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-rw-r--r--lib/asn1_decoder.c487
1 files changed, 487 insertions, 0 deletions
diff --git a/lib/asn1_decoder.c b/lib/asn1_decoder.c
new file mode 100644
index 0000000..de2c8b5
--- /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) == 0x1f)) {
+ 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 == 0x80)) {
+ /* 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
+ * @datasize: 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) == 0x1f))
+ 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 == 0x80)) {
+ /* 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);
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