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 #include "tempfile.h"
   7
   8 static char *configured_signing_key;
   9 static const char *gpg_program = "gpg";
  10
  11 #define PGP_SIGNATURE "-----BEGIN PGP SIGNATURE-----"
  12 #define PGP_MESSAGE "-----BEGIN PGP MESSAGE-----"
  13
  14 void signature_check_clear(struct signature_check *sigc)
  15 {
  16         FREE_AND_NULL(sigc->payload);
  17         FREE_AND_NULL(sigc->gpg_output);
  18         FREE_AND_NULL(sigc->gpg_status);
  19         FREE_AND_NULL(sigc->signer);
  20         FREE_AND_NULL(sigc->key);
  21 }
  22
  23 static struct {
  24         char result;
  25         const char *check;
  26 } sigcheck_gpg_status[] = {
  27         { 'G', "\n[GNUPG:] GOODSIG " },
  28         { 'B', "\n[GNUPG:] BADSIG " },
  29         { 'U', "\n[GNUPG:] TRUST_NEVER" },
  30         { 'U', "\n[GNUPG:] TRUST_UNDEFINED" },
  31         { 'E', "\n[GNUPG:] ERRSIG "},
  32         { 'X', "\n[GNUPG:] EXPSIG "},
  33         { 'Y', "\n[GNUPG:] EXPKEYSIG "},
  34         { 'R', "\n[GNUPG:] REVKEYSIG "},
  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                         /* The ERRSIG message is not followed by signer information */
  57                         if (sigc-> result != 'E') {
  58                                 found += 17;
  59                                 next = strchrnul(found, '\n');
  60                                 sigc->signer = xmemdupz(found, next - found);
  61                         }
  62                 }
  63         }
  64 }
  65
  66 int check_signature(const char *payload, size_t plen, const char *signature,
  67         size_t slen, struct signature_check *sigc)
  68 {
  69         struct strbuf gpg_output = STRBUF_INIT;
  70         struct strbuf gpg_status = STRBUF_INIT;
  71         int status;
  72
  73         sigc->result = 'N';
  74
  75         status = verify_signed_buffer(payload, plen, signature, slen,
  76                                       &gpg_output, &gpg_status);
  77         if (status && !gpg_output.len)
  78                 goto out;
  79         sigc->payload = xmemdupz(payload, plen);
  80         sigc->gpg_output = strbuf_detach(&gpg_output, NULL);
  81         sigc->gpg_status = strbuf_detach(&gpg_status, NULL);
  82         parse_gpg_output(sigc);
  83
  84  out:
  85         strbuf_release(&gpg_status);
  86         strbuf_release(&gpg_output);
  87
  88         return sigc->result != 'G' && sigc->result != 'U';
  89 }
  90
  91 void print_signature_buffer(const struct signature_check *sigc, unsigned flags)
  92 {
  93         const char *output = flags & GPG_VERIFY_RAW ?
  94                 sigc->gpg_status : sigc->gpg_output;
  95
  96         if (flags & GPG_VERIFY_VERBOSE && sigc->payload)
  97                 fputs(sigc->payload, stdout);
  98
  99         if (output)
 100                 fputs(output, stderr);
 101 }
 102
 103 /*
 104  * Look at GPG signed content (e.g. a signed tag object), whose
 105  * payload is followed by a detached signature on it.  Return the
 106  * offset where the embedded detached signature begins, or the end of
 107  * the data when there is no such signature.
 108  */
 109 size_t parse_signature(const char *buf, unsigned long size)
 110 {
 111         char *eol;
 112         size_t len = 0;
 113         while (len < size && !starts_with(buf + len, PGP_SIGNATURE) &&
 114                         !starts_with(buf + len, PGP_MESSAGE)) {
 115                 eol = memchr(buf + len, '\n', size - len);
 116                 len += eol ? eol - (buf + len) + 1 : size - len;
 117         }
 118         return len;
 119 }
 120
 121 void set_signing_key(const char *key)
 122 {
 123         free(configured_signing_key);
 124         configured_signing_key = xstrdup(key);
 125 }
 126
 127 int git_gpg_config(const char *var, const char *value, void *cb)
 128 {
 129         if (!strcmp(var, "user.signingkey")) {
 130                 set_signing_key(value);
 131         }
 132         if (!strcmp(var, "gpg.program")) {
 133                 if (!value)
 134                         return config_error_nonbool(var);
 135                 gpg_program = xstrdup(value);
 136         }
 137         return 0;
 138 }
 139
 140 const char *get_signing_key(void)
 141 {
 142         if (configured_signing_key)
 143                 return configured_signing_key;
 144         return git_committer_info(IDENT_STRICT|IDENT_NO_DATE);
 145 }
 146
 147 /*
 148  * Create a detached signature for the contents of "buffer" and append
 149  * it after "signature"; "buffer" and "signature" can be the same
 150  * strbuf instance, which would cause the detached signature appended
 151  * at the end.
 152  */
 153 int sign_buffer(struct strbuf *buffer, struct strbuf *signature, const char *signing_key)
 154 {
 155         struct child_process gpg = CHILD_PROCESS_INIT;
 156         int ret;
 157         size_t i, j, bottom;
 158         struct strbuf gpg_status = STRBUF_INIT;
 159
 160         argv_array_pushl(&gpg.args,
 161                          gpg_program,
 162                          "--status-fd=2",
 163                          "-bsau", signing_key,
 164                          NULL);
 165
 166         bottom = signature->len;
 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         ret = pipe_command(&gpg, buffer->buf, buffer->len,
 174                            signature, 1024, &gpg_status, 0);
 175         sigchain_pop(SIGPIPE);
 176
 177         ret |= !strstr(gpg_status.buf, "\n[GNUPG:] SIG_CREATED ");
 178         strbuf_release(&gpg_status);
 179         if (ret)
 180                 return error(_("gpg failed to sign the data"));
 181
 182         /* Strip CR from the line endings, in case we are on Windows. */
 183         for (i = j = bottom; i < signature->len; i++)
 184                 if (signature->buf[i] != '\r') {
 185                         if (i != j)
 186                                 signature->buf[j] = signature->buf[i];
 187                         j++;
 188                 }
 189         strbuf_setlen(signature, j);
 190
 191         return 0;
 192 }
 193
 194 /*
 195  * Run "gpg" to see if the payload matches the detached signature.
 196  * gpg_output, when set, receives the diagnostic output from GPG.
 197  * gpg_status, when set, receives the status output from GPG.
 198  */
 199 int verify_signed_buffer(const char *payload, size_t payload_size,
 200                          const char *signature, size_t signature_size,
 201                          struct strbuf *gpg_output, struct strbuf *gpg_status)
 202 {
 203         struct child_process gpg = CHILD_PROCESS_INIT;
 204         static struct tempfile temp;
 205         int fd, ret;
 206         struct strbuf buf = STRBUF_INIT;
 207
 208         fd = mks_tempfile_t(&temp, ".git_vtag_tmpXXXXXX");
 209         if (fd < 0)
 210                 return error_errno(_("could not create temporary file"));
 211         if (write_in_full(fd, signature, signature_size) < 0) {
 212                 error_errno(_("failed writing detached signature to '%s'"),
 213                             temp.filename.buf);
 214                 delete_tempfile(&temp);
 215                 return -1;
 216         }
 217         close(fd);
 218
 219         argv_array_pushl(&gpg.args,
 220                          gpg_program,
 221                          "--status-fd=1",
 222                          "--keyid-format=long",
 223                          "--verify", temp.filename.buf, "-",
 224                          NULL);
 225
 226         if (!gpg_status)
 227                 gpg_status = &buf;
 228
 229         sigchain_push(SIGPIPE, SIG_IGN);
 230         ret = pipe_command(&gpg, payload, payload_size,
 231                            gpg_status, 0, gpg_output, 0);
 232         sigchain_pop(SIGPIPE);
 233
 234         delete_tempfile(&temp);
 235
 236         ret |= !strstr(gpg_status->buf, "\n[GNUPG:] GOODSIG ");
 237         strbuf_release(&buf); /* no matter it was used or not */
 238
 239         return ret;
 240 }