[linux-2.6-block.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 (dhowells@redhat.com)
 *
 * 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/module.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(datalen - dp < 2))
			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(n > datalen - dp))
					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;
			}
		} else {
			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:
	case ASN1_OP_MATCH_OR_SKIP:
	case ASN1_OP_MATCH_ACT:
	case ASN1_OP_MATCH_ACT_OR_SKIP:
	case ASN1_OP_MATCH_ANY:
	case ASN1_OP_MATCH_ANY_OR_SKIP:
	case ASN1_OP_MATCH_ANY_ACT:
	case ASN1_OP_MATCH_ANY_ACT_OR_SKIP:
	case ASN1_OP_COND_MATCH_OR_SKIP:
	case ASN1_OP_COND_MATCH_ACT_OR_SKIP:
	case ASN1_OP_COND_MATCH_ANY:
	case ASN1_OP_COND_MATCH_ANY_OR_SKIP:
	case ASN1_OP_COND_MATCH_ANY_ACT:
	case ASN1_OP_COND_MATCH_ANY_ACT_OR_SKIP:

		if (!(flags & FLAG_CONS)) {
			if (flags & FLAG_INDEFINITE_LENGTH) {
				size_t tmp = dp;

				ret = asn1_find_indefinite_length(
					data, datalen, &tmp, &len, &errmsg);
				if (ret < 0)
					goto error;
			}
			pr_debug("- LEAF: %zu\n", len);
		}

		if (op & ASN1_OP_MATCH__ACT) {
			unsigned char act;

			if (op & ASN1_OP_MATCH__ANY)
				act = machine[pc + 1];
			else
				act = machine[pc + 2];
			ret = actions[act](context, hdr, tag, data + dp, len);
			if (ret < 0)
				return ret;
		}

		if (!(flags & FLAG_CONS))
			dp += 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);
			if (ret < 0)
				return ret;
		}
		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);

MODULE_LICENSE("GPL");
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 (dhowells@redhat.com)
	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>
ccab6058	15	#include <linux/module.h>
42d5ec27 DH	16	#include <linux/asn1_decoder.h>
	17	#include <linux/asn1_ber_bytecode.h>
	18
	19	static const unsigned char asn1_op_lengths[ASN1_OP__NR] = {
	20	/* OPC TAG JMP ACT */
	21	[ASN1_OP_MATCH] = 1 + 1,
	22	[ASN1_OP_MATCH_OR_SKIP] = 1 + 1,
	23	[ASN1_OP_MATCH_ACT] = 1 + 1 + 1,
	24	[ASN1_OP_MATCH_ACT_OR_SKIP] = 1 + 1 + 1,
	25	[ASN1_OP_MATCH_JUMP] = 1 + 1 + 1,
	26	[ASN1_OP_MATCH_JUMP_OR_SKIP] = 1 + 1 + 1,
	27	[ASN1_OP_MATCH_ANY] = 1,
233ce79d	28	[ASN1_OP_MATCH_ANY_OR_SKIP] = 1,
42d5ec27	29	[ASN1_OP_MATCH_ANY_ACT] = 1 + 1,
233ce79d	30	[ASN1_OP_MATCH_ANY_ACT_OR_SKIP] = 1 + 1,
42d5ec27 DH	31	[ASN1_OP_COND_MATCH_OR_SKIP] = 1 + 1,
	32	[ASN1_OP_COND_MATCH_ACT_OR_SKIP] = 1 + 1 + 1,
	33	[ASN1_OP_COND_MATCH_JUMP_OR_SKIP] = 1 + 1 + 1,
	34	[ASN1_OP_COND_MATCH_ANY] = 1,
233ce79d	35	[ASN1_OP_COND_MATCH_ANY_OR_SKIP] = 1,
42d5ec27	36	[ASN1_OP_COND_MATCH_ANY_ACT] = 1 + 1,
233ce79d	37	[ASN1_OP_COND_MATCH_ANY_ACT_OR_SKIP] = 1 + 1,
42d5ec27 DH	38	[ASN1_OP_COND_FAIL] = 1,
	39	[ASN1_OP_COMPLETE] = 1,
	40	[ASN1_OP_ACT] = 1 + 1,
3f3af97d	41	[ASN1_OP_MAYBE_ACT] = 1 + 1,
42d5ec27 DH	42	[ASN1_OP_RETURN] = 1,
	43	[ASN1_OP_END_SEQ] = 1,
	44	[ASN1_OP_END_SEQ_OF] = 1 + 1,
	45	[ASN1_OP_END_SET] = 1,
	46	[ASN1_OP_END_SET_OF] = 1 + 1,
	47	[ASN1_OP_END_SEQ_ACT] = 1 + 1,
	48	[ASN1_OP_END_SEQ_OF_ACT] = 1 + 1 + 1,
	49	[ASN1_OP_END_SET_ACT] = 1 + 1,
	50	[ASN1_OP_END_SET_OF_ACT] = 1 + 1 + 1,
	51	};
	52
	53	/*
	54	* Find the length of an indefinite length object
dbadc176 DH	55	* @data: The data buffer
	56	* @datalen: The end of the innermost containing element in the buffer
	57	* @_dp: The data parse cursor (updated before returning)
	58	* @_len: Where to return the size of the element.
	59	* @_errmsg: Where to return a pointer to an error message on error
42d5ec27 DH	60	*/
42d5ec27 DH	61	static int asn1_find_indefinite_length(const unsigned char *data, size_t datalen,
dbadc176 DH	62	size_t _dp, size_t _len,
dbadc176 DH	63	const char **_errmsg)
42d5ec27 DH	64	{
42d5ec27 DH	65	unsigned char tag, tmp;
dbadc176	66	size_t dp = *_dp, len, n;
42d5ec27 DH	67	int indef_level = 1;
	68
	69	next_tag:
	70	if (unlikely(datalen - dp < 2)) {
	71	if (datalen == dp)
	72	goto missing_eoc;
	73	goto data_overrun_error;
	74	}
	75
	76	/* Extract a tag from the data */
	77	tag = data[dp++];
23c8a812	78	if (tag == ASN1_EOC) {
42d5ec27 DH	79	/* It appears to be an EOC. */
	80	if (data[dp++] != 0)
	81	goto invalid_eoc;
dbadc176 DH	82	if (--indef_level <= 0) {
	83	_len = dp - _dp;
	84	*_dp = dp;
	85	return 0;
	86	}
42d5ec27 DH	87	goto next_tag;
	88	}
	89
99cca91e	90	if (unlikely((tag & 0x1f) == ASN1_LONG_TAG)) {
42d5ec27 DH	91	do {
	92	if (unlikely(datalen - dp < 2))
	93	goto data_overrun_error;
	94	tmp = data[dp++];
	95	} while (tmp & 0x80);
	96	}
	97
	98	/* Extract the length */
	99	len = data[dp++];
23c8a812 DH	100	if (len <= 0x7f)
23c8a812 DH	101	goto check_length;
42d5ec27	102
99cca91e	103	if (unlikely(len == ASN1_INDEFINITE_LENGTH)) {
42d5ec27 DH	104	/* Indefinite length */
	105	if (unlikely((tag & ASN1_CONS_BIT) == ASN1_PRIM << 5))
	106	goto indefinite_len_primitive;
	107	indef_level++;
	108	goto next_tag;
	109	}
	110
	111	n = len - 0x80;
23c8a812	112	if (unlikely(n > sizeof(len) - 1))
42d5ec27 DH	113	goto length_too_long;
	114	if (unlikely(n > datalen - dp))
	115	goto data_overrun_error;
23c8a812 DH	116	len = 0;
23c8a812 DH	117	for (; n > 0; n--) {
42d5ec27 DH	118	len <<= 8;
	119	len \|= data[dp++];
	120	}
23c8a812 DH	121	check_length:
	122	if (len > datalen - dp)
	123	goto data_overrun_error;
42d5ec27 DH	124	dp += len;
	125	goto next_tag;
	126
	127	length_too_long:
	128	*_errmsg = "Unsupported length";
	129	goto error;
	130	indefinite_len_primitive:
	131	*_errmsg = "Indefinite len primitive not permitted";
	132	goto error;
	133	invalid_eoc:
	134	*_errmsg = "Invalid length EOC";
	135	goto error;
	136	data_overrun_error:
	137	*_errmsg = "Data overrun error";
	138	goto error;
	139	missing_eoc:
	140	*_errmsg = "Missing EOC in indefinite len cons";
	141	error:
dbadc176	142	*_dp = dp;
42d5ec27 DH	143	return -1;
	144	}
	145
	146	/**
	147	* asn1_ber_decoder - Decoder BER/DER/CER ASN.1 according to pattern
	148	* @decoder: The decoder definition (produced by asn1_compiler)
	149	* @context: The caller's context (to be passed to the action functions)
	150	* @data: The encoded data
548bbff9	151	* @datalen: The size of the encoded data
42d5ec27 DH	152	*
	153	* Decode BER/DER/CER encoded ASN.1 data according to a bytecode pattern
	154	* produced by asn1_compiler. Action functions are called on marked tags to
	155	* allow the caller to retrieve significant data.
	156	*
	157	* LIMITATIONS:
	158	*
	159	* To keep down the amount of stack used by this function, the following limits
	160	* have been imposed:
	161	*
	162	* (1) This won't handle datalen > 65535 without increasing the size of the
	163	* cons stack elements and length_too_long checking.
	164	*
	165	* (2) The stack of constructed types is 10 deep. If the depth of non-leaf
	166	* constructed types exceeds this, the decode will fail.
	167	*
	168	* (3) The SET type (not the SET OF type) isn't really supported as tracking
	169	* what members of the set have been seen is a pain.
	170	*/
	171	int asn1_ber_decoder(const struct asn1_decoder *decoder,
	172	void *context,
	173	const unsigned char *data,
	174	size_t datalen)
	175	{
	176	const unsigned char *machine = decoder->machine;
	177	const asn1_action_t *actions = decoder->actions;
	178	size_t machlen = decoder->machlen;
	179	enum asn1_opcode op;
	180	unsigned char tag = 0, csp = 0, jsp = 0, optag = 0, hdr = 0;
	181	const char *errmsg;
	182	size_t pc = 0, dp = 0, tdp = 0, len = 0;
	183	int ret;
	184
	185	unsigned char flags = 0;
	186	#define FLAG_INDEFINITE_LENGTH 0x01
	187	#define FLAG_MATCHED 0x02
3f3af97d	188	#define FLAG_LAST_MATCHED 0x04 /* Last tag matched */
42d5ec27 DH	189	#define FLAG_CONS 0x20 /* Corresponds to CONS bit in the opcode tag
	190	* - ie. whether or not we are going to parse
	191	* a compound type.
	192	*/
	193
	194	#define NR_CONS_STACK 10
	195	unsigned short cons_dp_stack[NR_CONS_STACK];
	196	unsigned short cons_datalen_stack[NR_CONS_STACK];
	197	unsigned char cons_hdrlen_stack[NR_CONS_STACK];
	198	#define NR_JUMP_STACK 10
	199	unsigned char jump_stack[NR_JUMP_STACK];
	200
	201	if (datalen > 65535)
	202	return -EMSGSIZE;
	203
	204	next_op:
	205	pr_debug("next_op: pc=\e[32m%zu\e[m/%zu dp=\e[33m%zu\e[m/%zu C=%d J=%d\n",
	206	pc, machlen, dp, datalen, csp, jsp);
	207	if (unlikely(pc >= machlen))
	208	goto machine_overrun_error;
	209	op = machine[pc];
	210	if (unlikely(pc + asn1_op_lengths[op] > machlen))
	211	goto machine_overrun_error;
	212
	213	/* If this command is meant to match a tag, then do that before
	214	* evaluating the command.
	215	*/
	216	if (op <= ASN1_OP__MATCHES_TAG) {
	217	unsigned char tmp;
	218
	219	/* Skip conditional matches if possible */
0d62e9dd DH	220	if ((op & ASN1_OP_MATCH__COND && flags & FLAG_MATCHED) \|\|
0d62e9dd DH	221	(op & ASN1_OP_MATCH__SKIP && dp == datalen)) {
3f3af97d	222	flags &= ~FLAG_LAST_MATCHED;
42d5ec27 DH	223	pc += asn1_op_lengths[op];
	224	goto next_op;
	225	}
	226
	227	flags = 0;
	228	hdr = 2;
	229
	230	/* Extract a tag from the data */
624f5ab8	231	if (unlikely(datalen - dp < 2))
42d5ec27 DH	232	goto data_overrun_error;
42d5ec27 DH	233	tag = data[dp++];
99cca91e	234	if (unlikely((tag & 0x1f) == ASN1_LONG_TAG))
42d5ec27 DH	235	goto long_tag_not_supported;
	236
	237	if (op & ASN1_OP_MATCH__ANY) {
	238	pr_debug("- any %02x\n", tag);
	239	} else {
	240	/* Extract the tag from the machine
	241	* - Either CONS or PRIM are permitted in the data if
	242	* CONS is not set in the op stream, otherwise CONS
	243	* is mandatory.
	244	*/
	245	optag = machine[pc + 1];
	246	flags \|= optag & FLAG_CONS;
	247
	248	/* Determine whether the tag matched */
	249	tmp = optag ^ tag;
	250	tmp &= ~(optag & ASN1_CONS_BIT);
	251	pr_debug("- match? %02x %02x %02x\n", tag, optag, tmp);
	252	if (tmp != 0) {
	253	/* All odd-numbered tags are MATCH_OR_SKIP. */
	254	if (op & ASN1_OP_MATCH__SKIP) {
	255	pc += asn1_op_lengths[op];
	256	dp--;
	257	goto next_op;
	258	}
	259	goto tag_mismatch;
	260	}
	261	}
	262	flags \|= FLAG_MATCHED;
	263
	264	len = data[dp++];
	265	if (len > 0x7f) {
99cca91e	266	if (unlikely(len == ASN1_INDEFINITE_LENGTH)) {
42d5ec27 DH	267	/* Indefinite length */
	268	if (unlikely(!(tag & ASN1_CONS_BIT)))
	269	goto indefinite_len_primitive;
	270	flags \|= FLAG_INDEFINITE_LENGTH;
	271	if (unlikely(2 > datalen - dp))
	272	goto data_overrun_error;
	273	} else {
	274	int n = len - 0x80;
	275	if (unlikely(n > 2))
	276	goto length_too_long;
624f5ab8	277	if (unlikely(n > datalen - dp))
42d5ec27 DH	278	goto data_overrun_error;
	279	hdr += n;
	280	for (len = 0; n > 0; n--) {
	281	len <<= 8;
	282	len \|= data[dp++];
	283	}
	284	if (unlikely(len > datalen - dp))
	285	goto data_overrun_error;
	286	}
2eb9eabf EB	287	} else {
	288	if (unlikely(len > datalen - dp))
	289	goto data_overrun_error;
42d5ec27 DH	290	}
	291
	292	if (flags & FLAG_CONS) {
	293	/* For expected compound forms, we stack the positions
	294	* of the start and end of the data.
	295	*/
	296	if (unlikely(csp >= NR_CONS_STACK))
	297	goto cons_stack_overflow;
	298	cons_dp_stack[csp] = dp;
	299	cons_hdrlen_stack[csp] = hdr;
	300	if (!(flags & FLAG_INDEFINITE_LENGTH)) {
	301	cons_datalen_stack[csp] = datalen;
	302	datalen = dp + len;
	303	} else {
	304	cons_datalen_stack[csp] = 0;
	305	}
	306	csp++;
	307	}
	308
	309	pr_debug("- TAG: %02x %zu%s\n",
	310	tag, len, flags & FLAG_CONS ? " CONS" : "");
	311	tdp = dp;
	312	}
	313
	314	/* Decide how to handle the operation */
	315	switch (op) {
42d5ec27 DH	316	case ASN1_OP_MATCH:
42d5ec27 DH	317	case ASN1_OP_MATCH_OR_SKIP:
e0058f3a EB	318	case ASN1_OP_MATCH_ACT:
e0058f3a EB	319	case ASN1_OP_MATCH_ACT_OR_SKIP:
42d5ec27	320	case ASN1_OP_MATCH_ANY:
233ce79d	321	case ASN1_OP_MATCH_ANY_OR_SKIP:
e0058f3a EB	322	case ASN1_OP_MATCH_ANY_ACT:
e0058f3a EB	323	case ASN1_OP_MATCH_ANY_ACT_OR_SKIP:
42d5ec27	324	case ASN1_OP_COND_MATCH_OR_SKIP:
e0058f3a	325	case ASN1_OP_COND_MATCH_ACT_OR_SKIP:
42d5ec27	326	case ASN1_OP_COND_MATCH_ANY:
233ce79d	327	case ASN1_OP_COND_MATCH_ANY_OR_SKIP:
e0058f3a EB	328	case ASN1_OP_COND_MATCH_ANY_ACT:
	329	case ASN1_OP_COND_MATCH_ANY_ACT_OR_SKIP:
	330
42d5ec27 DH	331	if (!(flags & FLAG_CONS)) {
42d5ec27 DH	332	if (flags & FLAG_INDEFINITE_LENGTH) {
e0058f3a EB	333	size_t tmp = dp;
e0058f3a EB	334
dbadc176	335	ret = asn1_find_indefinite_length(
e0058f3a	336	data, datalen, &tmp, &len, &errmsg);
dbadc176	337	if (ret < 0)
42d5ec27 DH	338	goto error;
	339	}
	340	pr_debug("- LEAF: %zu\n", len);
42d5ec27	341	}
e0058f3a EB	342
	343	if (op & ASN1_OP_MATCH__ACT) {
	344	unsigned char act;
	345
	346	if (op & ASN1_OP_MATCH__ANY)
	347	act = machine[pc + 1];
	348	else
	349	act = machine[pc + 2];
	350	ret = actions[act](context, hdr, tag, data + dp, len);
	351	if (ret < 0)
	352	return ret;
	353	}
	354
	355	if (!(flags & FLAG_CONS))
	356	dp += len;
42d5ec27 DH	357	pc += asn1_op_lengths[op];
	358	goto next_op;
	359
	360	case ASN1_OP_MATCH_JUMP:
	361	case ASN1_OP_MATCH_JUMP_OR_SKIP:
	362	case ASN1_OP_COND_MATCH_JUMP_OR_SKIP:
	363	pr_debug("- MATCH_JUMP\n");
	364	if (unlikely(jsp == NR_JUMP_STACK))
	365	goto jump_stack_overflow;
	366	jump_stack[jsp++] = pc + asn1_op_lengths[op];
	367	pc = machine[pc + 2];
	368	goto next_op;
	369
	370	case ASN1_OP_COND_FAIL:
	371	if (unlikely(!(flags & FLAG_MATCHED)))
	372	goto tag_mismatch;
	373	pc += asn1_op_lengths[op];
	374	goto next_op;
	375
	376	case ASN1_OP_COMPLETE:
	377	if (unlikely(jsp != 0 \|\| csp != 0)) {
	378	pr_err("ASN.1 decoder error: Stacks not empty at completion (%u, %u)\n",
	379	jsp, csp);
	380	return -EBADMSG;
	381	}
	382	return 0;
	383
	384	case ASN1_OP_END_SET:
	385	case ASN1_OP_END_SET_ACT:
	386	if (unlikely(!(flags & FLAG_MATCHED)))
	387	goto tag_mismatch;
	388	case ASN1_OP_END_SEQ:
	389	case ASN1_OP_END_SET_OF:
	390	case ASN1_OP_END_SEQ_OF:
	391	case ASN1_OP_END_SEQ_ACT:
	392	case ASN1_OP_END_SET_OF_ACT:
	393	case ASN1_OP_END_SEQ_OF_ACT:
	394	if (unlikely(csp <= 0))
	395	goto cons_stack_underflow;
	396	csp--;
	397	tdp = cons_dp_stack[csp];
	398	hdr = cons_hdrlen_stack[csp];
	399	len = datalen;
	400	datalen = cons_datalen_stack[csp];
	401	pr_debug("- end cons t=%zu dp=%zu l=%zu/%zu\n",
	402	tdp, dp, len, datalen);
	403	if (datalen == 0) {
	404	/* Indefinite length - check for the EOC. */
	405	datalen = len;
	406	if (unlikely(datalen - dp < 2))
	407	goto data_overrun_error;
	408	if (data[dp++] != 0) {
	409	if (op & ASN1_OP_END__OF) {
	410	dp--;
	411	csp++;
	412	pc = machine[pc + 1];
	413	pr_debug("- continue\n");
	414	goto next_op;
	415	}
	416	goto missing_eoc;
	417	}
	418	if (data[dp++] != 0)
	419	goto invalid_eoc;
	420	len = dp - tdp - 2;
421	} else {
422	if (dp < len && (op & ASN1_OP_END__OF)) {
423	datalen = len;
424	csp++;
425	pc = machine[pc + 1];
426	pr_debug("- continue\n");
427	goto next_op;
428	}
429	if (dp != len)
430	goto cons_length_error;
431	len -= tdp;
432	pr_debug("- cons len l=%zu d=%zu\n", len, dp - tdp);
433	}
434
435	if (op & ASN1_OP_END__ACT) {
436	unsigned char act;
437	if (op & ASN1_OP_END__OF)
438	act = machine[pc + 2];
439	else
440	act = machine[pc + 1];
441	ret = actions[act](context, hdr, 0, data + tdp, len);
81a7be2c EB	442	if (ret < 0)
81a7be2c EB	443	return ret;
42d5ec27 DH	444	}
	445	pc += asn1_op_lengths[op];
	446	goto next_op;
	447
3f3af97d DH	448	case ASN1_OP_MAYBE_ACT:
	449	if (!(flags & FLAG_LAST_MATCHED)) {
	450	pc += asn1_op_lengths[op];
	451	goto next_op;
	452	}
42d5ec27 DH	453	case ASN1_OP_ACT:
42d5ec27 DH	454	ret = actions[machine[pc + 1]](context, hdr, tag, data + tdp, len);
3f3af97d DH	455	if (ret < 0)
3f3af97d DH	456	return ret;
42d5ec27 DH	457	pc += asn1_op_lengths[op];
	458	goto next_op;
	459
	460	case ASN1_OP_RETURN:
	461	if (unlikely(jsp <= 0))
	462	goto jump_stack_underflow;
	463	pc = jump_stack[--jsp];
3f3af97d	464	flags \|= FLAG_MATCHED \| FLAG_LAST_MATCHED;
42d5ec27 DH	465	goto next_op;
	466
	467	default:
	468	break;
	469	}
	470
	471	/* Shouldn't reach here */
3f3af97d DH	472	pr_err("ASN.1 decoder error: Found reserved opcode (%u) pc=%zu\n",
3f3af97d DH	473	op, pc);
42d5ec27 DH	474	return -EBADMSG;
	475
	476	data_overrun_error:
	477	errmsg = "Data overrun error";
	478	goto error;
	479	machine_overrun_error:
	480	errmsg = "Machine overrun error";
	481	goto error;
	482	jump_stack_underflow:
	483	errmsg = "Jump stack underflow";
	484	goto error;
	485	jump_stack_overflow:
	486	errmsg = "Jump stack overflow";
	487	goto error;
	488	cons_stack_underflow:
	489	errmsg = "Cons stack underflow";
	490	goto error;
	491	cons_stack_overflow:
	492	errmsg = "Cons stack overflow";
	493	goto error;
	494	cons_length_error:
	495	errmsg = "Cons length error";
	496	goto error;
	497	missing_eoc:
	498	errmsg = "Missing EOC in indefinite len cons";
	499	goto error;
	500	invalid_eoc:
	501	errmsg = "Invalid length EOC";
	502	goto error;
	503	length_too_long:
	504	errmsg = "Unsupported length";
	505	goto error;
	506	indefinite_len_primitive:
	507	errmsg = "Indefinite len primitive not permitted";
	508	goto error;
	509	tag_mismatch:
	510	errmsg = "Unexpected tag";
	511	goto error;
	512	long_tag_not_supported:
	513	errmsg = "Long tag not supported";
	514	error:
	515	pr_debug("\nASN1: %s [m=%zu d=%zu ot=%02x t=%02x l=%zu]\n",
	516	errmsg, pc, dp, optag, tag, len);
	517	return -EBADMSG;
	518	}
	519	EXPORT_SYMBOL_GPL(asn1_ber_decoder);
ccab6058 TA	520
ccab6058 TA	521	MODULE_LICENSE("GPL");