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// SPDX-License-Identifier: AGPL-3.0-or-later
/* PASST - Plug A Simple Socket Transport
* for qemu/UNIX domain socket mode
*
* PASTA - Pack A Subtle Tap Abstraction
* for network namespace/tap device mode
*
* pasta.c - pasta (namespace) specific implementations
*
* Copyright (c) 2020-2021 Red Hat GmbH
* Author: Stefano Brivio <sbrivio@redhat.com>
*
* #syscalls:pasta clone waitid exit exit_group rt_sigprocmask
* #syscalls:pasta rt_sigreturn|sigreturn ppc64:sigreturn s390x:sigreturn
*/
#include <sched.h>
#include <stdio.h>
#include <string.h>
#include <errno.h>
#include <limits.h>
#include <stdlib.h>
#include <stdint.h>
#include <unistd.h>
#include <syslog.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <sys/wait.h>
#include <signal.h>
#include <dirent.h>
#include <arpa/inet.h>
#include <netinet/in.h>
#include <net/ethernet.h>
#include <sys/syscall.h>
#include "util.h"
#include "passt.h"
#include "netlink.h"
/* PID of child, in case we created a namespace */
static int pasta_child_pid;
/**
* pasta_child_handler() - Exit once shell exits (if we started it), reap clones
* @signal: Unused, handler deals with SIGCHLD only
*/
void pasta_child_handler(int signal)
{
siginfo_t infop;
(void)signal;
if (signal != SIGCHLD)
return;
if (pasta_child_pid &&
!waitid(P_PID, pasta_child_pid, &infop, WEXITED | WNOHANG)) {
if (infop.si_pid == pasta_child_pid)
exit(EXIT_SUCCESS);
/* Nothing to do, detached PID namespace going away */
}
waitid(P_ALL, 0, NULL, WEXITED | WNOHANG);
waitid(P_ALL, 0, NULL, WEXITED | WNOHANG);
}
/**
* pasta_wait_for_ns() - Busy loop until we can enter the target namespace
* @arg: Execution context
*
* Return: 0
*/
static int pasta_wait_for_ns(void *arg)
{
struct ctx *c = (struct ctx *)arg;
char ns[PATH_MAX];
if (c->netns_only)
goto netns;
snprintf(ns, PATH_MAX, "/proc/%i/ns/user", pasta_child_pid);
do
while ((c->pasta_userns_fd = open(ns, O_RDONLY)) < 0);
while (setns(c->pasta_userns_fd, CLONE_NEWUSER) &&
!close(c->pasta_userns_fd));
netns:
snprintf(ns, PATH_MAX, "/proc/%i/ns/net", pasta_child_pid);
do
while ((c->pasta_netns_fd = open(ns, O_RDONLY)) < 0);
while (setns(c->pasta_netns_fd, CLONE_NEWNET) &&
!close(c->pasta_netns_fd));
return 0;
}
/**
* struct pasta_setup_ns_arg - Argument for pasta_setup_ns()
* @c: Execution context
* @euid: Effective UID of caller
*/
struct pasta_setup_ns_arg {
struct ctx *c;
int euid;
};
/**
* pasta_setup_ns() - Map credentials, enable access to ping sockets, run shell
* @arg: See @pasta_setup_ns_arg
*
* Return: this function never returns
*/
static int pasta_setup_ns(void *arg)
{
struct pasta_setup_ns_arg *a = (struct pasta_setup_ns_arg *)arg;
char *shell;
int fd;
if (!a->c->netns_only) {
char buf[BUFSIZ];
snprintf(buf, BUFSIZ, "%i %i %i", 0, a->euid, 1);
fd = open("/proc/self/uid_map", O_WRONLY);
if (write(fd, buf, strlen(buf)) < 0)
warn("Cannot set uid_map in namespace");
close(fd);
fd = open("/proc/self/setgroups", O_WRONLY);
if (write(fd, "deny", sizeof("deny")) < 0)
warn("Cannot write to setgroups in namespace");
close(fd);
fd = open("/proc/self/gid_map", O_WRONLY);
if (write(fd, buf, strlen(buf)) < 0)
warn("Cannot set gid_map in namespace");
close(fd);
}
fd = open("/proc/sys/net/ipv4/ping_group_range", O_WRONLY);
if (write(fd, "0 0", strlen("0 0")) < 0)
warn("Cannot set ping_group_range, ICMP requests might fail");
close(fd);
shell = getenv("SHELL") ? getenv("SHELL") : "/bin/sh";
if (strstr(shell, "/bash"))
execve(shell, ((char *[]) { shell, "-l", NULL }), environ);
else
execve(shell, ((char *[]) { shell, NULL }), environ);
perror("execve");
exit(EXIT_FAILURE);
}
/**
* pasta_start_ns() - Fork shell in new namespace if target ns is not given
* @c: Execution context
*/
void pasta_start_ns(struct ctx *c)
{
struct pasta_setup_ns_arg arg = { .c = c, .euid = geteuid() };
char ns_fn_stack[NS_FN_STACK_SIZE];
c->foreground = 1;
if (!c->debug)
c->quiet = 1;
pasta_child_pid = clone(pasta_setup_ns,
ns_fn_stack + sizeof(ns_fn_stack) / 2,
(c->netns_only ? 0 : CLONE_NEWNET) |
CLONE_NEWIPC | CLONE_NEWPID | CLONE_NEWUSER |
CLONE_NEWUTS,
(void *)&arg);
if (pasta_child_pid == -1) {
perror("clone");
exit(EXIT_FAILURE);
}
drop_caps();
if (pasta_child_pid) {
NS_CALL(pasta_wait_for_ns, c);
return;
}
}
/**
* pasta_ns_conf() - Set up loopback and tap interfaces in namespace as needed
* @c: Execution context
*/
void pasta_ns_conf(struct ctx *c)
{
nl_link(1, 1 /* lo */, MAC_ZERO, 1, 0);
if (c->pasta_conf_ns) {
int prefix_len;
nl_link(1, c->pasta_ifi, c->mac_guest, 1, c->mtu);
if (c->v4) {
prefix_len = __builtin_popcount(c->mask4);
nl_addr(1, c->pasta_ifi, AF_INET, &c->addr4,
&prefix_len, NULL);
nl_route(1, c->pasta_ifi, AF_INET, &c->gw4);
}
if (c->v6) {
prefix_len = 64;
nl_addr(1, c->pasta_ifi, AF_INET6, &c->addr6,
&prefix_len, NULL);
nl_route(1, c->pasta_ifi, AF_INET6, &c->gw6);
}
} else {
nl_link(1, c->pasta_ifi, c->mac_guest, 0, 0);
}
proto_update_l2_buf(c->mac_guest, NULL, NULL);
}
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