269 lines
7.2 KiB
C
Executable file
269 lines
7.2 KiB
C
Executable file
/* $OpenBSD: bs_ber.c,v 1.11 2021/05/16 10:58:27 jsing Exp $ */
|
|
/*
|
|
* Copyright (c) 2014, Google Inc.
|
|
*
|
|
* Permission to use, copy, modify, and/or distribute this software for any
|
|
* purpose with or without fee is hereby granted, provided that the above
|
|
* copyright notice and this permission notice appear in all copies.
|
|
*
|
|
* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
|
|
* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
|
|
* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
|
|
* SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
|
|
* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION
|
|
* OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
|
|
* CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
|
|
*/
|
|
|
|
#include <string.h>
|
|
|
|
#include "bytestring.h"
|
|
|
|
/*
|
|
* kMaxDepth is a just a sanity limit. The code should be such that the length
|
|
* of the input being processes always decreases. None the less, a very large
|
|
* input could otherwise cause the stack to overflow.
|
|
*/
|
|
static const unsigned int kMaxDepth = 2048;
|
|
|
|
/* Non-strict version that allows a relaxed DER with indefinite form. */
|
|
static int
|
|
cbs_nonstrict_get_any_asn1_element(CBS *cbs, CBS *out, unsigned int *out_tag,
|
|
size_t *out_header_len)
|
|
{
|
|
return cbs_get_any_asn1_element_internal(cbs, out,
|
|
out_tag, out_header_len, 0);
|
|
}
|
|
|
|
/*
|
|
* cbs_find_indefinite walks an ASN.1 structure in |orig_in| and sets
|
|
* |*indefinite_found| depending on whether an indefinite length element was
|
|
* found. The value of |orig_in| is not modified.
|
|
*
|
|
* Returns one on success (i.e. |*indefinite_found| was set) and zero on error.
|
|
*/
|
|
static int
|
|
cbs_find_indefinite(const CBS *orig_in, char *indefinite_found,
|
|
unsigned int depth)
|
|
{
|
|
CBS in;
|
|
|
|
if (depth > kMaxDepth)
|
|
return 0;
|
|
|
|
CBS_init(&in, CBS_data(orig_in), CBS_len(orig_in));
|
|
|
|
while (CBS_len(&in) > 0) {
|
|
CBS contents;
|
|
unsigned int tag;
|
|
size_t header_len;
|
|
|
|
if (!cbs_nonstrict_get_any_asn1_element(&in, &contents, &tag,
|
|
&header_len))
|
|
return 0;
|
|
|
|
/* Indefinite form not allowed by DER. */
|
|
if (CBS_len(&contents) == header_len && header_len > 0 &&
|
|
CBS_data(&contents)[header_len - 1] == 0x80) {
|
|
*indefinite_found = 1;
|
|
return 1;
|
|
}
|
|
if (tag & CBS_ASN1_CONSTRUCTED) {
|
|
if (!CBS_skip(&contents, header_len) ||
|
|
!cbs_find_indefinite(&contents, indefinite_found,
|
|
depth + 1))
|
|
return 0;
|
|
}
|
|
}
|
|
|
|
*indefinite_found = 0;
|
|
return 1;
|
|
}
|
|
|
|
/*
|
|
* is_primitive_type returns true if |tag| likely a primitive type. Normally
|
|
* one can just test the "constructed" bit in the tag but, in BER, even
|
|
* primitive tags can have the constructed bit if they have indefinite
|
|
* length.
|
|
*/
|
|
static char
|
|
is_primitive_type(unsigned int tag)
|
|
{
|
|
return (tag & 0xc0) == 0 &&
|
|
(tag & 0x1f) != (CBS_ASN1_SEQUENCE & 0x1f) &&
|
|
(tag & 0x1f) != (CBS_ASN1_SET & 0x1f);
|
|
}
|
|
|
|
/*
|
|
* is_eoc returns true if |header_len| and |contents|, as returned by
|
|
* |cbs_nonstrict_get_any_asn1_element|, indicate an "end of contents" (EOC)
|
|
* value.
|
|
*/
|
|
static char
|
|
is_eoc(size_t header_len, CBS *contents)
|
|
{
|
|
const unsigned char eoc[] = {0x0, 0x0};
|
|
|
|
return header_len == 2 && CBS_mem_equal(contents, eoc, 2);
|
|
}
|
|
|
|
/*
|
|
* cbs_convert_indefinite reads data with DER encoding (but relaxed to allow
|
|
* indefinite form) from |in| and writes definite form DER data to |out|. If
|
|
* |squash_header| is set then the top-level of elements from |in| will not
|
|
* have their headers written. This is used when concatenating the fragments of
|
|
* an indefinite length, primitive value. If |looking_for_eoc| is set then any
|
|
* EOC elements found will cause the function to return after consuming it.
|
|
* It returns one on success and zero on error.
|
|
*/
|
|
static int
|
|
cbs_convert_indefinite(CBS *in, CBB *out, char squash_header,
|
|
char looking_for_eoc, unsigned int depth)
|
|
{
|
|
if (depth > kMaxDepth)
|
|
return 0;
|
|
|
|
while (CBS_len(in) > 0) {
|
|
CBS contents;
|
|
unsigned int tag;
|
|
size_t header_len;
|
|
CBB *out_contents, out_contents_storage;
|
|
|
|
if (!cbs_nonstrict_get_any_asn1_element(in, &contents, &tag,
|
|
&header_len))
|
|
return 0;
|
|
|
|
out_contents = out;
|
|
|
|
if (CBS_len(&contents) == header_len) {
|
|
if (is_eoc(header_len, &contents))
|
|
return looking_for_eoc;
|
|
|
|
if (header_len > 0 &&
|
|
CBS_data(&contents)[header_len - 1] == 0x80) {
|
|
/*
|
|
* This is an indefinite length element. If
|
|
* it's a SEQUENCE or SET then we just need to
|
|
* write the out the contents as normal, but
|
|
* with a concrete length prefix.
|
|
*
|
|
* If it's a something else then the contents
|
|
* will be a series of DER elements of the same
|
|
* type which need to be concatenated.
|
|
*/
|
|
const char context_specific = (tag & 0xc0)
|
|
== 0x80;
|
|
char squash_child_headers =
|
|
is_primitive_type(tag);
|
|
|
|
/*
|
|
* This is a hack, but it sufficies to handle
|
|
* NSS's output. If we find an indefinite
|
|
* length, context-specific tag with a definite,
|
|
* primtive tag inside it, then we assume that
|
|
* the context-specific tag is implicit and the
|
|
* tags within are fragments of a primitive type
|
|
* that need to be concatenated.
|
|
*/
|
|
if (context_specific &&
|
|
(tag & CBS_ASN1_CONSTRUCTED)) {
|
|
CBS in_copy, inner_contents;
|
|
unsigned int inner_tag;
|
|
size_t inner_header_len;
|
|
|
|
CBS_init(&in_copy, CBS_data(in),
|
|
CBS_len(in));
|
|
if (!cbs_nonstrict_get_any_asn1_element(
|
|
&in_copy, &inner_contents,
|
|
&inner_tag, &inner_header_len))
|
|
return 0;
|
|
|
|
if (CBS_len(&inner_contents) >
|
|
inner_header_len &&
|
|
is_primitive_type(inner_tag))
|
|
squash_child_headers = 1;
|
|
}
|
|
|
|
if (!squash_header) {
|
|
unsigned int out_tag = tag;
|
|
|
|
if (squash_child_headers)
|
|
out_tag &=
|
|
~CBS_ASN1_CONSTRUCTED;
|
|
|
|
if (!CBB_add_asn1(out,
|
|
&out_contents_storage, out_tag))
|
|
return 0;
|
|
|
|
out_contents = &out_contents_storage;
|
|
}
|
|
|
|
if (!cbs_convert_indefinite(in, out_contents,
|
|
squash_child_headers,
|
|
1 /* looking for eoc */, depth + 1))
|
|
return 0;
|
|
|
|
if (out_contents != out && !CBB_flush(out))
|
|
return 0;
|
|
|
|
continue;
|
|
}
|
|
}
|
|
|
|
if (!squash_header) {
|
|
if (!CBB_add_asn1(out, &out_contents_storage, tag))
|
|
return 0;
|
|
|
|
out_contents = &out_contents_storage;
|
|
}
|
|
|
|
if (!CBS_skip(&contents, header_len))
|
|
return 0;
|
|
|
|
if (tag & CBS_ASN1_CONSTRUCTED) {
|
|
if (!cbs_convert_indefinite(&contents, out_contents,
|
|
0 /* don't squash header */,
|
|
0 /* not looking for eoc */, depth + 1))
|
|
return 0;
|
|
} else {
|
|
if (!CBB_add_bytes(out_contents, CBS_data(&contents),
|
|
CBS_len(&contents)))
|
|
return 0;
|
|
}
|
|
|
|
if (out_contents != out && !CBB_flush(out))
|
|
return 0;
|
|
}
|
|
|
|
return looking_for_eoc == 0;
|
|
}
|
|
|
|
int
|
|
CBS_asn1_indefinite_to_definite(CBS *in, uint8_t **out, size_t *out_len)
|
|
{
|
|
CBB cbb;
|
|
|
|
/*
|
|
* First, do a quick walk to find any indefinite-length elements. Most
|
|
* of the time we hope that there aren't any and thus we can quickly
|
|
* return.
|
|
*/
|
|
char conversion_needed;
|
|
if (!cbs_find_indefinite(in, &conversion_needed, 0))
|
|
return 0;
|
|
|
|
if (!conversion_needed) {
|
|
*out = NULL;
|
|
*out_len = 0;
|
|
return 1;
|
|
}
|
|
|
|
if (!CBB_init(&cbb, CBS_len(in)))
|
|
return 0;
|
|
if (!cbs_convert_indefinite(in, &cbb, 0, 0, 0)) {
|
|
CBB_cleanup(&cbb);
|
|
return 0;
|
|
}
|
|
|
|
return CBB_finish(&cbb, out, out_len);
|
|
}
|