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Diffstat (limited to 'src/der.c')
| -rw-r--r-- | src/der.c | 404 |
1 files changed, 404 insertions, 0 deletions
diff --git a/src/der.c b/src/der.c new file mode 100644 index 0000000..4e22caf --- /dev/null +++ b/src/der.c @@ -0,0 +1,404 @@ +/*- + * Copyright (c) 2016 Christos Zoulas + * All rights reserved. + * + * Redistribution and use in source and binary forms, with or without + * modification, are permitted provided that the following conditions + * are met: + * 1. Redistributions of source code must retain the above copyright + * notice, this list of conditions and the following disclaimer. + * 2. Redistributions in binary form must reproduce the above copyright + * notice, this list of conditions and the following disclaimer in the + * documentation and/or other materials provided with the distribution. + * + * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS + * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED + * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR + * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS + * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR + * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF + * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS + * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN + * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) + * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE + * POSSIBILITY OF SUCH DAMAGE. + */ +/* + * DER (Distinguished Encoding Rules) Parser + * + * Sources: + * https://en.wikipedia.org/wiki/X.690 + * http://fm4dd.com/openssl/certexamples.htm + * http://blog.engelke.com/2014/10/17/parsing-ber-and-der-encoded-asn-1-objects/ + */ +#ifndef TEST_DER +#include "file.h" + +#ifndef lint +FILE_RCSID("@(#)$File: der.c,v 1.12 2017/02/10 18:14:01 christos Exp $") +#endif +#endif + +#include <sys/types.h> + +#include <stdio.h> +#include <fcntl.h> +#include <stdlib.h> +#include <string.h> +#include <ctype.h> + +#ifndef TEST_DER +#include "magic.h" +#include "der.h" +#else +#include <sys/mman.h> +#include <sys/stat.h> +#include <err.h> +#endif + +#define DER_BAD ((uint32_t)-1) + +#define DER_CLASS_UNIVERSAL 0 +#define DER_CLASS_APPLICATION 1 +#define DER_CLASS_CONTEXT 2 +#define DER_CLASS_PRIVATE 3 +#ifdef DEBUG_DER +static const char der_class[] = "UACP"; +#endif + +#define DER_TYPE_PRIMITIVE 0 +#define DER_TYPE_CONSTRUCTED 1 +#ifdef DEBUG_DER +static const char der_type[] = "PC"; +#endif + +#define DER_TAG_EOC 0x00 +#define DER_TAG_BOOLEAN 0x01 +#define DER_TAG_INTEGER 0x02 +#define DER_TAG_BIT STRING 0x03 +#define DER_TAG_OCTET_STRING 0x04 +#define DER_TAG_NULL 0x05 +#define DER_TAG_OBJECT_IDENTIFIER 0x06 +#define DER_TAG_OBJECT_DESCRIPTOR 0x07 +#define DER_TAG_EXTERNAL 0x08 +#define DER_TAG_REAL 0x09 +#define DER_TAG_ENUMERATED 0x0a +#define DER_TAG_EMBEDDED_PDV 0x0b +#define DER_TAG_UTF8_STRING 0x0c +#define DER_TAG_RELATIVE_OID 0x0d +#define DER_TAG_RESERVED_1 0x0e +#define DER_TAG_RESERVED_2 0x0f +#define DER_TAG_SEQUENCE 0x10 +#define DER_TAG_SET 0x11 +#define DER_TAG_NUMERIC_STRING 0x12 +#define DER_TAG_PRINTABLE_STRING 0x13 +#define DER_TAG_T61_STRING 0x14 +#define DER_TAG_VIDEOTEX_STRING 0x15 +#define DER_TAG_IA5_STRING 0x16 +#define DER_TAG_UTCTIME 0x17 +#define DER_TAG_GENERALIZED_TIME 0x18 +#define DER_TAG_GRAPHIC_STRING 0x19 +#define DER_TAG_VISIBLE_STRING 0x1a +#define DER_TAG_GENERAL_STRING 0x1b +#define DER_TAG_UNIVERSAL_STRING 0x1c +#define DER_TAG_CHARACTER_STRING 0x1d +#define DER_TAG_BMP_STRING 0x1e +#define DER_TAG_LONG 0x1f + +static const char *der__tag[] = { + "eoc", "bool", "int", "bit_str", "octet_str", + "null", "obj_id", "obj_desc", "ext", "real", + "enum", "embed", "utf8_str", "oid", "res1", + "res2", "seq", "set", "num_str", "prt_str", + "t61_str", "vid_str", "ia5_str", "utc_time", + "gen_time", "gr_str", "vis_str", "gen_str", + "char_str", "bmp_str", "long" +}; + +#ifdef DEBUG_DER +#define DPRINTF(a) printf a +#else +#define DPRINTF(a) +#endif + +#ifdef TEST_DER +static uint8_t +getclass(uint8_t c) +{ + return c >> 6; +} + +static uint8_t +gettype(uint8_t c) +{ + return (c >> 5) & 1; +} +#endif + +static uint32_t +gettag(const uint8_t *c, size_t *p, size_t l) +{ + uint32_t tag; + + if (*p >= l) + return DER_BAD; + + tag = c[(*p)++] & 0x1f; + + if (tag != 0x1f) + return tag; + + if (*p >= l) + return DER_BAD; + + while (c[*p] >= 0x80) { + tag = tag * 128 + c[(*p)++] - 0x80; + if (*p >= l) + return DER_BAD; + } + return tag; +} + +/* + * Read the length of a DER tag from the input. + * + * `c` is the input, `p` is an output parameter that specifies how much of the + * input we consumed, and `l` is the maximum input length. + * + * Returns the length, or DER_BAD if the end of the input is reached or the + * length exceeds the remaining input. + */ +static uint32_t +getlength(const uint8_t *c, size_t *p, size_t l) +{ + uint8_t digits, i; + size_t len; + int is_onebyte_result; + + if (*p >= l) + return DER_BAD; + + /* + * Digits can either be 0b0 followed by the result, or 0b1 + * followed by the number of digits of the result. In either case, + * we verify that we can read so many bytes from the input. + */ + is_onebyte_result = (c[*p] & 0x80) == 0; + digits = c[(*p)++] & 0x7f; + if (*p + digits >= l) + return DER_BAD; + + if (is_onebyte_result) + return digits; + + /* + * Decode len. We've already verified that we're allowed to read + * `digits` bytes. + */ + len = 0; + for (i = 0; i < digits; i++) + len = (len << 8) | c[(*p)++]; + + if (*p + len >= l) + return DER_BAD; + return CAST(uint32_t, len); +} + +static const char * +der_tag(char *buf, size_t len, uint32_t tag) +{ + if (tag < DER_TAG_LONG) + strlcpy(buf, der__tag[tag], len); + else + snprintf(buf, len, "%#x", tag); + return buf; +} + +#ifndef TEST_DER +static int +der_data(char *buf, size_t blen, uint32_t tag, const void *q, uint32_t len) +{ + const uint8_t *d = CAST(const uint8_t *, q); + switch (tag) { + case DER_TAG_PRINTABLE_STRING: + case DER_TAG_UTF8_STRING: + case DER_TAG_IA5_STRING: + case DER_TAG_UTCTIME: + return snprintf(buf, blen, "%.*s", len, (const char *)q); + default: + break; + } + + for (uint32_t i = 0; i < len; i++) { + uint32_t z = i << 1; + if (z < blen - 2) + snprintf(buf + z, blen - z, "%.2x", d[i]); + } + return len * 2; +} + +int32_t +der_offs(struct magic_set *ms, struct magic *m, size_t nbytes) +{ + const uint8_t *b = RCAST(const uint8_t *, ms->search.s); + size_t offs = 0, len = ms->search.s_len ? ms->search.s_len : nbytes; + + if (gettag(b, &offs, len) == DER_BAD) + return -1; + DPRINTF(("%s1: %d %zu %u\n", __func__, ms->offset, offs, m->offset)); + + uint32_t tlen = getlength(b, &offs, len); + if (tlen == DER_BAD) + return -1; + DPRINTF(("%s2: %d %zu %u\n", __func__, ms->offset, offs, tlen)); + + offs += ms->offset + m->offset; + DPRINTF(("cont_level = %d\n", m->cont_level)); +#ifdef DEBUG_DER + for (size_t i = 0; i < m->cont_level; i++) + printf("cont_level[%zu] = %u\n", i, ms->c.li[i].off); +#endif + if (m->cont_level != 0) { + if (offs + tlen > nbytes) + return -1; + ms->c.li[m->cont_level - 1].off = CAST(int, offs + tlen); + DPRINTF(("cont_level[%u] = %u\n", m->cont_level - 1, + ms->c.li[m->cont_level - 1].off)); + } + return CAST(int32_t, offs); +} + +int +der_cmp(struct magic_set *ms, struct magic *m) +{ + const uint8_t *b = RCAST(const uint8_t *, ms->search.s); + const char *s = m->value.s; + size_t offs = 0, len = ms->search.s_len; + uint32_t tag, tlen; + char buf[128]; + + tag = gettag(b, &offs, len); + if (tag == DER_BAD) + return -1; + + tlen = getlength(b, &offs, len); + if (tlen == DER_BAD) + return -1; + + der_tag(buf, sizeof(buf), tag); + if ((ms->flags & MAGIC_DEBUG) != 0) + fprintf(stderr, "%s: tag %p got=%s exp=%s\n", __func__, b, + buf, s); + size_t slen = strlen(buf); + + if (strncmp(buf, s, slen) != 0) + return 0; + + s += slen; + +again: + switch (*s) { + case '\0': + return 1; + case '=': + s++; + goto val; + default: + if (!isdigit((unsigned char)*s)) + return 0; + + slen = 0; + do + slen = slen * 10 + *s - '0'; + while (isdigit((unsigned char)*++s)); + if ((ms->flags & MAGIC_DEBUG) != 0) + fprintf(stderr, "%s: len %zu %u\n", __func__, + slen, tlen); + if (tlen != slen) + return 0; + goto again; + } +val: + DPRINTF(("%s: before data %zu %u\n", __func__, offs, tlen)); + der_data(buf, sizeof(buf), tag, b + offs, tlen); + if ((ms->flags & MAGIC_DEBUG) != 0) + fprintf(stderr, "%s: data %s %s\n", __func__, buf, s); + if (strcmp(buf, s) != 0 && strcmp("x", s) != 0) + return 0; + strlcpy(ms->ms_value.s, buf, sizeof(ms->ms_value.s)); + return 1; +} +#endif + +#ifdef TEST_DER +static void +printtag(uint32_t tag, const void *q, uint32_t len) +{ + const uint8_t *d = q; + switch (tag) { + case DER_TAG_PRINTABLE_STRING: + case DER_TAG_UTF8_STRING: + printf("%.*s\n", len, (const char *)q); + return; + default: + break; + } + + for (uint32_t i = 0; i < len; i++) + printf("%.2x", d[i]); + printf("\n"); +} + +static void +printdata(size_t level, const void *v, size_t x, size_t l) +{ + const uint8_t *p = v, *ep = p + l; + size_t ox; + char buf[128]; + + while (p + x < ep) { + const uint8_t *q; + uint8_t c = getclass(p[x]); + uint8_t t = gettype(p[x]); + ox = x; + if (x != 0) + printf("%.2x %.2x %.2x\n", p[x - 1], p[x], p[x + 1]); + uint32_t tag = gettag(p, &x, ep - p + x); + if (p + x >= ep) + break; + uint32_t len = getlength(p, &x, ep - p + x); + + printf("%zu %zu-%zu %c,%c,%s,%u:", level, ox, x, + der_class[c], der_type[t], + der_tag(buf, sizeof(buf), tag), len); + q = p + x; + if (p + len > ep) + errx(EXIT_FAILURE, "corrupt der"); + printtag(tag, q, len); + if (t != DER_TYPE_PRIMITIVE) + printdata(level + 1, p, x, len + x); + x += len; + } +} + +int +main(int argc, char *argv[]) +{ + int fd; + struct stat st; + size_t l; + void *p; + + if ((fd = open(argv[1], O_RDONLY)) == -1) + err(EXIT_FAILURE, "open `%s'", argv[1]); + if (fstat(fd, &st) == -1) + err(EXIT_FAILURE, "stat `%s'", argv[1]); + l = (size_t)st.st_size; + if ((p = mmap(NULL, l, PROT_READ, MAP_FILE, fd, 0)) == MAP_FAILED) + err(EXIT_FAILURE, "mmap `%s'", argv[1]); + + printdata(0, p, 0, l); + munmap(p, l); + return 0; +} +#endif |