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