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 int 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         return sigc->result != 'G' && sigc->result != 'U';
  86 }
  87
  88 void print_signature_buffer(const struct signature_check *sigc, unsigned flags)
  89 {
  90         const char *output = flags & GPG_VERIFY_RAW ?
  91                 sigc->gpg_status : sigc->gpg_output;
  92
  93         if (flags & GPG_VERIFY_VERBOSE && sigc->payload)
  94                 fputs(sigc->payload, stdout);
  95
  96         if (output)
  97                 fputs(output, stderr);
  98 }
  99
 100 /*
 101  * Look at GPG signed content (e.g. a signed tag object), whose
 102  * payload is followed by a detached signature on it.  Return the
 103  * offset where the embedded detached signature begins, or the end of
 104  * the data when there is no such signature.
 105  */
 106 size_t parse_signature(const char *buf, unsigned long size)
 107 {
 108         char *eol;
 109         size_t len = 0;
 110         while (len < size && !starts_with(buf + len, PGP_SIGNATURE) &&
 111                         !starts_with(buf + len, PGP_MESSAGE)) {
 112                 eol = memchr(buf + len, '\n', size - len);
 113                 len += eol ? eol - (buf + len) + 1 : size - len;
 114         }
 115         return len;
 116 }
 117
 118 void set_signing_key(const char *key)
 119 {
 120         free(configured_signing_key);
 121         configured_signing_key = xstrdup(key);
 122 }
 123
 124 int git_gpg_config(const char *var, const char *value, void *cb)
 125 {
 126         if (!strcmp(var, "user.signingkey")) {
 127                 set_signing_key(value);
 128         }
 129         if (!strcmp(var, "gpg.program")) {
 130                 if (!value)
 131                         return config_error_nonbool(var);
 132                 gpg_program = xstrdup(value);
 133         }
 134         return 0;
 135 }
 136
 137 const char *get_signing_key(void)
 138 {
 139         if (configured_signing_key)
 140                 return configured_signing_key;
 141         return git_committer_info(IDENT_STRICT|IDENT_NO_DATE);
 142 }
 143
 144 /*
 145  * Create a detached signature for the contents of "buffer" and append
 146  * it after "signature"; "buffer" and "signature" can be the same
 147  * strbuf instance, which would cause the detached signature appended
 148  * at the end.
 149  */
 150 int sign_buffer(struct strbuf *buffer, struct strbuf *signature, const char *signing_key)
 151 {
 152         struct child_process gpg = CHILD_PROCESS_INIT;
 153         const char *args[4];
 154         ssize_t len;
 155         size_t i, j, bottom;
 156
 157         gpg.argv = args;
 158         gpg.in = -1;
 159         gpg.out = -1;
 160         args[0] = gpg_program;
 161         args[1] = "-bsau";
 162         args[2] = signing_key;
 163         args[3] = NULL;
 164
 165         if (start_command(&gpg))
 166                 return error(_("could not run gpg."));
 167
 168         /*
 169          * When the username signingkey is bad, program could be terminated
 170          * because gpg exits without reading and then write gets SIGPIPE.
 171          */
 172         sigchain_push(SIGPIPE, SIG_IGN);
 173
 174         if (write_in_full(gpg.in, buffer->buf, buffer->len) != buffer->len) {
 175                 close(gpg.in);
 176                 close(gpg.out);
 177                 finish_command(&gpg);
 178                 return error(_("gpg did not accept the data"));
 179         }
 180         close(gpg.in);
 181
 182         bottom = signature->len;
 183         len = strbuf_read(signature, gpg.out, 1024);
 184         close(gpg.out);
 185
 186         sigchain_pop(SIGPIPE);
 187
 188         if (finish_command(&gpg) || !len || len < 0)
 189                 return error(_("gpg failed to sign the data"));
 190
 191         /* Strip CR from the line endings, in case we are on Windows. */
 192         for (i = j = bottom; i < signature->len; i++)
 193                 if (signature->buf[i] != '\r') {
 194                         if (i != j)
 195                                 signature->buf[j] = signature->buf[i];
 196                         j++;
 197                 }
 198         strbuf_setlen(signature, j);
 199
 200         return 0;
 201 }
 202
 203 /*
 204  * Run "gpg" to see if the payload matches the detached signature.
 205  * gpg_output, when set, receives the diagnostic output from GPG.
 206  * gpg_status, when set, receives the status output from GPG.
 207  */
 208 int verify_signed_buffer(const char *payload, size_t payload_size,
 209                          const char *signature, size_t signature_size,
 210                          struct strbuf *gpg_output, struct strbuf *gpg_status)
 211 {
 212         struct child_process gpg = CHILD_PROCESS_INIT;
 213         const char *args_gpg[] = {NULL, "--status-fd=1", "--verify", "FILE", "-", NULL};
 214         char path[PATH_MAX];
 215         int fd, ret;
 216         struct strbuf buf = STRBUF_INIT;
 217         struct strbuf *pbuf = &buf;
 218
 219         args_gpg[0] = gpg_program;
 220         fd = git_mkstemp(path, PATH_MAX, ".git_vtag_tmpXXXXXX");
 221         if (fd < 0)
 222                 return error_errno(_("could not create temporary file '%s'"), path);
 223         if (write_in_full(fd, signature, signature_size) < 0)
 224                 return error_errno(_("failed writing detached signature to '%s'"), path);
 225         close(fd);
 226
 227         gpg.argv = args_gpg;
 228         gpg.in = -1;
 229         gpg.out = -1;
 230         if (gpg_output)
 231                 gpg.err = -1;
 232         args_gpg[3] = path;
 233         if (start_command(&gpg)) {
 234                 unlink(path);
 235                 return error(_("could not run gpg."));
 236         }
 237
 238         sigchain_push(SIGPIPE, SIG_IGN);
 239         write_in_full(gpg.in, payload, payload_size);
 240         close(gpg.in);
 241
 242         if (gpg_output) {
 243                 strbuf_read(gpg_output, gpg.err, 0);
 244                 close(gpg.err);
 245         }
 246         if (gpg_status)
 247                 pbuf = gpg_status;
 248         strbuf_read(pbuf, gpg.out, 0);
 249         close(gpg.out);
 250
 251         ret = finish_command(&gpg);
 252         sigchain_pop(SIGPIPE);
 253
 254         unlink_or_warn(path);
 255
 256         ret |= !strstr(pbuf->buf, "\n[GNUPG:] GOODSIG ");
 257         strbuf_release(&buf); /* no matter it was used or not */
 258
 259         return ret;
 260 }