secasn1d.c

来自「支持SSL v2/v3, TLS, PKCS #5, PKCS #7, PKCS」· C语言 代码 · 共 2,402 行 · 第 1/5 页

    /*
     * Inherit the missing status of our child, and do the ugly
     * backing-up if necessary.
     * (Only IMPLICIT or POINTER should encounter such; all other cases
     * should have confirmed a tag *before* pushing a child.)
     */
    state->missing = state->child->missing;
    if (state->missing) {
	PORT_Assert (state->place == afterImplicit
		     || state->place == afterPointer);
	state->found_tag_number = state->child->found_tag_number;
	state->found_tag_modifiers = state->child->found_tag_modifiers;
	state->endofcontents = state->child->endofcontents;
    }

    /*
     * Add in number of bytes consumed by child.
     * (Only EXPLICIT should have already consumed bytes itself.)
     */
    PORT_Assert (state->place == afterExplicit || state->consumed == 0);
    state->consumed += state->child->consumed;

    /*
     * Subtract from bytes pending; this only applies to a definite-length
     * EXPLICIT field.
     */
    if (state->pending) {
	PORT_Assert (!state->indefinite);
	PORT_Assert (state->place == afterExplicit);

	/*
	 * If we had a definite-length explicit, then what the child
	 * consumed should be what was left pending.
	 */
	if (state->pending != state->child->consumed) {
	    if (state->pending < state->child->consumed) {
		PORT_SetError (SEC_ERROR_BAD_DER);
		state->top->status = decodeError;
		return;
	    }
	    /*
	     * Okay, this is a hack.  It *should* be an error whether
	     * pending is too big or too small, but it turns out that
	     * we had a bug in our *old* DER encoder that ended up
	     * counting an explicit header twice in the case where
	     * the underlying type was an ANY.  So, because we cannot
	     * prevent receiving these (our own certificate server can
	     * send them to us), we need to be lenient and accept them.
	     * To do so, we need to pretend as if we read all of the
	     * bytes that the header said we would find, even though
	     * we actually came up short.
	     */
	    state->consumed += (state->pending - state->child->consumed);
	}
	state->pending = 0;
    }

    /*
     * Indicate that we are done with child.
     */
    state->child->consumed = 0;

    /*
     * And move on to final state.
     * (Technically everybody could move to afterEndOfContents except
     * for an indefinite-length EXPLICIT; for simplicity though we assert
     * that but let the end-of-contents code do the real determination.)
     */
    PORT_Assert (state->place == afterExplicit || (! state->indefinite));
    state->place = beforeEndOfContents;
}


static void
sec_asn1d_prepare_for_end_of_contents (sec_asn1d_state *state)
{
    PORT_Assert (state->place == beforeEndOfContents);

    if (state->indefinite) {
	state->place = duringEndOfContents;
	state->pending = 2;
    } else {
	state->place = afterEndOfContents;
    }
}


static unsigned long
sec_asn1d_parse_end_of_contents (sec_asn1d_state *state,
				 const char *buf, unsigned long len)
{
    int i;

    PORT_Assert (state->pending <= 2);
    PORT_Assert (state->place == duringEndOfContents);

    if (len == 0) {
	state->top->status = needBytes;
	return 0;
    }

    if (state->pending < len)
	len = state->pending;

    for (i = 0; i < len; i++) {
	if (buf[i] != 0) {
	    /*
	     * We expect to find only zeros; if not, just give up.
	     */
	    PORT_SetError (SEC_ERROR_BAD_DER);
	    state->top->status = decodeError;
	    return 0;
	}
    }

    state->pending -= len;

    if (state->pending == 0) {
	state->place = afterEndOfContents;
	state->endofcontents = PR_TRUE;
    }

    return len;
}


static void
sec_asn1d_pop_state (sec_asn1d_state *state)
{
#if 0	/* XXX I think this should always be handled explicitly by parent? */
    /*
     * Account for our child.
     */
    if (state->child != NULL) {
	state->consumed += state->child->consumed;
	if (state->pending) {
	    PORT_Assert (!state->indefinite);
	    PORT_Assert (state->child->consumed <= state->pending);
	    state->pending -= state->child->consumed;
	}
	state->child->consumed = 0;
    }
#endif	/* XXX */

    /*
     * Free our child.
     */
    sec_asn1d_free_child (state, PR_FALSE);

    /*
     * Just make my parent be the current state.  It will then clean
     * up after me and free me (or reuse me).
     */
    state->top->current = state->parent;
}

static sec_asn1d_state *
sec_asn1d_before_choice
(
  sec_asn1d_state *state
)
{
  sec_asn1d_state *child;

  if( state->allocate ) {
    void *dest;

    dest = sec_asn1d_zalloc(state->top->their_pool, state->theTemplate->size);
    if( (void *)NULL == dest ) {
      state->top->status = decodeError;
      return (sec_asn1d_state *)NULL;
    }

    state->dest = (char *)dest + state->theTemplate->offset;
  }

  child = sec_asn1d_push_state(state->top, state->theTemplate + 1, 
                               state->dest, PR_FALSE);
  if( (sec_asn1d_state *)NULL == child ) {
    return (sec_asn1d_state *)NULL;
  }

  sec_asn1d_scrub_state(child);
  child = sec_asn1d_init_state_based_on_template(child);
  if( (sec_asn1d_state *)NULL == child ) {
    return (sec_asn1d_state *)NULL;
  }

  child->optional = PR_TRUE;

  state->place = duringChoice;

  return child;
}

static sec_asn1d_state *
sec_asn1d_during_choice
(
  sec_asn1d_state *state
)
{
  sec_asn1d_state *child = state->child;
  
  PORT_Assert((sec_asn1d_state *)NULL != child);

  if( child->missing ) {
    unsigned char child_found_tag_modifiers = 0;
    unsigned long child_found_tag_number = 0;

    child->theTemplate++;

    if( 0 == child->theTemplate->kind ) {
      /* Ran out of choices */
      PORT_SetError(SEC_ERROR_BAD_DER);
      state->top->status = decodeError;
      return (sec_asn1d_state *)NULL;
    }

    state->consumed += child->consumed;

    /* cargo'd from next_in_sequence innards */
    if( state->pending ) {
      PORT_Assert(!state->indefinite);
      PORT_Assert(child->consumed <= state->pending);
      state->pending -= child->consumed;
      if( 0 == state->pending ) {
        /* XXX uh.. not sure if I should have stopped this
         * from happening before. */
        PORT_Assert(0);
        PORT_SetError(SEC_ERROR_BAD_DER);
        state->top->status = decodeError;
        return (sec_asn1d_state *)NULL;
      }
    }

    child->consumed = 0;
    sec_asn1d_scrub_state(child);

    /* move it on top again */
    state->top->current = child;

    child_found_tag_modifiers = child->found_tag_modifiers;
    child_found_tag_number = child->found_tag_number;

    child = sec_asn1d_init_state_based_on_template(child);
    if( (sec_asn1d_state *)NULL == child ) {
      return (sec_asn1d_state *)NULL;
    }

    /* copy our findings to the new top */
    child->found_tag_modifiers = child_found_tag_modifiers;
    child->found_tag_number = child_found_tag_number;

    child->optional = PR_TRUE;
    child->place = afterIdentifier;

    return child;
  } else {
    if( (void *)NULL != state->dest ) {
      /* Store the enum */
      int *which = (int *)((char *)state->dest + state->theTemplate->offset);
      *which = (int)child->theTemplate->size;
    }

    child->place = notInUse;

    state->place = afterChoice;
    return state;
  }
}

static void
sec_asn1d_after_choice
(
  sec_asn1d_state *state
)
{
  state->consumed += state->child->consumed;
  state->child->consumed = 0;
  state->place = afterEndOfContents;
  sec_asn1d_pop_state(state);
}

unsigned long
sec_asn1d_uinteger(SECItem *src)
{
    unsigned long value;
    int len;

    if (src->len > 5 || (src->len > 4 && src->data[0] == 0))
	return 0;

    value = 0;
    len = src->len;
    while (len) {
	value <<= 8;
	value |= src->data[--len];
    }
    return value;
}

SECStatus
SEC_ASN1DecodeInteger(SECItem *src, unsigned long *value)
{
    unsigned long v;
    int i;
    
    if (src->len > sizeof(unsigned long))
	return SECFailure;

    if (src->data[0] & 0x80)
	v = -1;		/* signed and negative - start with all 1's */
    else
	v = 0;

    for (i= 0; i < src->len; i++) {
	/* shift in next byte */
	v <<= 8;
	v |= src->data[i];
    }
    *value = v;
    return SECSuccess;
}

#ifdef DEBUG_ASN1D_STATES
static void
dump_states
(
  SEC_ASN1DecoderContext *cx
)
{
  sec_asn1d_state *state;

  for( state = cx->current; state->parent; state = state->parent ) {
    ;
  }

  for( ; state; state = state->child ) {
    int i;
    for( i = 0; i < state->depth; i++ ) {
      printf("  ");
    }

    printf("%s: template[0]->kind = 0x%02x, expect tag number = 0x%02x\n",
           (state == cx->current) ? "STATE" : "State",
           state->theTemplate->kind, state->expect_tag_number);
  }

  return;
}
#endif /* DEBUG_ASN1D_STATES */

SECStatus
SEC_ASN1DecoderUpdate (SEC_ASN1DecoderContext *cx,
		       const char *buf, unsigned long len)
{
    sec_asn1d_state *state = NULL;
    unsigned long consumed;
    SEC_ASN1EncodingPart what;


    if (cx->status == needBytes)
	cx->status = keepGoing;

    while (cx->status == keepGoing) {
	state = cx->current;
	what = SEC_ASN1_Contents;
	consumed = 0;
#ifdef DEBUG_ASN1D_STATES
        printf("\nPLACE = %s, next byte = 0x%02x\n",
               (state->place >= 0 && state->place <= notInUse) ?
               place_names[ state->place ] : "(undefined)",
               (unsigned int)((unsigned char *)buf)[ consumed ]);
        dump_states(cx);
#endif /* DEBUG_ASN1D_STATES */
	switch (state->place) {
	  case beforeIdentifier:
	    consumed = sec_asn1d_parse_identifier (state, buf, len);
	    what = SEC_ASN1_Identifier;
	    break;
	  case duringIdentifier:
	    consumed = sec_asn1d_parse_more_identifier (state, buf, len);
	    what = SEC_ASN1_Identifier;
	    break;
	  case afterIdentifier:
	    sec_asn1d_confirm_identifier (state);
	    break;
	  case beforeLength:
	    consumed = sec_asn1d_parse_length (state, buf, len);
	    what = SEC_ASN1_Length;
	    break;
	  case duringLength:
	    consumed = sec_asn1d_parse_more_length (state, buf, len);
	    what = SEC_ASN1_Length;
	    break;
	  case afterLength:
	    sec_asn1d_prepare_for_contents (state);
	    break;
	  case beforeBitString:
	    consumed = sec_asn1d_parse_bit_string (state, buf, len);
	    break;
	  case duringBitString:
	    consumed = sec_asn1d_parse_more_bit_string (state, buf, len);
	    break;
	  case duringConstructedString:
	    sec_asn1d_next_substring (state);
	    break;
	  case duringGroup:
	    sec_asn1d_next_in_group (state);
	    break;
	  case duringLeaf:
	    consumed = sec_asn1d_parse_leaf (state, buf, len);
	    break;
	  case duringSaveEncoding:
	    sec_asn1d_reuse_encoding (state);
	    break;
	  case duringSequence:
	    sec_asn1d_next_in_sequence (state);
	    break;
	  case afterConstructedString:
	    sec_asn1d_concat_substrings (state);
	    break;
	  case afterExplicit:
	  case afterImplicit:
	  case afterInline:
	  case afterPointer:
	    sec_asn1d_absorb_child (state);
	    break;
	  case afterGroup:
	    sec_asn1d_concat_group (state);
	    break;
	  case afterSaveEncoding:
	    /* XXX comment! */
	    return SECSuccess;
	  case beforeEndOfContents:
	    sec_asn1d_prepare_for_end_of_contents (state);
	    break;
	  case duringEndOfContents:
	    consumed = sec_asn1d_parse_end_of_contents (state, buf, len);
	    what = SEC_ASN1_EndOfContents;
	    break;
	  case afterEndOfContents:
	    sec_asn1d_pop_state (state);
	    break;
          case beforeChoice:
            state = sec_asn1d_before_choice(state);
            break;
          case duringChoice:
            state = sec_asn1d_during_choice(state);
            break;
          case afterChoice:
            sec_asn1d_after_choice(state);
            break;
	  case notInUse:
	  default:
	    /* This is not an error, but rather a plain old BUG! */
	    PORT_Assert (0);
	    PORT_SetError (SEC_ERROR_BAD_DER);
	    cx->status = decodeError;
	    break;
	}

	if (cx->status == decodeError)
	    break;

	/* We should not consume more than we have.  */
	PORT_Assert (consumed <= len);

	/* It might have changed, so we have to update our local copy.  */
	state = cx->current;

	/* If it is NULL, we have popped all the way to the top.  */
	if (state == NULL) {
	    PORT_Assert (consumed == 0);
#if 0	/* XXX I want this here, but it seems that we have situations (like
	 * downloading a pkcs7 cert chain from some issuers) that give us a
	 * length which is greater than the entire encoding.  So