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