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 void check_signature(const char *payload, size_t plen, const char *signature,
  64         size_t slen, struct signature_check *sigc)
  65 {
  66         struct strbuf gpg_output = STRBUF_INIT;
  67         struct strbuf gpg_status = STRBUF_INIT;
  68         int status;
  69
  70         sigc->result = 'N';
  71
  72         status = verify_signed_buffer(payload, plen, signature, slen,
  73                                       &gpg_output, &gpg_status);
  74         if (status && !gpg_output.len)
  75                 goto out;
  76         sigc->payload = xmemdupz(payload, plen);
  77         sigc->gpg_output = strbuf_detach(&gpg_output, NULL);
  78         sigc->gpg_status = strbuf_detach(&gpg_status, NULL);
  79         parse_gpg_output(sigc);
  80
  81  out:
  82         strbuf_release(&gpg_status);
  83         strbuf_release(&gpg_output);
  84 }
  85
  86 /*
  87  * Look at GPG signed content (e.g. a signed tag object), whose
  88  * payload is followed by a detached signature on it.  Return the
  89  * offset where the embedded detached signature begins, or the end of
  90  * the data when there is no such signature.
  91  */
  92 size_t parse_signature(const char *buf, unsigned long size)
  93 {
  94         char *eol;
  95         size_t len = 0;
  96         while (len < size && !starts_with(buf + len, PGP_SIGNATURE) &&
  97                         !starts_with(buf + len, PGP_MESSAGE)) {
  98                 eol = memchr(buf + len, '\n', size - len);
  99                 len += eol ? eol - (buf + len) + 1 : size - len;
 100         }
 101         return len;
 102 }
 103
 104 void set_signing_key(const char *key)
 105 {
 106         free(configured_signing_key);
 107         configured_signing_key = xstrdup(key);
 108 }
 109
 110 int git_gpg_config(const char *var, const char *value, void *cb)
 111 {
 112         if (!strcmp(var, "user.signingkey")) {
 113                 set_signing_key(value);
 114         }
 115         if (!strcmp(var, "gpg.program")) {
 116                 if (!value)
 117                         return config_error_nonbool(var);
 118                 gpg_program = xstrdup(value);
 119         }
 120         return 0;
 121 }
 122
 123 const char *get_signing_key(void)
 124 {
 125         if (configured_signing_key)
 126                 return configured_signing_key;
 127         return git_committer_info(IDENT_STRICT|IDENT_NO_DATE);
 128 }
 129
 130 /*
 131  * Create a detached signature for the contents of "buffer" and append
 132  * it after "signature"; "buffer" and "signature" can be the same
 133  * strbuf instance, which would cause the detached signature appended
 134  * at the end.
 135  */
 136 int sign_buffer(struct strbuf *buffer, struct strbuf *signature, const char *signing_key)
 137 {
 138         struct child_process gpg = CHILD_PROCESS_INIT;
 139         const char *args[4];
 140         ssize_t len;
 141         size_t i, j, bottom;
 142
 143         gpg.argv = args;
 144         gpg.in = -1;
 145         gpg.out = -1;
 146         args[0] = gpg_program;
 147         args[1] = "-bsau";
 148         args[2] = signing_key;
 149         args[3] = NULL;
 150
 151         if (start_command(&gpg))
 152                 return error(_("could not run gpg."));
 153
 154         /*
 155          * When the username signingkey is bad, program could be terminated
 156          * because gpg exits without reading and then write gets SIGPIPE.
 157          */
 158         sigchain_push(SIGPIPE, SIG_IGN);
 159
 160         if (write_in_full(gpg.in, buffer->buf, buffer->len) != buffer->len) {
 161                 close(gpg.in);
 162                 close(gpg.out);
 163                 finish_command(&gpg);
 164                 return error(_("gpg did not accept the data"));
 165         }
 166         close(gpg.in);
 167
 168         bottom = signature->len;
 169         len = strbuf_read(signature, gpg.out, 1024);
 170         close(gpg.out);
 171
 172         sigchain_pop(SIGPIPE);
 173
 174         if (finish_command(&gpg) || !len || len < 0)
 175                 return error(_("gpg failed to sign the data"));
 176
 177         /* Strip CR from the line endings, in case we are on Windows. */
 178         for (i = j = bottom; i < signature->len; i++)
 179                 if (signature->buf[i] != '\r') {
 180                         if (i != j)
 181                                 signature->buf[j] = signature->buf[i];
 182                         j++;
 183                 }
 184         strbuf_setlen(signature, j);
 185
 186         return 0;
 187 }
 188
 189 /*
 190  * Run "gpg" to see if the payload matches the detached signature.
 191  * gpg_output, when set, receives the diagnostic output from GPG.
 192  * gpg_status, when set, receives the status output from GPG.
 193  */
 194 int verify_signed_buffer(const char *payload, size_t payload_size,
 195                          const char *signature, size_t signature_size,
 196                          struct strbuf *gpg_output, struct strbuf *gpg_status)
 197 {
 198         struct child_process gpg = CHILD_PROCESS_INIT;
 199         const char *args_gpg[] = {NULL, "--status-fd=1", "--verify", "FILE", "-", NULL};
 200         char path[PATH_MAX];
 201         int fd, ret;
 202         struct strbuf buf = STRBUF_INIT;
 203         struct strbuf *pbuf = &buf;
 204
 205         args_gpg[0] = gpg_program;
 206         fd = git_mkstemp(path, PATH_MAX, ".git_vtag_tmpXXXXXX");
 207         if (fd < 0)
 208                 return error(_("could not create temporary file '%s': %s"),
 209                              path, strerror(errno));
 210         if (write_in_full(fd, signature, signature_size) < 0)
 211                 return error(_("failed writing detached signature to '%s': %s"),
 212                              path, strerror(errno));
 213         close(fd);
 214
 215         gpg.argv = args_gpg;
 216         gpg.in = -1;
 217         gpg.out = -1;
 218         if (gpg_output)
 219                 gpg.err = -1;
 220         args_gpg[3] = path;
 221         if (start_command(&gpg)) {
 222                 unlink(path);
 223                 return error(_("could not run gpg."));
 224         }
 225
 226         write_in_full(gpg.in, payload, payload_size);
 227         close(gpg.in);
 228
 229         if (gpg_output) {
 230                 strbuf_read(gpg_output, gpg.err, 0);
 231                 close(gpg.err);
 232         }
 233         if (gpg_status)
 234                 pbuf = gpg_status;
 235         strbuf_read(pbuf, gpg.out, 0);
 236         close(gpg.out);
 237
 238         ret = finish_command(&gpg);
 239
 240         unlink_or_warn(path);
 241
 242         ret |= !strstr(pbuf->buf, "\n[GNUPG:] GOODSIG ");
 243         strbuf_release(&buf); /* no matter it was used or not */
 244
 245         return ret;
 246 }