+
+int write_datum_fd(int fd, const gnutls_datum_t* d) {
+ if (d->size != write(fd, d->data, d->size)) {
+ err("failed to write body of datum.\n");
+ return -1;
+ }
+ return 0;
+}
+
+
+int write_datum_fd_with_length(int fd, const gnutls_datum_t* d) {
+ uint32_t len;
+ int looks_negative = (d->data[0] & 0x80);
+ unsigned char zero = 0;
+
+ /* if the first bit is 1, then the datum will appear negative in the
+ MPI encoding style used by OpenSSH. In that case, we'll increase
+ the length by one, and dump out one more byte */
+
+ if (looks_negative) {
+ len = htonl(d->size + 1);
+ } else {
+ len = htonl(d->size);
+ }
+ if (write(fd, &len, sizeof(len)) != sizeof(len)) {
+ err("failed to write size of datum.\n");
+ return -2;
+ }
+ if (looks_negative) {
+ if (write(fd, &zero, 1) != 1) {
+ err("failed to write padding byte for MPI.\n");
+ return -2;
+ }
+ }
+ return write_datum_fd(fd, d);
+}
+
+int write_data_fd_with_length(int fd, const gnutls_datum_t** d, unsigned int num) {
+ unsigned int i;
+ int ret;
+
+ for (i = 0; i < num; i++)
+ if (ret = write_datum_fd_with_length(fd, d[i]), ret != 0)
+ return ret;
+
+ return 0;
+}
+
+
+int datum_from_string(gnutls_datum_t* d, const char* str) {
+ d->size = strlen(str);
+ d->data = gnutls_realloc(d->data, d->size);
+ if (d->data == 0)
+ return ENOMEM;
+ memcpy(d->data, str, d->size);
+ return 0;
+}
+
+
+int create_writing_pipe(pid_t* pid, const char* path, char* const argv[]) {
+ int p[2];
+ int ret;
+
+ if (pid == NULL) {
+ err("bad pointer passed to create_writing_pipe()\n");
+ return -1;
+ }
+
+ if (ret = pipe(p), ret == -1) {
+ err("failed to create a pipe (error: %d \"%s\")\n", errno, strerror(errno));
+ return -1;
+ }
+
+ *pid = fork();
+ if (*pid == -1) {
+ err("Failed to fork (error: %d \"%s\")\n", errno, strerror(errno));
+ return -1;
+ }
+ if (*pid == 0) { /* this is the child */
+ close(p[1]); /* close unused write end */
+
+ if (0 != dup2(p[0], 0)) { /* map the reading end into stdin */
+ err("Failed to transfer reading file descriptor to stdin (error: %d \"%s\")\n", errno, strerror(errno));
+ exit(1);
+ }
+ execv(path, argv);
+ err("exec %s failed (error: %d \"%s\")\n", path, errno, strerror(errno));
+ /* close the open file descriptors */
+ close(p[0]);
+ close(0);
+
+ exit(1);
+ } else { /* this is the parent */
+ close(p[0]); /* close unused read end */
+ return p[1];
+ }
+}
+
+int validate_ssh_host_userid(const char* userid) {
+ char* oldlocale = setlocale(LC_ALL, "C");
+
+ /* choke if userid does not match the expected format
+ ("ssh://fully.qualified.domain.name") */
+ if (strncmp("ssh://", userid, strlen("ssh://")) != 0) {
+ err("The user ID should start with ssh:// for a host key\n");
+ goto fail;
+ }
+ /* so that isalnum will work properly */
+ userid += strlen("ssh://");
+ while (0 != (*userid)) {
+ if (!isalnum(*userid)) {
+ err("label did not start with a letter or a digit! (%s)\n", userid);
+ goto fail;
+ }
+ userid++;
+ while (isalnum(*userid) || ('-' == (*userid)))
+ userid++;
+ if (('.' == (*userid)) || (0 == (*userid))) { /* clean end of label:
+ check last char
+ isalnum */
+ if (!isalnum(*(userid - 1))) {
+ err("label did not end with a letter or a digit!\n");
+ goto fail;
+ }
+ if ('.' == (*userid)) /* advance to the start of the next label */
+ userid++;
+ } else {
+ err("invalid character in domain name: %c\n", *userid);
+ goto fail;
+ }
+ }
+ /* ensure that the last character is valid: */
+ if (!isalnum(*(userid - 1))) {
+ err("hostname did not end with a letter or a digit!\n");
+ goto fail;
+ }
+ /* FIXME: fqdn's can be unicode now, thanks to RFC 3490 -- how do we
+ make sure that we've got an OK string? */
+
+ return 0;
+
+ fail:
+ setlocale(LC_ALL, oldlocale);
+ return 1;
+}
+
+/* http://tools.ietf.org/html/rfc4880#section-5.5.2 */
+size_t get_openpgp_mpi_size(gnutls_datum_t* d) {
+ return 2 + d->size;
+}
+
+int write_openpgp_mpi_to_fd(int fd, gnutls_datum_t* d) {
+ uint16_t x;
+
+ x = d->size * 8;
+ x = htons(x);
+
+ write(fd, &x, sizeof(x));
+ write(fd, d->data, d->size);
+
+ return 0;
+}