[linux.git] / lib / asn1_decoder.c

// SPDX-License-Identifier: GPL-2.0-or-later
/* Decoder for ASN.1 BER/DER/CER encoded bytestream
 *
 * Copyright (C) 2012 Red Hat, Inc. All Rights Reserved.
 * Written by David Howells ([email protected])
 */

#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;
		fallthrough;

	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;
		}
		fallthrough;

	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
b4d0d230	1	// SPDX-License-Identifier: GPL-2.0-or-later
42d5ec27 DH	2	/* Decoder for ASN.1 BER/DER/CER encoded bytestream
	3	*
	4	* Copyright (C) 2012 Red Hat, Inc. All Rights Reserved.
	5	* Written by David Howells ([email protected])
42d5ec27 DH	6	*/
	7
	8	#include <linux/export.h>
	9	#include <linux/kernel.h>
	10	#include <linux/errno.h>
ccab6058	11	#include <linux/module.h>
42d5ec27 DH	12	#include <linux/asn1_decoder.h>
	13	#include <linux/asn1_ber_bytecode.h>
	14
	15	static const unsigned char asn1_op_lengths[ASN1_OP__NR] = {
	16	/* OPC TAG JMP ACT */
	17	[ASN1_OP_MATCH] = 1 + 1,
	18	[ASN1_OP_MATCH_OR_SKIP] = 1 + 1,
	19	[ASN1_OP_MATCH_ACT] = 1 + 1 + 1,
	20	[ASN1_OP_MATCH_ACT_OR_SKIP] = 1 + 1 + 1,
	21	[ASN1_OP_MATCH_JUMP] = 1 + 1 + 1,
	22	[ASN1_OP_MATCH_JUMP_OR_SKIP] = 1 + 1 + 1,
	23	[ASN1_OP_MATCH_ANY] = 1,
233ce79d	24	[ASN1_OP_MATCH_ANY_OR_SKIP] = 1,
42d5ec27	25	[ASN1_OP_MATCH_ANY_ACT] = 1 + 1,
233ce79d	26	[ASN1_OP_MATCH_ANY_ACT_OR_SKIP] = 1 + 1,
42d5ec27 DH	27	[ASN1_OP_COND_MATCH_OR_SKIP] = 1 + 1,
	28	[ASN1_OP_COND_MATCH_ACT_OR_SKIP] = 1 + 1 + 1,
	29	[ASN1_OP_COND_MATCH_JUMP_OR_SKIP] = 1 + 1 + 1,
	30	[ASN1_OP_COND_MATCH_ANY] = 1,
233ce79d	31	[ASN1_OP_COND_MATCH_ANY_OR_SKIP] = 1,
42d5ec27	32	[ASN1_OP_COND_MATCH_ANY_ACT] = 1 + 1,
233ce79d	33	[ASN1_OP_COND_MATCH_ANY_ACT_OR_SKIP] = 1 + 1,
42d5ec27 DH	34	[ASN1_OP_COND_FAIL] = 1,
	35	[ASN1_OP_COMPLETE] = 1,
	36	[ASN1_OP_ACT] = 1 + 1,
3f3af97d	37	[ASN1_OP_MAYBE_ACT] = 1 + 1,
42d5ec27 DH	38	[ASN1_OP_RETURN] = 1,
	39	[ASN1_OP_END_SEQ] = 1,
	40	[ASN1_OP_END_SEQ_OF] = 1 + 1,
	41	[ASN1_OP_END_SET] = 1,
	42	[ASN1_OP_END_SET_OF] = 1 + 1,
	43	[ASN1_OP_END_SEQ_ACT] = 1 + 1,
	44	[ASN1_OP_END_SEQ_OF_ACT] = 1 + 1 + 1,
	45	[ASN1_OP_END_SET_ACT] = 1 + 1,
	46	[ASN1_OP_END_SET_OF_ACT] = 1 + 1 + 1,
	47	};
	48
	49	/*
	50	* Find the length of an indefinite length object
dbadc176 DH	51	* @data: The data buffer
	52	* @datalen: The end of the innermost containing element in the buffer
	53	* @_dp: The data parse cursor (updated before returning)
	54	* @_len: Where to return the size of the element.
	55	* @_errmsg: Where to return a pointer to an error message on error
42d5ec27 DH	56	*/
42d5ec27 DH	57	static int asn1_find_indefinite_length(const unsigned char *data, size_t datalen,
dbadc176 DH	58	size_t _dp, size_t _len,
dbadc176 DH	59	const char **_errmsg)
42d5ec27 DH	60	{
42d5ec27 DH	61	unsigned char tag, tmp;
dbadc176	62	size_t dp = *_dp, len, n;
42d5ec27 DH	63	int indef_level = 1;
	64
	65	next_tag:
	66	if (unlikely(datalen - dp < 2)) {
	67	if (datalen == dp)
	68	goto missing_eoc;
	69	goto data_overrun_error;
	70	}
	71
	72	/* Extract a tag from the data */
	73	tag = data[dp++];
23c8a812	74	if (tag == ASN1_EOC) {
42d5ec27 DH	75	/* It appears to be an EOC. */
	76	if (data[dp++] != 0)
	77	goto invalid_eoc;
dbadc176 DH	78	if (--indef_level <= 0) {
	79	_len = dp - _dp;
	80	*_dp = dp;
	81	return 0;
	82	}
42d5ec27 DH	83	goto next_tag;
	84	}
	85
99cca91e	86	if (unlikely((tag & 0x1f) == ASN1_LONG_TAG)) {
42d5ec27 DH	87	do {
	88	if (unlikely(datalen - dp < 2))
	89	goto data_overrun_error;
	90	tmp = data[dp++];
	91	} while (tmp & 0x80);
	92	}
	93
	94	/* Extract the length */
	95	len = data[dp++];
23c8a812 DH	96	if (len <= 0x7f)
23c8a812 DH	97	goto check_length;
42d5ec27	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;
23c8a812	108	if (unlikely(n > sizeof(len) - 1))
42d5ec27 DH	109	goto length_too_long;
	110	if (unlikely(n > datalen - dp))
	111	goto data_overrun_error;
23c8a812 DH	112	len = 0;
23c8a812 DH	113	for (; n > 0; n--) {
42d5ec27 DH	114	len <<= 8;
	115	len \|= data[dp++];
	116	}
23c8a812 DH	117	check_length:
	118	if (len > datalen - dp)
	119	goto data_overrun_error;
42d5ec27 DH	120	dp += len;
	121	goto next_tag;
	122
	123	length_too_long:
	124	*_errmsg = "Unsupported length";
	125	goto error;
	126	indefinite_len_primitive:
	127	*_errmsg = "Indefinite len primitive not permitted";
	128	goto error;
	129	invalid_eoc:
	130	*_errmsg = "Invalid length EOC";
	131	goto error;
	132	data_overrun_error:
	133	*_errmsg = "Data overrun error";
	134	goto error;
	135	missing_eoc:
	136	*_errmsg = "Missing EOC in indefinite len cons";
	137	error:
dbadc176	138	*_dp = dp;
42d5ec27 DH	139	return -1;
	140	}
	141
	142	/**
	143	* asn1_ber_decoder - Decoder BER/DER/CER ASN.1 according to pattern
	144	* @decoder: The decoder definition (produced by asn1_compiler)
	145	* @context: The caller's context (to be passed to the action functions)
	146	* @data: The encoded data
548bbff9	147	* @datalen: The size of the encoded data
42d5ec27 DH	148	*
	149	* Decode BER/DER/CER encoded ASN.1 data according to a bytecode pattern
	150	* produced by asn1_compiler. Action functions are called on marked tags to
	151	* allow the caller to retrieve significant data.
	152	*
	153	* LIMITATIONS:
	154	*
	155	* To keep down the amount of stack used by this function, the following limits
	156	* have been imposed:
	157	*
	158	* (1) This won't handle datalen > 65535 without increasing the size of the
	159	* cons stack elements and length_too_long checking.
	160	*
	161	* (2) The stack of constructed types is 10 deep. If the depth of non-leaf
	162	* constructed types exceeds this, the decode will fail.
	163	*
	164	* (3) The SET type (not the SET OF type) isn't really supported as tracking
	165	* what members of the set have been seen is a pain.
	166	*/
	167	int asn1_ber_decoder(const struct asn1_decoder *decoder,
	168	void *context,
	169	const unsigned char *data,
	170	size_t datalen)
	171	{
	172	const unsigned char *machine = decoder->machine;
	173	const asn1_action_t *actions = decoder->actions;
	174	size_t machlen = decoder->machlen;
	175	enum asn1_opcode op;
	176	unsigned char tag = 0, csp = 0, jsp = 0, optag = 0, hdr = 0;
	177	const char *errmsg;
	178	size_t pc = 0, dp = 0, tdp = 0, len = 0;
	179	int ret;
	180
	181	unsigned char flags = 0;
	182	#define FLAG_INDEFINITE_LENGTH 0x01
	183	#define FLAG_MATCHED 0x02
3f3af97d	184	#define FLAG_LAST_MATCHED 0x04 /* Last tag matched */
42d5ec27 DH	185	#define FLAG_CONS 0x20 /* Corresponds to CONS bit in the opcode tag
	186	* - ie. whether or not we are going to parse
	187	* a compound type.
	188	*/
	189
	190	#define NR_CONS_STACK 10
	191	unsigned short cons_dp_stack[NR_CONS_STACK];
	192	unsigned short cons_datalen_stack[NR_CONS_STACK];
	193	unsigned char cons_hdrlen_stack[NR_CONS_STACK];
	194	#define NR_JUMP_STACK 10
	195	unsigned char jump_stack[NR_JUMP_STACK];
	196
	197	if (datalen > 65535)
	198	return -EMSGSIZE;
	199
	200	next_op:
	201	pr_debug("next_op: pc=\e[32m%zu\e[m/%zu dp=\e[33m%zu\e[m/%zu C=%d J=%d\n",
	202	pc, machlen, dp, datalen, csp, jsp);
	203	if (unlikely(pc >= machlen))
	204	goto machine_overrun_error;
	205	op = machine[pc];
	206	if (unlikely(pc + asn1_op_lengths[op] > machlen))
	207	goto machine_overrun_error;
	208
	209	/* If this command is meant to match a tag, then do that before
	210	* evaluating the command.
	211	*/
	212	if (op <= ASN1_OP__MATCHES_TAG) {
	213	unsigned char tmp;
	214
	215	/* Skip conditional matches if possible */
0d62e9dd DH	216	if ((op & ASN1_OP_MATCH__COND && flags & FLAG_MATCHED) \|\|
0d62e9dd DH	217	(op & ASN1_OP_MATCH__SKIP && dp == datalen)) {
3f3af97d	218	flags &= ~FLAG_LAST_MATCHED;
42d5ec27 DH	219	pc += asn1_op_lengths[op];
	220	goto next_op;
	221	}
	222
	223	flags = 0;
	224	hdr = 2;
	225
	226	/* Extract a tag from the data */
624f5ab8	227	if (unlikely(datalen - dp < 2))
42d5ec27 DH	228	goto data_overrun_error;
42d5ec27 DH	229	tag = data[dp++];
99cca91e	230	if (unlikely((tag & 0x1f) == ASN1_LONG_TAG))
42d5ec27 DH	231	goto long_tag_not_supported;
	232
	233	if (op & ASN1_OP_MATCH__ANY) {
	234	pr_debug("- any %02x\n", tag);
	235	} else {
	236	/* Extract the tag from the machine
	237	* - Either CONS or PRIM are permitted in the data if
	238	* CONS is not set in the op stream, otherwise CONS
	239	* is mandatory.
	240	*/
	241	optag = machine[pc + 1];
	242	flags \|= optag & FLAG_CONS;
	243
	244	/* Determine whether the tag matched */
	245	tmp = optag ^ tag;
	246	tmp &= ~(optag & ASN1_CONS_BIT);
	247	pr_debug("- match? %02x %02x %02x\n", tag, optag, tmp);
	248	if (tmp != 0) {
	249	/* All odd-numbered tags are MATCH_OR_SKIP. */
	250	if (op & ASN1_OP_MATCH__SKIP) {
	251	pc += asn1_op_lengths[op];
	252	dp--;
	253	goto next_op;
	254	}
	255	goto tag_mismatch;
	256	}
	257	}
	258	flags \|= FLAG_MATCHED;
	259
	260	len = data[dp++];
	261	if (len > 0x7f) {
99cca91e	262	if (unlikely(len == ASN1_INDEFINITE_LENGTH)) {
42d5ec27 DH	263	/* Indefinite length */
	264	if (unlikely(!(tag & ASN1_CONS_BIT)))
	265	goto indefinite_len_primitive;
	266	flags \|= FLAG_INDEFINITE_LENGTH;
	267	if (unlikely(2 > datalen - dp))
	268	goto data_overrun_error;
	269	} else {
	270	int n = len - 0x80;
	271	if (unlikely(n > 2))
	272	goto length_too_long;
624f5ab8	273	if (unlikely(n > datalen - dp))
42d5ec27 DH	274	goto data_overrun_error;
	275	hdr += n;
	276	for (len = 0; n > 0; n--) {
	277	len <<= 8;
	278	len \|= data[dp++];
	279	}
	280	if (unlikely(len > datalen - dp))
	281	goto data_overrun_error;
	282	}
2eb9eabf EB	283	} else {
	284	if (unlikely(len > datalen - dp))
	285	goto data_overrun_error;
42d5ec27 DH	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) {
42d5ec27 DH	312	case ASN1_OP_MATCH:
42d5ec27 DH	313	case ASN1_OP_MATCH_OR_SKIP:
e0058f3a EB	314	case ASN1_OP_MATCH_ACT:
e0058f3a EB	315	case ASN1_OP_MATCH_ACT_OR_SKIP:
42d5ec27	316	case ASN1_OP_MATCH_ANY:
233ce79d	317	case ASN1_OP_MATCH_ANY_OR_SKIP:
e0058f3a EB	318	case ASN1_OP_MATCH_ANY_ACT:
e0058f3a EB	319	case ASN1_OP_MATCH_ANY_ACT_OR_SKIP:
42d5ec27	320	case ASN1_OP_COND_MATCH_OR_SKIP:
e0058f3a	321	case ASN1_OP_COND_MATCH_ACT_OR_SKIP:
42d5ec27	322	case ASN1_OP_COND_MATCH_ANY:
233ce79d	323	case ASN1_OP_COND_MATCH_ANY_OR_SKIP:
e0058f3a EB	324	case ASN1_OP_COND_MATCH_ANY_ACT:
	325	case ASN1_OP_COND_MATCH_ANY_ACT_OR_SKIP:
	326
42d5ec27 DH	327	if (!(flags & FLAG_CONS)) {
42d5ec27 DH	328	if (flags & FLAG_INDEFINITE_LENGTH) {
e0058f3a EB	329	size_t tmp = dp;
e0058f3a EB	330
dbadc176	331	ret = asn1_find_indefinite_length(
e0058f3a	332	data, datalen, &tmp, &len, &errmsg);
dbadc176	333	if (ret < 0)
42d5ec27 DH	334	goto error;
	335	}
	336	pr_debug("- LEAF: %zu\n", len);
42d5ec27	337	}
e0058f3a EB	338
	339	if (op & ASN1_OP_MATCH__ACT) {
	340	unsigned char act;
	341
	342	if (op & ASN1_OP_MATCH__ANY)
	343	act = machine[pc + 1];
	344	else
	345	act = machine[pc + 2];
	346	ret = actions[act](context, hdr, tag, data + dp, len);
	347	if (ret < 0)
	348	return ret;
	349	}
	350
	351	if (!(flags & FLAG_CONS))
	352	dp += len;
42d5ec27 DH	353	pc += asn1_op_lengths[op];
	354	goto next_op;
	355
	356	case ASN1_OP_MATCH_JUMP:
	357	case ASN1_OP_MATCH_JUMP_OR_SKIP:
	358	case ASN1_OP_COND_MATCH_JUMP_OR_SKIP:
	359	pr_debug("- MATCH_JUMP\n");
	360	if (unlikely(jsp == NR_JUMP_STACK))
	361	goto jump_stack_overflow;
	362	jump_stack[jsp++] = pc + asn1_op_lengths[op];
	363	pc = machine[pc + 2];
	364	goto next_op;
	365
	366	case ASN1_OP_COND_FAIL:
	367	if (unlikely(!(flags & FLAG_MATCHED)))
	368	goto tag_mismatch;
	369	pc += asn1_op_lengths[op];
	370	goto next_op;
	371
	372	case ASN1_OP_COMPLETE:
	373	if (unlikely(jsp != 0 \|\| csp != 0)) {
	374	pr_err("ASN.1 decoder error: Stacks not empty at completion (%u, %u)\n",
	375	jsp, csp);
	376	return -EBADMSG;
	377	}
	378	return 0;
	379
	380	case ASN1_OP_END_SET:
	381	case ASN1_OP_END_SET_ACT:
	382	if (unlikely(!(flags & FLAG_MATCHED)))
	383	goto tag_mismatch;
4c1ca831	384	fallthrough;
afb33e40	385
42d5ec27 DH	386	case ASN1_OP_END_SEQ:
	387	case ASN1_OP_END_SET_OF:
	388	case ASN1_OP_END_SEQ_OF:
	389	case ASN1_OP_END_SEQ_ACT:
	390	case ASN1_OP_END_SET_OF_ACT:
	391	case ASN1_OP_END_SEQ_OF_ACT:
	392	if (unlikely(csp <= 0))
	393	goto cons_stack_underflow;
	394	csp--;
	395	tdp = cons_dp_stack[csp];
	396	hdr = cons_hdrlen_stack[csp];
	397	len = datalen;
	398	datalen = cons_datalen_stack[csp];
	399	pr_debug("- end cons t=%zu dp=%zu l=%zu/%zu\n",
	400	tdp, dp, len, datalen);
	401	if (datalen == 0) {
	402	/* Indefinite length - check for the EOC. */
	403	datalen = len;
	404	if (unlikely(datalen - dp < 2))
	405	goto data_overrun_error;
	406	if (data[dp++] != 0) {
	407	if (op & ASN1_OP_END__OF) {
	408	dp--;
	409	csp++;
	410	pc = machine[pc + 1];
	411	pr_debug("- continue\n");
	412	goto next_op;
	413	}
	414	goto missing_eoc;
	415	}
	416	if (data[dp++] != 0)
	417	goto invalid_eoc;
	418	len = dp - tdp - 2;
	419	} else {
	420	if (dp < len && (op & ASN1_OP_END__OF)) {
	421	datalen = len;
	422	csp++;
	423	pc = machine[pc + 1];
	424	pr_debug("- continue\n");
	425	goto next_op;
	426	}
	427	if (dp != len)
	428	goto cons_length_error;
	429	len -= tdp;
	430	pr_debug("- cons len l=%zu d=%zu\n", len, dp - tdp);
	431	}
	432
	433	if (op & ASN1_OP_END__ACT) {
	434	unsigned char act;
	435	if (op & ASN1_OP_END__OF)
	436	act = machine[pc + 2];
	437	else
	438	act = machine[pc + 1];
	439	ret = actions[act](context, hdr, 0, data + tdp, len);
81a7be2c EB	440	if (ret < 0)
81a7be2c EB	441	return ret;
42d5ec27 DH	442	}
	443	pc += asn1_op_lengths[op];
	444	goto next_op;
	445
3f3af97d DH	446	case ASN1_OP_MAYBE_ACT:
	447	if (!(flags & FLAG_LAST_MATCHED)) {
	448	pc += asn1_op_lengths[op];
	449	goto next_op;
	450	}
4c1ca831	451	fallthrough;
afb33e40	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");