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Move self-isolation code into a separate file

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passt/pasta contains a number of routines designed to isolate passt from
the rest of the system for security.  These are spread through util.c and
passt.c.  Move them together into a new isolation.c file.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
This commit is contained in:
David Gibson 2022-09-12 22:24:03 +10:00 • committed by Stefano Brivio
parent 5d3b50c100
commit d72a1e7bb9
8 changed files with 189 additions and 169 deletions

113
passt.c
View file

@ -19,51 +19,25 @@
* created in a separate network namespace).
*/
#include <sched.h>
#include <stdio.h>
#include <sys/epoll.h>
#include <sys/socket.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <dirent.h>
#include <fcntl.h>
#include <sys/mman.h>
#include <sys/resource.h>
#include <sys/uio.h>
#include <sys/syscall.h>
#include <sys/wait.h>
#include <sys/mount.h>
#include <netinet/ip.h>
#include <net/ethernet.h>
#include <libgen.h>
#include <stdlib.h>
#include <unistd.h>
#include <net/if.h>
#include <netdb.h>
#include <string.h>
#include <errno.h>
#include <time.h>
#include <syslog.h>
#include <sys/stat.h>
#include <sys/prctl.h>
#include <stddef.h>
#include <netinet/udp.h>
#include <netinet/tcp.h>
#include <netinet/if_ether.h>
#include <linux/seccomp.h>
#include <linux/audit.h>
#include <linux/filter.h>
#include <linux/icmpv6.h>
#include "util.h"
#include "seccomp.h"
#include "passt.h"
#include "dhcp.h"
#include "dhcpv6.h"
#include "icmp.h"
#include "tcp.h"
#include "udp.h"
#include "isolation.h"
#include "pcap.h"
#include "tap.h"
#include "conf.h"
@ -166,91 +140,6 @@ void proto_update_l2_buf(const unsigned char *eth_d, const unsigned char *eth_s,
udp_update_l2_buf(eth_d, eth_s, ip_da);
}
/**
* seccomp() - Set up seccomp filters depending on mode, won't return on failure
* @c: Execution context
*/
static void seccomp(const struct ctx *c)
{
struct sock_fprog prog;
if (c->mode == MODE_PASST) {
prog.len = (unsigned short)ARRAY_SIZE(filter_passt);
prog.filter = filter_passt;
} else {
prog.len = (unsigned short)ARRAY_SIZE(filter_pasta);
prog.filter = filter_pasta;
}
if (prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0) ||
prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &prog)) {
perror("prctl");
exit(EXIT_FAILURE);
}
}
/**
* sandbox() - Unshare IPC, mount, PID, UTS, and user namespaces, "unmount" root
*
* Return: negative error code on failure, zero on success
*/
static int sandbox(struct ctx *c)
{
int flags = CLONE_NEWIPC | CLONE_NEWNS | CLONE_NEWUTS;
if (!c->netns_only) {
if (c->pasta_userns_fd == -1)
flags |= CLONE_NEWUSER;
else
setns(c->pasta_userns_fd, CLONE_NEWUSER);
}
c->pasta_userns_fd = -1;
/* If we run in foreground, we have no chance to actually move to a new
* PID namespace. For passt, use CLONE_NEWPID anyway, in case somebody
* ever gets around seccomp profiles -- there's no harm in passing it.
*/
if (!c->foreground || c->mode == MODE_PASST)
flags |= CLONE_NEWPID;
if (unshare(flags)) {
perror("unshare");
return -errno;
}
if (mount("", "/", "", MS_UNBINDABLE | MS_REC, NULL)) {
perror("mount /");
return -errno;
}
if (mount("", TMPDIR, "tmpfs",
MS_NODEV | MS_NOEXEC | MS_NOSUID | MS_RDONLY,
"nr_inodes=2,nr_blocks=0")) {
perror("mount tmpfs");
return -errno;
}
if (chdir(TMPDIR)) {
perror("chdir");
return -errno;
}
if (syscall(SYS_pivot_root, ".", ".")) {
perror("pivot_root");
return -errno;
}
if (umount2(".", MNT_DETACH | UMOUNT_NOFOLLOW)) {
perror("umount2");
return -errno;
}
drop_caps(); /* Relative to the new user namespace this time. */
return 0;
}
/**
* exit_handler() - Signal handler for SIGQUIT and SIGTERM
* @unused: Unused, handler deals with SIGQUIT and SIGTERM only