Edit
IABSD.fr/src/lib/libssl/bs_ber.c
jsing
- lib/libssl/bs_ber.c
-
/* $OpenBSD: bs_ber.c,v 1.9 2016/12/03 12:34:35 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 <openssl/opensslconf.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); }