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child.c
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child.c
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/* SPDX-License-Identifier: GPL-2.0-or-later
* Copyright (c) 2023 hmgle.
* Author: hmgle <dustgle@gmail.com>
*/
#ifndef _GNU_SOURCE
#define _GNU_SOURCE
#endif
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sched.h>
#include <errno.h>
#include <arpa/inet.h>
#include <sys/ioctl.h>
#include <net/route.h>
#include "util.h"
#include "log.h"
#include "passt.h"
#include "pasta.h"
#include "child.h"
static int up_network_interface(char *interface_name) {
int sockfd;
struct ifreq ifr;
sockfd = socket(AF_INET, SOCK_DGRAM, 0);
if (sockfd < 0) {
perror("socket");
return -1;
}
memset(&ifr, 0, sizeof(ifr));
#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Wstringop-truncation"
strncpy(ifr.ifr_name, interface_name, IFNAMSIZ - 1);
#pragma GCC diagnostic pop
if (ioctl(sockfd, SIOCGIFFLAGS, &ifr) < 0) {
perror("ioctl(SIOCGIFFLAGS)");
return -1;
}
ifr.ifr_flags |= IFF_UP;
if (ioctl(sockfd, SIOCSIFFLAGS, &ifr) < 0) {
perror("ioctl(SIOCSIFFLAGS)");
return -1;
}
return 0;
}
static int set_ip4(const char *interface, const char *ip4_addr, const char *mask)
{
int fd;
struct ifreq ifr;
struct sockaddr_in* addr;
int ret;
fd = socket(AF_INET, SOCK_DGRAM, 0);
if (fd < 0) {
perror("socket");
return -1;
}
memset(&ifr, 0, sizeof(struct ifreq));
ifr.ifr_addr.sa_family = AF_INET;
#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Wstringop-truncation"
strncpy(ifr.ifr_name, interface, IFNAMSIZ - 1);
#pragma GCC diagnostic pop
addr = (struct sockaddr_in*)&ifr.ifr_addr;
if (inet_pton(AF_INET, ip4_addr, &addr->sin_addr) != 1) {
warn("%s is not a valid IPv4 network address", ip4_addr);
ret = EXIT_FAILURE;
goto end;
}
ret = ioctl(fd, SIOCSIFADDR, &ifr);
if (ret) {
perror("SIOCSIFADDR");
goto end;
}
if (inet_pton(AF_INET, mask, &addr->sin_addr) != 1) {
warn("%s is not a valid IPv4 network address", mask);
ret = EXIT_FAILURE;
goto end;
}
ret = ioctl(fd, SIOCSIFNETMASK, &ifr);
if (ret)
perror("SIOCSIFNETMASK");
end:
close(fd);
return ret;
}
struct in6_ifreq {
struct in6_addr ifr6_addr;
uint32_t ifr6_prefixlen;
int ifr6_ifindex;
};
static int set_ip6(const char *interface, const char *ip6_addr)
{
int fd;
struct ifreq ifr;
struct in6_ifreq ifr6;
int ret;
fd = socket(AF_INET6, SOCK_DGRAM, IPPROTO_IP);
if (fd < 0) {
perror("socket");
return -1;
}
memset(&ifr, 0, sizeof(struct ifreq));
#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Wstringop-truncation"
strncpy(ifr.ifr_name, interface, IFNAMSIZ - 1);
#pragma GCC diagnostic pop
ret = ioctl(fd, SIOGIFINDEX, &ifr);
if (ret) {
perror("SIOGIFINDEX");
goto end;
}
if (inet_pton(AF_INET6, ip6_addr, &ifr6.ifr6_addr) != 1) {
warn("%s is not a valid IPv6 network address", ip6_addr);
ret = EXIT_FAILURE;
goto end;
}
ifr6.ifr6_ifindex = ifr.ifr_ifindex;
ifr6.ifr6_prefixlen = 64;
ret = ioctl(fd, SIOCSIFADDR, &ifr6);
if (ret)
perror("SIOCSIFADDR");
end:
close(fd);
return ret;
}
static int add_routing_table(char *interface, const char *ip4_addr)
{
int sockfd;
struct rtentry rt;
sockfd = socket(AF_INET, SOCK_DGRAM, 0);
if (sockfd == -1) {
perror("socket");
return -1;
}
memset(&rt, 0, sizeof(rt));
struct sockaddr_in *sockinfo = (struct sockaddr_in *)&rt.rt_gateway;
sockinfo->sin_family = AF_INET;
sockinfo->sin_addr.s_addr = inet_addr(ip4_addr);
sockinfo = (struct sockaddr_in *)&rt.rt_dst;
sockinfo->sin_family = AF_INET;
sockinfo->sin_addr.s_addr = INADDR_ANY;
sockinfo = (struct sockaddr_in *)&rt.rt_genmask;
sockinfo->sin_family = AF_INET;
sockinfo->sin_addr.s_addr = INADDR_ANY;
rt.rt_flags = RTF_UP | RTF_GATEWAY;
rt.rt_dev = interface;
if (ioctl(sockfd, SIOCADDRT, &rt) < 0)
perror("ioctl");
close(sockfd);
return 0;
}
static int add_routing_ip6_table(const char *interface_name, const char *ip6_addr) {
int sockfd;
struct in6_rtmsg route;
struct sockaddr_in6 *addr;
int ret;
memset(&route, 0, sizeof(route));
// Set gateway address
addr = (struct sockaddr_in6 *)&route.rtmsg_gateway;
addr->sin6_family = AF_INET6;
if (inet_pton(AF_INET6, ip6_addr, &addr->sin6_addr) != 1) {
warn("%s is not a valid IPv6 network address", ip6_addr);
return EXIT_FAILURE;
}
// Set prefix length
route.rtmsg_dst_len = 64;
memset(&addr->sin6_addr, 0, sizeof(addr->sin6_addr));
route.rtmsg_flags = RTF_UP;
route.rtmsg_ifindex = if_nametoindex(interface_name);
sockfd = socket(AF_INET6, SOCK_DGRAM, 0);
if (sockfd < 0) {
perror("socket");
return -1;
}
ret = ioctl(sockfd, SIOCADDRT, &route);
if (ret < 0)
perror("ioctl(SIOCADDRT)");
close(sockfd);
return ret;
}
static void do_child(int argc, char **argv)
{
char *args[argc + 1];
int i;
for (i = 0; i < argc; i++)
args[i] = argv[i];
args[argc] = NULL;
execvp(args[0], args);
perror("execvp");
exit(EXIT_FAILURE);
}
pid_t pasta_start_child(struct ctx *c, uid_t uid, gid_t gid, int argc, char **argv)
{
pid_t ch_pid;
sigset_t set, oldset;
sigprocmask(SIG_SETMASK, NULL, &oldset);
sigemptyset(&set);
sigaddset(&set, SIGUSR1);
sigprocmask(SIG_BLOCK, &set, NULL);
ch_pid = fork();
if (ch_pid == -1) {
perror("fork");
exit(EXIT_FAILURE);
} else if (ch_pid == 0) {
if (unshare(CLONE_NEWUSER | CLONE_NEWNET) == -1) {
perror("unshare1");
exit(EXIT_FAILURE);
}
char *uidmap = NULL;
char *gidmap = NULL;
if (asprintf(&uidmap, "0 %u 1", uid) < 0 ||
asprintf(&gidmap, "0 %u 1", gid) < 0) {
perror("asprintf");
exit(EXIT_FAILURE);
}
if (write_file("/proc/self/uid_map", uidmap) ||
write_file("/proc/self/setgroups", "deny") ||
write_file("/proc/self/gid_map", gidmap)) {
warn("Couldn't configure user mappings");
exit(EXIT_FAILURE);
}
kill(getppid(), SIGUSR1);
/* Wait for the parent to be ready: see main() */
sigprocmask(SIG_SETMASK, NULL, &oldset);
sigwaitinfo(&set, NULL);
sigprocmask(SIG_SETMASK, &oldset, NULL);
/* network config */
if (up_network_interface(c->pasta_ifn) < 0)
exit(EXIT_FAILURE);
char ipaddrbuf[INET_ADDRSTRLEN], maskbuf[INET_ADDRSTRLEN];
char routerbuf[INET_ADDRSTRLEN];
uint32_t mask = htonl(0xffffffff << (32 - c->ip4.prefix_len));
if (c->ifi4) {
inet_ntop(AF_INET, &c->ip4.addr, ipaddrbuf, sizeof(ipaddrbuf));
inet_ntop(AF_INET, &mask, maskbuf, sizeof(maskbuf));
inet_ntop(AF_INET, &c->ip4.gw, routerbuf, sizeof(routerbuf));
if (set_ip4(c->pasta_ifn, ipaddrbuf, maskbuf))
exit(EXIT_FAILURE);
if (add_routing_table(c->pasta_ifn, routerbuf))
exit(EXIT_FAILURE);
}
if (c->ifi6) {
inet_ntop(AF_INET, &c->ip6.addr, ipaddrbuf, sizeof(ipaddrbuf));
inet_ntop(AF_INET, &c->ip6.gw, routerbuf, sizeof(routerbuf));
if (set_ip6(c->pasta_ifn, ipaddrbuf))
exit(EXIT_FAILURE);
if (add_routing_ip6_table(c->pasta_ifn, routerbuf))
exit(EXIT_FAILURE);
}
if (write_file("/proc/sys/net/ipv4/ping_group_range", "0 0"))
warn("Cannot set ping_group_range, ICMP requests might fail");
if (unshare(CLONE_NEWUSER) == -1) {
perror("unshare2");
exit(EXIT_FAILURE);
}
sprintf(uidmap, "%u 0 1", uid);
sprintf(gidmap, "%u 0 1", gid);
if (write_file("/proc/self/uid_map", uidmap) ||
write_file("/proc/self/setgroups", "deny") ||
write_file("/proc/self/gid_map", gidmap)) {
warn("Couldn't configure user mappings");
exit(EXIT_FAILURE);
}
free(uidmap);
free(gidmap);
do_child(argc, argv);
}
pasta_child_pid = ch_pid;
sigwaitinfo(&set, NULL);
sigprocmask(SIG_SETMASK, &oldset, NULL);
return ch_pid;
}