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+/*-
+ * 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 1.27 2022/09/24 20:30:13 christos Exp $")
+#endif
+#else
+#define SIZE_T_FORMAT "z"
+#define CAST(a, b) ((a)(b))
+#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 CAST(uint32_t, -1)
+
+#define DER_CLASS_UNIVERSAL 0
+#define DER_CLASS_APPLICATION 1
+#define DER_CLASS_CONTEXT 2
+#define DER_CLASS_PRIVATE 3
+#if defined(DEBUG_DER) || defined(TEST_DER)
+static const char der_class[] = "UACP";
+#endif
+
+#define DER_TYPE_PRIMITIVE 0
+#define DER_TYPE_CONSTRUCTED 1
+#if defined(DEBUG_DER) || defined(TEST_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_TIME 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_DATE 0x1f
+#define DER_TAG_TIME_OF_DAY 0x20
+#define DER_TAG_DATE_TIME 0x21
+#define DER_TAG_DURATION 0x22
+#define DER_TAG_OID_IRI 0x23
+#define DER_TAG_RELATIVE_OID_IRI 0x24
+#define DER_TAG_LAST 0x25
+
+static const char *der__tag[] = {
+ "eoc", "bool", "int", "bit_str", "octet_str",
+ "null", "obj_id", "obj_desc", "ext", "real",
+ "enum", "embed", "utf8_str", "rel_oid", "time",
+ "res2", "seq", "set", "num_str", "prt_str",
+ "t61_str", "vid_str", "ia5_str", "utc_time", "gen_time",
+ "gr_str", "vis_str", "gen_str", "univ_str", "char_str",
+ "bmp_str", "date", "tod", "datetime", "duration",
+ "oid-iri", "rel-oid-iri",
+};
+
+#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) {
+ DPRINTF(("%s:[1] %zu >= %zu\n", __func__, *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) {
+ DPRINTF(("%s:[2] %zu + %u >= %zu\n", __func__, *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 (len > UINT32_MAX - *p || *p + len > l) {
+ DPRINTF(("%s:[3] bad len %zu + %zu >= %zu\n",
+ __func__, *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_LAST)
+ 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)
+{
+ uint32_t i;
+ 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:
+ return snprintf(buf, blen, "%.*s", len, RCAST(const char *, q));
+ case DER_TAG_UTCTIME:
+ if (len < 12)
+ break;
+ return snprintf(buf, blen,
+ "20%c%c-%c%c-%c%c %c%c:%c%c:%c%c GMT", d[0], d[1], d[2],
+ d[3], d[4], d[5], d[6], d[7], d[8], d[9], d[10], d[11]);
+ default:
+ break;
+ }
+
+ for (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) {
+ DPRINTF(("%s: bad tag 1\n", __func__));
+ return -1;
+ }
+ DPRINTF(("%s1: %u %" SIZE_T_FORMAT "u %d\n", __func__, ms->offset,
+ offs, m->offset));
+
+ uint32_t tlen = getlength(b, &offs, len);
+ if (tlen == DER_BAD) {
+ DPRINTF(("%s: bad tag 2\n", __func__));
+ return -1;
+ }
+ DPRINTF(("%s2: %u %" SIZE_T_FORMAT "u %u\n", __func__, ms->offset,
+ offs, tlen));
+
+ offs += ms->offset + m->offset;
+ DPRINTF(("cont_level = %d\n", m->cont_level));
+#ifdef DEBUG_DER
+ size_t i;
+ for (i = 0; i < m->cont_level; i++)
+ printf("cont_level[%" SIZE_T_FORMAT "u] = %d\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] = %d\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];
+
+ DPRINTF(("%s: compare %zu bytes\n", __func__, len));
+
+ tag = gettag(b, &offs, len);
+ if (tag == DER_BAD) {
+ DPRINTF(("%s: bad tag 1\n", __func__));
+ return -1;
+ }
+
+ DPRINTF(("%s1: %d %" SIZE_T_FORMAT "u %d\n", __func__, ms->offset,
+ offs, m->offset));
+
+ tlen = getlength(b, &offs, len);
+ if (tlen == DER_BAD) {
+ DPRINTF(("%s: bad tag 2\n", __func__));
+ 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) {
+ DPRINTF(("%s: no string match %s != %s\n", __func__, buf, s));
+ return 0;
+ }
+
+ s += slen;
+
+again:
+ switch (*s) {
+ case '\0':
+ DPRINTF(("%s: EOF match\n", __func__));
+ return 1;
+ case '=':
+ s++;
+ goto val;
+ default:
+ if (!isdigit(CAST(unsigned char, *s))) {
+ DPRINTF(("%s: no digit %c\n", __func__, *s));
+ return 0;
+ }
+
+ slen = 0;
+ do
+ slen = slen * 10 + *s - '0';
+ while (isdigit(CAST(unsigned char, *++s)));
+ if ((ms->flags & MAGIC_DEBUG) != 0)
+ fprintf(stderr, "%s: len %" SIZE_T_FORMAT "u %u\n",
+ __func__, slen, tlen);
+ if (tlen != slen) {
+ DPRINTF(("%s: len %u != %zu\n", __func__, tlen, slen));
+ return 0;
+ }
+ goto again;
+ }
+val:
+ DPRINTF(("%s: before data %" SIZE_T_FORMAT "u %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) {
+ DPRINTF(("%s: no string match %s != %s\n", __func__, buf, s));
+ return 0;
+ }
+ strlcpy(ms->ms_value.s, buf, sizeof(ms->ms_value.s));
+ DPRINTF(("%s: complete match\n", __func__));
+ 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:
+ case DER_TAG_IA5_STRING:
+ case DER_TAG_UTCTIME:
+ 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("%" SIZE_T_FORMAT "u %" SIZE_T_FORMAT "u-%"
+ SIZE_T_FORMAT "u %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