gpg-interface.c

   1 #include "cache.h"
   2 #include "run-command.h"
   3 #include "strbuf.h"
   4 #include "gpg-interface.h"
   5 #include "sigchain.h"
   6
   7 static char *configured_signing_key;
   8 static const char *gpg_program = "gpg";
   9
  10 #define PGP_SIGNATURE "-----BEGIN PGP SIGNATURE-----"
  11 #define PGP_MESSAGE "-----BEGIN PGP MESSAGE-----"
  12
  13 void signature_check_clear(struct signature_check *sigc)
  14 {
  15         free(sigc->payload);
  16         free(sigc->gpg_output);
  17         free(sigc->gpg_status);
  18         free(sigc->signer);
  19         free(sigc->key);
  20         sigc->payload = NULL;
  21         sigc->gpg_output = NULL;
  22         sigc->gpg_status = NULL;
  23         sigc->signer = NULL;
  24         sigc->key = NULL;
  25 }
  26
  27 static struct {
  28         char result;
  29         const char *check;
  30 } sigcheck_gpg_status[] = {
  31         { 'G', "\n[GNUPG:] GOODSIG " },
  32         { 'B', "\n[GNUPG:] BADSIG " },
  33         { 'U', "\n[GNUPG:] TRUST_NEVER" },
  34         { 'U', "\n[GNUPG:] TRUST_UNDEFINED" },
  35 };
  36
  37 void parse_gpg_output(struct signature_check *sigc)
  38 {
  39         const char *buf = sigc->gpg_status;
  40         int i;
  41
  42         /* Iterate over all search strings */
  43         for (i = 0; i < ARRAY_SIZE(sigcheck_gpg_status); i++) {
  44                 const char *found, *next;
  45
  46                 if (!skip_prefix(buf, sigcheck_gpg_status[i].check + 1, &found)) {
  47                         found = strstr(buf, sigcheck_gpg_status[i].check);
  48                         if (!found)
  49                                 continue;
  50                         found += strlen(sigcheck_gpg_status[i].check);
  51                 }
  52                 sigc->result = sigcheck_gpg_status[i].result;
  53                 /* The trust messages are not followed by key/signer information */
  54                 if (sigc->result != 'U') {
  55                         sigc->key = xmemdupz(found, 16);
  56                         found += 17;
  57                         next = strchrnul(found, '\n');
  58                         sigc->signer = xmemdupz(found, next - found);
  59                 }
  60         }
  61 }
  62
  63 /*
  64  * Look at GPG signed content (e.g. a signed tag object), whose
  65  * payload is followed by a detached signature on it.  Return the
  66  * offset where the embedded detached signature begins, or the end of
  67  * the data when there is no such signature.
  68  */
  69 size_t parse_signature(const char *buf, unsigned long size)
  70 {
  71         char *eol;
  72         size_t len = 0;
  73         while (len < size && !starts_with(buf + len, PGP_SIGNATURE) &&
  74                         !starts_with(buf + len, PGP_MESSAGE)) {
  75                 eol = memchr(buf + len, '\n', size - len);
  76                 len += eol ? eol - (buf + len) + 1 : size - len;
  77         }
  78         return len;
  79 }
  80
  81 void set_signing_key(const char *key)
  82 {
  83         free(configured_signing_key);
  84         configured_signing_key = xstrdup(key);
  85 }
  86
  87 int git_gpg_config(const char *var, const char *value, void *cb)
  88 {
  89         if (!strcmp(var, "user.signingkey")) {
  90                 set_signing_key(value);
  91         }
  92         if (!strcmp(var, "gpg.program")) {
  93                 if (!value)
  94                         return config_error_nonbool(var);
  95                 gpg_program = xstrdup(value);
  96         }
  97         return 0;
  98 }
  99
 100 const char *get_signing_key(void)
 101 {
 102         if (configured_signing_key)
 103                 return configured_signing_key;
 104         return git_committer_info(IDENT_STRICT|IDENT_NO_DATE);
 105 }
 106
 107 /*
 108  * Create a detached signature for the contents of "buffer" and append
 109  * it after "signature"; "buffer" and "signature" can be the same
 110  * strbuf instance, which would cause the detached signature appended
 111  * at the end.
 112  */
 113 int sign_buffer(struct strbuf *buffer, struct strbuf *signature, const char *signing_key)
 114 {
 115         struct child_process gpg;
 116         const char *args[4];
 117         ssize_t len;
 118         size_t i, j, bottom;
 119
 120         memset(&gpg, 0, sizeof(gpg));
 121         gpg.argv = args;
 122         gpg.in = -1;
 123         gpg.out = -1;
 124         args[0] = gpg_program;
 125         args[1] = "-bsau";
 126         args[2] = signing_key;
 127         args[3] = NULL;
 128
 129         if (start_command(&gpg))
 130                 return error(_("could not run gpg."));
 131
 132         /*
 133          * When the username signingkey is bad, program could be terminated
 134          * because gpg exits without reading and then write gets SIGPIPE.
 135          */
 136         sigchain_push(SIGPIPE, SIG_IGN);
 137
 138         if (write_in_full(gpg.in, buffer->buf, buffer->len) != buffer->len) {
 139                 close(gpg.in);
 140                 close(gpg.out);
 141                 finish_command(&gpg);
 142                 return error(_("gpg did not accept the data"));
 143         }
 144         close(gpg.in);
 145
 146         bottom = signature->len;
 147         len = strbuf_read(signature, gpg.out, 1024);
 148         close(gpg.out);
 149
 150         sigchain_pop(SIGPIPE);
 151
 152         if (finish_command(&gpg) || !len || len < 0)
 153                 return error(_("gpg failed to sign the data"));
 154
 155         /* Strip CR from the line endings, in case we are on Windows. */
 156         for (i = j = bottom; i < signature->len; i++)
 157                 if (signature->buf[i] != '\r') {
 158                         if (i != j)
 159                                 signature->buf[j] = signature->buf[i];
 160                         j++;
 161                 }
 162         strbuf_setlen(signature, j);
 163
 164         return 0;
 165 }
 166
 167 /*
 168  * Run "gpg" to see if the payload matches the detached signature.
 169  * gpg_output, when set, receives the diagnostic output from GPG.
 170  * gpg_status, when set, receives the status output from GPG.
 171  */
 172 int verify_signed_buffer(const char *payload, size_t payload_size,
 173                          const char *signature, size_t signature_size,
 174                          struct strbuf *gpg_output, struct strbuf *gpg_status)
 175 {
 176         struct child_process gpg;
 177         const char *args_gpg[] = {NULL, "--status-fd=1", "--verify", "FILE", "-", NULL};
 178         char path[PATH_MAX];
 179         int fd, ret;
 180         struct strbuf buf = STRBUF_INIT;
 181         struct strbuf *pbuf = &buf;
 182
 183         args_gpg[0] = gpg_program;
 184         fd = git_mkstemp(path, PATH_MAX, ".git_vtag_tmpXXXXXX");
 185         if (fd < 0)
 186                 return error(_("could not create temporary file '%s': %s"),
 187                              path, strerror(errno));
 188         if (write_in_full(fd, signature, signature_size) < 0)
 189                 return error(_("failed writing detached signature to '%s': %s"),
 190                              path, strerror(errno));
 191         close(fd);
 192
 193         memset(&gpg, 0, sizeof(gpg));
 194         gpg.argv = args_gpg;
 195         gpg.in = -1;
 196         gpg.out = -1;
 197         if (gpg_output)
 198                 gpg.err = -1;
 199         args_gpg[3] = path;
 200         if (start_command(&gpg)) {
 201                 unlink(path);
 202                 return error(_("could not run gpg."));
 203         }
 204
 205         write_in_full(gpg.in, payload, payload_size);
 206         close(gpg.in);
 207
 208         if (gpg_output) {
 209                 strbuf_read(gpg_output, gpg.err, 0);
 210                 close(gpg.err);
 211         }
 212         if (gpg_status)
 213                 pbuf = gpg_status;
 214         strbuf_read(pbuf, gpg.out, 0);
 215         close(gpg.out);
 216
 217         ret = finish_command(&gpg);
 218
 219         unlink_or_warn(path);
 220
 221         ret |= !strstr(pbuf->buf, "\n[GNUPG:] GOODSIG ");
 222         strbuf_release(&buf); /* no matter it was used or not */
 223
 224         return ret;
 225 }