[linux.git] / lib / asn1_decoder.c

/* Decoder for ASN.1 BER/DER/CER encoded bytestream
 *
 * Copyright (C) 2012 Red Hat, Inc. All Rights Reserved.
 * Written by David Howells ([email protected])
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public Licence
 * as published by the Free Software Foundation; either version
 * 2 of the Licence, or (at your option) any later version.
 */

#include <linux/export.h>
#include <linux/kernel.h>
#include <linux/errno.h>
#include <linux/asn1_decoder.h>
#include <linux/asn1_ber_bytecode.h>

static const unsigned char asn1_op_lengths[ASN1_OP__NR] = {
	/*					OPC TAG JMP ACT */
	[ASN1_OP_MATCH]				= 1 + 1,
	[ASN1_OP_MATCH_OR_SKIP]			= 1 + 1,
	[ASN1_OP_MATCH_ACT]			= 1 + 1     + 1,
	[ASN1_OP_MATCH_ACT_OR_SKIP]		= 1 + 1     + 1,
	[ASN1_OP_MATCH_JUMP]			= 1 + 1 + 1,
	[ASN1_OP_MATCH_JUMP_OR_SKIP]		= 1 + 1 + 1,
	[ASN1_OP_MATCH_ANY]			= 1,
	[ASN1_OP_MATCH_ANY_ACT]			= 1         + 1,
	[ASN1_OP_COND_MATCH_OR_SKIP]		= 1 + 1,
	[ASN1_OP_COND_MATCH_ACT_OR_SKIP]	= 1 + 1     + 1,
	[ASN1_OP_COND_MATCH_JUMP_OR_SKIP]	= 1 + 1 + 1,
	[ASN1_OP_COND_MATCH_ANY]		= 1,
	[ASN1_OP_COND_MATCH_ANY_ACT]		= 1         + 1,
	[ASN1_OP_COND_FAIL]			= 1,
	[ASN1_OP_COMPLETE]			= 1,
	[ASN1_OP_ACT]				= 1         + 1,
	[ASN1_OP_RETURN]			= 1,
	[ASN1_OP_END_SEQ]			= 1,
	[ASN1_OP_END_SEQ_OF]			= 1     + 1,
	[ASN1_OP_END_SET]			= 1,
	[ASN1_OP_END_SET_OF]			= 1     + 1,
	[ASN1_OP_END_SEQ_ACT]			= 1         + 1,
	[ASN1_OP_END_SEQ_OF_ACT]		= 1     + 1 + 1,
	[ASN1_OP_END_SET_ACT]			= 1         + 1,
	[ASN1_OP_END_SET_OF_ACT]		= 1     + 1 + 1,
};

/*
 * Find the length of an indefinite length object
 * @data: The data buffer
 * @datalen: The end of the innermost containing element in the buffer
 * @_dp: The data parse cursor (updated before returning)
 * @_len: Where to return the size of the element.
 * @_errmsg: Where to return a pointer to an error message on error
 */
static int asn1_find_indefinite_length(const unsigned char *data, size_t datalen,
				       size_t *_dp, size_t *_len,
				       const char **_errmsg)
{
	unsigned char tag, tmp;
	size_t dp = *_dp, len, n;
	int indef_level = 1;

next_tag:
	if (unlikely(datalen - dp < 2)) {
		if (datalen == dp)
			goto missing_eoc;
		goto data_overrun_error;
	}

	/* Extract a tag from the data */
	tag = data[dp++];
	if (tag == 0) {
		/* It appears to be an EOC. */
		if (data[dp++] != 0)
			goto invalid_eoc;
		if (--indef_level <= 0) {
			*_len = dp - *_dp;
			*_dp = dp;
			return 0;
		}
		goto next_tag;
	}

	if (unlikely((tag & 0x1f) == ASN1_LONG_TAG)) {
		do {
			if (unlikely(datalen - dp < 2))
				goto data_overrun_error;
			tmp = data[dp++];
		} while (tmp & 0x80);
	}

	/* Extract the length */
	len = data[dp++];
	if (len <= 0x7f) {
		dp += len;
		goto next_tag;
	}

	if (unlikely(len == ASN1_INDEFINITE_LENGTH)) {
		/* Indefinite length */
		if (unlikely((tag & ASN1_CONS_BIT) == ASN1_PRIM << 5))
			goto indefinite_len_primitive;
		indef_level++;
		goto next_tag;
	}

	n = len - 0x80;
	if (unlikely(n > sizeof(size_t) - 1))
		goto length_too_long;
	if (unlikely(n > datalen - dp))
		goto data_overrun_error;
	for (len = 0; n > 0; n--) {
		len <<= 8;
		len |= data[dp++];
	}
	dp += len;
	goto next_tag;

length_too_long:
	*_errmsg = "Unsupported length";
	goto error;
indefinite_len_primitive:
	*_errmsg = "Indefinite len primitive not permitted";
	goto error;
invalid_eoc:
	*_errmsg = "Invalid length EOC";
	goto error;
data_overrun_error:
	*_errmsg = "Data overrun error";
	goto error;
missing_eoc:
	*_errmsg = "Missing EOC in indefinite len cons";
error:
	*_dp = dp;
	return -1;
}

/**
 * asn1_ber_decoder - Decoder BER/DER/CER ASN.1 according to pattern
 * @decoder: The decoder definition (produced by asn1_compiler)
 * @context: The caller's context (to be passed to the action functions)
 * @data: The encoded data
 * @datasize: The size of the encoded data
 *
 * Decode BER/DER/CER encoded ASN.1 data according to a bytecode pattern
 * produced by asn1_compiler.  Action functions are called on marked tags to
 * allow the caller to retrieve significant data.
 *
 * LIMITATIONS:
 *
 * To keep down the amount of stack used by this function, the following limits
 * have been imposed:
 *
 *  (1) This won't handle datalen > 65535 without increasing the size of the
 *	cons stack elements and length_too_long checking.
 *
 *  (2) The stack of constructed types is 10 deep.  If the depth of non-leaf
 *	constructed types exceeds this, the decode will fail.
 *
 *  (3) The SET type (not the SET OF type) isn't really supported as tracking
 *	what members of the set have been seen is a pain.
 */
int asn1_ber_decoder(const struct asn1_decoder *decoder,
		     void *context,
		     const unsigned char *data,
		     size_t datalen)
{
	const unsigned char *machine = decoder->machine;
	const asn1_action_t *actions = decoder->actions;
	size_t machlen = decoder->machlen;
	enum asn1_opcode op;
	unsigned char tag = 0, csp = 0, jsp = 0, optag = 0, hdr = 0;
	const char *errmsg;
	size_t pc = 0, dp = 0, tdp = 0, len = 0;
	int ret;

	unsigned char flags = 0;
#define FLAG_INDEFINITE_LENGTH	0x01
#define FLAG_MATCHED		0x02
#define FLAG_CONS		0x20 /* Corresponds to CONS bit in the opcode tag
				      * - ie. whether or not we are going to parse
				      *   a compound type.
				      */

#define NR_CONS_STACK 10
	unsigned short cons_dp_stack[NR_CONS_STACK];
	unsigned short cons_datalen_stack[NR_CONS_STACK];
	unsigned char cons_hdrlen_stack[NR_CONS_STACK];
#define NR_JUMP_STACK 10
	unsigned char jump_stack[NR_JUMP_STACK];

	if (datalen > 65535)
		return -EMSGSIZE;

next_op:
	pr_debug("next_op: pc=\e[32m%zu\e[m/%zu dp=\e[33m%zu\e[m/%zu C=%d J=%d\n",
		 pc, machlen, dp, datalen, csp, jsp);
	if (unlikely(pc >= machlen))
		goto machine_overrun_error;
	op = machine[pc];
	if (unlikely(pc + asn1_op_lengths[op] > machlen))
		goto machine_overrun_error;

	/* If this command is meant to match a tag, then do that before
	 * evaluating the command.
	 */
	if (op <= ASN1_OP__MATCHES_TAG) {
		unsigned char tmp;

		/* Skip conditional matches if possible */
		if ((op & ASN1_OP_MATCH__COND &&
		     flags & FLAG_MATCHED) ||
		    dp == datalen) {
			pc += asn1_op_lengths[op];
			goto next_op;
		}

		flags = 0;
		hdr = 2;

		/* Extract a tag from the data */
		if (unlikely(dp >= datalen - 1))
			goto data_overrun_error;
		tag = data[dp++];
		if (unlikely((tag & 0x1f) == ASN1_LONG_TAG))
			goto long_tag_not_supported;

		if (op & ASN1_OP_MATCH__ANY) {
			pr_debug("- any %02x\n", tag);
		} else {
			/* Extract the tag from the machine
			 * - Either CONS or PRIM are permitted in the data if
			 *   CONS is not set in the op stream, otherwise CONS
			 *   is mandatory.
			 */
			optag = machine[pc + 1];
			flags |= optag & FLAG_CONS;

			/* Determine whether the tag matched */
			tmp = optag ^ tag;
			tmp &= ~(optag & ASN1_CONS_BIT);
			pr_debug("- match? %02x %02x %02x\n", tag, optag, tmp);
			if (tmp != 0) {
				/* All odd-numbered tags are MATCH_OR_SKIP. */
				if (op & ASN1_OP_MATCH__SKIP) {
					pc += asn1_op_lengths[op];
					dp--;
					goto next_op;
				}
				goto tag_mismatch;
			}
		}
		flags |= FLAG_MATCHED;

		len = data[dp++];
		if (len > 0x7f) {
			if (unlikely(len == ASN1_INDEFINITE_LENGTH)) {
				/* Indefinite length */
				if (unlikely(!(tag & ASN1_CONS_BIT)))
					goto indefinite_len_primitive;
				flags |= FLAG_INDEFINITE_LENGTH;
				if (unlikely(2 > datalen - dp))
					goto data_overrun_error;
			} else {
				int n = len - 0x80;
				if (unlikely(n > 2))
					goto length_too_long;
				if (unlikely(dp >= datalen - n))
					goto data_overrun_error;
				hdr += n;
				for (len = 0; n > 0; n--) {
					len <<= 8;
					len |= data[dp++];
				}
				if (unlikely(len > datalen - dp))
					goto data_overrun_error;
			}
		}

		if (flags & FLAG_CONS) {
			/* For expected compound forms, we stack the positions
			 * of the start and end of the data.
			 */
			if (unlikely(csp >= NR_CONS_STACK))
				goto cons_stack_overflow;
			cons_dp_stack[csp] = dp;
			cons_hdrlen_stack[csp] = hdr;
			if (!(flags & FLAG_INDEFINITE_LENGTH)) {
				cons_datalen_stack[csp] = datalen;
				datalen = dp + len;
			} else {
				cons_datalen_stack[csp] = 0;
			}
			csp++;
		}

		pr_debug("- TAG: %02x %zu%s\n",
			 tag, len, flags & FLAG_CONS ? " CONS" : "");
		tdp = dp;
	}

	/* Decide how to handle the operation */
	switch (op) {
	case ASN1_OP_MATCH_ANY_ACT:
	case ASN1_OP_COND_MATCH_ANY_ACT:
		ret = actions[machine[pc + 1]](context, hdr, tag, data + dp, len);
		if (ret < 0)
			return ret;
		goto skip_data;

	case ASN1_OP_MATCH_ACT:
	case ASN1_OP_MATCH_ACT_OR_SKIP:
	case ASN1_OP_COND_MATCH_ACT_OR_SKIP:
		ret = actions[machine[pc + 2]](context, hdr, tag, data + dp, len);
		if (ret < 0)
			return ret;
		goto skip_data;

	case ASN1_OP_MATCH:
	case ASN1_OP_MATCH_OR_SKIP:
	case ASN1_OP_MATCH_ANY:
	case ASN1_OP_COND_MATCH_OR_SKIP:
	case ASN1_OP_COND_MATCH_ANY:
	skip_data:
		if (!(flags & FLAG_CONS)) {
			if (flags & FLAG_INDEFINITE_LENGTH) {
				ret = asn1_find_indefinite_length(
					data, datalen, &dp, &len, &errmsg);
				if (ret < 0)
					goto error;
			} else {
				dp += len;
			}
			pr_debug("- LEAF: %zu\n", len);
		}
		pc += asn1_op_lengths[op];
		goto next_op;

	case ASN1_OP_MATCH_JUMP:
	case ASN1_OP_MATCH_JUMP_OR_SKIP:
	case ASN1_OP_COND_MATCH_JUMP_OR_SKIP:
		pr_debug("- MATCH_JUMP\n");
		if (unlikely(jsp == NR_JUMP_STACK))
			goto jump_stack_overflow;
		jump_stack[jsp++] = pc + asn1_op_lengths[op];
		pc = machine[pc + 2];
		goto next_op;

	case ASN1_OP_COND_FAIL:
		if (unlikely(!(flags & FLAG_MATCHED)))
			goto tag_mismatch;
		pc += asn1_op_lengths[op];
		goto next_op;

	case ASN1_OP_COMPLETE:
		if (unlikely(jsp != 0 || csp != 0)) {
			pr_err("ASN.1 decoder error: Stacks not empty at completion (%u, %u)\n",
			       jsp, csp);
			return -EBADMSG;
		}
		return 0;

	case ASN1_OP_END_SET:
	case ASN1_OP_END_SET_ACT:
		if (unlikely(!(flags & FLAG_MATCHED)))
			goto tag_mismatch;
	case ASN1_OP_END_SEQ:
	case ASN1_OP_END_SET_OF:
	case ASN1_OP_END_SEQ_OF:
	case ASN1_OP_END_SEQ_ACT:
	case ASN1_OP_END_SET_OF_ACT:
	case ASN1_OP_END_SEQ_OF_ACT:
		if (unlikely(csp <= 0))
			goto cons_stack_underflow;
		csp--;
		tdp = cons_dp_stack[csp];
		hdr = cons_hdrlen_stack[csp];
		len = datalen;
		datalen = cons_datalen_stack[csp];
		pr_debug("- end cons t=%zu dp=%zu l=%zu/%zu\n",
			 tdp, dp, len, datalen);
		if (datalen == 0) {
			/* Indefinite length - check for the EOC. */
			datalen = len;
			if (unlikely(datalen - dp < 2))
				goto data_overrun_error;
			if (data[dp++] != 0) {
				if (op & ASN1_OP_END__OF) {
					dp--;
					csp++;
					pc = machine[pc + 1];
					pr_debug("- continue\n");
					goto next_op;
				}
				goto missing_eoc;
			}
			if (data[dp++] != 0)
				goto invalid_eoc;
			len = dp - tdp - 2;
		} else {
			if (dp < len && (op & ASN1_OP_END__OF)) {
				datalen = len;
				csp++;
				pc = machine[pc + 1];
				pr_debug("- continue\n");
				goto next_op;
			}
			if (dp != len)
				goto cons_length_error;
			len -= tdp;
			pr_debug("- cons len l=%zu d=%zu\n", len, dp - tdp);
		}

		if (op & ASN1_OP_END__ACT) {
			unsigned char act;
			if (op & ASN1_OP_END__OF)
				act = machine[pc + 2];
			else
				act = machine[pc + 1];
			ret = actions[act](context, hdr, 0, data + tdp, len);
		}
		pc += asn1_op_lengths[op];
		goto next_op;

	case ASN1_OP_ACT:
		ret = actions[machine[pc + 1]](context, hdr, tag, data + tdp, len);
		pc += asn1_op_lengths[op];
		goto next_op;

	case ASN1_OP_RETURN:
		if (unlikely(jsp <= 0))
			goto jump_stack_underflow;
		pc = jump_stack[--jsp];
		goto next_op;

	default:
		break;
	}

	/* Shouldn't reach here */
	pr_err("ASN.1 decoder error: Found reserved opcode (%u)\n", op);
	return -EBADMSG;

data_overrun_error:
	errmsg = "Data overrun error";
	goto error;
machine_overrun_error:
	errmsg = "Machine overrun error";
	goto error;
jump_stack_underflow:
	errmsg = "Jump stack underflow";
	goto error;
jump_stack_overflow:
	errmsg = "Jump stack overflow";
	goto error;
cons_stack_underflow:
	errmsg = "Cons stack underflow";
	goto error;
cons_stack_overflow:
	errmsg = "Cons stack overflow";
	goto error;
cons_length_error:
	errmsg = "Cons length error";
	goto error;
missing_eoc:
	errmsg = "Missing EOC in indefinite len cons";
	goto error;
invalid_eoc:
	errmsg = "Invalid length EOC";
	goto error;
length_too_long:
	errmsg = "Unsupported length";
	goto error;
indefinite_len_primitive:
	errmsg = "Indefinite len primitive not permitted";
	goto error;
tag_mismatch:
	errmsg = "Unexpected tag";
	goto error;
long_tag_not_supported:
	errmsg = "Long tag not supported";
error:
	pr_debug("\nASN1: %s [m=%zu d=%zu ot=%02x t=%02x l=%zu]\n",
		 errmsg, pc, dp, optag, tag, len);
	return -EBADMSG;
}
EXPORT_SYMBOL_GPL(asn1_ber_decoder);
Commit	Line	Data
42d5ec27 DH	1	/* Decoder for ASN.1 BER/DER/CER encoded bytestream
	2	*
	3	* Copyright (C) 2012 Red Hat, Inc. All Rights Reserved.
	4	* Written by David Howells ([email protected])
	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	#include <linux/export.h>
	13	#include <linux/kernel.h>
	14	#include <linux/errno.h>
	15	#include <linux/asn1_decoder.h>
	16	#include <linux/asn1_ber_bytecode.h>
	17
	18	static const unsigned char asn1_op_lengths[ASN1_OP__NR] = {
	19	/* OPC TAG JMP ACT */
	20	[ASN1_OP_MATCH] = 1 + 1,
	21	[ASN1_OP_MATCH_OR_SKIP] = 1 + 1,
	22	[ASN1_OP_MATCH_ACT] = 1 + 1 + 1,
	23	[ASN1_OP_MATCH_ACT_OR_SKIP] = 1 + 1 + 1,
	24	[ASN1_OP_MATCH_JUMP] = 1 + 1 + 1,
	25	[ASN1_OP_MATCH_JUMP_OR_SKIP] = 1 + 1 + 1,
	26	[ASN1_OP_MATCH_ANY] = 1,
	27	[ASN1_OP_MATCH_ANY_ACT] = 1 + 1,
	28	[ASN1_OP_COND_MATCH_OR_SKIP] = 1 + 1,
	29	[ASN1_OP_COND_MATCH_ACT_OR_SKIP] = 1 + 1 + 1,
	30	[ASN1_OP_COND_MATCH_JUMP_OR_SKIP] = 1 + 1 + 1,
	31	[ASN1_OP_COND_MATCH_ANY] = 1,
	32	[ASN1_OP_COND_MATCH_ANY_ACT] = 1 + 1,
	33	[ASN1_OP_COND_FAIL] = 1,
	34	[ASN1_OP_COMPLETE] = 1,
	35	[ASN1_OP_ACT] = 1 + 1,
	36	[ASN1_OP_RETURN] = 1,
	37	[ASN1_OP_END_SEQ] = 1,
	38	[ASN1_OP_END_SEQ_OF] = 1 + 1,
	39	[ASN1_OP_END_SET] = 1,
	40	[ASN1_OP_END_SET_OF] = 1 + 1,
	41	[ASN1_OP_END_SEQ_ACT] = 1 + 1,
	42	[ASN1_OP_END_SEQ_OF_ACT] = 1 + 1 + 1,
	43	[ASN1_OP_END_SET_ACT] = 1 + 1,
	44	[ASN1_OP_END_SET_OF_ACT] = 1 + 1 + 1,
	45	};
	46
	47	/*
	48	* Find the length of an indefinite length object
dbadc176 DH	49	* @data: The data buffer
	50	* @datalen: The end of the innermost containing element in the buffer
	51	* @_dp: The data parse cursor (updated before returning)
	52	* @_len: Where to return the size of the element.
	53	* @_errmsg: Where to return a pointer to an error message on error
42d5ec27 DH	54	*/
42d5ec27 DH	55	static int asn1_find_indefinite_length(const unsigned char *data, size_t datalen,
dbadc176 DH	56	size_t _dp, size_t _len,
dbadc176 DH	57	const char **_errmsg)
42d5ec27 DH	58	{
42d5ec27 DH	59	unsigned char tag, tmp;
dbadc176	60	size_t dp = *_dp, len, n;
42d5ec27 DH	61	int indef_level = 1;
	62
	63	next_tag:
	64	if (unlikely(datalen - dp < 2)) {
	65	if (datalen == dp)
	66	goto missing_eoc;
	67	goto data_overrun_error;
	68	}
	69
	70	/* Extract a tag from the data */
	71	tag = data[dp++];
	72	if (tag == 0) {
	73	/* It appears to be an EOC. */
	74	if (data[dp++] != 0)
	75	goto invalid_eoc;
dbadc176 DH	76	if (--indef_level <= 0) {
	77	_len = dp - _dp;
	78	*_dp = dp;
	79	return 0;
	80	}
42d5ec27 DH	81	goto next_tag;
	82	}
	83
99cca91e	84	if (unlikely((tag & 0x1f) == ASN1_LONG_TAG)) {
42d5ec27 DH	85	do {
	86	if (unlikely(datalen - dp < 2))
	87	goto data_overrun_error;
	88	tmp = data[dp++];
	89	} while (tmp & 0x80);
	90	}
	91
	92	/* Extract the length */
	93	len = data[dp++];
f3537f91	94	if (len <= 0x7f) {
42d5ec27 DH	95	dp += len;
	96	goto next_tag;
	97	}
	98
99cca91e	99	if (unlikely(len == ASN1_INDEFINITE_LENGTH)) {
42d5ec27 DH	100	/* Indefinite length */
	101	if (unlikely((tag & ASN1_CONS_BIT) == ASN1_PRIM << 5))
	102	goto indefinite_len_primitive;
	103	indef_level++;
	104	goto next_tag;
	105	}
	106
	107	n = len - 0x80;
	108	if (unlikely(n > sizeof(size_t) - 1))
	109	goto length_too_long;
	110	if (unlikely(n > datalen - dp))
	111	goto data_overrun_error;
	112	for (len = 0; n > 0; n--) {
	113	len <<= 8;
	114	len \|= data[dp++];
	115	}
	116	dp += len;
	117	goto next_tag;
	118
	119	length_too_long:
	120	*_errmsg = "Unsupported length";
	121	goto error;
	122	indefinite_len_primitive:
	123	*_errmsg = "Indefinite len primitive not permitted";
	124	goto error;
	125	invalid_eoc:
	126	*_errmsg = "Invalid length EOC";
	127	goto error;
	128	data_overrun_error:
	129	*_errmsg = "Data overrun error";
	130	goto error;
	131	missing_eoc:
	132	*_errmsg = "Missing EOC in indefinite len cons";
	133	error:
dbadc176	134	*_dp = dp;
42d5ec27 DH	135	return -1;
	136	}
	137
	138	/**
	139	* asn1_ber_decoder - Decoder BER/DER/CER ASN.1 according to pattern
	140	* @decoder: The decoder definition (produced by asn1_compiler)
	141	* @context: The caller's context (to be passed to the action functions)
	142	* @data: The encoded data
	143	* @datasize: The size of the encoded data
	144	*
	145	* Decode BER/DER/CER encoded ASN.1 data according to a bytecode pattern
	146	* produced by asn1_compiler. Action functions are called on marked tags to
	147	* allow the caller to retrieve significant data.
	148	*
	149	* LIMITATIONS:
	150	*
	151	* To keep down the amount of stack used by this function, the following limits
	152	* have been imposed:
	153	*
	154	* (1) This won't handle datalen > 65535 without increasing the size of the
	155	* cons stack elements and length_too_long checking.
	156	*
	157	* (2) The stack of constructed types is 10 deep. If the depth of non-leaf
	158	* constructed types exceeds this, the decode will fail.
	159	*
	160	* (3) The SET type (not the SET OF type) isn't really supported as tracking
	161	* what members of the set have been seen is a pain.
	162	*/
	163	int asn1_ber_decoder(const struct asn1_decoder *decoder,
	164	void *context,
	165	const unsigned char *data,
	166	size_t datalen)
	167	{
	168	const unsigned char *machine = decoder->machine;
	169	const asn1_action_t *actions = decoder->actions;
	170	size_t machlen = decoder->machlen;
	171	enum asn1_opcode op;
	172	unsigned char tag = 0, csp = 0, jsp = 0, optag = 0, hdr = 0;
	173	const char *errmsg;
	174	size_t pc = 0, dp = 0, tdp = 0, len = 0;
	175	int ret;
	176
	177	unsigned char flags = 0;
	178	#define FLAG_INDEFINITE_LENGTH 0x01
	179	#define FLAG_MATCHED 0x02
	180	#define FLAG_CONS 0x20 /* Corresponds to CONS bit in the opcode tag
	181	* - ie. whether or not we are going to parse
	182	* a compound type.
	183	*/
	184
	185	#define NR_CONS_STACK 10
	186	unsigned short cons_dp_stack[NR_CONS_STACK];
	187	unsigned short cons_datalen_stack[NR_CONS_STACK];
	188	unsigned char cons_hdrlen_stack[NR_CONS_STACK];
	189	#define NR_JUMP_STACK 10
	190	unsigned char jump_stack[NR_JUMP_STACK];
	191
	192	if (datalen > 65535)
	193	return -EMSGSIZE;
	194
	195	next_op:
	196	pr_debug("next_op: pc=\e[32m%zu\e[m/%zu dp=\e[33m%zu\e[m/%zu C=%d J=%d\n",
	197	pc, machlen, dp, datalen, csp, jsp);
	198	if (unlikely(pc >= machlen))
199	goto machine_overrun_error;
200	op = machine[pc];
201	if (unlikely(pc + asn1_op_lengths[op] > machlen))
202	goto machine_overrun_error;
203
204	/* If this command is meant to match a tag, then do that before
205	* evaluating the command.
206	*/
207	if (op <= ASN1_OP__MATCHES_TAG) {
208	unsigned char tmp;
209
210	/* Skip conditional matches if possible */
211	if ((op & ASN1_OP_MATCH__COND &&
212	flags & FLAG_MATCHED) \|\|
213	dp == datalen) {
214	pc += asn1_op_lengths[op];
215	goto next_op;
216	}
217
218	flags = 0;
219	hdr = 2;
220
221	/* Extract a tag from the data */
222	if (unlikely(dp >= datalen - 1))
223	goto data_overrun_error;
224	tag = data[dp++];
99cca91e	225	if (unlikely((tag & 0x1f) == ASN1_LONG_TAG))
42d5ec27 DH	226	goto long_tag_not_supported;
	227
	228	if (op & ASN1_OP_MATCH__ANY) {
	229	pr_debug("- any %02x\n", tag);
	230	} else {
	231	/* Extract the tag from the machine
	232	* - Either CONS or PRIM are permitted in the data if
	233	* CONS is not set in the op stream, otherwise CONS
	234	* is mandatory.
	235	*/
	236	optag = machine[pc + 1];
	237	flags \|= optag & FLAG_CONS;
	238
	239	/* Determine whether the tag matched */
	240	tmp = optag ^ tag;
	241	tmp &= ~(optag & ASN1_CONS_BIT);
	242	pr_debug("- match? %02x %02x %02x\n", tag, optag, tmp);
	243	if (tmp != 0) {
	244	/* All odd-numbered tags are MATCH_OR_SKIP. */
	245	if (op & ASN1_OP_MATCH__SKIP) {
	246	pc += asn1_op_lengths[op];
	247	dp--;
	248	goto next_op;
	249	}
	250	goto tag_mismatch;
	251	}
	252	}
	253	flags \|= FLAG_MATCHED;
	254
	255	len = data[dp++];
	256	if (len > 0x7f) {
99cca91e	257	if (unlikely(len == ASN1_INDEFINITE_LENGTH)) {
42d5ec27 DH	258	/* Indefinite length */
	259	if (unlikely(!(tag & ASN1_CONS_BIT)))
	260	goto indefinite_len_primitive;
	261	flags \|= FLAG_INDEFINITE_LENGTH;
	262	if (unlikely(2 > datalen - dp))
	263	goto data_overrun_error;
	264	} else {
	265	int n = len - 0x80;
	266	if (unlikely(n > 2))
	267	goto length_too_long;
	268	if (unlikely(dp >= datalen - n))
	269	goto data_overrun_error;
	270	hdr += n;
	271	for (len = 0; n > 0; n--) {
	272	len <<= 8;
	273	len \|= data[dp++];
	274	}
	275	if (unlikely(len > datalen - dp))
	276	goto data_overrun_error;
	277	}
	278	}
	279
	280	if (flags & FLAG_CONS) {
	281	/* For expected compound forms, we stack the positions
	282	* of the start and end of the data.
	283	*/
	284	if (unlikely(csp >= NR_CONS_STACK))
	285	goto cons_stack_overflow;
	286	cons_dp_stack[csp] = dp;
	287	cons_hdrlen_stack[csp] = hdr;
	288	if (!(flags & FLAG_INDEFINITE_LENGTH)) {
	289	cons_datalen_stack[csp] = datalen;
	290	datalen = dp + len;
	291	} else {
	292	cons_datalen_stack[csp] = 0;
	293	}
	294	csp++;
	295	}
	296
	297	pr_debug("- TAG: %02x %zu%s\n",
	298	tag, len, flags & FLAG_CONS ? " CONS" : "");
	299	tdp = dp;
	300	}
	301
	302	/* Decide how to handle the operation */
	303	switch (op) {
	304	case ASN1_OP_MATCH_ANY_ACT:
	305	case ASN1_OP_COND_MATCH_ANY_ACT:
	306	ret = actions[machine[pc + 1]](context, hdr, tag, data + dp, len);
	307	if (ret < 0)
	308	return ret;
	309	goto skip_data;
	310
	311	case ASN1_OP_MATCH_ACT:
	312	case ASN1_OP_MATCH_ACT_OR_SKIP:
	313	case ASN1_OP_COND_MATCH_ACT_OR_SKIP:
	314	ret = actions[machine[pc + 2]](context, hdr, tag, data + dp, len);
	315	if (ret < 0)
	316	return ret;
	317	goto skip_data;
	318
	319	case ASN1_OP_MATCH:
	320	case ASN1_OP_MATCH_OR_SKIP:
	321	case ASN1_OP_MATCH_ANY:
322	case ASN1_OP_COND_MATCH_OR_SKIP:
323	case ASN1_OP_COND_MATCH_ANY:
324	skip_data:
325	if (!(flags & FLAG_CONS)) {
326	if (flags & FLAG_INDEFINITE_LENGTH) {
dbadc176 DH	327	ret = asn1_find_indefinite_length(
	328	data, datalen, &dp, &len, &errmsg);
	329	if (ret < 0)
42d5ec27	330	goto error;
dbadc176 DH	331	} else {
dbadc176 DH	332	dp += len;
42d5ec27 DH	333	}
42d5ec27 DH	334	pr_debug("- LEAF: %zu\n", len);
42d5ec27 DH	335	}
	336	pc += asn1_op_lengths[op];
	337	goto next_op;
	338
	339	case ASN1_OP_MATCH_JUMP:
	340	case ASN1_OP_MATCH_JUMP_OR_SKIP:
	341	case ASN1_OP_COND_MATCH_JUMP_OR_SKIP:
	342	pr_debug("- MATCH_JUMP\n");
	343	if (unlikely(jsp == NR_JUMP_STACK))
	344	goto jump_stack_overflow;
	345	jump_stack[jsp++] = pc + asn1_op_lengths[op];
	346	pc = machine[pc + 2];
	347	goto next_op;
	348
	349	case ASN1_OP_COND_FAIL:
	350	if (unlikely(!(flags & FLAG_MATCHED)))
	351	goto tag_mismatch;
	352	pc += asn1_op_lengths[op];
	353	goto next_op;
	354
	355	case ASN1_OP_COMPLETE:
	356	if (unlikely(jsp != 0 \|\| csp != 0)) {
	357	pr_err("ASN.1 decoder error: Stacks not empty at completion (%u, %u)\n",
	358	jsp, csp);
	359	return -EBADMSG;
	360	}
	361	return 0;
	362
	363	case ASN1_OP_END_SET:
	364	case ASN1_OP_END_SET_ACT:
	365	if (unlikely(!(flags & FLAG_MATCHED)))
	366	goto tag_mismatch;
	367	case ASN1_OP_END_SEQ:
	368	case ASN1_OP_END_SET_OF:
	369	case ASN1_OP_END_SEQ_OF:
	370	case ASN1_OP_END_SEQ_ACT:
	371	case ASN1_OP_END_SET_OF_ACT:
	372	case ASN1_OP_END_SEQ_OF_ACT:
	373	if (unlikely(csp <= 0))
	374	goto cons_stack_underflow;
	375	csp--;
	376	tdp = cons_dp_stack[csp];
	377	hdr = cons_hdrlen_stack[csp];
	378	len = datalen;
	379	datalen = cons_datalen_stack[csp];
	380	pr_debug("- end cons t=%zu dp=%zu l=%zu/%zu\n",
	381	tdp, dp, len, datalen);
	382	if (datalen == 0) {
	383	/* Indefinite length - check for the EOC. */
	384	datalen = len;
	385	if (unlikely(datalen - dp < 2))
	386	goto data_overrun_error;
	387	if (data[dp++] != 0) {
	388	if (op & ASN1_OP_END__OF) {
	389	dp--;
	390	csp++;
	391	pc = machine[pc + 1];
	392	pr_debug("- continue\n");
	393	goto next_op;
	394	}
	395	goto missing_eoc;
	396	}
	397	if (data[dp++] != 0)
	398	goto invalid_eoc;
399	len = dp - tdp - 2;
400	} else {
401	if (dp < len && (op & ASN1_OP_END__OF)) {
402	datalen = len;
403	csp++;
404	pc = machine[pc + 1];
405	pr_debug("- continue\n");
406	goto next_op;
407	}
408	if (dp != len)
409	goto cons_length_error;
410	len -= tdp;
411	pr_debug("- cons len l=%zu d=%zu\n", len, dp - tdp);
412	}
413
414	if (op & ASN1_OP_END__ACT) {
415	unsigned char act;
416	if (op & ASN1_OP_END__OF)
417	act = machine[pc + 2];
418	else
419	act = machine[pc + 1];
420	ret = actions[act](context, hdr, 0, data + tdp, len);
421	}
422	pc += asn1_op_lengths[op];
423	goto next_op;
424
425	case ASN1_OP_ACT:
426	ret = actions[machine[pc + 1]](context, hdr, tag, data + tdp, len);
427	pc += asn1_op_lengths[op];
428	goto next_op;
429
430	case ASN1_OP_RETURN:
431	if (unlikely(jsp <= 0))
432	goto jump_stack_underflow;
433	pc = jump_stack[--jsp];
434	goto next_op;
435
436	default:
437	break;
438	}
439
440	/* Shouldn't reach here */
441	pr_err("ASN.1 decoder error: Found reserved opcode (%u)\n", op);
442	return -EBADMSG;
443
444	data_overrun_error:
445	errmsg = "Data overrun error";
446	goto error;
447	machine_overrun_error:
448	errmsg = "Machine overrun error";
449	goto error;
450	jump_stack_underflow:
451	errmsg = "Jump stack underflow";
452	goto error;
453	jump_stack_overflow:
454	errmsg = "Jump stack overflow";
455	goto error;
456	cons_stack_underflow:
457	errmsg = "Cons stack underflow";
458	goto error;
459	cons_stack_overflow:
460	errmsg = "Cons stack overflow";
461	goto error;
462	cons_length_error:
463	errmsg = "Cons length error";
464	goto error;
465	missing_eoc:
466	errmsg = "Missing EOC in indefinite len cons";
467	goto error;
468	invalid_eoc:
469	errmsg = "Invalid length EOC";
470	goto error;
471	length_too_long:
472	errmsg = "Unsupported length";
473	goto error;
474	indefinite_len_primitive:
475	errmsg = "Indefinite len primitive not permitted";
476	goto error;
477	tag_mismatch:
478	errmsg = "Unexpected tag";
479	goto error;
480	long_tag_not_supported:
481	errmsg = "Long tag not supported";
482	error:
483	pr_debug("\nASN1: %s [m=%zu d=%zu ot=%02x t=%02x l=%zu]\n",
484	errmsg, pc, dp, optag, tag, len);
485	return -EBADMSG;
486	}
487	EXPORT_SYMBOL_GPL(asn1_ber_decoder);