1/*-
2 * SPDX-License-Identifier: BSD-2-Clause
3 *
4 * Copyright (c) 2014 The FreeBSD Foundation
5 *
6 * This software was developed by Edward Tomasz Napierala under sponsorship
7 * from the FreeBSD Foundation.
8 *
9 * Redistribution and use in source and binary forms, with or without
10 * modification, are permitted provided that the following conditions
11 * are met:
12 * 1. Redistributions of source code must retain the above copyright
13 *    notice, this list of conditions and the following disclaimer.
14 * 2. Redistributions in binary form must reproduce the above copyright
15 *    notice, this list of conditions and the following disclaimer in the
16 *    documentation and/or other materials provided with the distribution.
17 *
18 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
19 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
20 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
21 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
22 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
23 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
24 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
25 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
26 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
27 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
28 * SUCH DAMAGE.
29 *
30 */
31
32#include <sys/param.h>
33#include <sys/capsicum.h>
34#include <sys/types.h>
35#include <sys/stat.h>
36#include <assert.h>
37#include <capsicum_helpers.h>
38#include <err.h>
39#include <errno.h>
40#include <stdio.h>
41#include <stdlib.h>
42#include <string.h>
43#include <unistd.h>
44
45#include <openssl/evp.h>
46#include <openssl/err.h>
47#include <openssl/pem.h>
48
49#include "uefisign.h"
50
51static void
52load(struct executable *x)
53{
54	int error, fd;
55	struct stat sb;
56	char *buf;
57	size_t nread, len;
58
59	fd = fileno(x->x_fp);
60
61	error = fstat(fd, &sb);
62	if (error != 0)
63		err(1, "%s: fstat", x->x_path);
64
65	len = sb.st_size;
66	if (len <= 0)
67		errx(1, "%s: file is empty", x->x_path);
68
69	buf = malloc(len);
70	if (buf == NULL)
71		err(1, "%s: cannot malloc %zd bytes", x->x_path, len);
72
73	nread = fread(buf, len, 1, x->x_fp);
74	if (nread != 1)
75		err(1, "%s: fread", x->x_path);
76
77	x->x_buf = buf;
78	x->x_len = len;
79}
80
81static void
82digest_range(struct executable *x, EVP_MD_CTX *mdctx, off_t off, size_t len)
83{
84	int ok;
85
86	range_check(x, off, len, "chunk");
87
88	ok = EVP_DigestUpdate(mdctx, x->x_buf + off, len);
89	if (ok == 0) {
90		ERR_print_errors_fp(stderr);
91		errx(1, "EVP_DigestUpdate(3) failed");
92	}
93}
94
95static void
96digest(struct executable *x)
97{
98	EVP_MD_CTX *mdctx;
99	const EVP_MD *md;
100	size_t sum_of_bytes_hashed;
101	int i, ok;
102
103	/*
104	 * Windows Authenticode Portable Executable Signature Format
105	 * spec version 1.0 specifies MD5 and SHA1.  However, pesign
106	 * and sbsign both use SHA256, so do the same.
107	 */
108	md = EVP_get_digestbyname(DIGEST);
109	if (md == NULL) {
110		ERR_print_errors_fp(stderr);
111		errx(1, "EVP_get_digestbyname(\"%s\") failed", DIGEST);
112	}
113
114	mdctx = EVP_MD_CTX_create();
115	if (mdctx == NULL) {
116		ERR_print_errors_fp(stderr);
117		errx(1, "EVP_MD_CTX_create(3) failed");
118	}
119
120	ok = EVP_DigestInit_ex(mdctx, md, NULL);
121	if (ok == 0) {
122		ERR_print_errors_fp(stderr);
123		errx(1, "EVP_DigestInit_ex(3) failed");
124	}
125
126	/*
127	 * According to the Authenticode spec, we need to compute
128	 * the digest in a rather... specific manner; see "Calculating
129	 * the PE Image Hash" part of the spec for details.
130	 *
131	 * First, everything from 0 to before the PE checksum.
132	 */
133	digest_range(x, mdctx, 0, x->x_checksum_off);
134
135	/*
136	 * Second, from after the PE checksum to before the Certificate
137	 * entry in Data Directory.
138	 */
139	digest_range(x, mdctx, x->x_checksum_off + x->x_checksum_len,
140	    x->x_certificate_entry_off -
141	    (x->x_checksum_off + x->x_checksum_len));
142
143	/*
144	 * Then, from after the Certificate entry to the end of headers.
145	 */
146	digest_range(x, mdctx,
147	    x->x_certificate_entry_off + x->x_certificate_entry_len,
148	    x->x_headers_len -
149	    (x->x_certificate_entry_off + x->x_certificate_entry_len));
150
151	/*
152	 * Then, each section in turn, as specified in the PE Section Table.
153	 *
154	 * XXX: Sorting.
155	 */
156	sum_of_bytes_hashed = x->x_headers_len;
157	for (i = 0; i < x->x_nsections; i++) {
158		digest_range(x, mdctx,
159		    x->x_section_off[i], x->x_section_len[i]);
160		sum_of_bytes_hashed += x->x_section_len[i];
161	}
162
163	/*
164	 * I believe this can happen with overlapping sections.
165	 */
166	if (sum_of_bytes_hashed > x->x_len)
167		errx(1, "number of bytes hashed is larger than file size");
168
169	/*
170	 * I can't really explain this one; just do what the spec says.
171	 */
172	if (sum_of_bytes_hashed < x->x_len) {
173		digest_range(x, mdctx, sum_of_bytes_hashed,
174		    x->x_len - (signature_size(x) + sum_of_bytes_hashed));
175	}
176
177	ok = EVP_DigestFinal_ex(mdctx, x->x_digest, &x->x_digest_len);
178	if (ok == 0) {
179		ERR_print_errors_fp(stderr);
180		errx(1, "EVP_DigestFinal_ex(3) failed");
181	}
182
183	EVP_MD_CTX_destroy(mdctx);
184}
185
186static void
187show_digest(const struct executable *x)
188{
189	int i;
190
191	printf("computed %s digest ", DIGEST);
192	for (i = 0; i < (int)x->x_digest_len; i++)
193		printf("%02x", (unsigned char)x->x_digest[i]);
194	printf("; digest len %u\n", x->x_digest_len);
195}
196
197static void
198send_digest(const struct executable *x, int pipefd)
199{
200
201	send_chunk(x->x_digest, x->x_digest_len, pipefd);
202}
203
204static void
205receive_signature(struct executable *x, int pipefd)
206{
207
208	receive_chunk(&x->x_signature, &x->x_signature_len, pipefd);
209}
210
211static void
212save(struct executable *x, FILE *fp, const char *path)
213{
214	size_t nwritten;
215
216	assert(fp != NULL);
217	assert(path != NULL);
218
219	nwritten = fwrite(x->x_buf, x->x_len, 1, fp);
220	if (nwritten != 1)
221		err(1, "%s: fwrite", path);
222}
223
224int
225child(const char *inpath, const char *outpath, int pipefd,
226    bool Vflag, bool vflag)
227{
228	FILE *outfp = NULL, *infp = NULL;
229	struct executable *x;
230
231	infp = checked_fopen(inpath, "r");
232	if (outpath != NULL)
233		outfp = checked_fopen(outpath, "w");
234
235	if (caph_enter() < 0)
236		err(1, "cap_enter");
237
238	x = calloc(1, sizeof(*x));
239	if (x == NULL)
240		err(1, "calloc");
241	x->x_path = inpath;
242	x->x_fp = infp;
243
244	load(x);
245	parse(x);
246	if (Vflag) {
247		if (signature_size(x) == 0)
248			errx(1, "file not signed");
249
250		printf("file contains signature\n");
251		if (vflag) {
252			digest(x);
253			show_digest(x);
254			show_certificate(x);
255		}
256	} else {
257		if (signature_size(x) != 0)
258			errx(1, "file already signed");
259
260		digest(x);
261		if (vflag)
262			show_digest(x);
263		send_digest(x, pipefd);
264		receive_signature(x, pipefd);
265		update(x);
266		save(x, outfp, outpath);
267	}
268
269	return (0);
270}
271