DXR is a code search and navigation tool aimed at making sense of large projects. It supports full-text and regex searches as well as structural queries.

Line Code
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 446 447 448 449 450 451 452 453 454 455 456 457 458 459 460 461 462 463 464 465 466 467 468 469 470 471 472 473 474 475 476 477 478 479 480 481 482 483 484 485 486 487 488 489 490 491 492 493 494 495 496 497 498 499 500 501 502 503 504 505 506 507 508 509 510 511 512 513 514 515 516 517 518 519 520 521 522 523 524 525 526 527 528 529 530 531 532 533 534 535 536 537 538 539 540 541 542 543 544 545 546 547 548 549 550 551 552 553 554 555 556 557 558 559 560 561 562 563 564 565 566 567 568 569 570 571 572 573 574 575 576 577 578 579 580 581 582 583 584 585 586 587 588 589 590 591 592 593 594 595 596 597 598 599 600 601 602 603 604 605 606 607 608 609 610 611 612 613 614 615 616 617 618 619 620 621 622 623 624 625 626 627 628 629 630 631 632 633 634 635 636 637 638 639 640 641 642 643 644 645 646 647 648 649 650 651 652 653 654 655 656 657 658 659 660 661 662 663 664 665 666 667 668 669 670 671 672 673 674 675 676 677 678 679 680 681 682 683 684 685 686 687 688 689 690 691 692 693 694 695 696 697 698 699 700 701 702 703 704 705 706 707 708 709 710 711 712 713 714 715 716 717 718 719 720 721 722 723 724 725 726 727 728 729 730 731 732 733 734 735 736 737 738 739 740 741 742 743 744 745 746 747 748 749 750 751 752 753 754 755 756 757 758 759 760 761 762 763 764 765 766 767 768 769 770 771 772 773 774 775 776 777 778 779 780 781 782 783 784 785 786 787 788 789 790 791 792 793 794 795 796 797 798 799 800 801 802 803 804 805 806 807 808 809 810 811 812 813 814 815 816 817 818 819 820 821 822 823 824 825 826 827 828 829 830 831 832 833 834 835 836 837 838 839 840 841 842 843 844 845 846 847 848 849 850 851 852 853 854 855 856 857 858 859 860 861 862 863 864 865 866 867 868 869 870 871 872 873 874 875 876 877 878 879 880 881 882 883 884 885 886 887 888 889 890 891 892 893 894 895 896 897
/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

/*
    Optimized ASN.1 DER decoder
    
*/

#include "secerr.h"
#include "secasn1.h" /* for SEC_ASN1GetSubtemplate */
#include "secitem.h"

/*
 * simple definite-length ASN.1 decoder
 */

static unsigned char* definite_length_decoder(const unsigned char *buf,
                                              const unsigned int length,
                                              unsigned int *data_length,
                                              PRBool includeTag)
{
    unsigned char tag;
    unsigned int used_length= 0;
    unsigned int data_len;

    if (used_length >= length)
    {
        return NULL;
    }
    tag = buf[used_length++];

    /* blow out when we come to the end */
    if (tag == 0)
    {
        return NULL;
    }

    if (used_length >= length)
    {
        return NULL;
    }
    data_len = buf[used_length++];

    if (data_len&0x80)
    {
        int  len_count = data_len & 0x7f;

        data_len = 0;

        while (len_count-- > 0)
        {
            if (used_length >= length)
            {
                return NULL;
            }
            data_len = (data_len << 8) | buf[used_length++];
        }
    }

    if (data_len > (length-used_length) )
    {
        return NULL;
    }
    if (includeTag) data_len += used_length;

    *data_length = data_len;
    return ((unsigned char*)buf + (includeTag ? 0 : used_length));
}

static SECStatus GetItem(SECItem* src, SECItem* dest, PRBool includeTag)
{
    if ( (!src) || (!dest) || (!src->data && src->len) )
    {
        PORT_SetError(SEC_ERROR_INVALID_ARGS);
        return SECFailure;
    }

    if (!src->len)
    {
        /* reaching the end of the buffer is not an error */
        dest->data = NULL;
        dest->len = 0;
        return SECSuccess;
    }

    dest->data = definite_length_decoder(src->data,  src->len, &dest->len,
        includeTag);
    if (dest->data == NULL)
    {
        PORT_SetError(SEC_ERROR_BAD_DER);
        return SECFailure;
    }
    src->len -= (dest->data - src->data) + dest->len;
    src->data = dest->data + dest->len;
    return SECSuccess;
}

/* check if the actual component's type matches the type in the template */

static SECStatus MatchComponentType(const SEC_ASN1Template* templateEntry,
                                    SECItem* item, PRBool* match, void* dest)
{
    unsigned long kind = 0;
    unsigned char tag = 0;

    if ( (!item) || (!item->data && item->len) || (!templateEntry) || (!match) )
    {
        PORT_SetError(SEC_ERROR_INVALID_ARGS);
        return SECFailure;
    }

    if (!item->len)
    {
        *match = PR_FALSE;
        return SECSuccess;
    }

    kind = templateEntry->kind;
    tag = *(unsigned char*) item->data;

    if ( ( (kind & SEC_ASN1_INLINE) ||
           (kind & SEC_ASN1_POINTER) ) &&
           (0 == (kind & SEC_ASN1_TAG_MASK) ) )
    {
        /* These cases are special because the template's "kind" does not
           give us the information for the ASN.1 tag of the next item. It can
           only be figured out from the subtemplate. */
        if (!(kind & SEC_ASN1_OPTIONAL))
        {
            /* This is a required component. If there is a type mismatch,
               the decoding of the subtemplate will fail, so assume this
               is a match at the parent level and let it fail later. This
               avoids a redundant check in matching cases */
            *match = PR_TRUE;
            return SECSuccess;
        }
        else
        {
            /* optional component. This is the hard case. Now we need to
               look at the subtemplate to get the expected kind */
            const SEC_ASN1Template* subTemplate = 
                SEC_ASN1GetSubtemplate (templateEntry, dest, PR_FALSE);
            if (!subTemplate)
            {
                PORT_SetError(SEC_ERROR_BAD_TEMPLATE);
                return SECFailure;
            }
            if ( (subTemplate->kind & SEC_ASN1_INLINE) ||
                 (subTemplate->kind & SEC_ASN1_POINTER) )
            {
                /* disallow nesting SEC_ASN1_POINTER and SEC_ASN1_INLINE,
                   otherwise you may get a false positive due to the recursion
                   optimization above that always matches the type if the
                   component is required . Nesting these should never be
                   required, so that no one should miss this ability */
                PORT_SetError(SEC_ERROR_BAD_TEMPLATE);
                return SECFailure;
            }
            return MatchComponentType(subTemplate, item, match,
                                      (void*)((char*)dest + templateEntry->offset));
        }
    }

    if (kind & SEC_ASN1_CHOICE)
    {
        /* we need to check the component's tag against each choice's tag */
        /* XXX it would be nice to save the index of the choice here so that
           DecodeChoice wouldn't have to do this again. However, due to the
           recursivity of MatchComponentType, we don't know if we are in a
           required or optional component, so we can't write anywhere in
           the destination within this function */
        unsigned choiceIndex = 1;
        const SEC_ASN1Template* choiceEntry;
        while ( (choiceEntry = &templateEntry[choiceIndex++]) && (choiceEntry->kind))
        {
            if ( (SECSuccess == MatchComponentType(choiceEntry, item, match,
                                (void*)((char*)dest + choiceEntry->offset))) &&
                 (PR_TRUE == *match) )
            {
                return SECSuccess;
            }
        }
	/* no match, caller must decide if this is BAD DER, or not. */
        *match = PR_FALSE;
        return SECSuccess;
    }

    if (kind & SEC_ASN1_ANY)
    {
        /* SEC_ASN1_ANY always matches */
        *match = PR_TRUE;
        return SECSuccess;
    }

    if ( (0 == ((unsigned char)kind & SEC_ASN1_TAGNUM_MASK)) &&
         (!(kind & SEC_ASN1_EXPLICIT)) &&
         ( ( (kind & SEC_ASN1_SAVE) ||
             (kind & SEC_ASN1_SKIP) ) &&
           (!(kind & SEC_ASN1_OPTIONAL)) 
         )
       )
    {
        /* when saving or skipping a required component,  a type is not
           required in the template. This is for legacy support of
           SEC_ASN1_SAVE and SEC_ASN1_SKIP only. XXX I would like to
           deprecate these usages and always require a type, as this
           disables type checking, and effectively forbids us from
           transparently ignoring optional components we aren't aware of */
        *match = PR_TRUE;
        return SECSuccess;
    }

    /* first, do a class check */
    if ( (tag & SEC_ASN1_CLASS_MASK) !=
         (((unsigned char)kind) & SEC_ASN1_CLASS_MASK) )
    {
#ifdef DEBUG
        /* this is only to help debugging of the decoder in case of problems */
        unsigned char tagclass = tag & SEC_ASN1_CLASS_MASK;
        unsigned char expectedclass = (unsigned char)kind & SEC_ASN1_CLASS_MASK;
        tagclass = tagclass;
        expectedclass = expectedclass;
#endif
        *match = PR_FALSE;
        return SECSuccess;
    }

    /* now do a tag check */
    if ( ((unsigned char)kind & SEC_ASN1_TAGNUM_MASK) !=
         (tag & SEC_ASN1_TAGNUM_MASK))
    {
        *match = PR_FALSE;
        return SECSuccess;
    }

    /* now, do a method check. This depends on the class */
    switch (tag & SEC_ASN1_CLASS_MASK)
    {
    case SEC_ASN1_UNIVERSAL:
        /* For types of the SEC_ASN1_UNIVERSAL class, we know which must be
           primitive or constructed based on the tag */
        switch (tag & SEC_ASN1_TAGNUM_MASK)
        {
        case SEC_ASN1_SEQUENCE:
        case SEC_ASN1_SET:
        case SEC_ASN1_EMBEDDED_PDV:
            /* this component must be a constructed type */
            /* XXX add any new universal constructed type here */
            if (tag & SEC_ASN1_CONSTRUCTED)
            {
                *match = PR_TRUE;
                return SECSuccess;
            }
            break;

        default:
            /* this component must be a primitive type */
            if (! (tag & SEC_ASN1_CONSTRUCTED))
            {
                *match = PR_TRUE;
                return SECSuccess;
            }
            break;
        }
        break;

    default:
        /* for all other classes, we check the method based on the template */
        if ( (unsigned char)(kind & SEC_ASN1_METHOD_MASK) ==
             (tag & SEC_ASN1_METHOD_MASK) )
        {
            *match = PR_TRUE;
            return SECSuccess;
        }
        /* method does not match between template and component */
        break;
    }

    *match = PR_FALSE;
    return SECSuccess;
}

#ifdef DEBUG

static SECStatus CheckSequenceTemplate(const SEC_ASN1Template* sequenceTemplate)
{
    SECStatus rv = SECSuccess;
    const SEC_ASN1Template* sequenceEntry = NULL;
    unsigned long seqIndex = 0;
    unsigned long lastEntryIndex = 0;
    unsigned long ambiguityIndex = 0;
    PRBool foundAmbiguity = PR_FALSE;

    do
    {
        sequenceEntry = &sequenceTemplate[seqIndex++];
        if (sequenceEntry->kind)
        {
            /* ensure that we don't have an optional component of SEC_ASN1_ANY
               in the middle of the sequence, since we could not handle it */
            /* XXX this function needs to dig into the subtemplates to find
               the next tag */
            if ( (PR_FALSE == foundAmbiguity) &&
                 (sequenceEntry->kind & SEC_ASN1_OPTIONAL) &&
                 (sequenceEntry->kind & SEC_ASN1_ANY) )
            {
                foundAmbiguity = PR_TRUE;
                ambiguityIndex = seqIndex - 1;
            }
        }
    } while (sequenceEntry->kind);

    lastEntryIndex = seqIndex - 2;

    if (PR_FALSE != foundAmbiguity)
    {
        if (ambiguityIndex < lastEntryIndex)
        {
            /* ambiguity can only be tolerated on the last entry */
            PORT_SetError(SEC_ERROR_BAD_TEMPLATE);
            rv = SECFailure;
        }
    }

    /* XXX also enforce ASN.1 requirement that tags be
       distinct for consecutive optional components */

    return rv;
}

#endif

static SECStatus DecodeItem(void* dest,
                     const SEC_ASN1Template* templateEntry,
                     SECItem* src, PRArenaPool* arena, PRBool checkTag);

static SECStatus DecodeSequence(void* dest,
                     const SEC_ASN1Template* templateEntry,
                     SECItem* src, PRArenaPool* arena)
{
    SECStatus rv = SECSuccess;
    SECItem source;
    SECItem sequence;
    const SEC_ASN1Template* sequenceTemplate = &(templateEntry[1]);
    const SEC_ASN1Template* sequenceEntry = NULL;
    unsigned long seqindex = 0;

#ifdef DEBUG
    /* for a sequence, we need to validate the template. */
    rv = CheckSequenceTemplate(sequenceTemplate);
#endif

    source = *src;

    /* get the sequence */
    if (SECSuccess == rv)
    {
        rv = GetItem(&source, &sequence, PR_FALSE);
    }

    /* process it */
    if (SECSuccess == rv)
    do
    {
        sequenceEntry = &sequenceTemplate[seqindex++];
        if ( (sequenceEntry && sequenceEntry->kind) &&
             (sequenceEntry->kind != SEC_ASN1_SKIP_REST) )
        {
            rv = DecodeItem(dest, sequenceEntry, &sequence, arena, PR_TRUE);
        }
    } while ( (SECSuccess == rv) &&
              (sequenceEntry->kind &&
               sequenceEntry->kind != SEC_ASN1_SKIP_REST) );
    /* we should have consumed all the bytes in the sequence by now
       unless the caller doesn't care about the rest of the sequence */
    if (SECSuccess == rv && sequence.len &&
        sequenceEntry && sequenceEntry->kind != SEC_ASN1_SKIP_REST)
    {
        /* it isn't 100% clear whether this is a bad DER or a bad template.
           The problem is that logically, they don't match - there is extra
           data in the DER that the template doesn't know about */
        PORT_SetError(SEC_ERROR_BAD_DER);
        rv = SECFailure;
    }

    return rv;
}

static SECStatus DecodeInline(void* dest,
                     const SEC_ASN1Template* templateEntry,
                     SECItem* src, PRArenaPool* arena, PRBool checkTag)
{
    const SEC_ASN1Template* inlineTemplate = 
        SEC_ASN1GetSubtemplate (templateEntry, dest, PR_FALSE);
    return DecodeItem((void*)((char*)dest + templateEntry->offset),
                            inlineTemplate, src, arena, checkTag);
}

static SECStatus DecodePointer(void* dest,
                     const SEC_ASN1Template* templateEntry,
                     SECItem* src, PRArenaPool* arena, PRBool checkTag)
{
    const SEC_ASN1Template* ptrTemplate = 
        SEC_ASN1GetSubtemplate (templateEntry, dest, PR_FALSE);
    void* subdata = PORT_ArenaZAlloc(arena, ptrTemplate->size);
    *(void**)((char*)dest + templateEntry->offset) = subdata;
    if (subdata)
    {
        return DecodeItem(subdata, ptrTemplate, src, arena, checkTag);
    }
    else
    {
        PORT_SetError(SEC_ERROR_NO_MEMORY);
        return SECFailure;
    }
}

static SECStatus DecodeImplicit(void* dest,
                     const SEC_ASN1Template* templateEntry,
                     SECItem* src, PRArenaPool* arena)
{
    if (templateEntry->kind & SEC_ASN1_POINTER)
    {
        return DecodePointer((void*)((char*)dest ),
                             templateEntry, src, arena, PR_FALSE);
    }
    else
    {
        return DecodeInline((void*)((char*)dest ),
                             templateEntry, src, arena, PR_FALSE);
    }
}

static SECStatus DecodeChoice(void* dest,
                     const SEC_ASN1Template* templateEntry,
                     SECItem* src, PRArenaPool* arena)
{
    SECStatus rv = SECSuccess;
    SECItem choice;
    const SEC_ASN1Template* choiceTemplate = &(templateEntry[1]);
    const SEC_ASN1Template* choiceEntry = NULL;
    unsigned long choiceindex = 0;

    /* XXX for a choice component, we should validate the template to make
       sure the tags are distinct, in debug builds. This hasn't been
       implemented yet */
    /* rv = CheckChoiceTemplate(sequenceTemplate); */

    /* process it */
    do
    {
        choice = *src;
        choiceEntry = &choiceTemplate[choiceindex++];
        if (choiceEntry->kind)
        {
            rv = DecodeItem(dest, choiceEntry, &choice, arena, PR_TRUE);
        }
    } while ( (SECFailure == rv) && (choiceEntry->kind));

    if (SECFailure == rv)
    {
        /* the component didn't match any of the choices */
        PORT_SetError(SEC_ERROR_BAD_DER);
    }
    else
    {
        /* set the type in the union here */
        int *which = (int *)((char *)dest + templateEntry->offset);
        *which = (int)choiceEntry->size;
    }

    /* we should have consumed all the bytes by now */
    /* fail if we have not */
    if (SECSuccess == rv && choice.len)
    {
        /* there is extra data that isn't listed in the template */
        PORT_SetError(SEC_ERROR_BAD_DER);
        rv = SECFailure;
    }
    return rv;
}

static SECStatus DecodeGroup(void* dest,
                     const SEC_ASN1Template* templateEntry,
                     SECItem* src, PRArenaPool* arena)
{
    SECStatus rv = SECSuccess;
    SECItem source;
    SECItem group;
    PRUint32 totalEntries = 0;
    PRUint32 entryIndex = 0;
    void** entries = NULL;

    const SEC_ASN1Template* subTemplate =
        SEC_ASN1GetSubtemplate (templateEntry, dest, PR_FALSE);

    source = *src;

    /* get the group */
    if (SECSuccess == rv)
    {
        rv = GetItem(&source, &group, PR_FALSE);
    }

    /* XXX we should check the subtemplate in debug builds */
    if (SECSuccess == rv)
    {
        /* first, count the number of entries. Benchmarking showed that this
           counting pass is more efficient than trying to allocate entries as
           we read the DER, even if allocating many entries at a time
        */
        SECItem counter = group;
        do
        {
            SECItem anitem;
            rv = GetItem(&counter, &anitem, PR_TRUE);
            if (SECSuccess == rv && (anitem.len) )
            {
                totalEntries++;
            }
        }  while ( (SECSuccess == rv) && (counter.len) );

        if (SECSuccess == rv)
        {
            /* allocate room for pointer array and entries */
            /* we want to allocate the array even if there is 0 entry */
            entries = (void**)PORT_ArenaZAlloc(arena, sizeof(void*)*
                                          (totalEntries + 1 ) + /* the extra one is for NULL termination */
                                          subTemplate->size*totalEntries); 

            if (entries)
            {
                entries[totalEntries] = NULL; /* terminate the array */
            }
            else
            {
                PORT_SetError(SEC_ERROR_NO_MEMORY);
                rv = SECFailure;
            }
            if (SECSuccess == rv)
            {
                void* entriesData = (unsigned char*)entries + (unsigned long)(sizeof(void*)*(totalEntries + 1 ));
                /* and fix the pointers in the array */
                PRUint32 entriesIndex = 0;
                for (entriesIndex = 0;entriesIndex<totalEntries;entriesIndex++)
                {
                    entries[entriesIndex] =
                        (char*)entriesData + (subTemplate->size*entriesIndex);
                }
            }
        }
    }

    if (SECSuccess == rv && totalEntries)
    do
    {
        if (!(entryIndex<totalEntries))
        {
            rv = SECFailure;
            break;
        }
        rv = DecodeItem(entries[entryIndex++], subTemplate, &group, arena, PR_TRUE);
    } while ( (SECSuccess == rv) && (group.len) );
    /* we should be at the end of the set by now */    
    /* save the entries where requested */
    memcpy(((char*)dest + templateEntry->offset), &entries, sizeof(void**));

    return rv;
}

static SECStatus DecodeExplicit(void* dest,
                     const SEC_ASN1Template* templateEntry,
                     SECItem* src, PRArenaPool* arena)
{
    SECStatus rv = SECSuccess;
    SECItem subItem;
    SECItem constructed = *src;

    rv = GetItem(&constructed, &subItem, PR_FALSE);

    if (SECSuccess == rv)
    {
        if (templateEntry->kind & SEC_ASN1_POINTER)
        {
            rv = DecodePointer(dest, templateEntry, &subItem, arena, PR_TRUE);
        }
        else
        {
            rv = DecodeInline(dest, templateEntry, &subItem, arena, PR_TRUE);
        }
    }

    return rv;
}

/* new decoder implementation. This is a recursive function */

static SECStatus DecodeItem(void* dest,
                     const SEC_ASN1Template* templateEntry,
                     SECItem* src, PRArenaPool* arena, PRBool checkTag)
{
    SECStatus rv = SECSuccess;
    SECItem temp;
    SECItem mark;
    PRBool pop = PR_FALSE;
    PRBool decode = PR_TRUE;
    PRBool save = PR_FALSE;
    unsigned long kind;
    PRBool match = PR_TRUE;
    PRBool optional = PR_FALSE;

    PR_ASSERT(src && dest && templateEntry && arena);
#if 0
    if (!src || !dest || !templateEntry || !arena)
    {
        PORT_SetError(SEC_ERROR_INVALID_ARGS);
        rv = SECFailure;
    }
#endif

    if (SECSuccess == rv)
    {
        /* do the template validation */
        kind = templateEntry->kind;
        optional = (0 != (kind & SEC_ASN1_OPTIONAL));
        if (!kind)
        {
            PORT_SetError(SEC_ERROR_BAD_TEMPLATE);
            rv = SECFailure;
        }
    }

    if (SECSuccess == rv)
    {
#ifdef DEBUG
        if (kind & SEC_ASN1_DEBUG_BREAK)
        {
            /* when debugging the decoder or a template that fails to
            decode, put SEC_ASN1_DEBUG in the component that gives you
            trouble. The decoder will then get to this block and assert.
            If you want to debug the rest of the code, you can set a
            breakpoint and set dontassert to PR_TRUE, which will let
            you skip over the assert and continue the debugging session
            past it. */
            PRBool dontassert = PR_FALSE;
            PR_ASSERT(dontassert); /* set bkpoint here & set dontassert*/
        }
#endif

        if ((kind & SEC_ASN1_SKIP) ||
            (kind & SEC_ASN1_SAVE))
        {
            /* if skipping or saving this component, don't decode it */
            decode = PR_FALSE;
        }
    
        if (kind & (SEC_ASN1_SAVE | SEC_ASN1_OPTIONAL))
        {
            /* if saving this component, or if it is optional, we may not want to
               move past it, so save the position in case we have to rewind */
            mark = *src;
            if (kind & SEC_ASN1_SAVE)
            {
                save = PR_TRUE;
                if (0 == (kind & SEC_ASN1_SKIP))
                {
                    /* we will for sure have to rewind when saving this
                       component and not skipping it. This is true for all
                       legacy uses of SEC_ASN1_SAVE where the following entry
                       in the template would causes the same component to be
                       processed again */
                    pop = PR_TRUE;
                }
            }
        }

        rv = GetItem(src, &temp, PR_TRUE);
    }

    if (SECSuccess == rv)
    {
        /* now check if the component matches what we expect in the template */

        if (PR_TRUE == checkTag)

        {
            rv = MatchComponentType(templateEntry, &temp, &match, dest);
        }

        if ( (SECSuccess == rv) && (PR_TRUE != match) )
        {
            if (kind & SEC_ASN1_OPTIONAL)
            {

                /* the optional component is missing. This is not fatal. */
                /* Rewind, don't decode, and don't save */
                pop = PR_TRUE;
                decode = PR_FALSE;
                save = PR_FALSE;
            }
            else
            {
                /* a required component is missing. abort */
                PORT_SetError(SEC_ERROR_BAD_DER);
                rv = SECFailure;
            }
        }
    }

    if ((SECSuccess == rv) && (PR_TRUE == decode))
    {
        /* the order of processing here is is the tricky part */
        /* we start with our special cases */
        /* first, check the component class */
        if (kind & SEC_ASN1_INLINE)
        {
            /* decode inline template */
            rv = DecodeInline(dest, templateEntry, &temp , arena, PR_TRUE);
        }

        else
        if (kind & SEC_ASN1_EXPLICIT)
        {
            rv = DecodeExplicit(dest, templateEntry, &temp, arena);
        }
        else
        if ( (SEC_ASN1_UNIVERSAL != (kind & SEC_ASN1_CLASS_MASK)) &&

              (!(kind & SEC_ASN1_EXPLICIT)))
        {

            /* decode implicitly tagged components */
            rv = DecodeImplicit(dest, templateEntry, &temp , arena);
        }
        else
        if (kind & SEC_ASN1_POINTER)
        {
            rv = DecodePointer(dest, templateEntry, &temp, arena, PR_TRUE);
        }
        else
        if (kind & SEC_ASN1_CHOICE)
        {
            rv = DecodeChoice(dest, templateEntry, &temp, arena);
        }
        else
        if (kind & SEC_ASN1_ANY)
        {
            /* catch-all ANY type, don't decode */
            save = PR_TRUE;
            if (kind & SEC_ASN1_INNER)
            {
                /* skip the tag and length */
                SECItem newtemp = temp;
                rv = GetItem(&newtemp, &temp, PR_FALSE);
            }
        }
        else
        if (kind & SEC_ASN1_GROUP)
        {
            if ( (SEC_ASN1_SEQUENCE == (kind & SEC_ASN1_TAGNUM_MASK)) ||
                 (SEC_ASN1_SET == (kind & SEC_ASN1_TAGNUM_MASK)) )
            {
                rv = DecodeGroup(dest, templateEntry, &temp , arena);
            }
            else
            {
                /* a group can only be a SET OF or SEQUENCE OF */
                PORT_SetError(SEC_ERROR_BAD_TEMPLATE);
                rv = SECFailure;
            }
        }
        else
        if (SEC_ASN1_SEQUENCE == (kind & SEC_ASN1_TAGNUM_MASK))
        {
            /* plain SEQUENCE */
            rv = DecodeSequence(dest, templateEntry, &temp , arena);
        }
        else
        {
            /* handle all other types as "save" */
            /* we should only get here for primitive universal types */
            SECItem newtemp = temp;
            rv = GetItem(&newtemp, &temp, PR_FALSE);
            save = PR_TRUE;
            if ((SECSuccess == rv) &&
                SEC_ASN1_UNIVERSAL == (kind & SEC_ASN1_CLASS_MASK))
            {
                unsigned long tagnum = kind & SEC_ASN1_TAGNUM_MASK;
                if ( temp.len == 0 && (tagnum == SEC_ASN1_BOOLEAN ||
                                       tagnum == SEC_ASN1_INTEGER ||
                                       tagnum == SEC_ASN1_BIT_STRING ||
                                       tagnum == SEC_ASN1_OBJECT_ID ||
                                       tagnum == SEC_ASN1_ENUMERATED ||
                                       tagnum == SEC_ASN1_UTC_TIME ||
                                       tagnum == SEC_ASN1_GENERALIZED_TIME) )
                {
                    /* these types MUST have at least one content octet */
                    PORT_SetError(SEC_ERROR_BAD_DER);
                    rv = SECFailure;
                }
                else
                switch (tagnum)
                {
                /* special cases of primitive types */
                case SEC_ASN1_INTEGER:
                    {
                        /* remove leading zeroes if the caller requested
                           siUnsignedInteger
                           This is to allow RSA key operations to work */
                        SECItem* destItem = (SECItem*) ((char*)dest +
                                            templateEntry->offset);
                        if (destItem && (siUnsignedInteger == destItem->type))
                        {
                            while (temp.len > 1 && temp.data[0] == 0)
                            {              /* leading 0 */
                                temp.data++;
                                temp.len--;
                            }
                        }
                        break;
                    }

                case SEC_ASN1_BIT_STRING:
                    {
                        /* change the length in the SECItem to be the number
                           of bits */
                        temp.len = (temp.len-1)*8 - (temp.data[0] & 0x7);
                        temp.data++;
                        break;
                    }

                default:
                    {
                        break;
                    }
                }
            }
        }
    }

    if ((SECSuccess == rv) && (PR_TRUE == save))
    {
        SECItem* destItem = (SECItem*) ((char*)dest + templateEntry->offset);
        if (destItem)
        {
            /* we leave the type alone in the destination SECItem.
               If part of the destination was allocated by the decoder, in
               cases of POINTER, SET OF and SEQUENCE OF, then type is set to
               siBuffer due to the use of PORT_ArenaZAlloc*/
            destItem->data = temp.len ? temp.data : NULL;
            destItem->len = temp.len;
        }
        else
        {
            PORT_SetError(SEC_ERROR_INVALID_ARGS);
            rv = SECFailure;
        }
    }

    if (PR_TRUE == pop)
    {
        /* we don't want to move ahead, so restore the position */
        *src = mark;
    }
    return rv;
}

/* the function below is the public one */

SECStatus SEC_QuickDERDecodeItem(PRArenaPool* arena, void* dest,
                     const SEC_ASN1Template* templateEntry,
                     const SECItem* src)
{
    SECStatus rv = SECSuccess;
    SECItem newsrc;

    if (!arena || !templateEntry || !src)
    {
        PORT_SetError(SEC_ERROR_INVALID_ARGS);
        rv = SECFailure;
    }

    if (SECSuccess == rv)
    {
        newsrc = *src;
        rv = DecodeItem(dest, templateEntry, &newsrc, arena, PR_TRUE);
        if (SECSuccess == rv && newsrc.len)
        {
            rv = SECFailure;
            PORT_SetError(SEC_ERROR_EXTRA_INPUT);
        }
    }

    return rv;
}