gpg-interface.c

   1 #include "cache.h"
   2 #include "config.h"
   3 #include "run-command.h"
   4 #include "strbuf.h"
   5 #include "gpg-interface.h"
   6 #include "sigchain.h"
   7 #include "tempfile.h"
   8
   9 static char *configured_signing_key;
  10 static const char *gpg_program = "gpg";
  11
  12 #define PGP_SIGNATURE "-----BEGIN PGP SIGNATURE-----"
  13 #define PGP_MESSAGE "-----BEGIN PGP MESSAGE-----"
  14
  15 void signature_check_clear(struct signature_check *sigc)
  16 {
  17         free(sigc->payload);
  18         free(sigc->gpg_output);
  19         free(sigc->gpg_status);
  20         free(sigc->signer);
  21         free(sigc->key);
  22         sigc->payload = NULL;
  23         sigc->gpg_output = NULL;
  24         sigc->gpg_status = NULL;
  25         sigc->signer = NULL;
  26         sigc->key = NULL;
  27 }
  28
  29 static struct {
  30         char result;
  31         const char *check;
  32 } sigcheck_gpg_status[] = {
  33         { 'G', "\n[GNUPG:] GOODSIG " },
  34         { 'B', "\n[GNUPG:] BADSIG " },
  35         { 'U', "\n[GNUPG:] TRUST_NEVER" },
  36         { 'U', "\n[GNUPG:] TRUST_UNDEFINED" },
  37         { 'E', "\n[GNUPG:] ERRSIG "},
  38         { 'X', "\n[GNUPG:] EXPSIG "},
  39         { 'Y', "\n[GNUPG:] EXPKEYSIG "},
  40         { 'R', "\n[GNUPG:] REVKEYSIG "},
  41 };
  42
  43 void parse_gpg_output(struct signature_check *sigc)
  44 {
  45         const char *buf = sigc->gpg_status;
  46         int i;
  47
  48         /* Iterate over all search strings */
  49         for (i = 0; i < ARRAY_SIZE(sigcheck_gpg_status); i++) {
  50                 const char *found, *next;
  51
  52                 if (!skip_prefix(buf, sigcheck_gpg_status[i].check + 1, &found)) {
  53                         found = strstr(buf, sigcheck_gpg_status[i].check);
  54                         if (!found)
  55                                 continue;
  56                         found += strlen(sigcheck_gpg_status[i].check);
  57                 }
  58                 sigc->result = sigcheck_gpg_status[i].result;
  59                 /* The trust messages are not followed by key/signer information */
  60                 if (sigc->result != 'U') {
  61                         sigc->key = xmemdupz(found, 16);
  62                         /* The ERRSIG message is not followed by signer information */
  63                         if (sigc-> result != 'E') {
  64                                 found += 17;
  65                                 next = strchrnul(found, '\n');
  66                                 sigc->signer = xmemdupz(found, next - found);
  67                         }
  68                 }
  69         }
  70 }
  71
  72 int check_signature(const char *payload, size_t plen, const char *signature,
  73         size_t slen, struct signature_check *sigc)
  74 {
  75         struct strbuf gpg_output = STRBUF_INIT;
  76         struct strbuf gpg_status = STRBUF_INIT;
  77         int status;
  78
  79         sigc->result = 'N';
  80
  81         status = verify_signed_buffer(payload, plen, signature, slen,
  82                                       &gpg_output, &gpg_status);
  83         if (status && !gpg_output.len)
  84                 goto out;
  85         sigc->payload = xmemdupz(payload, plen);
  86         sigc->gpg_output = strbuf_detach(&gpg_output, NULL);
  87         sigc->gpg_status = strbuf_detach(&gpg_status, NULL);
  88         parse_gpg_output(sigc);
  89
  90  out:
  91         strbuf_release(&gpg_status);
  92         strbuf_release(&gpg_output);
  93
  94         return sigc->result != 'G' && sigc->result != 'U';
  95 }
  96
  97 void print_signature_buffer(const struct signature_check *sigc, unsigned flags)
  98 {
  99         const char *output = flags & GPG_VERIFY_RAW ?
 100                 sigc->gpg_status : sigc->gpg_output;
 101
 102         if (flags & GPG_VERIFY_VERBOSE && sigc->payload)
 103                 fputs(sigc->payload, stdout);
 104
 105         if (output)
 106                 fputs(output, stderr);
 107 }
 108
 109 /*
 110  * Look at GPG signed content (e.g. a signed tag object), whose
 111  * payload is followed by a detached signature on it.  Return the
 112  * offset where the embedded detached signature begins, or the end of
 113  * the data when there is no such signature.
 114  */
 115 size_t parse_signature(const char *buf, unsigned long size)
 116 {
 117         char *eol;
 118         size_t len = 0;
 119         while (len < size && !starts_with(buf + len, PGP_SIGNATURE) &&
 120                         !starts_with(buf + len, PGP_MESSAGE)) {
 121                 eol = memchr(buf + len, '\n', size - len);
 122                 len += eol ? eol - (buf + len) + 1 : size - len;
 123         }
 124         return len;
 125 }
 126
 127 void set_signing_key(const char *key)
 128 {
 129         free(configured_signing_key);
 130         configured_signing_key = xstrdup(key);
 131 }
 132
 133 int git_gpg_config(const char *var, const char *value, void *cb)
 134 {
 135         if (!strcmp(var, "user.signingkey")) {
 136                 set_signing_key(value);
 137         }
 138         if (!strcmp(var, "gpg.program")) {
 139                 if (!value)
 140                         return config_error_nonbool(var);
 141                 gpg_program = xstrdup(value);
 142         }
 143         return 0;
 144 }
 145
 146 const char *get_signing_key(void)
 147 {
 148         if (configured_signing_key)
 149                 return configured_signing_key;
 150         return git_committer_info(IDENT_STRICT|IDENT_NO_DATE);
 151 }
 152
 153 /*
 154  * Create a detached signature for the contents of "buffer" and append
 155  * it after "signature"; "buffer" and "signature" can be the same
 156  * strbuf instance, which would cause the detached signature appended
 157  * at the end.
 158  */
 159 int sign_buffer(struct strbuf *buffer, struct strbuf *signature, const char *signing_key)
 160 {
 161         struct child_process gpg = CHILD_PROCESS_INIT;
 162         int ret;
 163         size_t i, j, bottom;
 164         struct strbuf gpg_status = STRBUF_INIT;
 165
 166         argv_array_pushl(&gpg.args,
 167                          gpg_program,
 168                          "--status-fd=2",
 169                          "-bsau", signing_key,
 170                          NULL);
 171
 172         bottom = signature->len;
 173
 174         /*
 175          * When the username signingkey is bad, program could be terminated
 176          * because gpg exits without reading and then write gets SIGPIPE.
 177          */
 178         sigchain_push(SIGPIPE, SIG_IGN);
 179         ret = pipe_command(&gpg, buffer->buf, buffer->len,
 180                            signature, 1024, &gpg_status, 0);
 181         sigchain_pop(SIGPIPE);
 182
 183         ret |= !strstr(gpg_status.buf, "\n[GNUPG:] SIG_CREATED ");
 184         strbuf_release(&gpg_status);
 185         if (ret)
 186                 return error(_("gpg failed to sign the data"));
 187
 188         /* Strip CR from the line endings, in case we are on Windows. */
 189         for (i = j = bottom; i < signature->len; i++)
 190                 if (signature->buf[i] != '\r') {
 191                         if (i != j)
 192                                 signature->buf[j] = signature->buf[i];
 193                         j++;
 194                 }
 195         strbuf_setlen(signature, j);
 196
 197         return 0;
 198 }
 199
 200 /*
 201  * Run "gpg" to see if the payload matches the detached signature.
 202  * gpg_output, when set, receives the diagnostic output from GPG.
 203  * gpg_status, when set, receives the status output from GPG.
 204  */
 205 int verify_signed_buffer(const char *payload, size_t payload_size,
 206                          const char *signature, size_t signature_size,
 207                          struct strbuf *gpg_output, struct strbuf *gpg_status)
 208 {
 209         struct child_process gpg = CHILD_PROCESS_INIT;
 210         static struct tempfile temp;
 211         int fd, ret;
 212         struct strbuf buf = STRBUF_INIT;
 213
 214         fd = mks_tempfile_t(&temp, ".git_vtag_tmpXXXXXX");
 215         if (fd < 0)
 216                 return error_errno(_("could not create temporary file"));
 217         if (write_in_full(fd, signature, signature_size) < 0) {
 218                 error_errno(_("failed writing detached signature to '%s'"),
 219                             temp.filename.buf);
 220                 delete_tempfile(&temp);
 221                 return -1;
 222         }
 223         close(fd);
 224
 225         argv_array_pushl(&gpg.args,
 226                          gpg_program,
 227                          "--status-fd=1",
 228                          "--keyid-format=long",
 229                          "--verify", temp.filename.buf, "-",
 230                          NULL);
 231
 232         if (!gpg_status)
 233                 gpg_status = &buf;
 234
 235         sigchain_push(SIGPIPE, SIG_IGN);
 236         ret = pipe_command(&gpg, payload, payload_size,
 237                            gpg_status, 0, gpg_output, 0);
 238         sigchain_pop(SIGPIPE);
 239
 240         delete_tempfile(&temp);
 241
 242         ret |= !strstr(gpg_status->buf, "\n[GNUPG:] GOODSIG ");
 243         strbuf_release(&buf); /* no matter it was used or not */
 244
 245         return ret;
 246 }