vger/main.c
Omar Polo 16a5ed7b30 drop unnecessary unveil(NULL, NULL)
the next line is a call to pledge, that alone is will block further
calls to unveil(2) since ``unveil'' isn't in the set of pledges.
2021-03-09 19:14:42 +01:00

499 lines
12 KiB
C

#include <sys/types.h>
#include <sys/stat.h>
#include <sys/wait.h>
#include <dirent.h>
#include <err.h>
#include <errno.h>
#include <fcntl.h>
#include <limits.h>
#include <pwd.h>
#include <stdarg.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <syslog.h>
#include <unistd.h>
#include "mimes.h"
#include "opts.h"
#include "utils.h"
#define GEMINI_PART 9
/* 2014 + 1
* see https://gemini.circumlunar.space/docs/specification.html.
* fgets() reads at most size-1 (1024 here)
*/
#define GEMINI_REQUEST_MAX 1025
int virtualhost;
void autoindex(const char *);
void cgi(const char *cgicmd);
void display_file(const char *);
void status(const int, const char *);
void status_redirect(const int, const char *);
void status_error(const int, const char*);
void drop_privileges(const char *, const char *);
void
drop_privileges(const char *user, const char *path)
{
struct passwd *pw;
int chrooted = 0;
/*
* use chroot() if an user is specified requires root user to be
* running the program to run chroot() and then drop privileges
*/
if (strlen(user) > 0) {
/* is root? */
if (getuid() != 0) {
errlog("chroot requires program to be run as root");
}
/* search user uid from name */
if ((pw = getpwnam(user)) == NULL) {
errlog("the user %s can't be found on the system", user);
}
/* chroot worked? */
if (chroot(path) != 0) {
errlog("the chroot_dir %s can't be used for chroot", path);
}
chrooted = 1;
if (chdir("/") == -1) {
errlog("failed to chdir(\"/\")");
}
/* drop privileges */
if (setgroups(1, &pw->pw_gid) ||
setresgid(pw->pw_gid, pw->pw_gid, pw->pw_gid) ||
setresuid(pw->pw_uid, pw->pw_uid, pw->pw_uid)) {
errlog("dropping privileges to user %s (uid=%i) failed",
user, pw->pw_uid);
}
/* base directory is now / */
estrlcpy(chroot_dir, "/", sizeof(chroot_dir));
}
#ifdef __OpenBSD__
/*
* prevent access to files other than the one in path
*/
if (chrooted) {
eunveil("/", "r");
} else {
eunveil(path, "r");
}
/* permission to execute what's inside cgipath */
if (strlen(cgibin) > 0) {
/* first, build the full path of cgi (not in chroot) */
char cgifullpath[PATH_MAX] = {'\0'};
estrlcpy(cgifullpath, path, sizeof(cgifullpath));
estrlcat(cgifullpath, cgibin, sizeof(cgifullpath));
eunveil(cgifullpath, "rx");
}
/*
* prevent system calls other parsing queryfor fread file and
* write to stdio
*/
if (strlen(cgibin) > 0) {
/* cgi need execlp() (exec) and fork() (proc) */
epledge("stdio rpath exec proc", NULL);
} else {
epledge("stdio rpath", NULL);
}
#endif
}
void
status(const int code, const char *file_mime)
{
printf("%i %s; %s\r\n",
code, file_mime, lang);
}
void
status_redirect(const int code, const char *url)
{
printf("%i %s\r\n",
code, url);
}
void
status_error(const int code, const char *reason)
{
printf("%i %s\r\n",
code, reason);
}
void
display_file(const char *uri)
{
FILE *fd = NULL;
struct stat sb = {0};
ssize_t nread = 0;
const char *file_mime;
char *buffer[BUFSIZ];
char target[FILENAME_MAX] = {'\0'};
char fp[PATH_MAX] = {'\0'};
char tmp[PATH_MAX] = {'\0'}; /* used to build temporary path */
/* build file path inside chroot */
estrlcpy(fp, chroot_dir, sizeof(fp));
estrlcat(fp, uri, sizeof(fp));
/* this is to check if path exists and obtain metadata later */
if (stat(fp, &sb) == -1) {
/* check if fp is a symbolic link
* if so, redirect using its target */
if (lstat(fp, &sb) != -1 && S_ISLNK(sb.st_mode) == 1)
goto redirect;
else
goto err;
}
/* check if directory */
if (S_ISDIR(sb.st_mode) != 0) {
if (fp[strlen(fp) -1 ] != '/') {
/* no ending "/", redirect to "path/" */
if (virtualhost)
estrlcat(tmp, "gemini://", sizeof(tmp));
estrlcat(tmp, uri, sizeof(tmp));
estrlcat(tmp, "/", sizeof(tmp));
status_redirect(31, tmp);
return;
} else {
/* there is a leading "/", display index.gmi */
estrlcpy(tmp, fp, sizeof(tmp));
estrlcat(tmp, "index.gmi", sizeof(tmp));
/* check if index.gmi exists or show autoindex */
if (stat(tmp, &sb) == 0) {
estrlcpy(fp, tmp, sizeof(fp));
} else if (doautoidx != 0) {
autoindex(fp);
return;
} else {
goto err;
}
}
}
/* open the file requested */
if ((fd = fopen(fp, "r")) == NULL) { goto err; }
file_mime = get_file_mime(fp, default_mime);
status(20, file_mime);
/* read the file byte after byte in buffer and write it to stdout */
while ((nread = fread(buffer, 1, sizeof(buffer), fd)) != 0)
fwrite(buffer, 1, nread, stdout);
goto closefd;
syslog(LOG_DAEMON, "path served %s", fp);
return;
err:
/* return an error code and no content */
status_error(51, "file not found");
syslog(LOG_DAEMON, "path invalid %s", fp);
goto closefd;
redirect:
/* read symbolic link target to redirect */
if (readlink(fp, target, FILENAME_MAX) == -1) {
goto err;
}
status_redirect(30, target);
syslog(LOG_DAEMON, "redirection from %s to %s", fp, target);
closefd:
if (S_ISREG(sb.st_mode) != 0) {
fclose(fd);
}
}
void
autoindex(const char *path)
{
int n = 0;
char *pos = NULL;
struct dirent **namelist; /* this must be freed at last */
syslog(LOG_DAEMON, "autoindex: %s", path);
/* display link to parent */
char parent[PATH_MAX] = {'\0'};
/* parent is "path" without chroot_dir */
estrlcpy(parent, path+strlen(chroot_dir), sizeof(parent));
/* remove ending '/' */
while (parent[strlen(parent)-1] == '/') {
parent[strlen(parent)-1] = '\0';
}
/* remove last part after '/' */
pos = strrchr(parent, '/');
if (pos != NULL) {
pos[1] = '\0'; /* at worse, parent is now "/" */
}
/* use alphasort to always have the same order on every system */
if ((n = scandir(path, &namelist, NULL, alphasort)) < 0) {
status_error(50, "Internal server error");
errlog("Can't scan %s", path);
} else {
status(20, "text/gemini");
printf("=> %s ../\n", parent);
for(int j = 0; j < n; j++) {
/* skip self and parent */
if ((strcmp(namelist[j]->d_name, ".") == 0) ||
(strcmp(namelist[j]->d_name, "..") == 0)) {
continue;
}
/* add "/" at the end of a directory path */
if (namelist[j]->d_type == DT_DIR) {
printf("=> ./%s/ %s/\n", namelist[j]->d_name, namelist[j]->d_name);
} else {
printf("=> ./%s %s\n", namelist[j]->d_name, namelist[j]->d_name);
}
free(namelist[j]);
}
free(namelist);
}
}
void
cgi(const char *cgicmd)
{
int pipedes[2] = {0};
pid_t pid;
/* get a pipe to get stdout */
if (pipe(pipedes) != 0) {
status(42, "text/gemini");
err(1, "pipe failed");
}
pid = fork();
if (pid < 0) {
close(pipedes[0]);
close(pipedes[1]);
status(42, "text/gemini");
err(1, "fork failed");
}
if (pid > 0) { /* parent */
char buf[3];
size_t nread = 0;
FILE *output = NULL;
close(pipedes[1]); /* make sure entry is closed so fread() gets EOF */
/* use fread/fwrite because are buffered */
output = fdopen(pipedes[0], "r");
if (output == NULL) {
status(42, "text/gemini");
err(1, "fdopen failed");
}
/* read pipe output */
while ((nread = fread(buf, 1, sizeof(buf), output)) != 0) {
fwrite(buf, 1, nread, stdout);
}
close(pipedes[0]);
fclose(output);
wait(NULL); /* wait for child to terminate */
exit(0);
} else if (pid == 0) { /* child */
dup2(pipedes[1], STDOUT_FILENO); /* set pipe output equal to stdout */
close(pipedes[1]); /* no need this file descriptor : it is now stdout */
execlp(cgicmd, cgicmd, NULL);
/* if execlp is ok, this will never be reached */
status(42, "text/gemini");
errlog("error when trying to execlp %s", cgicmd);
}
}
int
main(int argc, char **argv)
{
char request [GEMINI_REQUEST_MAX] = {'\0'};
char hostname [GEMINI_REQUEST_MAX] = {'\0'};
char uri [PATH_MAX] = {'\0'};
char user [_SC_LOGIN_NAME_MAX] = "";
char query[PATH_MAX] = {'\0'};
int option = 0;
char *pos = NULL;
while ((option = getopt(argc, argv, ":d:l:m:u:c:vi")) != -1) {
switch (option) {
case 'd':
estrlcpy(chroot_dir, optarg, sizeof(chroot_dir));
break;
case 'l':
estrlcpy(lang, "lang=", sizeof(lang));
estrlcat(lang, optarg, sizeof(lang));
break;
case 'm':
estrlcpy(default_mime, optarg, sizeof(default_mime));
break;
case 'u':
estrlcpy(user, optarg, sizeof(user));
break;
case 'c':
estrlcpy(cgibin, optarg, sizeof(cgibin));
break;
case 'v':
virtualhost = 1;
break;
case 'i':
doautoidx = 1;
break;
}
}
/*
* do chroot if an user is supplied run pledge/unveil if OpenBSD
*/
drop_privileges(user, chroot_dir);
/*
* read 1024 chars from stdin
* to get the request
*/
if (fgets(request, GEMINI_REQUEST_MAX, stdin) == NULL) {
/* EOF reached before reading anything */
if (feof(stdin)) {
status(59, "request is too short and probably empty");
errlog("request is too short and probably empty");
/* error before reading anything */
} else if (ferror(stdin)) {
status(59, "Error while reading request");
errlog("Error while reading request: %s", request);
}
}
/* check if string ends with '\n', or to long */
if (request[strnlen(request, GEMINI_REQUEST_MAX) - 1] != '\n') {
status(59, "request is too long (1024 max)");
errlog("request is too long (1024 max): %s", request);
}
/* remove \r\n at the end of string */
pos = strchr(request, '\r');
if (pos != NULL)
*pos = '\0';
/*
* check if the beginning of the request starts with
* gemini://
*/
if (strncmp(request, "gemini://", GEMINI_PART) != 0) {
/* error code url malformed */
errlog("request «%s» doesn't match gemini://",
request);
}
syslog(LOG_DAEMON, "request %s", request);
/* remove the gemini:// part */
memmove(request, request + GEMINI_PART, strlen(request) +1 - GEMINI_PART);
/* remove all "/.." for safety reasons */
while ((pos = strstr(request, "/..")) != NULL ) {
memmove(request, pos+3, strlen(pos) +1 - 3); /* "/.." = 3 */
}
/*
* look for the first / after the hostname
* in order to split hostname and uri
*/
pos = strchr(request, '/');
if (pos != NULL) {
/* if there is a / found */
/* separate hostname and uri */
estrlcpy(uri, pos, strlen(pos)+1);
/* just keep hostname in request */
pos[0] = '\0';
}
/* check if client added :port at end of request */
pos = strchr(request, ':');
if (pos != NULL) {
/* end string at :*/
pos[0] = '\0';
}
/* copy hostname from request */
estrlcpy(hostname, request, sizeof(hostname));
/* look for "?" if any to set query for cgi, or remove it*/
pos = strchr(uri, '?');
if (pos != NULL) {
estrlcpy(query, pos+1, sizeof(query));
esetenv("QUERY_STRING", query, 1);
pos[0] = '\0';
}
/*
* if virtualhost feature is actived looking under the chroot_path +
* hostname directory gemini://foobar/hello will look for
* chroot_path/foobar/hello
*/
if (virtualhost) {
if (strlen(uri) == 0) {
estrlcpy(uri, "/index.gmi", sizeof(uri));
}
char tmp[PATH_MAX] = {'\0'};
estrlcpy(tmp, hostname, sizeof(tmp));
estrlcat(tmp, uri, sizeof(tmp));
estrlcpy(uri, tmp, sizeof(uri));
}
/* check if uri is cgibin */
if ((strlen(cgibin) > 0) &&
(strncmp(uri, cgibin, strlen(cgibin)) == 0)) {
/* cgipath with chroot_dir at the beginning */
char cgipath[PATH_MAX] = {'\0'};
estrlcpy(cgipath, chroot_dir, sizeof(cgipath));
estrlcat(cgipath, uri, sizeof(cgipath));
/* set env variables for CGI */
/* see https://lists.orbitalfox.eu/archives/gemini/2020/000315.html */
esetenv("GATEWAY_INTERFACE", "CGI/1.1", 1);
esetenv("SERVER_PROTOCOL", "GEMINI", 1);
esetenv("SERVER_SOFTWARE", "vger/1", 1);
/* look for an extension to find PATH_INFO */
pos = strrchr(cgipath, '.');
if (pos != NULL) {
/* found a dot */
pos = strchr(pos, '/');
if (pos != NULL) {
setenv("PATH_INFO", pos, 1);
pos[0] = '\0'; /* keep only script name */
}
}
esetenv("SCRIPT_NAME", cgipath, 1);
esetenv("SERVER_NAME", hostname, 1);
cgi(cgipath);
} else {
//TODO: percent decoding here
/* open file and send it to stdout */
display_file(uri);
}
return (0);
}