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