pr_debug("Got invalid time [tag %02x]: '%*phN'\n",
 563                  tag, (int)vlen, value);
 564         return -EBADMSG;
 565 }
 566 EXPORT_SYMBOL_GPL(x509_decode_time);
 567
 568 int x509_note_not_before(void *context, size_t hdrlen,
 569                          unsigned char tag,
 570                          const void *value, size_t vlen)
 571 {
 572         struct x509_parse_context *ctx = context;
 573         return x509_decode_time(&ctx->cert->valid_from, hdrlen, tag, value, vlen);
 574 }
 575
 576 int x509_note_not_after(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         return x509_decode_time(&ctx->cert->valid_to, hdrlen, tag, value, vlen);
 582 }
 583
 584 /*
 585  * Note a key identifier-based AuthorityKeyIdentifier
 586  */
 587 int x509_akid_note_kid(void *context, size_t hdrlen,
 588                        unsigned char tag,
 589                        const void *value, size_t vlen)
 590 {
 591         struct x509_parse_context *ctx = context;
 592         struct asymmetric_key_id *kid;
 593
 594         pr_debug("AKID: keyid: %*phN\n", (int)vlen, value);
 595
 596         if (ctx->cert->sig->auth_ids[1])
 597                 return 0;
 598
 599         kid = asymmetric_key_generate_id(value, vlen, "", 0);
 600         if (IS_ERR(kid))
 601                 return PTR_ERR(kid);
 602         pr_debug("authkeyid %*phN\n", kid->len, kid->data);
 603         ctx->cert->sig->auth_ids[1] = kid;
 604         return 0;
 605 }
 606
 607 /*
 608  * Note a directoryName in an AuthorityKeyIdentifier
 609  */
 610 int x509_akid_note_name(void *context, size_t hdrlen,
 611                         unsigned char tag,
 612                         const void *value, size_t vlen)
 613 {
 614         struct x509_parse_context *ctx = context;
 615
 616         pr_debug("AKID: name: %*phN\n", (int)vlen, value);
 617
 618         ctx->akid_raw_issuer = value;
 619         ctx->akid_raw_issuer_size = vlen;
 620         return 0;
 621 }
 622
 623 /*
 624  * Note a serial number in an AuthorityKeyIdentifier
 625  */
 626 int x509_akid_note_serial(void *context, size_t hdrlen,
 627                           unsigned char tag,
 628                           const void *value, size_t vlen)
 629 {
 630         struct x509_parse_context *ctx = context;
 631         struct asymmetric_key_id *kid;
 632
 633         pr_debug("AKID: serial: %*phN\n", (int)vlen, value);
 634
 635         if (!ctx->akid_raw_issuer || ctx->cert->sig->auth_ids[0])
 636                 return 0;
 637
 638         kid = asymmetric_key_generate_id(value,
 639                                          vlen,
 640                                          ctx->akid_raw_issuer,
 641                                          ctx->akid_raw_issuer_size);
 642         if (IS_ERR(kid))
 643                 return PTR_ERR(kid);
 644
 645         pr_debug("authkeyid %*phN\n", kid->len, kid->data);
 646         ctx->cert->sig->auth_ids[0] = kid;
 647         return 0;
 648 }