Initial import

1 files changed, 487 insertions, 0 deletions

diff --git a/lib/asn1_decoder.c b/lib/asn1_decoder.c
new file mode 100644
index 000000000..1a000bb05
--- /dev/null
+++ b/lib/asn1_decoder.c
@@ -0,0 +1,487 @@
+/* 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/asn1_decoder.h>
+#include <linux/asn1_ber_bytecode.h>
+
+static const unsigned char asn1_op_lengths[ASN1_OP__NR] = {
+	/*					OPC TAG JMP ACT */
+	[ASN1_OP_MATCH]				= 1 + 1,
+	[ASN1_OP_MATCH_OR_SKIP]			= 1 + 1,
+	[ASN1_OP_MATCH_ACT]			= 1 + 1     + 1,
+	[ASN1_OP_MATCH_ACT_OR_SKIP]		= 1 + 1     + 1,
+	[ASN1_OP_MATCH_JUMP]			= 1 + 1 + 1,
+	[ASN1_OP_MATCH_JUMP_OR_SKIP]		= 1 + 1 + 1,
+	[ASN1_OP_MATCH_ANY]			= 1,
+	[ASN1_OP_MATCH_ANY_ACT]			= 1         + 1,
+	[ASN1_OP_COND_MATCH_OR_SKIP]		= 1 + 1,
+	[ASN1_OP_COND_MATCH_ACT_OR_SKIP]	= 1 + 1     + 1,
+	[ASN1_OP_COND_MATCH_JUMP_OR_SKIP]	= 1 + 1 + 1,
+	[ASN1_OP_COND_MATCH_ANY]		= 1,
+	[ASN1_OP_COND_MATCH_ANY_ACT]		= 1         + 1,
+	[ASN1_OP_COND_FAIL]			= 1,
+	[ASN1_OP_COMPLETE]			= 1,
+	[ASN1_OP_ACT]				= 1         + 1,
+	[ASN1_OP_RETURN]			= 1,
+	[ASN1_OP_END_SEQ]			= 1,
+	[ASN1_OP_END_SEQ_OF]			= 1     + 1,
+	[ASN1_OP_END_SET]			= 1,
+	[ASN1_OP_END_SET_OF]			= 1     + 1,
+	[ASN1_OP_END_SEQ_ACT]			= 1         + 1,
+	[ASN1_OP_END_SEQ_OF_ACT]		= 1     + 1 + 1,
+	[ASN1_OP_END_SET_ACT]			= 1         + 1,
+	[ASN1_OP_END_SET_OF_ACT]		= 1     + 1 + 1,
+};
+
+/*
+ * Find the length of an indefinite length object
+ * @data: The data buffer
+ * @datalen: The end of the innermost containing element in the buffer
+ * @_dp: The data parse cursor (updated before returning)
+ * @_len: Where to return the size of the element.
+ * @_errmsg: Where to return a pointer to an error message on error
+ */
+static int asn1_find_indefinite_length(const unsigned char *data, size_t datalen,
+				       size_t *_dp, size_t *_len,
+				       const char **_errmsg)
+{
+	unsigned char tag, tmp;
+	size_t dp = *_dp, len, n;
+	int indef_level = 1;
+
+next_tag:
+	if (unlikely(datalen - dp < 2)) {
+		if (datalen == dp)
+			goto missing_eoc;
+		goto data_overrun_error;
+	}
+
+	/* Extract a tag from the data */
+	tag = data[dp++];
+	if (tag == 0) {
+		/* It appears to be an EOC. */
+		if (data[dp++] != 0)
+			goto invalid_eoc;
+		if (--indef_level <= 0) {
+			*_len = dp - *_dp;
+			*_dp = dp;
+			return 0;
+		}
+		goto next_tag;
+	}
+
+	if (unlikely((tag & 0x1f) == ASN1_LONG_TAG)) {
+		do {
+			if (unlikely(datalen - dp < 2))
+				goto data_overrun_error;
+			tmp = data[dp++];
+		} while (tmp & 0x80);
+	}
+
+	/* Extract the length */
+	len = data[dp++];
+	if (len <= 0x7f) {
+		dp += len;
+		goto next_tag;
+	}
+
+	if (unlikely(len == ASN1_INDEFINITE_LENGTH)) {
+		/* Indefinite length */
+		if (unlikely((tag & ASN1_CONS_BIT) == ASN1_PRIM << 5))
+			goto indefinite_len_primitive;
+		indef_level++;
+		goto next_tag;
+	}
+
+	n = len - 0x80;
+	if (unlikely(n > sizeof(size_t) - 1))
+		goto length_too_long;
+	if (unlikely(n > datalen - dp))
+		goto data_overrun_error;
+	for (len = 0; n > 0; n--) {
+		len <<= 8;
+		len |= data[dp++];
+	}
+	dp += len;
+	goto next_tag;
+
+length_too_long:
+	*_errmsg = "Unsupported length";
+	goto error;
+indefinite_len_primitive:
+	*_errmsg = "Indefinite len primitive not permitted";
+	goto error;
+invalid_eoc:
+	*_errmsg = "Invalid length EOC";
+	goto error;
+data_overrun_error:
+	*_errmsg = "Data overrun error";
+	goto error;
+missing_eoc:
+	*_errmsg = "Missing EOC in indefinite len cons";
+error:
+	*_dp = dp;
+	return -1;
+}
+
+/**
+ * asn1_ber_decoder - Decoder BER/DER/CER ASN.1 according to pattern
+ * @decoder: The decoder definition (produced by asn1_compiler)
+ * @context: The caller's context (to be passed to the action functions)
+ * @data: The encoded data
+ * @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_CONS		0x20 /* Corresponds to CONS bit in the opcode tag
+				      * - ie. whether or not we are going to parse
+				      *   a compound type.
+				      */
+
+#define NR_CONS_STACK 10
+	unsigned short cons_dp_stack[NR_CONS_STACK];
+	unsigned short cons_datalen_stack[NR_CONS_STACK];
+	unsigned char cons_hdrlen_stack[NR_CONS_STACK];
+#define NR_JUMP_STACK 10
+	unsigned char jump_stack[NR_JUMP_STACK];
+
+	if (datalen > 65535)
+		return -EMSGSIZE;
+
+next_op:
+	pr_debug("next_op: pc=\e[32m%zu\e[m/%zu dp=\e[33m%zu\e[m/%zu C=%d J=%d\n",
+		 pc, machlen, dp, datalen, csp, jsp);
+	if (unlikely(pc >= machlen))
+		goto machine_overrun_error;
+	op = machine[pc];
+	if (unlikely(pc + asn1_op_lengths[op] > machlen))
+		goto machine_overrun_error;
+
+	/* If this command is meant to match a tag, then do that before
+	 * evaluating the command.
+	 */
+	if (op <= ASN1_OP__MATCHES_TAG) {
+		unsigned char tmp;
+
+		/* Skip conditional matches if possible */
+		if ((op & ASN1_OP_MATCH__COND &&
+		     flags & FLAG_MATCHED) ||
+		    dp == datalen) {
+			pc += asn1_op_lengths[op];
+			goto next_op;
+		}
+
+		flags = 0;
+		hdr = 2;
+
+		/* Extract a tag from the data */
+		if (unlikely(dp >= datalen - 1))
+			goto data_overrun_error;
+		tag = data[dp++];
+		if (unlikely((tag & 0x1f) == ASN1_LONG_TAG))
+			goto long_tag_not_supported;
+
+		if (op & ASN1_OP_MATCH__ANY) {
+			pr_debug("- any %02x\n", tag);
+		} else {
+			/* Extract the tag from the machine
+			 * - Either CONS or PRIM are permitted in the data if
+			 *   CONS is not set in the op stream, otherwise CONS
+			 *   is mandatory.
+			 */
+			optag = machine[pc + 1];
+			flags |= optag & FLAG_CONS;
+
+			/* Determine whether the tag matched */
+			tmp = optag ^ tag;
+			tmp &= ~(optag & ASN1_CONS_BIT);
+			pr_debug("- match? %02x %02x %02x\n", tag, optag, tmp);
+			if (tmp != 0) {
+				/* All odd-numbered tags are MATCH_OR_SKIP. */
+				if (op & ASN1_OP_MATCH__SKIP) {
+					pc += asn1_op_lengths[op];
+					dp--;
+					goto next_op;
+				}
+				goto tag_mismatch;
+			}
+		}
+		flags |= FLAG_MATCHED;
+
+		len = data[dp++];
+		if (len > 0x7f) {
+			if (unlikely(len == ASN1_INDEFINITE_LENGTH)) {
+				/* Indefinite length */
+				if (unlikely(!(tag & ASN1_CONS_BIT)))
+					goto indefinite_len_primitive;
+				flags |= FLAG_INDEFINITE_LENGTH;
+				if (unlikely(2 > datalen - dp))
+					goto data_overrun_error;
+			} else {
+				int n = len - 0x80;
+				if (unlikely(n > 2))
+					goto length_too_long;
+				if (unlikely(dp >= datalen - n))
+					goto data_overrun_error;
+				hdr += n;
+				for (len = 0; n > 0; n--) {
+					len <<= 8;
+					len |= data[dp++];
+				}
+				if (unlikely(len > datalen - dp))
+					goto data_overrun_error;
+			}
+		}
+
+		if (flags & FLAG_CONS) {
+			/* For expected compound forms, we stack the positions
+			 * of the start and end of the data.
+			 */
+			if (unlikely(csp >= NR_CONS_STACK))
+				goto cons_stack_overflow;
+			cons_dp_stack[csp] = dp;
+			cons_hdrlen_stack[csp] = hdr;
+			if (!(flags & FLAG_INDEFINITE_LENGTH)) {
+				cons_datalen_stack[csp] = datalen;
+				datalen = dp + len;
+			} else {
+				cons_datalen_stack[csp] = 0;
+			}
+			csp++;
+		}
+
+		pr_debug("- TAG: %02x %zu%s\n",
+			 tag, len, flags & FLAG_CONS ? " CONS" : "");
+		tdp = dp;
+	}
+
+	/* Decide how to handle the operation */
+	switch (op) {
+	case ASN1_OP_MATCH_ANY_ACT:
+	case ASN1_OP_COND_MATCH_ANY_ACT:
+		ret = actions[machine[pc + 1]](context, hdr, tag, data + dp, len);
+		if (ret < 0)
+			return ret;
+		goto skip_data;
+
+	case ASN1_OP_MATCH_ACT:
+	case ASN1_OP_MATCH_ACT_OR_SKIP:
+	case ASN1_OP_COND_MATCH_ACT_OR_SKIP:
+		ret = actions[machine[pc + 2]](context, hdr, tag, data + dp, len);
+		if (ret < 0)
+			return ret;
+		goto skip_data;
+
+	case ASN1_OP_MATCH:
+	case ASN1_OP_MATCH_OR_SKIP:
+	case ASN1_OP_MATCH_ANY:
+	case ASN1_OP_COND_MATCH_OR_SKIP:
+	case ASN1_OP_COND_MATCH_ANY:
+	skip_data:
+		if (!(flags & FLAG_CONS)) {
+			if (flags & FLAG_INDEFINITE_LENGTH) {
+				ret = asn1_find_indefinite_length(
+					data, datalen, &dp, &len, &errmsg);
+				if (ret < 0)
+					goto error;
+			} else {
+				dp += len;
+			}
+			pr_debug("- LEAF: %zu\n", len);
+		}
+		pc += asn1_op_lengths[op];
+		goto next_op;
+
+	case ASN1_OP_MATCH_JUMP:
+	case ASN1_OP_MATCH_JUMP_OR_SKIP:
+	case ASN1_OP_COND_MATCH_JUMP_OR_SKIP:
+		pr_debug("- MATCH_JUMP\n");
+		if (unlikely(jsp == NR_JUMP_STACK))
+			goto jump_stack_overflow;
+		jump_stack[jsp++] = pc + asn1_op_lengths[op];
+		pc = machine[pc + 2];
+		goto next_op;
+
+	case ASN1_OP_COND_FAIL:
+		if (unlikely(!(flags & FLAG_MATCHED)))
+			goto tag_mismatch;
+		pc += asn1_op_lengths[op];
+		goto next_op;
+
+	case ASN1_OP_COMPLETE:
+		if (unlikely(jsp != 0 || csp != 0)) {
+			pr_err("ASN.1 decoder error: Stacks not empty at completion (%u, %u)\n",
+			       jsp, csp);
+			return -EBADMSG;
+		}
+		return 0;
+
+	case ASN1_OP_END_SET:
+	case ASN1_OP_END_SET_ACT:
+		if (unlikely(!(flags & FLAG_MATCHED)))
+			goto tag_mismatch;
+	case ASN1_OP_END_SEQ:
+	case ASN1_OP_END_SET_OF:
+	case ASN1_OP_END_SEQ_OF:
+	case ASN1_OP_END_SEQ_ACT:
+	case ASN1_OP_END_SET_OF_ACT:
+	case ASN1_OP_END_SEQ_OF_ACT:
+		if (unlikely(csp <= 0))
+			goto cons_stack_underflow;
+		csp--;
+		tdp = cons_dp_stack[csp];
+		hdr = cons_hdrlen_stack[csp];
+		len = datalen;
+		datalen = cons_datalen_stack[csp];
+		pr_debug("- end cons t=%zu dp=%zu l=%zu/%zu\n",
+			 tdp, dp, len, datalen);
+		if (datalen == 0) {
+			/* Indefinite length - check for the EOC. */
+			datalen = len;
+			if (unlikely(datalen - dp < 2))
+				goto data_overrun_error;
+			if (data[dp++] != 0) {
+				if (op & ASN1_OP_END__OF) {
+					dp--;
+					csp++;
+					pc = machine[pc + 1];
+					pr_debug("- continue\n");
+					goto next_op;
+				}
+				goto missing_eoc;
+			}
+			if (data[dp++] != 0)
+				goto invalid_eoc;
+			len = dp - tdp - 2;
+		} else {
+			if (dp < len && (op & ASN1_OP_END__OF)) {
+				datalen = len;
+				csp++;
+				pc = machine[pc + 1];
+				pr_debug("- continue\n");
+				goto next_op;
+			}
+			if (dp != len)
+				goto cons_length_error;
+			len -= tdp;
+			pr_debug("- cons len l=%zu d=%zu\n", len, dp - tdp);
+		}
+
+		if (op & ASN1_OP_END__ACT) {
+			unsigned char act;
+			if (op & ASN1_OP_END__OF)
+				act = machine[pc + 2];
+			else
+				act = machine[pc + 1];
+			ret = actions[act](context, hdr, 0, data + tdp, len);
+		}
+		pc += asn1_op_lengths[op];
+		goto next_op;
+
+	case ASN1_OP_ACT:
+		ret = actions[machine[pc + 1]](context, hdr, tag, data + tdp, len);
+		pc += asn1_op_lengths[op];
+		goto next_op;
+
+	case ASN1_OP_RETURN:
+		if (unlikely(jsp <= 0))
+			goto jump_stack_underflow;
+		pc = jump_stack[--jsp];
+		goto next_op;
+
+	default:
+		break;
+	}
+
+	/* Shouldn't reach here */
+	pr_err("ASN.1 decoder error: Found reserved opcode (%u)\n", op);
+	return -EBADMSG;
+
+data_overrun_error:
+	errmsg = "Data overrun error";
+	goto error;
+machine_overrun_error:
+	errmsg = "Machine overrun error";
+	goto error;
+jump_stack_underflow:
+	errmsg = "Jump stack underflow";
+	goto error;
+jump_stack_overflow:
+	errmsg = "Jump stack overflow";
+	goto error;
+cons_stack_underflow:
+	errmsg = "Cons stack underflow";
+	goto error;
+cons_stack_overflow:
+	errmsg = "Cons stack overflow";
+	goto error;
+cons_length_error:
+	errmsg = "Cons length error";
+	goto error;
+missing_eoc:
+	errmsg = "Missing EOC in indefinite len cons";
+	goto error;
+invalid_eoc:
+	errmsg = "Invalid length EOC";
+	goto error;
+length_too_long:
+	errmsg = "Unsupported length";
+	goto error;
+indefinite_len_primitive:
+	errmsg = "Indefinite len primitive not permitted";
+	goto error;
+tag_mismatch:
+	errmsg = "Unexpected tag";
+	goto error;
+long_tag_not_supported:
+	errmsg = "Long tag not supported";
+error:
+	pr_debug("\nASN1: %s [m=%zu d=%zu ot=%02x t=%02x l=%zu]\n",
+		 errmsg, pc, dp, optag, tag, len);
+	return -EBADMSG;
+}
+EXPORT_SYMBOL_GPL(asn1_ber_decoder);