[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_OR_SKIP]		= 1,
	[ASN1_OP_MATCH_ANY_ACT]			= 1         + 1,
	[ASN1_OP_MATCH_ANY_ACT_OR_SKIP]		= 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_OR_SKIP]	= 1,
	[ASN1_OP_COND_MATCH_ANY_ACT]		= 1         + 1,
	[ASN1_OP_COND_MATCH_ANY_ACT_OR_SKIP]	= 1         + 1,
	[ASN1_OP_COND_FAIL]			= 1,
	[ASN1_OP_COMPLETE]			= 1,
	[ASN1_OP_ACT]				= 1         + 1,
	[ASN1_OP_MAYBE_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 == ASN1_EOC) {
		/* 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)
		goto check_length;

	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(len) - 1))
		goto length_too_long;
	if (unlikely(n > datalen - dp))
		goto data_overrun_error;
	len = 0;
	for (; n > 0; n--) {
		len <<= 8;
		len |= data[dp++];
	}
check_length:
	if (len > datalen - dp)
		goto data_overrun_error;
	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
 * @datalen: 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_LAST_MATCHED	0x04 /* Last tag matched */
#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) ||
		    (op & ASN1_OP_MATCH__SKIP && dp == datalen)) {
			flags &= ~FLAG_LAST_MATCHED;
			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_MATCH_ANY_ACT_OR_SKIP:
	case ASN1_OP_COND_MATCH_ANY_ACT:
	case ASN1_OP_COND_MATCH_ANY_ACT_OR_SKIP:
		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_MATCH_ANY_OR_SKIP:
	case ASN1_OP_COND_MATCH_OR_SKIP:
	case ASN1_OP_COND_MATCH_ANY:
	case ASN1_OP_COND_MATCH_ANY_OR_SKIP:
	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_MAYBE_ACT:
		if (!(flags & FLAG_LAST_MATCHED)) {
			pc += asn1_op_lengths[op];
			goto next_op;
		}
	case ASN1_OP_ACT:
		ret = actions[machine[pc + 1]](context, hdr, tag, data + tdp, len);
		if (ret < 0)
			return ret;
		pc += asn1_op_lengths[op];
		goto next_op;

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

	default:
		break;
	}

	/* Shouldn't reach here */
	pr_err("ASN.1 decoder error: Found reserved opcode (%u) pc=%zu\n",
	       op, pc);
	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,
233ce79d	27	[ASN1_OP_MATCH_ANY_OR_SKIP] = 1,
42d5ec27	28	[ASN1_OP_MATCH_ANY_ACT] = 1 + 1,
233ce79d	29	[ASN1_OP_MATCH_ANY_ACT_OR_SKIP] = 1 + 1,
42d5ec27 DH	30	[ASN1_OP_COND_MATCH_OR_SKIP] = 1 + 1,
	31	[ASN1_OP_COND_MATCH_ACT_OR_SKIP] = 1 + 1 + 1,
	32	[ASN1_OP_COND_MATCH_JUMP_OR_SKIP] = 1 + 1 + 1,
	33	[ASN1_OP_COND_MATCH_ANY] = 1,
233ce79d	34	[ASN1_OP_COND_MATCH_ANY_OR_SKIP] = 1,
42d5ec27	35	[ASN1_OP_COND_MATCH_ANY_ACT] = 1 + 1,
233ce79d	36	[ASN1_OP_COND_MATCH_ANY_ACT_OR_SKIP] = 1 + 1,
42d5ec27 DH	37	[ASN1_OP_COND_FAIL] = 1,
	38	[ASN1_OP_COMPLETE] = 1,
	39	[ASN1_OP_ACT] = 1 + 1,
3f3af97d	40	[ASN1_OP_MAYBE_ACT] = 1 + 1,
42d5ec27 DH	41	[ASN1_OP_RETURN] = 1,
	42	[ASN1_OP_END_SEQ] = 1,
	43	[ASN1_OP_END_SEQ_OF] = 1 + 1,
	44	[ASN1_OP_END_SET] = 1,
	45	[ASN1_OP_END_SET_OF] = 1 + 1,
	46	[ASN1_OP_END_SEQ_ACT] = 1 + 1,
	47	[ASN1_OP_END_SEQ_OF_ACT] = 1 + 1 + 1,
	48	[ASN1_OP_END_SET_ACT] = 1 + 1,
	49	[ASN1_OP_END_SET_OF_ACT] = 1 + 1 + 1,
	50	};
	51
	52	/*
	53	* Find the length of an indefinite length object
dbadc176 DH	54	* @data: The data buffer
	55	* @datalen: The end of the innermost containing element in the buffer
	56	* @_dp: The data parse cursor (updated before returning)
	57	* @_len: Where to return the size of the element.
	58	* @_errmsg: Where to return a pointer to an error message on error
42d5ec27 DH	59	*/
42d5ec27 DH	60	static int asn1_find_indefinite_length(const unsigned char *data, size_t datalen,
dbadc176 DH	61	size_t _dp, size_t _len,
dbadc176 DH	62	const char **_errmsg)
42d5ec27 DH	63	{
42d5ec27 DH	64	unsigned char tag, tmp;
dbadc176	65	size_t dp = *_dp, len, n;
42d5ec27 DH	66	int indef_level = 1;
	67
	68	next_tag:
	69	if (unlikely(datalen - dp < 2)) {
	70	if (datalen == dp)
	71	goto missing_eoc;
	72	goto data_overrun_error;
	73	}
	74
	75	/* Extract a tag from the data */
	76	tag = data[dp++];
23c8a812	77	if (tag == ASN1_EOC) {
42d5ec27 DH	78	/* It appears to be an EOC. */
	79	if (data[dp++] != 0)
	80	goto invalid_eoc;
dbadc176 DH	81	if (--indef_level <= 0) {
	82	_len = dp - _dp;
	83	*_dp = dp;
	84	return 0;
	85	}
42d5ec27 DH	86	goto next_tag;
	87	}
	88
99cca91e	89	if (unlikely((tag & 0x1f) == ASN1_LONG_TAG)) {
42d5ec27 DH	90	do {
	91	if (unlikely(datalen - dp < 2))
	92	goto data_overrun_error;
	93	tmp = data[dp++];
	94	} while (tmp & 0x80);
	95	}
	96
	97	/* Extract the length */
	98	len = data[dp++];
23c8a812 DH	99	if (len <= 0x7f)
23c8a812 DH	100	goto check_length;
42d5ec27	101
99cca91e	102	if (unlikely(len == ASN1_INDEFINITE_LENGTH)) {
42d5ec27 DH	103	/* Indefinite length */
	104	if (unlikely((tag & ASN1_CONS_BIT) == ASN1_PRIM << 5))
	105	goto indefinite_len_primitive;
	106	indef_level++;
	107	goto next_tag;
	108	}
	109
	110	n = len - 0x80;
23c8a812	111	if (unlikely(n > sizeof(len) - 1))
42d5ec27 DH	112	goto length_too_long;
	113	if (unlikely(n > datalen - dp))
	114	goto data_overrun_error;
23c8a812 DH	115	len = 0;
23c8a812 DH	116	for (; n > 0; n--) {
42d5ec27 DH	117	len <<= 8;
	118	len \|= data[dp++];
	119	}
23c8a812 DH	120	check_length:
	121	if (len > datalen - dp)
	122	goto data_overrun_error;
42d5ec27 DH	123	dp += len;
	124	goto next_tag;
	125
	126	length_too_long:
	127	*_errmsg = "Unsupported length";
	128	goto error;
	129	indefinite_len_primitive:
	130	*_errmsg = "Indefinite len primitive not permitted";
	131	goto error;
	132	invalid_eoc:
	133	*_errmsg = "Invalid length EOC";
	134	goto error;
	135	data_overrun_error:
	136	*_errmsg = "Data overrun error";
	137	goto error;
	138	missing_eoc:
	139	*_errmsg = "Missing EOC in indefinite len cons";
	140	error:
dbadc176	141	*_dp = dp;
42d5ec27 DH	142	return -1;
	143	}
	144
	145	/**
	146	* asn1_ber_decoder - Decoder BER/DER/CER ASN.1 according to pattern
	147	* @decoder: The decoder definition (produced by asn1_compiler)
	148	* @context: The caller's context (to be passed to the action functions)
	149	* @data: The encoded data
548bbff9	150	* @datalen: The size of the encoded data
42d5ec27 DH	151	*
	152	* Decode BER/DER/CER encoded ASN.1 data according to a bytecode pattern
	153	* produced by asn1_compiler. Action functions are called on marked tags to
	154	* allow the caller to retrieve significant data.
	155	*
	156	* LIMITATIONS:
	157	*
	158	* To keep down the amount of stack used by this function, the following limits
	159	* have been imposed:
	160	*
	161	* (1) This won't handle datalen > 65535 without increasing the size of the
	162	* cons stack elements and length_too_long checking.
	163	*
	164	* (2) The stack of constructed types is 10 deep. If the depth of non-leaf
	165	* constructed types exceeds this, the decode will fail.
	166	*
	167	* (3) The SET type (not the SET OF type) isn't really supported as tracking
	168	* what members of the set have been seen is a pain.
	169	*/
	170	int asn1_ber_decoder(const struct asn1_decoder *decoder,
	171	void *context,
	172	const unsigned char *data,
	173	size_t datalen)
	174	{
	175	const unsigned char *machine = decoder->machine;
	176	const asn1_action_t *actions = decoder->actions;
	177	size_t machlen = decoder->machlen;
	178	enum asn1_opcode op;
	179	unsigned char tag = 0, csp = 0, jsp = 0, optag = 0, hdr = 0;
	180	const char *errmsg;
	181	size_t pc = 0, dp = 0, tdp = 0, len = 0;
	182	int ret;
	183
	184	unsigned char flags = 0;
	185	#define FLAG_INDEFINITE_LENGTH 0x01
	186	#define FLAG_MATCHED 0x02
3f3af97d	187	#define FLAG_LAST_MATCHED 0x04 /* Last tag matched */
42d5ec27 DH	188	#define FLAG_CONS 0x20 /* Corresponds to CONS bit in the opcode tag
	189	* - ie. whether or not we are going to parse
	190	* a compound type.
	191	*/
	192
	193	#define NR_CONS_STACK 10
	194	unsigned short cons_dp_stack[NR_CONS_STACK];
	195	unsigned short cons_datalen_stack[NR_CONS_STACK];
	196	unsigned char cons_hdrlen_stack[NR_CONS_STACK];
	197	#define NR_JUMP_STACK 10
	198	unsigned char jump_stack[NR_JUMP_STACK];
	199
	200	if (datalen > 65535)
	201	return -EMSGSIZE;
	202
	203	next_op:
	204	pr_debug("next_op: pc=\e[32m%zu\e[m/%zu dp=\e[33m%zu\e[m/%zu C=%d J=%d\n",
	205	pc, machlen, dp, datalen, csp, jsp);
	206	if (unlikely(pc >= machlen))
	207	goto machine_overrun_error;
	208	op = machine[pc];
	209	if (unlikely(pc + asn1_op_lengths[op] > machlen))
	210	goto machine_overrun_error;
	211
	212	/* If this command is meant to match a tag, then do that before
	213	* evaluating the command.
	214	*/
	215	if (op <= ASN1_OP__MATCHES_TAG) {
	216	unsigned char tmp;
	217
	218	/* Skip conditional matches if possible */
0d62e9dd DH	219	if ((op & ASN1_OP_MATCH__COND && flags & FLAG_MATCHED) \|\|
0d62e9dd DH	220	(op & ASN1_OP_MATCH__SKIP && dp == datalen)) {
3f3af97d	221	flags &= ~FLAG_LAST_MATCHED;
42d5ec27 DH	222	pc += asn1_op_lengths[op];
	223	goto next_op;
	224	}
	225
	226	flags = 0;
	227	hdr = 2;
	228
	229	/* Extract a tag from the data */
	230	if (unlikely(dp >= datalen - 1))
	231	goto data_overrun_error;
	232	tag = data[dp++];
99cca91e	233	if (unlikely((tag & 0x1f) == ASN1_LONG_TAG))
42d5ec27 DH	234	goto long_tag_not_supported;
	235
	236	if (op & ASN1_OP_MATCH__ANY) {
	237	pr_debug("- any %02x\n", tag);
	238	} else {
	239	/* Extract the tag from the machine
	240	* - Either CONS or PRIM are permitted in the data if
	241	* CONS is not set in the op stream, otherwise CONS
	242	* is mandatory.
	243	*/
	244	optag = machine[pc + 1];
	245	flags \|= optag & FLAG_CONS;
	246
	247	/* Determine whether the tag matched */
	248	tmp = optag ^ tag;
	249	tmp &= ~(optag & ASN1_CONS_BIT);
	250	pr_debug("- match? %02x %02x %02x\n", tag, optag, tmp);
	251	if (tmp != 0) {
	252	/* All odd-numbered tags are MATCH_OR_SKIP. */
	253	if (op & ASN1_OP_MATCH__SKIP) {
	254	pc += asn1_op_lengths[op];
	255	dp--;
	256	goto next_op;
	257	}
	258	goto tag_mismatch;
	259	}
	260	}
	261	flags \|= FLAG_MATCHED;
	262
	263	len = data[dp++];
	264	if (len > 0x7f) {
99cca91e	265	if (unlikely(len == ASN1_INDEFINITE_LENGTH)) {
42d5ec27 DH	266	/* Indefinite length */
	267	if (unlikely(!(tag & ASN1_CONS_BIT)))
	268	goto indefinite_len_primitive;
	269	flags \|= FLAG_INDEFINITE_LENGTH;
	270	if (unlikely(2 > datalen - dp))
	271	goto data_overrun_error;
	272	} else {
	273	int n = len - 0x80;
	274	if (unlikely(n > 2))
	275	goto length_too_long;
	276	if (unlikely(dp >= datalen - n))
	277	goto data_overrun_error;
	278	hdr += n;
	279	for (len = 0; n > 0; n--) {
	280	len <<= 8;
	281	len \|= data[dp++];
	282	}
	283	if (unlikely(len > datalen - dp))
	284	goto data_overrun_error;
	285	}
	286	}
	287
	288	if (flags & FLAG_CONS) {
	289	/* For expected compound forms, we stack the positions
	290	* of the start and end of the data.
	291	*/
	292	if (unlikely(csp >= NR_CONS_STACK))
	293	goto cons_stack_overflow;
	294	cons_dp_stack[csp] = dp;
	295	cons_hdrlen_stack[csp] = hdr;
	296	if (!(flags & FLAG_INDEFINITE_LENGTH)) {
	297	cons_datalen_stack[csp] = datalen;
	298	datalen = dp + len;
	299	} else {
	300	cons_datalen_stack[csp] = 0;
	301	}
	302	csp++;
	303	}
	304
	305	pr_debug("- TAG: %02x %zu%s\n",
	306	tag, len, flags & FLAG_CONS ? " CONS" : "");
	307	tdp = dp;
	308	}
	309
	310	/* Decide how to handle the operation */
	311	switch (op) {
	312	case ASN1_OP_MATCH_ANY_ACT:
233ce79d	313	case ASN1_OP_MATCH_ANY_ACT_OR_SKIP:
42d5ec27	314	case ASN1_OP_COND_MATCH_ANY_ACT:
233ce79d	315	case ASN1_OP_COND_MATCH_ANY_ACT_OR_SKIP:
42d5ec27 DH	316	ret = actions[machine[pc + 1]](context, hdr, tag, data + dp, len);
	317	if (ret < 0)
	318	return ret;
	319	goto skip_data;
	320
	321	case ASN1_OP_MATCH_ACT:
	322	case ASN1_OP_MATCH_ACT_OR_SKIP:
	323	case ASN1_OP_COND_MATCH_ACT_OR_SKIP:
	324	ret = actions[machine[pc + 2]](context, hdr, tag, data + dp, len);
	325	if (ret < 0)
	326	return ret;
	327	goto skip_data;
	328
	329	case ASN1_OP_MATCH:
	330	case ASN1_OP_MATCH_OR_SKIP:
	331	case ASN1_OP_MATCH_ANY:
233ce79d	332	case ASN1_OP_MATCH_ANY_OR_SKIP:
42d5ec27 DH	333	case ASN1_OP_COND_MATCH_OR_SKIP:
42d5ec27 DH	334	case ASN1_OP_COND_MATCH_ANY:
233ce79d	335	case ASN1_OP_COND_MATCH_ANY_OR_SKIP:
42d5ec27 DH	336	skip_data:
	337	if (!(flags & FLAG_CONS)) {
	338	if (flags & FLAG_INDEFINITE_LENGTH) {
dbadc176 DH	339	ret = asn1_find_indefinite_length(
	340	data, datalen, &dp, &len, &errmsg);
	341	if (ret < 0)
42d5ec27	342	goto error;
dbadc176 DH	343	} else {
dbadc176 DH	344	dp += len;
42d5ec27 DH	345	}
42d5ec27 DH	346	pr_debug("- LEAF: %zu\n", len);
42d5ec27 DH	347	}
	348	pc += asn1_op_lengths[op];
	349	goto next_op;
	350
	351	case ASN1_OP_MATCH_JUMP:
	352	case ASN1_OP_MATCH_JUMP_OR_SKIP:
	353	case ASN1_OP_COND_MATCH_JUMP_OR_SKIP:
	354	pr_debug("- MATCH_JUMP\n");
	355	if (unlikely(jsp == NR_JUMP_STACK))
	356	goto jump_stack_overflow;
	357	jump_stack[jsp++] = pc + asn1_op_lengths[op];
	358	pc = machine[pc + 2];
	359	goto next_op;
	360
	361	case ASN1_OP_COND_FAIL:
	362	if (unlikely(!(flags & FLAG_MATCHED)))
	363	goto tag_mismatch;
	364	pc += asn1_op_lengths[op];
	365	goto next_op;
	366
	367	case ASN1_OP_COMPLETE:
	368	if (unlikely(jsp != 0 \|\| csp != 0)) {
	369	pr_err("ASN.1 decoder error: Stacks not empty at completion (%u, %u)\n",
	370	jsp, csp);
	371	return -EBADMSG;
	372	}
	373	return 0;
	374
	375	case ASN1_OP_END_SET:
	376	case ASN1_OP_END_SET_ACT:
	377	if (unlikely(!(flags & FLAG_MATCHED)))
	378	goto tag_mismatch;
	379	case ASN1_OP_END_SEQ:
	380	case ASN1_OP_END_SET_OF:
	381	case ASN1_OP_END_SEQ_OF:
	382	case ASN1_OP_END_SEQ_ACT:
	383	case ASN1_OP_END_SET_OF_ACT:
	384	case ASN1_OP_END_SEQ_OF_ACT:
	385	if (unlikely(csp <= 0))
	386	goto cons_stack_underflow;
	387	csp--;
	388	tdp = cons_dp_stack[csp];
	389	hdr = cons_hdrlen_stack[csp];
	390	len = datalen;
	391	datalen = cons_datalen_stack[csp];
	392	pr_debug("- end cons t=%zu dp=%zu l=%zu/%zu\n",
	393	tdp, dp, len, datalen);
	394	if (datalen == 0) {
	395	/* Indefinite length - check for the EOC. */
	396	datalen = len;
	397	if (unlikely(datalen - dp < 2))
	398	goto data_overrun_error;
	399	if (data[dp++] != 0) {
	400	if (op & ASN1_OP_END__OF) {
	401	dp--;
	402	csp++;
	403	pc = machine[pc + 1];
	404	pr_debug("- continue\n");
	405	goto next_op;
	406	}
	407	goto missing_eoc;
	408	}
	409	if (data[dp++] != 0)
	410	goto invalid_eoc;
411	len = dp - tdp - 2;
412	} else {
413	if (dp < len && (op & ASN1_OP_END__OF)) {
414	datalen = len;
415	csp++;
416	pc = machine[pc + 1];
417	pr_debug("- continue\n");
418	goto next_op;
419	}
420	if (dp != len)
421	goto cons_length_error;
422	len -= tdp;
423	pr_debug("- cons len l=%zu d=%zu\n", len, dp - tdp);
424	}
425
426	if (op & ASN1_OP_END__ACT) {
427	unsigned char act;
428	if (op & ASN1_OP_END__OF)
429	act = machine[pc + 2];
430	else
431	act = machine[pc + 1];
432	ret = actions[act](context, hdr, 0, data + tdp, len);
433	}
434	pc += asn1_op_lengths[op];
435	goto next_op;
436
3f3af97d DH	437	case ASN1_OP_MAYBE_ACT:
	438	if (!(flags & FLAG_LAST_MATCHED)) {
	439	pc += asn1_op_lengths[op];
	440	goto next_op;
	441	}
42d5ec27 DH	442	case ASN1_OP_ACT:
42d5ec27 DH	443	ret = actions[machine[pc + 1]](context, hdr, tag, data + tdp, len);
3f3af97d DH	444	if (ret < 0)
3f3af97d DH	445	return ret;
42d5ec27 DH	446	pc += asn1_op_lengths[op];
	447	goto next_op;
	448
	449	case ASN1_OP_RETURN:
	450	if (unlikely(jsp <= 0))
	451	goto jump_stack_underflow;
	452	pc = jump_stack[--jsp];
3f3af97d	453	flags \|= FLAG_MATCHED \| FLAG_LAST_MATCHED;
42d5ec27 DH	454	goto next_op;
	455
	456	default:
	457	break;
	458	}
	459
	460	/* Shouldn't reach here */
3f3af97d DH	461	pr_err("ASN.1 decoder error: Found reserved opcode (%u) pc=%zu\n",
3f3af97d DH	462	op, pc);
42d5ec27 DH	463	return -EBADMSG;
	464
	465	data_overrun_error:
	466	errmsg = "Data overrun error";
	467	goto error;
	468	machine_overrun_error:
	469	errmsg = "Machine overrun error";
	470	goto error;
	471	jump_stack_underflow:
	472	errmsg = "Jump stack underflow";
	473	goto error;
	474	jump_stack_overflow:
	475	errmsg = "Jump stack overflow";
	476	goto error;
	477	cons_stack_underflow:
	478	errmsg = "Cons stack underflow";
	479	goto error;
	480	cons_stack_overflow:
	481	errmsg = "Cons stack overflow";
	482	goto error;
	483	cons_length_error:
	484	errmsg = "Cons length error";
	485	goto error;
	486	missing_eoc:
	487	errmsg = "Missing EOC in indefinite len cons";
	488	goto error;
	489	invalid_eoc:
	490	errmsg = "Invalid length EOC";
	491	goto error;
	492	length_too_long:
	493	errmsg = "Unsupported length";
	494	goto error;
	495	indefinite_len_primitive:
	496	errmsg = "Indefinite len primitive not permitted";
	497	goto error;
	498	tag_mismatch:
	499	errmsg = "Unexpected tag";
	500	goto error;
	501	long_tag_not_supported:
	502	errmsg = "Long tag not supported";
	503	error:
	504	pr_debug("\nASN1: %s [m=%zu d=%zu ot=%02x t=%02x l=%zu]\n",
	505	errmsg, pc, dp, optag, tag, len);
	506	return -EBADMSG;
	507	}
	508	EXPORT_SYMBOL_GPL(asn1_ber_decoder);