constr_sequence.c

RSA加密/解密算法源码 asn1c-0.9.12

/*-
 * Copyright (c) 2003, 2004, 2005 Lev Walkin <[e-mail]>.
 * All rights reserved.
 * Redistribution and modifications are permitted subject to BSD license.
 */
#include <asn_internal.h>
#include <constr_SEQUENCE.h>
#include <assert.h>

/*
 * Number of bytes left for this structure.
 * (ctx->left) indicates the number of bytes _transferred_ for the structure.
 * (size) contains the number of bytes in the buffer passed.
 */
#define	LEFT	((size<(size_t)ctx->left)?size:(size_t)ctx->left)

/*
 * If the subprocessor function returns with an indication that it wants
 * more data, it may well be a fatal decoding problem, because the
 * size is constrained by the <TLV>'s L, even if the buffer size allows
 * reading more data.
 * For example, consider the buffer containing the following TLVs:
 * <T:5><L:1><V> <T:6>...
 * The TLV length clearly indicates that one byte is expected in V, but
 * if the V processor returns with "want more data" even if the buffer
 * contains way more data than the V processor have seen.
 */
#define	SIZE_VIOLATION	(ctx->left >= 0 && (size_t)ctx->left <= size)

/*
 * This macro "eats" the part of the buffer which is definitely "consumed",
 * i.e. was correctly converted into local representation or rightfully skipped.
 */
#undef	ADVANCE
#define	ADVANCE(num_bytes)	do {		\
		size_t num = num_bytes;		\
		ptr = ((char *)ptr) + num;	\
		size -= num;			\
		if(ctx->left >= 0)		\
			ctx->left -= num;	\
		consumed_myself += num;		\
	} while(0)

/*
 * Switch to the next phase of parsing.
 */
#undef	NEXT_PHASE
#undef	PHASE_OUT
#define	NEXT_PHASE(ctx)	do {			\
		ctx->phase++;			\
		ctx->step = 0;			\
	} while(0)
#define	PHASE_OUT(ctx)	do { ctx->phase = 10; } while(0)

/*
 * Return a standardized complex structure.
 */
#undef	RETURN
#define	RETURN(_code)	do {			\
		rval.code = _code;		\
		rval.consumed = consumed_myself;\
		return rval;			\
	} while(0)

/*
 * Check whether we are inside the extensions group.
 */
#define	IN_EXTENSION_GROUP(specs, memb_idx)	\
	( ((memb_idx) > (specs)->ext_after)	\
	&&((memb_idx) < (specs)->ext_before))


/*
 * Tags are canonically sorted in the tag2element map.
 */
static int
_t2e_cmp(const void *ap, const void *bp) {
	const asn_TYPE_tag2member_t *a = (const asn_TYPE_tag2member_t *)ap;
	const asn_TYPE_tag2member_t *b = (const asn_TYPE_tag2member_t *)bp;

	int a_class = BER_TAG_CLASS(a->el_tag);
	int b_class = BER_TAG_CLASS(b->el_tag);

	if(a_class == b_class) {
		ber_tlv_tag_t a_value = BER_TAG_VALUE(a->el_tag);
		ber_tlv_tag_t b_value = BER_TAG_VALUE(b->el_tag);

		if(a_value == b_value) {
			if(a->el_no > b->el_no)
				return 1;
			/*
			 * Important: we do not check
			 * for a->el_no <= b->el_no!
			 */
			return 0;
		} else if(a_value < b_value)
			return -1;
		else
			return 1;
	} else if(a_class < b_class) {
		return -1;
	} else {
		return 1;
	}
}


/*
 * The decoder of the SEQUENCE type.
 */
asn_dec_rval_t
SEQUENCE_decode_ber(asn_codec_ctx_t *opt_codec_ctx, asn_TYPE_descriptor_t *td,
	void **struct_ptr, void *ptr, size_t size, int tag_mode) {
	/*
	 * Bring closer parts of structure description.
	 */
	asn_SEQUENCE_specifics_t *specs = (asn_SEQUENCE_specifics_t *)td->specifics;
	asn_TYPE_member_t *elements = td->elements;

	/*
	 * Parts of the structure being constructed.
	 */
	void *st = *struct_ptr;	/* Target structure. */
	asn_struct_ctx_t *ctx;	/* Decoder context */

	ber_tlv_tag_t tlv_tag;	/* T from TLV */
	asn_dec_rval_t rval;	/* Return code from subparsers */

	ssize_t consumed_myself = 0;	/* Consumed bytes from ptr */
	int edx;			/* SEQUENCE element's index */

	ASN_DEBUG("Decoding %s as SEQUENCE", td->name);
	
	/*
	 * Create the target structure if it is not present already.
	 */
	if(st == 0) {
		st = *struct_ptr = CALLOC(1, specs->struct_size);
		if(st == 0) {
			RETURN(RC_FAIL);
		}
	}

	/*
	 * Restore parsing context.
	 */
	ctx = (asn_struct_ctx_t *)((char *)st + specs->ctx_offset);
	
	/*
	 * Start to parse where left previously
	 */
	switch(ctx->phase) {
	case 0:
		/*
		 * PHASE 0.
		 * Check that the set of tags associated with given structure
		 * perfectly fits our expectations.
		 */

		rval = ber_check_tags(opt_codec_ctx, td, ctx, ptr, size,
			tag_mode, 1, &ctx->left, 0);
		if(rval.code != RC_OK) {
			ASN_DEBUG("%s tagging check failed: %d",
				td->name, rval.code);
			return rval;
		}

		if(ctx->left >= 0)
			ctx->left += rval.consumed; /* ?Substracted below! */
		ADVANCE(rval.consumed);

		NEXT_PHASE(ctx);

		ASN_DEBUG("Structure consumes %ld bytes, buffer %ld",
			(long)ctx->left, (long)size);

		/* Fall through */
	case 1:
		/*
		 * PHASE 1.
		 * From the place where we've left it previously,
		 * try to decode the next member from the list of
		 * this structure's elements.
		 * (ctx->step) stores the member being processed
		 * between invocations and the microphase {0,1} of parsing
		 * that member:
		 * 	step = (<member_number> * 2 + <microphase>).
		 */
	  for(edx = (ctx->step >> 1); edx < td->elements_count;
			edx++, ctx->step = (ctx->step & ~1) + 2) {
		void *memb_ptr;		/* Pointer to the member */
		void **memb_ptr2;	/* Pointer to that pointer */
		ssize_t tag_len;	/* Length of TLV's T */
		int opt_edx_end;	/* Next non-optional element */
		int use_bsearch;
		int n;

		if(ctx->step & 1)
			goto microphase2;

		/*
		 * MICROPHASE 1: Synchronize decoding.
		 */
		ASN_DEBUG("In %s SEQUENCE left %d, edx=%d flags=%d"
				" opt=%d ec=%d",
			td->name, (int)ctx->left, edx,
			elements[edx].flags, elements[edx].optional,
			td->elements_count);

		if(ctx->left == 0	/* No more stuff is expected */
		&& (
			/* Explicit OPTIONAL specification reaches the end */
			(edx + elements[edx].optional
					== td->elements_count)
			||
			/* All extensions are optional */
			(IN_EXTENSION_GROUP(specs, edx)
				&& specs->ext_before > td->elements_count)
		   )
		) {
			ASN_DEBUG("End of SEQUENCE %s", td->name);
			/*
			 * Found the legitimate end of the structure.
			 */
			PHASE_OUT(ctx);
			RETURN(RC_OK);
		}

		/*
		 * Fetch the T from TLV.
		 */
		tag_len = ber_fetch_tag(ptr, LEFT, &tlv_tag);
		ASN_DEBUG("Current tag in %s SEQUENCE for element %d "
			"(%s) is %s encoded in %d bytes, of frame %ld",
			td->name, edx, elements[edx].name,
			ber_tlv_tag_string(tlv_tag), (int)tag_len, (long)LEFT);
		switch(tag_len) {
		case 0: if(!SIZE_VIOLATION) RETURN(RC_WMORE);
			/* Fall through */
		case -1: RETURN(RC_FAIL);
		}

		if(ctx->left < 0 && ((uint8_t *)ptr)[0] == 0) {
			if(LEFT < 2) {
				if(SIZE_VIOLATION)
					RETURN(RC_FAIL);
				else
					RETURN(RC_WMORE);
			} else if(((uint8_t *)ptr)[1] == 0) {
			ASN_DEBUG("edx = %d, opt = %d, ec=%d",
				edx, elements[edx].optional,
				td->elements_count);
				if((edx + elements[edx].optional
					== td->elements_count)
				|| (IN_EXTENSION_GROUP(specs, edx)
					&& specs->ext_before
						> td->elements_count)) {
					/*
					 * Yeah, baby! Found the terminator
					 * of the indefinite length structure.
					 */
					/*
					 * Proceed to the canonical
					 * finalization function.
					 * No advancing is necessary.
					 */
					goto phase3;
				}
			}
		}

		/*
		 * Find the next available type with this tag.
		 */
		use_bsearch = 0;
		opt_edx_end = edx + elements[edx].optional + 1;
		if(opt_edx_end > td->elements_count)
			opt_edx_end = td->elements_count;	/* Cap */
		else if(opt_edx_end - edx > 8) {
			/* Limit the scope of linear search... */
			opt_edx_end = edx + 8;
			use_bsearch = 1;
			/* ... and resort to bsearch() */
		}
		for(n = edx; n < opt_edx_end; n++) {
			if(BER_TAGS_EQUAL(tlv_tag, elements[n].tag)) {
				/*
				 * Found element corresponding to the tag
				 * being looked at.
				 * Reposition over the right element.
				 */
				edx = n;
				ctx->step = 1 + 2 * edx;	/* Remember! */
				goto microphase2;
			} else if(elements[n].flags & ATF_OPEN_TYPE) {
				/*
				 * This is the ANY type, which may bear
				 * any flag whatsoever.
				 */
				edx = n;
				ctx->step = 1 + 2 * edx;	/* Remember! */
				goto microphase2;
			} else if(elements[n].tag == (ber_tlv_tag_t)-1) {
				use_bsearch = 1;
				break;
			}
		}
		if(use_bsearch) {
			/*
			 * Resort to a binary search over
			 * sorted array of tags.
			 */
			asn_TYPE_tag2member_t *t2m;
			asn_TYPE_tag2member_t key;
			key.el_tag = tlv_tag;
			key.el_no = edx;
			t2m = (asn_TYPE_tag2member_t *)bsearch(&key,
				specs->tag2el, specs->tag2el_count,
				sizeof(specs->tag2el[0]), _t2e_cmp);
			if(t2m) {
				asn_TYPE_tag2member_t *best = 0;
				asn_TYPE_tag2member_t *t2m_f, *t2m_l;
				int edx_max = edx + elements[edx].optional;
				/*
				 * Rewind to the first element with that tag,
				 * `cause bsearch() does not guarantee order.
				 */
				t2m_f = t2m + t2m->toff_first;
				t2m_l = t2m + t2m->toff_last;
				for(t2m = t2m_f; t2m <= t2m_l; t2m++) {
					if(t2m->el_no > edx_max) break;
					if(t2m->el_no < edx) continue;
					best = t2m;
				}
				if(best) {
					edx = best->el_no;
					ctx->step = 1 + 2 * edx;
					goto microphase2;
				}
			}
			n = opt_edx_end;
		}
		if(n == opt_edx_end) {
			/*
			 * If tag is unknown, it may be either
			 * an unknown (thus, incorrect) tag,
			 * or an extension (...),
			 * or an end of the indefinite-length structure.
			 */
			if(!IN_EXTENSION_GROUP(specs, edx)) {
				ASN_DEBUG("Unexpected tag %s (at %d)",
					ber_tlv_tag_string(tlv_tag), edx);
				ASN_DEBUG("Expected tag %s (%s)%s",
					ber_tlv_tag_string(elements[edx].tag),
					elements[edx].name,
					elements[edx].optional
						?" or alternatives":"");
				RETURN(RC_FAIL);
			} else {
				/* Skip this tag */
				ssize_t skip;

				skip = ber_skip_length(opt_codec_ctx,
					BER_TLV_CONSTRUCTED(ptr),
					(char *)ptr + tag_len, LEFT - tag_len);
				ASN_DEBUG("Skip length %d in %s",
					(int)skip, td->name);
				switch(skip) {
				case 0: if(!SIZE_VIOLATION) RETURN(RC_WMORE);
					/* Fall through */
				case -1: RETURN(RC_FAIL);
				}

				ADVANCE(skip + tag_len);
				ctx->step -= 2;
				edx--;
				continue;  /* Try again with the next tag */
			}
		}

		/*
		 * MICROPHASE 2: Invoke the member-specific decoder.
		 */
		ctx->step |= 1;		/* Confirm entering next microphase */
	microphase2:
		ASN_DEBUG("Inside SEQUENCE %s MF2", td->name);
		
		/*
		 * Compute the position of the member inside a structure,
		 * and also a type of containment (it may be contained
		 * as pointer or using inline inclusion).
		 */
		if(elements[edx].flags & ATF_POINTER) {
			/* Member is a pointer to another structure */
			memb_ptr2 = (void **)((char *)st + elements[edx].memb_offset);
		} else {
			/*
			 * A pointer to a pointer
			 * holding the start of the structure
			 */
			memb_ptr = (char *)st + elements[edx].memb_offset;
			memb_ptr2 = &memb_ptr;
		}
		/*
		 * Invoke the member fetch routine according to member's type
		 */
		rval = elements[edx].type->ber_decoder(opt_codec_ctx,
				elements[edx].type,
				memb_ptr2, ptr, LEFT,
				elements[edx].tag_mode);
		ASN_DEBUG("In %s SEQUENCE decoded %d %s of %d "
			"in %d bytes rval.code %d, size=%d",
			td->name, edx, elements[edx].type->name,
			(int)LEFT, (int)rval.consumed, rval.code, (int)size);
		switch(rval.code) {
		case RC_OK:
			break;
		case RC_WMORE: /* More data expected */
			if(!SIZE_VIOLATION) {
				ADVANCE(rval.consumed);
				RETURN(RC_WMORE);
			}
			ASN_DEBUG("Size violation (c->l=%ld <= s=%ld)",
				(long)ctx->left, (long)size);
			/* Fall through */
		case RC_FAIL: /* Fatal error */
			RETURN(RC_FAIL);
		} /* switch(rval) */
		
		ADVANCE(rval.consumed);
	  }	/* for(all structure members) */

	phase3:
		ctx->phase = 3;
	case 3:	/* 00 and other tags expected */
	case 4:	/* only 00's expected */

		ASN_DEBUG("SEQUENCE %s Leftover: %ld, size = %ld",
			td->name, (long)ctx->left, (long)size);

		/*
		 * Skip everything until the end of the SEQUENCE.
		 */
		while(ctx->left) {
			ssize_t tl, ll;

			tl = ber_fetch_tag(ptr, LEFT, &tlv_tag);
			switch(tl) {
			case 0: if(!SIZE_VIOLATION) RETURN(RC_WMORE);
				/* Fall through */
			case -1: RETURN(RC_FAIL);
			}

			/*
			 * If expected <0><0>...
			 */
			if(ctx->left < 0
				&& ((uint8_t *)ptr)[0] == 0) {
				if(LEFT < 2) {
					if(SIZE_VIOLATION)
						RETURN(RC_FAIL);
					else
						RETURN(RC_WMORE);
				} else if(((uint8_t *)ptr)[1] == 0) {
					/*
					 * Correctly finished with <0><0>.
					 */
					ADVANCE(2);
					ctx->left++;
					ctx->phase = 4;
					continue;
				}
			}

			if(!IN_EXTENSION_GROUP(specs, td->elements_count)
			|| ctx->phase == 4) {
				ASN_DEBUG("Unexpected continuation "
					"of a non-extensible type "
					"%s (SEQUENCE): %s",
					td->name,
					ber_tlv_tag_string(tlv_tag));
				RETURN(RC_FAIL);
			}

			ll = ber_skip_length(opt_codec_ctx,
				BER_TLV_CONSTRUCTED(ptr),
				(char *)ptr + tl, LEFT - tl);
			switch(ll) {
			case 0: if(!SIZE_VIOLATION) RETURN(RC_WMORE);
				/* Fall through */
			case -1: RETURN(RC_FAIL);
			}

			ADVANCE(tl + ll);
		}

		PHASE_OUT(ctx);
	}