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 /*
  64  * Look at GPG signed content (e.g. a signed tag object), whose
  65  * payload is followed by a detached signature on it.  Return the
  66  * offset where the embedded detached signature begins, or the end of
  67  * the data when there is no such signature.
  68  */
  69 size_t parse_signature(const char *buf, unsigned long size)
  70 {
  71         char *eol;
  72         size_t len = 0;
  73         while (len < size && !starts_with(buf + len, PGP_SIGNATURE) &&
  74                         !starts_with(buf + len, PGP_MESSAGE)) {
  75                 eol = memchr(buf + len, '\n', size - len);
  76                 len += eol ? eol - (buf + len) + 1 : size - len;
  77         }
  78         return len;
  79 }
  80
  81 void set_signing_key(const char *key)
  82 {
  83         free(configured_signing_key);
  84         configured_signing_key = xstrdup(key);
  85 }
  86
  87 int git_gpg_config(const char *var, const char *value, void *cb)
  88 {
  89         if (!strcmp(var, "user.signingkey")) {
  90                 set_signing_key(value);
  91         }
  92         if (!strcmp(var, "gpg.program")) {
  93                 if (!value)
  94                         return config_error_nonbool(var);
  95                 gpg_program = xstrdup(value);
  96         }
  97         return 0;
  98 }
  99
 100 const char *get_signing_key(void)
 101 {
 102         if (configured_signing_key)
 103                 return configured_signing_key;
 104         return git_committer_info(IDENT_STRICT|IDENT_NO_DATE);
 105 }
 106
 107 /*
 108  * Create a detached signature for the contents of "buffer" and append
 109  * it after "signature"; "buffer" and "signature" can be the same
 110  * strbuf instance, which would cause the detached signature appended
 111  * at the end.
 112  */
 113 int sign_buffer(struct strbuf *buffer, struct strbuf *signature, const char *signing_key)
 114 {
 115         struct child_process gpg = CHILD_PROCESS_INIT;
 116         const char *args[4];
 117         ssize_t len;
 118         size_t i, j, bottom;
 119
 120         gpg.argv = args;
 121         gpg.in = -1;
 122         gpg.out = -1;
 123         args[0] = gpg_program;
 124         args[1] = "-bsau";
 125         args[2] = signing_key;
 126         args[3] = NULL;
 127
 128         if (start_command(&gpg))
 129                 return error(_("could not run gpg."));
 130
 131         /*
 132          * When the username signingkey is bad, program could be terminated
 133          * because gpg exits without reading and then write gets SIGPIPE.
 134          */
 135         sigchain_push(SIGPIPE, SIG_IGN);
 136
 137         if (write_in_full(gpg.in, buffer->buf, buffer->len) != buffer->len) {
 138                 close(gpg.in);
 139                 close(gpg.out);
 140                 finish_command(&gpg);
 141                 return error(_("gpg did not accept the data"));
 142         }
 143         close(gpg.in);
 144
 145         bottom = signature->len;
 146         len = strbuf_read(signature, gpg.out, 1024);
 147         close(gpg.out);
 148
 149         sigchain_pop(SIGPIPE);
 150
 151         if (finish_command(&gpg) || !len || len < 0)
 152                 return error(_("gpg failed to sign the data"));
 153
 154         /* Strip CR from the line endings, in case we are on Windows. */
 155         for (i = j = bottom; i < signature->len; i++)
 156                 if (signature->buf[i] != '\r') {
 157                         if (i != j)
 158                                 signature->buf[j] = signature->buf[i];
 159                         j++;
 160                 }
 161         strbuf_setlen(signature, j);
 162
 163         return 0;
 164 }
 165
 166 /*
 167  * Run "gpg" to see if the payload matches the detached signature.
 168  * gpg_output, when set, receives the diagnostic output from GPG.
 169  * gpg_status, when set, receives the status output from GPG.
 170  */
 171 int verify_signed_buffer(const char *payload, size_t payload_size,
 172                          const char *signature, size_t signature_size,
 173                          struct strbuf *gpg_output, struct strbuf *gpg_status)
 174 {
 175         struct child_process gpg = CHILD_PROCESS_INIT;
 176         const char *args_gpg[] = {NULL, "--status-fd=1", "--verify", "FILE", "-", NULL};
 177         char path[PATH_MAX];
 178         int fd, ret;
 179         struct strbuf buf = STRBUF_INIT;
 180         struct strbuf *pbuf = &buf;
 181
 182         args_gpg[0] = gpg_program;
 183         fd = git_mkstemp(path, PATH_MAX, ".git_vtag_tmpXXXXXX");
 184         if (fd < 0)
 185                 return error(_("could not create temporary file '%s': %s"),
 186                              path, strerror(errno));
 187         if (write_in_full(fd, signature, signature_size) < 0)
 188                 return error(_("failed writing detached signature to '%s': %s"),
 189                              path, strerror(errno));
 190         close(fd);
 191
 192         gpg.argv = args_gpg;
 193         gpg.in = -1;
 194         gpg.out = -1;
 195         if (gpg_output)
 196                 gpg.err = -1;
 197         args_gpg[3] = path;
 198         if (start_command(&gpg)) {
 199                 unlink(path);
 200                 return error(_("could not run gpg."));
 201         }
 202
 203         write_in_full(gpg.in, payload, payload_size);
 204         close(gpg.in);
 205
 206         if (gpg_output) {
 207                 strbuf_read(gpg_output, gpg.err, 0);
 208                 close(gpg.err);
 209         }
 210         if (gpg_status)
 211                 pbuf = gpg_status;
 212         strbuf_read(pbuf, gpg.out, 0);
 213         close(gpg.out);
 214
 215         ret = finish_command(&gpg);
 216
 217         unlink_or_warn(path);
 218
 219         ret |= !strstr(pbuf->buf, "\n[GNUPG:] GOODSIG ");
 220         strbuf_release(&buf); /* no matter it was used or not */
 221
 222         return ret;
 223 }