[J-u-boot.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])
 */

#ifdef __UBOOT__
#include <log.h>
#include <linux/compat.h>
#else
#include <linux/export.h>
#endif
#include <linux/kernel.h>
#include <linux/errno.h>
#ifndef __UBOOT__
#include <linux/module.h>
#endif
#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;
		/* fall through */

	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;
		}
		/* fall through */

	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
ab8a0e06 AT	1	// SPDX-License-Identifier: GPL-2.0-or-later
	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])
	6	*/
	7
	8	#ifdef __UBOOT__
f7ae49fc	9	#include <log.h>
ab8a0e06 AT	10	#include <linux/compat.h>
	11	#else
	12	#include <linux/export.h>
	13	#endif
	14	#include <linux/kernel.h>
	15	#include <linux/errno.h>
	16	#ifndef __UBOOT__
	17	#include <linux/module.h>
	18	#endif
	19	#include <linux/asn1_decoder.h>
	20	#include <linux/asn1_ber_bytecode.h>
	21
	22	static const unsigned char asn1_op_lengths[ASN1_OP__NR] = {
	23	/* OPC TAG JMP ACT */
	24	[ASN1_OP_MATCH] = 1 + 1,
	25	[ASN1_OP_MATCH_OR_SKIP] = 1 + 1,
	26	[ASN1_OP_MATCH_ACT] = 1 + 1 + 1,
	27	[ASN1_OP_MATCH_ACT_OR_SKIP] = 1 + 1 + 1,
	28	[ASN1_OP_MATCH_JUMP] = 1 + 1 + 1,
	29	[ASN1_OP_MATCH_JUMP_OR_SKIP] = 1 + 1 + 1,
	30	[ASN1_OP_MATCH_ANY] = 1,
	31	[ASN1_OP_MATCH_ANY_OR_SKIP] = 1,
	32	[ASN1_OP_MATCH_ANY_ACT] = 1 + 1,
	33	[ASN1_OP_MATCH_ANY_ACT_OR_SKIP] = 1 + 1,
	34	[ASN1_OP_COND_MATCH_OR_SKIP] = 1 + 1,
	35	[ASN1_OP_COND_MATCH_ACT_OR_SKIP] = 1 + 1 + 1,
	36	[ASN1_OP_COND_MATCH_JUMP_OR_SKIP] = 1 + 1 + 1,
	37	[ASN1_OP_COND_MATCH_ANY] = 1,
	38	[ASN1_OP_COND_MATCH_ANY_OR_SKIP] = 1,
	39	[ASN1_OP_COND_MATCH_ANY_ACT] = 1 + 1,
	40	[ASN1_OP_COND_MATCH_ANY_ACT_OR_SKIP] = 1 + 1,
	41	[ASN1_OP_COND_FAIL] = 1,
	42	[ASN1_OP_COMPLETE] = 1,
	43	[ASN1_OP_ACT] = 1 + 1,
	44	[ASN1_OP_MAYBE_ACT] = 1 + 1,
	45	[ASN1_OP_RETURN] = 1,
	46	[ASN1_OP_END_SEQ] = 1,
	47	[ASN1_OP_END_SEQ_OF] = 1 + 1,
	48	[ASN1_OP_END_SET] = 1,
	49	[ASN1_OP_END_SET_OF] = 1 + 1,
	50	[ASN1_OP_END_SEQ_ACT] = 1 + 1,
	51	[ASN1_OP_END_SEQ_OF_ACT] = 1 + 1 + 1,
	52	[ASN1_OP_END_SET_ACT] = 1 + 1,
	53	[ASN1_OP_END_SET_OF_ACT] = 1 + 1 + 1,
	54	};
	55
	56	/*
	57	* Find the length of an indefinite length object
	58	* @data: The data buffer
	59	* @datalen: The end of the innermost containing element in the buffer
	60	* @_dp: The data parse cursor (updated before returning)
	61	* @_len: Where to return the size of the element.
	62	* @_errmsg: Where to return a pointer to an error message on error
	63	*/
	64	static int asn1_find_indefinite_length(const unsigned char *data, size_t datalen,
	65	size_t _dp, size_t _len,
	66	const char **_errmsg)
	67	{
	68	unsigned char tag, tmp;
	69	size_t dp = *_dp, len, n;
	70	int indef_level = 1;
	71
	72	next_tag:
	73	if (unlikely(datalen - dp < 2)) {
74	if (datalen == dp)
75	goto missing_eoc;
76	goto data_overrun_error;
77	}
78
79	/* Extract a tag from the data */
80	tag = data[dp++];
81	if (tag == ASN1_EOC) {
82	/* It appears to be an EOC. */
83	if (data[dp++] != 0)
84	goto invalid_eoc;
85	if (--indef_level <= 0) {
86	_len = dp - _dp;
87	*_dp = dp;
88	return 0;
89	}
90	goto next_tag;
91	}
92
93	if (unlikely((tag & 0x1f) == ASN1_LONG_TAG)) {
94	do {
95	if (unlikely(datalen - dp < 2))
96	goto data_overrun_error;
97	tmp = data[dp++];
98	} while (tmp & 0x80);
99	}
100
101	/* Extract the length */
102	len = data[dp++];
103	if (len <= 0x7f)
104	goto check_length;
105
106	if (unlikely(len == ASN1_INDEFINITE_LENGTH)) {
107	/* Indefinite length */
108	if (unlikely((tag & ASN1_CONS_BIT) == ASN1_PRIM << 5))
109	goto indefinite_len_primitive;
110	indef_level++;
111	goto next_tag;
112	}
113
114	n = len - 0x80;
115	if (unlikely(n > sizeof(len) - 1))
116	goto length_too_long;
117	if (unlikely(n > datalen - dp))
118	goto data_overrun_error;
119	len = 0;
120	for (; n > 0; n--) {
121	len <<= 8;
122	len \|= data[dp++];
123	}
124	check_length:
125	if (len > datalen - dp)
126	goto data_overrun_error;
127	dp += len;
128	goto next_tag;
129
130	length_too_long:
131	*_errmsg = "Unsupported length";
132	goto error;
133	indefinite_len_primitive:
134	*_errmsg = "Indefinite len primitive not permitted";
135	goto error;
136	invalid_eoc:
137	*_errmsg = "Invalid length EOC";
138	goto error;
139	data_overrun_error:
140	*_errmsg = "Data overrun error";
141	goto error;
142	missing_eoc:
143	*_errmsg = "Missing EOC in indefinite len cons";
144	error:
145	*_dp = dp;
146	return -1;
147	}
148
149	/**
150	* asn1_ber_decoder - Decoder BER/DER/CER ASN.1 according to pattern
151	* @decoder: The decoder definition (produced by asn1_compiler)
152	* @context: The caller's context (to be passed to the action functions)
153	* @data: The encoded data
154	* @datalen: The size of the encoded data
155	*
156	* Decode BER/DER/CER encoded ASN.1 data according to a bytecode pattern
157	* produced by asn1_compiler. Action functions are called on marked tags to
158	* allow the caller to retrieve significant data.
159	*
160	* LIMITATIONS:
161	*
162	* To keep down the amount of stack used by this function, the following limits
163	* have been imposed:
164	*
165	* (1) This won't handle datalen > 65535 without increasing the size of the
166	* cons stack elements and length_too_long checking.
167	*
168	* (2) The stack of constructed types is 10 deep. If the depth of non-leaf
169	* constructed types exceeds this, the decode will fail.
170	*
171	* (3) The SET type (not the SET OF type) isn't really supported as tracking
172	* what members of the set have been seen is a pain.
173	*/
174	int asn1_ber_decoder(const struct asn1_decoder *decoder,
175	void *context,
176	const unsigned char *data,
177	size_t datalen)
178	{
179	const unsigned char *machine = decoder->machine;
180	const asn1_action_t *actions = decoder->actions;
181	size_t machlen = decoder->machlen;
182	enum asn1_opcode op;
183	unsigned char tag = 0, csp = 0, jsp = 0, optag = 0, hdr = 0;
184	const char *errmsg;
185	size_t pc = 0, dp = 0, tdp = 0, len = 0;
186	int ret;
187
188	unsigned char flags = 0;
189	#define FLAG_INDEFINITE_LENGTH 0x01
190	#define FLAG_MATCHED 0x02
191	#define FLAG_LAST_MATCHED 0x04 /* Last tag matched */
192	#define FLAG_CONS 0x20 /* Corresponds to CONS bit in the opcode tag
193	* - ie. whether or not we are going to parse
194	* a compound type.
195	*/
196
197	#define NR_CONS_STACK 10
198	unsigned short cons_dp_stack[NR_CONS_STACK];
199	unsigned short cons_datalen_stack[NR_CONS_STACK];
200	unsigned char cons_hdrlen_stack[NR_CONS_STACK];
201	#define NR_JUMP_STACK 10
202	unsigned char jump_stack[NR_JUMP_STACK];
203
204	if (datalen > 65535)
205	return -EMSGSIZE;
206
207	next_op:
208	pr_debug("next_op: pc=\e[32m%zu\e[m/%zu dp=\e[33m%zu\e[m/%zu C=%d J=%d\n",
209	pc, machlen, dp, datalen, csp, jsp);
210	if (unlikely(pc >= machlen))
211	goto machine_overrun_error;
212	op = machine[pc];
213	if (unlikely(pc + asn1_op_lengths[op] > machlen))
214	goto machine_overrun_error;
215
216	/* If this command is meant to match a tag, then do that before
217	* evaluating the command.
218	*/
219	if (op <= ASN1_OP__MATCHES_TAG) {
220	unsigned char tmp;
221
222	/* Skip conditional matches if possible */
223	if ((op & ASN1_OP_MATCH__COND && flags & FLAG_MATCHED) \|\|
224	(op & ASN1_OP_MATCH__SKIP && dp == datalen)) {
225	flags &= ~FLAG_LAST_MATCHED;
226	pc += asn1_op_lengths[op];
227	goto next_op;
228	}
229
230	flags = 0;
231	hdr = 2;
232
233	/* Extract a tag from the data */
234	if (unlikely(datalen - dp < 2))
235	goto data_overrun_error;
236	tag = data[dp++];
237	if (unlikely((tag & 0x1f) == ASN1_LONG_TAG))
238	goto long_tag_not_supported;
239
240	if (op & ASN1_OP_MATCH__ANY) {
241	pr_debug("- any %02x\n", tag);
242	} else {
243	/* Extract the tag from the machine
244	* - Either CONS or PRIM are permitted in the data if
245	* CONS is not set in the op stream, otherwise CONS
246	* is mandatory.
247	*/
248	optag = machine[pc + 1];
249	flags \|= optag & FLAG_CONS;
250
251	/* Determine whether the tag matched */
252	tmp = optag ^ tag;
253	tmp &= ~(optag & ASN1_CONS_BIT);
254	pr_debug("- match? %02x %02x %02x\n", tag, optag, tmp);
255	if (tmp != 0) {
256	/* All odd-numbered tags are MATCH_OR_SKIP. */
257	if (op & ASN1_OP_MATCH__SKIP) {
258	pc += asn1_op_lengths[op];
259	dp--;
260	goto next_op;
261	}
262	goto tag_mismatch;
263	}
264	}
265	flags \|= FLAG_MATCHED;
266
267	len = data[dp++];
268	if (len > 0x7f) {
269	if (unlikely(len == ASN1_INDEFINITE_LENGTH)) {
270	/* Indefinite length */
271	if (unlikely(!(tag & ASN1_CONS_BIT)))
272	goto indefinite_len_primitive;
273	flags \|= FLAG_INDEFINITE_LENGTH;
274	if (unlikely(2 > datalen - dp))
275	goto data_overrun_error;
276	} else {
277	int n = len - 0x80;
278	if (unlikely(n > 2))
279	goto length_too_long;
280	if (unlikely(n > datalen - dp))
281	goto data_overrun_error;
282	hdr += n;
283	for (len = 0; n > 0; n--) {
284	len <<= 8;
285	len \|= data[dp++];
286	}
287	if (unlikely(len > datalen - dp))
288	goto data_overrun_error;
289	}
290	} else {
291	if (unlikely(len > datalen - dp))
292	goto data_overrun_error;
293	}
294
295	if (flags & FLAG_CONS) {
296	/* For expected compound forms, we stack the positions
297	* of the start and end of the data.
298	*/
299	if (unlikely(csp >= NR_CONS_STACK))
300	goto cons_stack_overflow;
301	cons_dp_stack[csp] = dp;
302	cons_hdrlen_stack[csp] = hdr;
303	if (!(flags & FLAG_INDEFINITE_LENGTH)) {
304	cons_datalen_stack[csp] = datalen;
305	datalen = dp + len;
306	} else {
307	cons_datalen_stack[csp] = 0;
308	}
309	csp++;
310	}
311
312	pr_debug("- TAG: %02x %zu%s\n",
313	tag, len, flags & FLAG_CONS ? " CONS" : "");
314	tdp = dp;
315	}
316
317	/* Decide how to handle the operation */
318	switch (op) {
319	case ASN1_OP_MATCH:
320	case ASN1_OP_MATCH_OR_SKIP:
321	case ASN1_OP_MATCH_ACT:
322	case ASN1_OP_MATCH_ACT_OR_SKIP:
323	case ASN1_OP_MATCH_ANY:
324	case ASN1_OP_MATCH_ANY_OR_SKIP:
325	case ASN1_OP_MATCH_ANY_ACT:
326	case ASN1_OP_MATCH_ANY_ACT_OR_SKIP:
327	case ASN1_OP_COND_MATCH_OR_SKIP:
328	case ASN1_OP_COND_MATCH_ACT_OR_SKIP:
329	case ASN1_OP_COND_MATCH_ANY:
330	case ASN1_OP_COND_MATCH_ANY_OR_SKIP:
331	case ASN1_OP_COND_MATCH_ANY_ACT:
332	case ASN1_OP_COND_MATCH_ANY_ACT_OR_SKIP:
333
334	if (!(flags & FLAG_CONS)) {
335	if (flags & FLAG_INDEFINITE_LENGTH) {
336	size_t tmp = dp;
337
338	ret = asn1_find_indefinite_length(
339	data, datalen, &tmp, &len, &errmsg);
340	if (ret < 0)
341	goto error;
342	}
343	pr_debug("- LEAF: %zu\n", len);
344	}
345
346	if (op & ASN1_OP_MATCH__ACT) {
347	unsigned char act;
348
349	if (op & ASN1_OP_MATCH__ANY)
350	act = machine[pc + 1];
351	else
352	act = machine[pc + 2];
353	ret = actions[act](context, hdr, tag, data + dp, len);
354	if (ret < 0)
355	return ret;
356	}
357
358	if (!(flags & FLAG_CONS))
359	dp += len;
360	pc += asn1_op_lengths[op];
361	goto next_op;
362
363	case ASN1_OP_MATCH_JUMP:
364	case ASN1_OP_MATCH_JUMP_OR_SKIP:
365	case ASN1_OP_COND_MATCH_JUMP_OR_SKIP:
366	pr_debug("- MATCH_JUMP\n");
367	if (unlikely(jsp == NR_JUMP_STACK))
368	goto jump_stack_overflow;
369	jump_stack[jsp++] = pc + asn1_op_lengths[op];
370	pc = machine[pc + 2];
371	goto next_op;
372
373	case ASN1_OP_COND_FAIL:
374	if (unlikely(!(flags & FLAG_MATCHED)))
375	goto tag_mismatch;
376	pc += asn1_op_lengths[op];
377	goto next_op;
378
379	case ASN1_OP_COMPLETE:
380	if (unlikely(jsp != 0 \|\| csp != 0)) {
381	pr_err("ASN.1 decoder error: Stacks not empty at completion (%u, %u)\n",
382	jsp, csp);
383	return -EBADMSG;
384	}
385	return 0;
386
387	case ASN1_OP_END_SET:
388	case ASN1_OP_END_SET_ACT:
389	if (unlikely(!(flags & FLAG_MATCHED)))
390	goto tag_mismatch;
391	/* fall through */
392
393	case ASN1_OP_END_SEQ:
394	case ASN1_OP_END_SET_OF:
395	case ASN1_OP_END_SEQ_OF:
396	case ASN1_OP_END_SEQ_ACT:
397	case ASN1_OP_END_SET_OF_ACT:
398	case ASN1_OP_END_SEQ_OF_ACT:
399	if (unlikely(csp <= 0))
400	goto cons_stack_underflow;
401	csp--;
402	tdp = cons_dp_stack[csp];
403	hdr = cons_hdrlen_stack[csp];
404	len = datalen;
405	datalen = cons_datalen_stack[csp];
406	pr_debug("- end cons t=%zu dp=%zu l=%zu/%zu\n",
407	tdp, dp, len, datalen);
408	if (datalen == 0) {
409	/* Indefinite length - check for the EOC. */
410	datalen = len;
411	if (unlikely(datalen - dp < 2))
412	goto data_overrun_error;
413	if (data[dp++] != 0) {
414	if (op & ASN1_OP_END__OF) {
415	dp--;
416	csp++;
417	pc = machine[pc + 1];
418	pr_debug("- continue\n");
419	goto next_op;
420	}
421	goto missing_eoc;
422	}
423	if (data[dp++] != 0)
424	goto invalid_eoc;
425	len = dp - tdp - 2;
426	} else {
427	if (dp < len && (op & ASN1_OP_END__OF)) {
428	datalen = len;
429	csp++;
430	pc = machine[pc + 1];
431	pr_debug("- continue\n");
432	goto next_op;
433	}
434	if (dp != len)
435	goto cons_length_error;
436	len -= tdp;
437	pr_debug("- cons len l=%zu d=%zu\n", len, dp - tdp);
438	}
439
440	if (op & ASN1_OP_END__ACT) {
441	unsigned char act;
442	if (op & ASN1_OP_END__OF)
443	act = machine[pc + 2];
444	else
445	act = machine[pc + 1];
446	ret = actions[act](context, hdr, 0, data + tdp, len);
447	if (ret < 0)
448	return ret;
449	}
450	pc += asn1_op_lengths[op];
451	goto next_op;
452
453	case ASN1_OP_MAYBE_ACT:
454	if (!(flags & FLAG_LAST_MATCHED)) {
455	pc += asn1_op_lengths[op];
456	goto next_op;
457	}
458	/* fall through */
459
460	case ASN1_OP_ACT:
461	ret = actions[machine[pc + 1]](context, hdr, tag, data + tdp, len);
462	if (ret < 0)
463	return ret;
464	pc += asn1_op_lengths[op];
465	goto next_op;
466
467	case ASN1_OP_RETURN:
468	if (unlikely(jsp <= 0))
469	goto jump_stack_underflow;
470	pc = jump_stack[--jsp];
471	flags \|= FLAG_MATCHED \| FLAG_LAST_MATCHED;
472	goto next_op;
473
474	default:
475	break;
476	}
477
478	/* Shouldn't reach here */
479	pr_err("ASN.1 decoder error: Found reserved opcode (%u) pc=%zu\n",
480	op, pc);
481	return -EBADMSG;
482
483	data_overrun_error:
484	errmsg = "Data overrun error";
485	goto error;
486	machine_overrun_error:
487	errmsg = "Machine overrun error";
488	goto error;
489	jump_stack_underflow:
490	errmsg = "Jump stack underflow";
491	goto error;
492	jump_stack_overflow:
493	errmsg = "Jump stack overflow";
494	goto error;
495	cons_stack_underflow:
496	errmsg = "Cons stack underflow";
497	goto error;
498	cons_stack_overflow:
499	errmsg = "Cons stack overflow";
500	goto error;
501	cons_length_error:
502	errmsg = "Cons length error";
503	goto error;
504	missing_eoc:
505	errmsg = "Missing EOC in indefinite len cons";
506	goto error;
507	invalid_eoc:
508	errmsg = "Invalid length EOC";
509	goto error;
510	length_too_long:
511	errmsg = "Unsupported length";
512	goto error;
513	indefinite_len_primitive:
514	errmsg = "Indefinite len primitive not permitted";
515	goto error;
516	tag_mismatch:
517	errmsg = "Unexpected tag";
518	goto error;
519	long_tag_not_supported:
520	errmsg = "Long tag not supported";
521	error:
522	pr_debug("\nASN1: %s [m=%zu d=%zu ot=%02x t=%02x l=%zu]\n",
523	errmsg, pc, dp, optag, tag, len);
524	return -EBADMSG;
525	}
526	EXPORT_SYMBOL_GPL(asn1_ber_decoder);
527
528	MODULE_LICENSE("GPL");