1 /*-
2 * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
3 *
4 * Copyright (c) 2014 The FreeBSD Foundation
5 * All rights reserved.
6 *
7 * This software was developed by Edward Tomasz Napierala under sponsorship
8 * from the FreeBSD Foundation.
9 *
10 * Redistribution and use in source and binary forms, with or without
11 * modification, are permitted provided that the following conditions
12 * are met:
13 * 1. Redistributions of source code must retain the above copyright
14 * notice, this list of conditions and the following disclaimer.
15 * 2. Redistributions in binary form must reproduce the above copyright
16 * notice, this list of conditions and the following disclaimer in the
17 * documentation and/or other materials provided with the distribution.
18 *
19 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
20 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
21 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
22 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
23 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
24 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
25 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
26 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
27 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
28 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
29 * SUCH DAMAGE.
30 *
31 */
32
33 #include <sys/cdefs.h>
34 __FBSDID("$FreeBSD: stable/12/usr.sbin/uefisign/child.c 336307 2018-07-15 17:21:19Z oshogbo $");
35
36 #include <sys/param.h>
37 #include <sys/capsicum.h>
38 #include <sys/types.h>
39 #include <sys/stat.h>
40 #include <assert.h>
41 #include <capsicum_helpers.h>
42 #include <err.h>
43 #include <errno.h>
44 #include <stdio.h>
45 #include <stdlib.h>
46 #include <string.h>
47 #include <unistd.h>
48
49 #include <openssl/evp.h>
50 #include <openssl/err.h>
51 #include <openssl/pem.h>
52
53 #include "uefisign.h"
54
55 static void
load(struct executable * x)56 load(struct executable *x)
57 {
58 int error, fd;
59 struct stat sb;
60 char *buf;
61 size_t nread, len;
62
63 fd = fileno(x->x_fp);
64
65 error = fstat(fd, &sb);
66 if (error != 0)
67 err(1, "%s: fstat", x->x_path);
68
69 len = sb.st_size;
70 if (len <= 0)
71 errx(1, "%s: file is empty", x->x_path);
72
73 buf = malloc(len);
74 if (buf == NULL)
75 err(1, "%s: cannot malloc %zd bytes", x->x_path, len);
76
77 nread = fread(buf, len, 1, x->x_fp);
78 if (nread != 1)
79 err(1, "%s: fread", x->x_path);
80
81 x->x_buf = buf;
82 x->x_len = len;
83 }
84
85 static void
digest_range(struct executable * x,EVP_MD_CTX * mdctx,off_t off,size_t len)86 digest_range(struct executable *x, EVP_MD_CTX *mdctx, off_t off, size_t len)
87 {
88 int ok;
89
90 range_check(x, off, len, "chunk");
91
92 ok = EVP_DigestUpdate(mdctx, x->x_buf + off, len);
93 if (ok == 0) {
94 ERR_print_errors_fp(stderr);
95 errx(1, "EVP_DigestUpdate(3) failed");
96 }
97 }
98
99 static void
digest(struct executable * x)100 digest(struct executable *x)
101 {
102 EVP_MD_CTX *mdctx;
103 const EVP_MD *md;
104 size_t sum_of_bytes_hashed;
105 int i, ok;
106
107 /*
108 * Windows Authenticode Portable Executable Signature Format
109 * spec version 1.0 specifies MD5 and SHA1. However, pesign
110 * and sbsign both use SHA256, so do the same.
111 */
112 md = EVP_get_digestbyname(DIGEST);
113 if (md == NULL) {
114 ERR_print_errors_fp(stderr);
115 errx(1, "EVP_get_digestbyname(\"%s\") failed", DIGEST);
116 }
117
118 mdctx = EVP_MD_CTX_create();
119 if (mdctx == NULL) {
120 ERR_print_errors_fp(stderr);
121 errx(1, "EVP_MD_CTX_create(3) failed");
122 }
123
124 ok = EVP_DigestInit_ex(mdctx, md, NULL);
125 if (ok == 0) {
126 ERR_print_errors_fp(stderr);
127 errx(1, "EVP_DigestInit_ex(3) failed");
128 }
129
130 /*
131 * According to the Authenticode spec, we need to compute
132 * the digest in a rather... specific manner; see "Calculating
133 * the PE Image Hash" part of the spec for details.
134 *
135 * First, everything from 0 to before the PE checksum.
136 */
137 digest_range(x, mdctx, 0, x->x_checksum_off);
138
139 /*
140 * Second, from after the PE checksum to before the Certificate
141 * entry in Data Directory.
142 */
143 digest_range(x, mdctx, x->x_checksum_off + x->x_checksum_len,
144 x->x_certificate_entry_off -
145 (x->x_checksum_off + x->x_checksum_len));
146
147 /*
148 * Then, from after the Certificate entry to the end of headers.
149 */
150 digest_range(x, mdctx,
151 x->x_certificate_entry_off + x->x_certificate_entry_len,
152 x->x_headers_len -
153 (x->x_certificate_entry_off + x->x_certificate_entry_len));
154
155 /*
156 * Then, each section in turn, as specified in the PE Section Table.
157 *
158 * XXX: Sorting.
159 */
160 sum_of_bytes_hashed = x->x_headers_len;
161 for (i = 0; i < x->x_nsections; i++) {
162 digest_range(x, mdctx,
163 x->x_section_off[i], x->x_section_len[i]);
164 sum_of_bytes_hashed += x->x_section_len[i];
165 }
166
167 /*
168 * I believe this can happen with overlapping sections.
169 */
170 if (sum_of_bytes_hashed > x->x_len)
171 errx(1, "number of bytes hashed is larger than file size");
172
173 /*
174 * I can't really explain this one; just do what the spec says.
175 */
176 if (sum_of_bytes_hashed < x->x_len) {
177 digest_range(x, mdctx, sum_of_bytes_hashed,
178 x->x_len - (signature_size(x) + sum_of_bytes_hashed));
179 }
180
181 ok = EVP_DigestFinal_ex(mdctx, x->x_digest, &x->x_digest_len);
182 if (ok == 0) {
183 ERR_print_errors_fp(stderr);
184 errx(1, "EVP_DigestFinal_ex(3) failed");
185 }
186
187 EVP_MD_CTX_destroy(mdctx);
188 }
189
190 static void
show_digest(const struct executable * x)191 show_digest(const struct executable *x)
192 {
193 int i;
194
195 printf("computed %s digest ", DIGEST);
196 for (i = 0; i < (int)x->x_digest_len; i++)
197 printf("%02x", (unsigned char)x->x_digest[i]);
198 printf("; digest len %u\n", x->x_digest_len);
199 }
200
201 static void
send_digest(const struct executable * x,int pipefd)202 send_digest(const struct executable *x, int pipefd)
203 {
204
205 send_chunk(x->x_digest, x->x_digest_len, pipefd);
206 }
207
208 static void
receive_signature(struct executable * x,int pipefd)209 receive_signature(struct executable *x, int pipefd)
210 {
211
212 receive_chunk(&x->x_signature, &x->x_signature_len, pipefd);
213 }
214
215 static void
save(struct executable * x,FILE * fp,const char * path)216 save(struct executable *x, FILE *fp, const char *path)
217 {
218 size_t nwritten;
219
220 assert(fp != NULL);
221 assert(path != NULL);
222
223 nwritten = fwrite(x->x_buf, x->x_len, 1, fp);
224 if (nwritten != 1)
225 err(1, "%s: fwrite", path);
226 }
227
228 int
child(const char * inpath,const char * outpath,int pipefd,bool Vflag,bool vflag)229 child(const char *inpath, const char *outpath, int pipefd,
230 bool Vflag, bool vflag)
231 {
232 FILE *outfp = NULL, *infp = NULL;
233 struct executable *x;
234
235 infp = checked_fopen(inpath, "r");
236 if (outpath != NULL)
237 outfp = checked_fopen(outpath, "w");
238
239 if (caph_enter() < 0)
240 err(1, "cap_enter");
241
242 x = calloc(1, sizeof(*x));
243 if (x == NULL)
244 err(1, "calloc");
245 x->x_path = inpath;
246 x->x_fp = infp;
247
248 load(x);
249 parse(x);
250 if (Vflag) {
251 if (signature_size(x) == 0)
252 errx(1, "file not signed");
253
254 printf("file contains signature\n");
255 if (vflag) {
256 digest(x);
257 show_digest(x);
258 show_certificate(x);
259 }
260 } else {
261 if (signature_size(x) != 0)
262 errx(1, "file already signed");
263
264 digest(x);
265 if (vflag)
266 show_digest(x);
267 send_digest(x, pipefd);
268 receive_signature(x, pipefd);
269 update(x);
270 save(x, outfp, outpath);
271 }
272
273 return (0);
274 }
275