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this way, we can sandbox the listener with seccomp (todo) or capsicum (already done) and still have CGI scripts. When we want to exec, we tell the executor what to do, the executor executes the scripts and send the fd backt to the listener.
198 lines
4.3 KiB
C
198 lines
4.3 KiB
C
/*
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* Copyright (c) 2021 Omar Polo <op@omarpolo.com>
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*
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* Permission to use, copy, modify, and distribute this software for any
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* purpose with or without fee is hereby granted, provided that the above
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* copyright notice and this permission notice appear in all copies.
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*
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* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
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* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
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* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
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* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
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* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
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* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
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* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
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*/
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#include <netdb.h>
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#include <err.h>
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#include <errno.h>
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#include <string.h>
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#include "gmid.h"
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/*
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* the inverse of this algorithm, i.e. starting from the start of the
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* path + strlen(cgi), and checking if each component, should be
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* faster. But it's tedious to write. This does the opposite: starts
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* from the end and strip one component at a time, until either an
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* executable is found or we emptied the path.
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*/
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int
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check_for_cgi(char *path, char *query, struct pollfd *fds, struct client *c)
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{
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char *end;
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end = strchr(path, '\0');
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/* NB: assume CGI is enabled and path matches cgi */
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while (end > path) {
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/* go up one level. UNIX paths are simple and POSIX
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* dirname, with its ambiguities on if the given path
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* is changed or not, gives me headaches. */
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while (*end != '/')
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end--;
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*end = '\0';
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switch (check_path(c, path, &c->fd)) {
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case FILE_EXECUTABLE:
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return start_cgi(path, end+1, query, fds,c);
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case FILE_MISSING:
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break;
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default:
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goto err;
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}
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*end = '/';
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end--;
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}
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err:
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if (!start_reply(fds, c, NOT_FOUND, "not found"))
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return 0;
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goodbye(fds, c);
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return 0;
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}
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int
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start_cgi(const char *spath, const char *relpath, const char *query,
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struct pollfd *fds, struct client *c)
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{
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char addr[NI_MAXHOST];
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const char *ruser, *cissuer, *chash;
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int e;
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e = getnameinfo((struct sockaddr*)&c->addr, sizeof(c->addr),
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addr, sizeof(addr),
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NULL, 0,
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NI_NUMERICHOST);
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if (e != 0)
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goto err;
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if (tls_peer_cert_provided(c->ctx)) {
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ruser = tls_peer_cert_subject(c->ctx);
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cissuer = tls_peer_cert_issuer(c->ctx);
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chash = tls_peer_cert_hash(c->ctx);
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} else {
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ruser = NULL;
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cissuer = NULL;
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chash = NULL;
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}
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if (!send_string(exfd, spath)
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|| !send_string(exfd, relpath)
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|| !send_string(exfd, query)
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|| !send_string(exfd, addr)
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|| !send_string(exfd, ruser)
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|| !send_string(exfd, cissuer)
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|| !send_string(exfd, chash)
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|| !send_vhost(exfd, c->host))
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goto err;
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close(c->fd);
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if ((c->fd = recv_fd(exfd)) == -1) {
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if (!start_reply(fds, c, TEMP_FAILURE, "internal server error"))
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return 0;
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goodbye(fds, c);
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return 0;
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}
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c->child = 1;
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c->state = S_SENDING;
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cgi_poll_on_child(fds, c);
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/* handle_cgi(fds, c); */
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return 0;
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err:
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/* fatal("cannot talk to the executor process: %s", strerror(errno)); */
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err(1, "cannot talk to the executor process");
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}
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void
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cgi_poll_on_child(struct pollfd *fds, struct client *c)
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{
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int fd;
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if (c->waiting_on_child)
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return;
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c->waiting_on_child = 1;
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fds->events = POLLIN;
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fd = fds->fd;
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fds->fd = c->fd;
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c->fd = fd;
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}
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void
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cgi_poll_on_client(struct pollfd *fds, struct client *c)
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{
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int fd;
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if (!c->waiting_on_child)
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return;
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c->waiting_on_child = 0;
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fd = fds->fd;
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fds->fd = c->fd;
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c->fd = fd;
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}
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void
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handle_cgi(struct pollfd *fds, struct client *c)
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{
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ssize_t r;
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/* ensure c->fd is the child and fds->fd the client */
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cgi_poll_on_client(fds, c);
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while (1) {
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if (c->len == 0) {
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if ((r = read(c->fd, c->sbuf, sizeof(c->sbuf))) == 0)
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goto end;
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if (r == -1) {
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if (errno == EAGAIN || errno == EWOULDBLOCK) {
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cgi_poll_on_child(fds, c);
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return;
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}
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goto end;
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}
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c->len = r;
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c->off = 0;
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}
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while (c->len > 0) {
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switch (r = tls_write(c->ctx, c->sbuf + c->off, c->len)) {
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case -1:
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goto end;
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case TLS_WANT_POLLOUT:
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fds->events = POLLOUT;
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return;
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case TLS_WANT_POLLIN:
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fds->events = POLLIN;
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return;
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default:
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c->off += r;
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c->len -= r;
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break;
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}
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}
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}
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end:
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goodbye(fds, c);
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}
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