usr.sbin/uefisign/child.c

   1 /*-
   2  * Copyright (c) 2014 The FreeBSD Foundation
   3  * All rights reserved.
   4  *
   5  * This software was developed by Edward Tomasz Napierala under sponsorship
   6  * from the FreeBSD Foundation.
   7  *
   8  * Redistribution and use in source and binary forms, with or without
   9  * modification, are permitted provided that the following conditions
  10  * are met:
  11  * 1. Redistributions of source code must retain the above copyright
  12  *    notice, this list of conditions and the following disclaimer.
  13  * 2. Redistributions in binary form must reproduce the above copyright
  14  *    notice, this list of conditions and the following disclaimer in the
  15  *    documentation and/or other materials provided with the distribution.
  16  *
  17  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
  18  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  19  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  20  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
  21  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  22  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  23  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  24  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  25  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  26  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  27  * SUCH DAMAGE.
  28  *
  29  */
  30
  31 #include <sys/cdefs.h>
  32 __FBSDID("$FreeBSD: head/usr.sbin/uefisign/child.c 305980 2016-09-19 16:07:32Z emaste $");
  33
  34 #include <sys/param.h>
  35 #include <sys/types.h>
  36 #include <sys/stat.h>
  37 #include <assert.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
  51 static void
  52 load(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
  81 static void
  82 digest_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
  95 static void
  96 digest(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
 186 static void
 187 show_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
 197 static void
 198 send_digest(const struct executable *x, int pipefd)
 199 {
 200
 201         send_chunk(x->x_digest, x->x_digest_len, pipefd);
 202 }
 203
 204 static void
 205 receive_signature(struct executable *x, int pipefd)
 206 {
 207
 208         receive_chunk(&x->x_signature, &x->x_signature_len, pipefd);
 209 }
 210
 211 static void
 212 save(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
 224 int
 225 child(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         x = calloc(1, sizeof(*x));
 236         if (x == NULL)
 237                 err(1, "calloc");
 238         x->x_path = inpath;
 239         x->x_fp = infp;
 240
 241         load(x);
 242         parse(x);
 243         if (Vflag) {
 244                 if (signature_size(x) == 0)
 245                         errx(1, "file not signed");
 246
 247                 printf("file contains signature\n");
 248                 if (vflag) {
 249                         digest(x);
 250                         show_digest(x);
 251                         show_certificate(x);
 252                 }
 253         } else {
 254                 if (signature_size(x) != 0)
 255                         errx(1, "file already signed");
 256
 257                 digest(x);
 258                 if (vflag)
 259                         show_digest(x);
 260                 send_digest(x, pipefd);
 261                 receive_signature(x, pipefd);
 262                 update(x);
 263                 save(x, outfp, outpath);
 264         }
 265
 266         return (0);
 267 }