linux/crypto/asymmetric_keys/x509_cert_parser.c
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   1/* X.509 certificate parser
   2 *
   3 * Copyright (C) 2012 Red Hat, Inc. All Rights Reserved.
   4 * Written by David Howells (dhowells@redhat.com)
   5 *
   6 * This program is free software; you can redistribute it and/or
   7 * modify it under the terms of the GNU General Public Licence
   8 * as published by the Free Software Foundation; either version
   9 * 2 of the Licence, or (at your option) any later version.
  10 */
  11
  12#define pr_fmt(fmt) "X.509: "fmt
  13#include <linux/kernel.h>
  14#include <linux/slab.h>
  15#include <linux/err.h>
  16#include <linux/oid_registry.h>
  17#include "public_key.h"
  18#include "x509_parser.h"
  19#include "x509-asn1.h"
  20#include "x509_rsakey-asn1.h"
  21
  22struct x509_parse_context {
  23        struct x509_certificate *cert;          /* Certificate being constructed */
  24        unsigned long   data;                   /* Start of data */
  25        const void      *cert_start;            /* Start of cert content */
  26        const void      *key;                   /* Key data */
  27        size_t          key_size;               /* Size of key data */
  28        enum OID        last_oid;               /* Last OID encountered */
  29        enum OID        algo_oid;               /* Algorithm OID */
  30        unsigned char   nr_mpi;                 /* Number of MPIs stored */
  31        u8              o_size;                 /* Size of organizationName (O) */
  32        u8              cn_size;                /* Size of commonName (CN) */
  33        u8              email_size;             /* Size of emailAddress */
  34        u16             o_offset;               /* Offset of organizationName (O) */
  35        u16             cn_offset;              /* Offset of commonName (CN) */
  36        u16             email_offset;           /* Offset of emailAddress */
  37};
  38
  39/*
  40 * Free an X.509 certificate
  41 */
  42void x509_free_certificate(struct x509_certificate *cert)
  43{
  44        if (cert) {
  45                public_key_destroy(cert->pub);
  46                kfree(cert->issuer);
  47                kfree(cert->subject);
  48                kfree(cert->fingerprint);
  49                kfree(cert->authority);
  50                kfree(cert);
  51        }
  52}
  53
  54/*
  55 * Parse an X.509 certificate
  56 */
  57struct x509_certificate *x509_cert_parse(const void *data, size_t datalen)
  58{
  59        struct x509_certificate *cert;
  60        struct x509_parse_context *ctx;
  61        long ret;
  62
  63        ret = -ENOMEM;
  64        cert = kzalloc(sizeof(struct x509_certificate), GFP_KERNEL);
  65        if (!cert)
  66                goto error_no_cert;
  67        cert->pub = kzalloc(sizeof(struct public_key), GFP_KERNEL);
  68        if (!cert->pub)
  69                goto error_no_ctx;
  70        ctx = kzalloc(sizeof(struct x509_parse_context), GFP_KERNEL);
  71        if (!ctx)
  72                goto error_no_ctx;
  73
  74        ctx->cert = cert;
  75        ctx->data = (unsigned long)data;
  76
  77        /* Attempt to decode the certificate */
  78        ret = asn1_ber_decoder(&x509_decoder, ctx, data, datalen);
  79        if (ret < 0)
  80                goto error_decode;
  81
  82        /* Decode the public key */
  83        ret = asn1_ber_decoder(&x509_rsakey_decoder, ctx,
  84                               ctx->key, ctx->key_size);
  85        if (ret < 0)
  86                goto error_decode;
  87
  88        kfree(ctx);
  89        return cert;
  90
  91error_decode:
  92        kfree(ctx);
  93error_no_ctx:
  94        x509_free_certificate(cert);
  95error_no_cert:
  96        return ERR_PTR(ret);
  97}
  98
  99/*
 100 * Note an OID when we find one for later processing when we know how
 101 * to interpret it.
 102 */
 103int x509_note_OID(void *context, size_t hdrlen,
 104             unsigned char tag,
 105             const void *value, size_t vlen)
 106{
 107        struct x509_parse_context *ctx = context;
 108
 109        ctx->last_oid = look_up_OID(value, vlen);
 110        if (ctx->last_oid == OID__NR) {
 111                char buffer[50];
 112                sprint_oid(value, vlen, buffer, sizeof(buffer));
 113                pr_debug("Unknown OID: [%lu] %s\n",
 114                         (unsigned long)value - ctx->data, buffer);
 115        }
 116        return 0;
 117}
 118
 119/*
 120 * Save the position of the TBS data so that we can check the signature over it
 121 * later.
 122 */
 123int x509_note_tbs_certificate(void *context, size_t hdrlen,
 124                              unsigned char tag,
 125                              const void *value, size_t vlen)
 126{
 127        struct x509_parse_context *ctx = context;
 128
 129        pr_debug("x509_note_tbs_certificate(,%zu,%02x,%ld,%zu)!\n",
 130                 hdrlen, tag, (unsigned long)value - ctx->data, vlen);
 131
 132        ctx->cert->tbs = value - hdrlen;
 133        ctx->cert->tbs_size = vlen + hdrlen;
 134        return 0;
 135}
 136
 137/*
 138 * Record the public key algorithm
 139 */
 140int x509_note_pkey_algo(void *context, size_t hdrlen,
 141                        unsigned char tag,
 142                        const void *value, size_t vlen)
 143{
 144        struct x509_parse_context *ctx = context;
 145
 146        pr_debug("PubKey Algo: %u\n", ctx->last_oid);
 147
 148        switch (ctx->last_oid) {
 149        case OID_md2WithRSAEncryption:
 150        case OID_md3WithRSAEncryption:
 151        default:
 152                return -ENOPKG; /* Unsupported combination */
 153
 154        case OID_md4WithRSAEncryption:
 155                ctx->cert->sig_hash_algo = PKEY_HASH_MD5;
 156                ctx->cert->sig_pkey_algo = PKEY_ALGO_RSA;
 157                break;
 158
 159        case OID_sha1WithRSAEncryption:
 160                ctx->cert->sig_hash_algo = PKEY_HASH_SHA1;
 161                ctx->cert->sig_pkey_algo = PKEY_ALGO_RSA;
 162                break;
 163
 164        case OID_sha256WithRSAEncryption:
 165                ctx->cert->sig_hash_algo = PKEY_HASH_SHA256;
 166                ctx->cert->sig_pkey_algo = PKEY_ALGO_RSA;
 167                break;
 168
 169        case OID_sha384WithRSAEncryption:
 170                ctx->cert->sig_hash_algo = PKEY_HASH_SHA384;
 171                ctx->cert->sig_pkey_algo = PKEY_ALGO_RSA;
 172                break;
 173
 174        case OID_sha512WithRSAEncryption:
 175                ctx->cert->sig_hash_algo = PKEY_HASH_SHA512;
 176                ctx->cert->sig_pkey_algo = PKEY_ALGO_RSA;
 177                break;
 178
 179        case OID_sha224WithRSAEncryption:
 180                ctx->cert->sig_hash_algo = PKEY_HASH_SHA224;
 181                ctx->cert->sig_pkey_algo = PKEY_ALGO_RSA;
 182                break;
 183        }
 184
 185        ctx->algo_oid = ctx->last_oid;
 186        return 0;
 187}
 188
 189/*
 190 * Note the whereabouts and type of the signature.
 191 */
 192int x509_note_signature(void *context, size_t hdrlen,
 193                        unsigned char tag,
 194                        const void *value, size_t vlen)
 195{
 196        struct x509_parse_context *ctx = context;
 197
 198        pr_debug("Signature type: %u size %zu\n", ctx->last_oid, vlen);
 199
 200        if (ctx->last_oid != ctx->algo_oid) {
 201                pr_warn("Got cert with pkey (%u) and sig (%u) algorithm OIDs\n",
 202                        ctx->algo_oid, ctx->last_oid);
 203                return -EINVAL;
 204        }
 205
 206        ctx->cert->sig = value;
 207        ctx->cert->sig_size = vlen;
 208        return 0;
 209}
 210
 211/*
 212 * Note some of the name segments from which we'll fabricate a name.
 213 */
 214int x509_extract_name_segment(void *context, size_t hdrlen,
 215                              unsigned char tag,
 216                              const void *value, size_t vlen)
 217{
 218        struct x509_parse_context *ctx = context;
 219
 220        switch (ctx->last_oid) {
 221        case OID_commonName:
 222                ctx->cn_size = vlen;
 223                ctx->cn_offset = (unsigned long)value - ctx->data;
 224                break;
 225        case OID_organizationName:
 226                ctx->o_size = vlen;
 227                ctx->o_offset = (unsigned long)value - ctx->data;
 228                break;
 229        case OID_email_address:
 230                ctx->email_size = vlen;
 231                ctx->email_offset = (unsigned long)value - ctx->data;
 232                break;
 233        default:
 234                break;
 235        }
 236
 237        return 0;
 238}
 239
 240/*
 241 * Fabricate and save the issuer and subject names
 242 */
 243static int x509_fabricate_name(struct x509_parse_context *ctx, size_t hdrlen,
 244                               unsigned char tag,
 245                               char **_name, size_t vlen)
 246{
 247        const void *name, *data = (const void *)ctx->data;
 248        size_t namesize;
 249        char *buffer;
 250
 251        if (*_name)
 252                return -EINVAL;
 253
 254        /* Empty name string if no material */
 255        if (!ctx->cn_size && !ctx->o_size && !ctx->email_size) {
 256                buffer = kmalloc(1, GFP_KERNEL);
 257                if (!buffer)
 258                        return -ENOMEM;
 259                buffer[0] = 0;
 260                goto done;
 261        }
 262
 263        if (ctx->cn_size && ctx->o_size) {
 264                /* Consider combining O and CN, but use only the CN if it is
 265                 * prefixed by the O, or a significant portion thereof.
 266                 */
 267                namesize = ctx->cn_size;
 268                name = data + ctx->cn_offset;
 269                if (ctx->cn_size >= ctx->o_size &&
 270                    memcmp(data + ctx->cn_offset, data + ctx->o_offset,
 271                           ctx->o_size) == 0)
 272                        goto single_component;
 273                if (ctx->cn_size >= 7 &&
 274                    ctx->o_size >= 7 &&
 275                    memcmp(data + ctx->cn_offset, data + ctx->o_offset, 7) == 0)
 276                        goto single_component;
 277
 278                buffer = kmalloc(ctx->o_size + 2 + ctx->cn_size + 1,
 279                                 GFP_KERNEL);
 280                if (!buffer)
 281                        return -ENOMEM;
 282
 283                memcpy(buffer,
 284                       data + ctx->o_offset, ctx->o_size);
 285                buffer[ctx->o_size + 0] = ':';
 286                buffer[ctx->o_size + 1] = ' ';
 287                memcpy(buffer + ctx->o_size + 2,
 288                       data + ctx->cn_offset, ctx->cn_size);
 289                buffer[ctx->o_size + 2 + ctx->cn_size] = 0;
 290                goto done;
 291
 292        } else if (ctx->cn_size) {
 293                namesize = ctx->cn_size;
 294                name = data + ctx->cn_offset;
 295        } else if (ctx->o_size) {
 296                namesize = ctx->o_size;
 297                name = data + ctx->o_offset;
 298        } else {
 299                namesize = ctx->email_size;
 300                name = data + ctx->email_offset;
 301        }
 302
 303single_component:
 304        buffer = kmalloc(namesize + 1, GFP_KERNEL);
 305        if (!buffer)
 306                return -ENOMEM;
 307        memcpy(buffer, name, namesize);
 308        buffer[namesize] = 0;
 309
 310done:
 311        *_name = buffer;
 312        ctx->cn_size = 0;
 313        ctx->o_size = 0;
 314        ctx->email_size = 0;
 315        return 0;
 316}
 317
 318int x509_note_issuer(void *context, size_t hdrlen,
 319                     unsigned char tag,
 320                     const void *value, size_t vlen)
 321{
 322        struct x509_parse_context *ctx = context;
 323        return x509_fabricate_name(ctx, hdrlen, tag, &ctx->cert->issuer, vlen);
 324}
 325
 326int x509_note_subject(void *context, size_t hdrlen,
 327                      unsigned char tag,
 328                      const void *value, size_t vlen)
 329{
 330        struct x509_parse_context *ctx = context;
 331        return x509_fabricate_name(ctx, hdrlen, tag, &ctx->cert->subject, vlen);
 332}
 333
 334/*
 335 * Extract the data for the public key algorithm
 336 */
 337int x509_extract_key_data(void *context, size_t hdrlen,
 338                          unsigned char tag,
 339                          const void *value, size_t vlen)
 340{
 341        struct x509_parse_context *ctx = context;
 342
 343        if (ctx->last_oid != OID_rsaEncryption)
 344                return -ENOPKG;
 345
 346        /* There seems to be an extraneous 0 byte on the front of the data */
 347        ctx->cert->pkey_algo = PKEY_ALGO_RSA;
 348        ctx->key = value + 1;
 349        ctx->key_size = vlen - 1;
 350        return 0;
 351}
 352
 353/*
 354 * Extract a RSA public key value
 355 */
 356int rsa_extract_mpi(void *context, size_t hdrlen,
 357                    unsigned char tag,
 358                    const void *value, size_t vlen)
 359{
 360        struct x509_parse_context *ctx = context;
 361        MPI mpi;
 362
 363        if (ctx->nr_mpi >= ARRAY_SIZE(ctx->cert->pub->mpi)) {
 364                pr_err("Too many public key MPIs in certificate\n");
 365                return -EBADMSG;
 366        }
 367
 368        mpi = mpi_read_raw_data(value, vlen);
 369        if (!mpi)
 370                return -ENOMEM;
 371
 372        ctx->cert->pub->mpi[ctx->nr_mpi++] = mpi;
 373        return 0;
 374}
 375
 376/*
 377 * Process certificate extensions that are used to qualify the certificate.
 378 */
 379int x509_process_extension(void *context, size_t hdrlen,
 380                           unsigned char tag,
 381                           const void *value, size_t vlen)
 382{
 383        struct x509_parse_context *ctx = context;
 384        const unsigned char *v = value;
 385        char *f;
 386        int i;
 387
 388        pr_debug("Extension: %u\n", ctx->last_oid);
 389
 390        if (ctx->last_oid == OID_subjectKeyIdentifier) {
 391                /* Get hold of the key fingerprint */
 392                if (vlen < 3)
 393                        return -EBADMSG;
 394                if (v[0] != ASN1_OTS || v[1] != vlen - 2)
 395                        return -EBADMSG;
 396                v += 2;
 397                vlen -= 2;
 398
 399                f = kmalloc(vlen * 2 + 1, GFP_KERNEL);
 400                if (!f)
 401                        return -ENOMEM;
 402                for (i = 0; i < vlen; i++)
 403                        sprintf(f + i * 2, "%02x", v[i]);
 404                pr_debug("fingerprint %s\n", f);
 405                ctx->cert->fingerprint = f;
 406                return 0;
 407        }
 408
 409        if (ctx->last_oid == OID_authorityKeyIdentifier) {
 410                /* Get hold of the CA key fingerprint */
 411                if (vlen < 5)
 412                        return -EBADMSG;
 413                if (v[0] != (ASN1_SEQ | (ASN1_CONS << 5)) ||
 414                    v[1] != vlen - 2 ||
 415                    v[2] != (ASN1_CONT << 6) ||
 416                    v[3] != vlen - 4)
 417                        return -EBADMSG;
 418                v += 4;
 419                vlen -= 4;
 420
 421                f = kmalloc(vlen * 2 + 1, GFP_KERNEL);
 422                if (!f)
 423                        return -ENOMEM;
 424                for (i = 0; i < vlen; i++)
 425                        sprintf(f + i * 2, "%02x", v[i]);
 426                pr_debug("authority   %s\n", f);
 427                ctx->cert->authority = f;
 428                return 0;
 429        }
 430
 431        return 0;
 432}
 433
 434/*
 435 * Record a certificate time.
 436 */
 437static int x509_note_time(struct tm *tm,  size_t hdrlen,
 438                          unsigned char tag,
 439                          const unsigned char *value, size_t vlen)
 440{
 441        const unsigned char *p = value;
 442
 443#define dec2bin(X) ((X) - '0')
 444#define DD2bin(P) ({ unsigned x = dec2bin(P[0]) * 10 + dec2bin(P[1]); P += 2; x; })
 445
 446        if (tag == ASN1_UNITIM) {
 447                /* UTCTime: YYMMDDHHMMSSZ */
 448                if (vlen != 13)
 449                        goto unsupported_time;
 450                tm->tm_year = DD2bin(p);
 451                if (tm->tm_year >= 50)
 452                        tm->tm_year += 1900;
 453                else
 454                        tm->tm_year += 2000;
 455        } else if (tag == ASN1_GENTIM) {
 456                /* GenTime: YYYYMMDDHHMMSSZ */
 457                if (vlen != 15)
 458                        goto unsupported_time;
 459                tm->tm_year = DD2bin(p) * 100 + DD2bin(p);
 460        } else {
 461                goto unsupported_time;
 462        }
 463
 464        tm->tm_year -= 1900;
 465        tm->tm_mon  = DD2bin(p) - 1;
 466        tm->tm_mday = DD2bin(p);
 467        tm->tm_hour = DD2bin(p);
 468        tm->tm_min  = DD2bin(p);
 469        tm->tm_sec  = DD2bin(p);
 470
 471        if (*p != 'Z')
 472                goto unsupported_time;
 473
 474        return 0;
 475
 476unsupported_time:
 477        pr_debug("Got unsupported time [tag %02x]: '%*.*s'\n",
 478                 tag, (int)vlen, (int)vlen, value);
 479        return -EBADMSG;
 480}
 481
 482int x509_note_not_before(void *context, size_t hdrlen,
 483                         unsigned char tag,
 484                         const void *value, size_t vlen)
 485{
 486        struct x509_parse_context *ctx = context;
 487        return x509_note_time(&ctx->cert->valid_from, hdrlen, tag, value, vlen);
 488}
 489
 490int x509_note_not_after(void *context, size_t hdrlen,
 491                        unsigned char tag,
 492                        const void *value, size_t vlen)
 493{
 494        struct x509_parse_context *ctx = context;
 495        return x509_note_time(&ctx->cert->valid_to, hdrlen, tag, value, vlen);
 496}
 497
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