mirror of
https://github.com/omar-polo/gmid.git
synced 2024-09-11 13:38:34 +02:00
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.
294 lines
6.0 KiB
C
294 lines
6.0 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 <err.h>
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#include <errno.h>
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#include <fcntl.h>
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#include <signal.h>
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#include <string.h>
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#include "gmid.h"
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int
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send_string(int fd, const char *str)
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{
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ssize_t len;
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if (str == NULL)
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len = 0;
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else
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len = strlen(str);
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if (write(fd, &len, sizeof(len)) != sizeof(len))
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return 0;
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if (len != 0)
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if (write(fd, str, len) != len)
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return 0;
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return 1;
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}
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int
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recv_string(int fd, char **ret)
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{
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ssize_t len;
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if (read(fd, &len, sizeof(len)) != sizeof(len))
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return 0;
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if (len == 0) {
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*ret = NULL;
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return 1;
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}
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if ((*ret = calloc(1, len+1)) == NULL)
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return 0;
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if (read(fd, *ret, len) != len)
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return 0;
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return 1;
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}
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int
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send_vhost(int fd, struct vhost *vhost)
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{
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ssize_t n;
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if (vhost < hosts || vhost > hosts + HOSTSLEN)
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return 0;
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n = hosts - vhost;
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return write(fd, &n, sizeof(n)) == sizeof(n);
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}
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int
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recv_vhost(int fd, struct vhost **vhost)
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{
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ssize_t n;
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if (read(fd, &n, sizeof(n)) != sizeof(n))
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return 0;
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if (n < 0 || n > HOSTSLEN)
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return 0;
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*vhost = &hosts[n];
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if ((*vhost)->domain == NULL)
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return 0;
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return 1;
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}
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/* send d though fd. see /usr/src/usr.sbin/syslogd/privsep_fdpass.c
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* for an example */
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int
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send_fd(int fd, int d)
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{
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struct msghdr msg;
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union {
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struct cmsghdr hdr;
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unsigned char buf[CMSG_SPACE(sizeof(int))];
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} cmsgbuf;
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struct cmsghdr *cmsg;
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struct iovec vec;
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int result = 1;
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ssize_t n;
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memset(&msg, 0, sizeof(msg));
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if (d >= 0) {
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msg.msg_control = &cmsgbuf.buf;
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msg.msg_controllen = sizeof(cmsgbuf.buf);
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cmsg = CMSG_FIRSTHDR(&msg);
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cmsg->cmsg_len = CMSG_LEN(sizeof(int));
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cmsg->cmsg_level = SOL_SOCKET;
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cmsg->cmsg_type = SCM_RIGHTS;
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*(int*)CMSG_DATA(cmsg) = d;
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} else
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result = 0;
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vec.iov_base = &result;
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vec.iov_len = sizeof(int);
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msg.msg_iov = &vec;
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msg.msg_iovlen = 1;
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if ((n = sendmsg(fd, &msg, 0)) == -1 || n != sizeof(int)) {
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fprintf(stderr, "sendmsg: got %zu but wanted %zu: (errno) %s",
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n, sizeof(int), strerror(errno));
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return 0;
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}
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return 1;
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}
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/* receive a descriptor via fd */
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int
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recv_fd(int fd)
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{
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struct msghdr msg;
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union {
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struct cmsghdr hdr;
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char buf[CMSG_SPACE(sizeof(int))];
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} cmsgbuf;
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struct cmsghdr *cmsg;
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struct iovec vec;
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ssize_t n;
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int result;
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memset(&msg, 0, sizeof(msg));
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vec.iov_base = &result;
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vec.iov_len = sizeof(int);
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msg.msg_iov = &vec;
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msg.msg_iovlen = 1;
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msg.msg_control = &cmsgbuf.buf;
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msg.msg_controllen = sizeof(cmsgbuf.buf);
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if ((n = recvmsg(fd, &msg, 0)) != sizeof(int)) {
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fprintf(stderr, "read %zu bytes bu wanted %zu\n", n, sizeof(int));
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return -1;
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}
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if (result) {
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cmsg = CMSG_FIRSTHDR(&msg);
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if (cmsg == NULL || cmsg->cmsg_type != SCM_RIGHTS)
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return -1;
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return (*(int *)CMSG_DATA(cmsg));
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} else
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return -1;
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}
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static inline void
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safe_setenv(const char *name, const char *val)
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{
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if (val == NULL)
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val = "";
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setenv(name, val, 1);
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}
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/* fd or -1 on error */
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static int
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launch_cgi(const char *spath, const char *relpath, const char *query,
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const char *addr, const char *ruser, const char *cissuer, const char *chash,
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struct vhost *vhost)
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{
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int p[2]; /* read end, write end */
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if (pipe2(p, O_NONBLOCK) == -1)
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return -1;
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switch (fork()) {
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case -1:
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return -1;
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case 0: { /* child */
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char *portno, *ex, *requri;
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char *argv[] = { NULL, NULL, NULL };
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close(p[0]);
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if (dup2(p[1], 1) == -1)
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goto childerr;
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if (asprintf(&portno, "%d", conf.port) == -1)
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goto childerr;
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if (asprintf(&ex, "%s/%s", vhost->dir, spath) == -1)
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goto childerr;
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if (asprintf(&requri, "%s%s%s", spath,
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(relpath != NULL && *relpath == '\0') ? "" : "/", relpath) == -1)
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goto childerr;
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argv[0] = argv[1] = ex;
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safe_setenv("GATEWAY_INTERFACE", "CGI/1.1");
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safe_setenv("SERVER_SOFTWARE", "gmid");
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safe_setenv("SERVER_PORT", portno);
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if (!strcmp(vhost->domain, "*"))
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safe_setenv("SERVER_NAME", vhost->domain);
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safe_setenv("SCRIPT_NAME", spath);
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safe_setenv("SCRIPT_EXECUTABLE", ex);
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safe_setenv("REQUEST_URI", requri);
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safe_setenv("REQUEST_RELATIVE", relpath);
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safe_setenv("QUERY_STRING", query);
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safe_setenv("REMOTE_HOST", addr);
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safe_setenv("REMOTE_ADDR", addr);
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safe_setenv("DOCUMENT_ROOT", vhost->dir);
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if (ruser != NULL) {
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safe_setenv("AUTH_TYPE", "Certificate");
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safe_setenv("REMOTE_USER", ruser);
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safe_setenv("TLS_CLIENT_ISSUER", cissuer);
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safe_setenv("TLS_CLIENT_HASH", chash);
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}
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execvp(ex, argv);
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goto childerr;
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}
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default:
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close(p[1]);
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return p[0];
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}
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childerr:
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dprintf(p[1], "%d internal server error\r\n", TEMP_FAILURE);
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_exit(1);
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}
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int
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executor_main(int fd)
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{
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char *spath, *relpath, *query, *addr, *ruser, *cissuer, *chash;
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struct vhost *vhost;
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int d;
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#ifdef __OpenBSD__
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pledge("stdio sendfd proc exec", NULL);
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#endif
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for (;;) {
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if (!recv_string(fd, &spath)
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|| !recv_string(fd, &relpath)
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|| !recv_string(fd, &query)
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|| !recv_string(fd, &addr)
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|| !recv_string(fd, &ruser)
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|| !recv_string(fd, &cissuer)
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|| !recv_string(fd, &chash)
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|| !recv_vhost(fd, &vhost))
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break;
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d = launch_cgi(spath, relpath, query,
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addr, ruser, cissuer, chash, vhost);
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if (!send_fd(fd, d))
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break;
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free(spath);
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free(relpath);
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free(query);
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free(addr);
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free(ruser);
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free(cissuer);
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free(chash);
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}
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/* kill all process in my group. This means the listener and
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* every pending CGI script. */
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kill(0, SIGINT);
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return 1;
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}
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