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