449 lines
10 KiB
C
449 lines
10 KiB
C
#include <sys/types.h>
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#include <sys/stat.h>
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#include <sys/wait.h>
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#include <dirent.h>
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#include <err.h>
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#include <errno.h>
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#include <fcntl.h>
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#include <limits.h>
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#include <pwd.h>
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#include <stdarg.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include <syslog.h>
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#include <unistd.h>
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#include "mimes.h"
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#include "opts.h"
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#include "utils.h"
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#define GEMINI_PART 9
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#define GEMINI_REQUEST_MAX 1024 /* see https://gemini.circumlunar.space/docs/specification.html */
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void autoindex(const char *);
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void cgi(const char *cgicmd);
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void display_file(const char *);
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void status(const int, const char *);
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void status_redirect(const int, const char *);
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void drop_privileges(const char *, const char *);
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void
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drop_privileges(const char *user, const char *path)
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{
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struct passwd *pw;
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int chrooted = 0;
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/*
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* use chroot() if an user is specified requires root user to be
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* running the program to run chroot() and then drop privileges
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*/
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if (strlen(user) > 0) {
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/* is root? */
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if (getuid() != 0) {
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errlog("chroot requires program to be run as root");
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}
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/* search user uid from name */
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if ((pw = getpwnam(user)) == NULL) {
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errlog("the user %s can't be found on the system", user);
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}
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/* chroot worked? */
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if (chroot(path) != 0) {
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errlog("the chroot_dir %s can't be used for chroot", path);
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}
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chrooted = 1;
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if (chdir("/") == -1) {
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errlog("failed to chdir(\"/\")");
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}
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/* drop privileges */
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if (setgroups(1, &pw->pw_gid) ||
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setresgid(pw->pw_gid, pw->pw_gid, pw->pw_gid) ||
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setresuid(pw->pw_uid, pw->pw_uid, pw->pw_uid)) {
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errlog("dropping privileges to user %s (uid=%i) failed",
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user, pw->pw_uid);
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}
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}
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#ifdef __OpenBSD__
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/*
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* prevent access to files other than the one in path
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*/
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if (chrooted) {
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eunveil("/", "r");
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} else {
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eunveil(path, "r");
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}
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if (strlen(cgibin) > 0) {
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char cgifullpath[PATH_MAX] = {'\0'};
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estrlcpy(cgifullpath, path, sizeof(cgifullpath));
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estrlcat(cgifullpath, cgibin, sizeof(cgifullpath));
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eunveil(cgifullpath, "rx");
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}
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/* no more unveil later */
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eunveil(NULL, NULL);
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/*
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* prevent system calls other parsing queryfor fread file and
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* write to stdio
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*/
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if (strlen(cgibin) > 0) {
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epledge("stdio rpath exec proc", NULL);
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} else {
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epledge("stdio rpath", NULL);
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}
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#endif
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}
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void
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status(const int code, const char *file_mime)
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{
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printf("%i %s; %s\r\n",
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code, file_mime, lang);
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}
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void
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status_redirect(const int code, const char *url)
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{
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printf("%i %s\r\n",
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code, url);
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}
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void
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display_file(const char *uri)
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{
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FILE *fd = NULL;
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struct stat sb = {0};
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ssize_t nread = 0;
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const char *file_mime;
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char *buffer[BUFSIZ];
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char target[FILENAME_MAX] = {'\0'};
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char fp[PATH_MAX] = {'\0'};
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/* build file path inside chroot */
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estrlcpy(fp, chroot_dir, sizeof(fp));
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estrlcat(fp, uri, sizeof(fp));
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/* this is to check if path exists and obtain metadata later */
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if (stat(fp, &sb) == -1) {
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/* check if fp is a symbolic link
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* if so, redirect using its target */
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if (lstat(fp, &sb) != -1 && S_ISLNK(sb.st_mode) == 1)
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goto redirect;
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else
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goto err;
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}
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/* check if directory */
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if (S_ISDIR(sb.st_mode) != 0) {
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if (fp[strlen(fp) -1 ] != '/') {
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/* no ending "/", redirect to "path/" */
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char new_uri[PATH_MAX] = {'\0'};
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estrlcpy(new_uri, uri, sizeof(new_uri));
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estrlcat(new_uri, "/", sizeof(new_uri));
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status_redirect(31, new_uri);
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return;
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} else {
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/* there is a leading "/", display index.gmi */
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char index_path[PATH_MAX] = {'\0'};
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estrlcpy(index_path, fp, sizeof(index_path));
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estrlcat(index_path, "index.gmi", sizeof(index_path));
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/* check if index.gmi exists or show autoindex */
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if (stat(index_path, &sb) == 0) {
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estrlcpy(fp, index_path, sizeof(fp));
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} else if (doautoidx != 0) {
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autoindex(fp);
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return;
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} else {
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goto err;
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}
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}
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}
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/* open the file requested */
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if ((fd = fopen(fp, "r")) == NULL) { goto err; }
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file_mime = get_file_mime(fp, default_mime);
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status(20, file_mime);
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/* read the file and write it to stdout */
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while ((nread = fread(buffer, 1, sizeof(buffer), fd)) != 0)
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fwrite(buffer, 1, nread, stdout);
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goto closefd;
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syslog(LOG_DAEMON, "path served %s", fp);
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return;
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err:
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/* return an error code and no content */
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status(51, "text/gemini");
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syslog(LOG_DAEMON, "path invalid %s", fp);
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goto closefd;
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redirect:
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/* read symbolic link target to redirect */
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if (readlink(fp, target, FILENAME_MAX) == -1) {
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goto err;
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}
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status_redirect(30, target);
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syslog(LOG_DAEMON, "redirection from %s to %s", fp, target);
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closefd:
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if (S_ISREG(sb.st_mode) != 0) {
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fclose(fd);
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}
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}
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void
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autoindex(const char *path)
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{
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int n = 0;
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struct dirent **namelist;
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syslog(LOG_DAEMON, "autoindex: %s", path);
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status(20, "text/gemini");
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if ((n = scandir(path, &namelist, NULL, alphasort)) < 0) {
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status(51, "text/gemini");
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errlog("Can't scan %s", path);
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} else {
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for(int j = 0; j < n; j++) {
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if ((strcmp(namelist[j]->d_name, ".") == 0) ||
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(strcmp(namelist[j]->d_name, "..") == 0)) {
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continue;
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}
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if (namelist[j]->d_type == DT_DIR) {
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printf("=> ./%s/ %s/\n", namelist[j]->d_name, namelist[j]->d_name);
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} else {
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printf("=> ./%s %s\n", namelist[j]->d_name, namelist[j]->d_name);
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}
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free(namelist[j]);
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}
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free(namelist);
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}
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}
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void
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cgi(const char *cgicmd)
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{
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int pipedes[2] = {0};
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pid_t pid;
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if (pipe(pipedes) != 0) {
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status(42, "text/gemini");
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err(1, "pipe failed");
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}
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pid = fork();
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if (pid < 0) {
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close(pipedes[0]);
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close(pipedes[1]);
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status(42, "text/gemini");
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err(1, "fork failed");
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}
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if (pid > 0) { /* parent */
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char buf[3];
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size_t nread = 0;
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FILE *output = NULL;
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close(pipedes[1]); /* make sure entry is closed so fread() gets EOF */
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/* use fread/fwrite because are buffered */
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output = fdopen(pipedes[0], "r");
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if (output == NULL) {
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status(42, "text/gemini");
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err(1, "fdopen failed");
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}
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/* read pipe output */
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while ((nread = fread(buf, 1, sizeof(buf), output)) != 0) {
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fwrite(buf, 1, nread, stdout);
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}
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close(pipedes[0]);
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fclose(output);
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wait(NULL); /* wait for child to terminate */
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exit(0);
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} else if (pid == 0) { /* child */
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dup2(pipedes[1], STDOUT_FILENO); /* set pipe output equal to stdout */
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close(pipedes[1]); /* no need this file descriptor : it is now stdout */
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execlp(cgicmd, cgicmd, NULL);
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/* if execlp is ok, this will never be reached */
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status(42, "text/gemini");
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errlog("error when trying to execlp %s", cgicmd);
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}
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}
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int
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main(int argc, char **argv)
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{
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char request [GEMINI_REQUEST_MAX] = {'\0'};
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char hostname [GEMINI_REQUEST_MAX] = {'\0'};
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char uri [PATH_MAX] = {'\0'};
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char user [_SC_LOGIN_NAME_MAX] = "";
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char query[PATH_MAX] = {'\0'};
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int virtualhost = 0;
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int option = 0;
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char *pos = NULL;
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while ((option = getopt(argc, argv, ":d:l:m:u:c:vi")) != -1) {
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switch (option) {
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case 'd':
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estrlcpy(chroot_dir, optarg, sizeof(chroot_dir));
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break;
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case 'l':
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estrlcpy(lang, "lang=", sizeof(lang));
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estrlcat(lang, optarg, sizeof(lang));
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break;
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case 'm':
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estrlcpy(default_mime, optarg, sizeof(default_mime));
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break;
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case 'u':
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estrlcpy(user, optarg, sizeof(user));
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break;
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case 'c':
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estrlcpy(cgibin, optarg, sizeof(cgibin));
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break;
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case 'v':
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virtualhost = 1;
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break;
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case 'i':
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doautoidx = 1;
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break;
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}
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}
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/*
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* do chroot if an user is supplied run pledge/unveil if OpenBSD
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*/
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drop_privileges(user, chroot_dir);
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/*
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* read 1024 chars from stdin
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* to get the request
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*/
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if (fgets(request, GEMINI_REQUEST_MAX, stdin) == NULL) {
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status(59, "request is too long (1024 max)");
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errlog("request is too long (1024 max): %s", request);
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}
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/* remove \r\n at the end of string */
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pos = strchr(request, '\r');
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if (pos != NULL)
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*pos = '\0';
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/*
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* check if the beginning of the request starts with
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* gemini://
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*/
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if (strncmp(request, "gemini://", GEMINI_PART) != 0) {
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/* error code url malformed */
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errlog("request «%s» doesn't match gemini://",
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request);
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}
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syslog(LOG_DAEMON, "request %s", request);
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/* remove the gemini:// part */
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memmove(request, request + GEMINI_PART, strlen(request) +1 - GEMINI_PART);
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/* remove all "/.." for safety reasons */
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while ((pos = strstr(request, "/..")) != NULL ) {
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memmove(request, pos+3, strlen(pos) +1 - 3); /* "/.." = 3 */
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}
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/*
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* look for the first / after the hostname
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* in order to split hostname and uri
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*/
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pos = strchr(request, '/');
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if (pos != NULL) {
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/* if there is a / found */
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/* separate hostname and uri */
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estrlcpy(uri, pos, strlen(pos)+1);
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/* just keep hostname in request */
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pos[0] = '\0';
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}
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/* check if client added :port at end of request */
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pos = strchr(request, ':');
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if (pos != NULL) {
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/* end string at :*/
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pos[0] = '\0';
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}
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/* copy hostname from request */
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estrlcpy(hostname, request, sizeof(hostname));
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/* look for "?" if any to set query for cgi, or remove it*/
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pos = strchr(uri, '?');
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if (pos != NULL) {
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estrlcpy(query, pos+1, sizeof(query));
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esetenv("QUERY_STRING", query, 1);
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pos[0] = '\0';
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}
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/*
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* if virtualhost feature is actived looking under the chroot_path +
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* hostname directory gemini://foobar/hello will look for
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* chroot_path/foobar/hello
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*/
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if (virtualhost) {
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if (strlen(uri) == 0) {
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estrlcpy(uri, "/index.gmi", sizeof(uri));
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}
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char tmp[PATH_MAX] = {'\0'};
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estrlcpy(tmp, hostname, sizeof(tmp));
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estrlcat(tmp, uri, sizeof(tmp));
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estrlcpy(uri, tmp, sizeof(uri));
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}
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/* check if uri is cgibin */
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if ((strlen(cgibin) > 0) &&
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(strncmp(uri, cgibin, strlen(cgibin)) == 0)) {
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char cgipath[PATH_MAX] = {'\0'};
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estrlcpy(cgipath, chroot_dir, sizeof(cgipath));
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estrlcat(cgipath, uri, sizeof(cgipath));
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/* set env variables for CGI */
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/* see https://lists.orbitalfox.eu/archives/gemini/2020/000315.html */
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esetenv("GATEWAY_INTERFACE", "CGI/1.1", 1);
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esetenv("SERVER_PROTOCOL", "GEMINI", 1);
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esetenv("SERVER_SOFTWARE", "vger/1", 1);
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/* look for an extension to find PATH_INFO */
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pos = strrchr(cgipath, '.');
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if (pos != NULL) {
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/* found a dot */
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pos = strchr(pos, '/');
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if (pos != NULL) {
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setenv("PATH_INFO", pos, 1);
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pos[0] = '\0'; /* keep only script name */
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}
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}
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esetenv("SCRIPT_NAME", cgipath, 1);
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esetenv("SERVER_NAME", hostname, 1);
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cgi(cgipath);
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} else {
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//TODO: percent decoding here
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/* open file and send it to stdout */
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display_file(uri);
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}
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return (0);
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}
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