From eb6c73cc11d6f8da5f19ef6d0794c41374dbfae4 Mon Sep 17 00:00:00 2001
From: lujingxiao <lujingxiao@huawei.com>
Date: Tue, 12 Feb 2019 19:07:09 +0800
Subject: [PATCH 89/94] Revert "nsenter:  clone /proc/self/exe to
 avoid exposing host binary to container"

reason: This reverts commit 275c8d34e6a6fa915ea4a4e47c45ce4c246a2410.
The origin patch is from discussion email, it is the early version,
which is different with the upstream:
https://github.com/opencontainers/runc/commit/0a8e4117e7f715d5fbeef398405813ce8e88558b
So revert this patch, and recommit with newer patch

Change-Id: Idb9250ce6dc86bd1a7640015b746c7afe8b03f49
Signed-off-by: lujingxiao <lujingxiao@huawei.com>
---
 libcontainer/nsenter/cloned_binary.c | 236 -----------------------------------
 libcontainer/nsenter/nsexec.c        |  11 --
 2 files changed, 247 deletions(-)
 delete mode 100644 libcontainer/nsenter/cloned_binary.c

diff --git a/libcontainer/nsenter/cloned_binary.c b/libcontainer/nsenter/cloned_binary.c
deleted file mode 100644
index ec383c1..0000000
--- a/libcontainer/nsenter/cloned_binary.c
+++ /dev/null
@@ -1,236 +0,0 @@
-#define _GNU_SOURCE
-#include <unistd.h>
-#include <stdio.h>
-#include <stdlib.h>
-#include <stdbool.h>
-#include <string.h>
-#include <limits.h>
-#include <fcntl.h>
-
-#include <sys/types.h>
-#include <sys/stat.h>
-#include <sys/vfs.h>
-#include <sys/mman.h>
-#include <sys/sendfile.h>
-#include <sys/syscall.h>
-
-#include <linux/magic.h>
-#include <linux/memfd.h>
-
-#define MEMFD_COMMENT "runc_cloned:/proc/self/exe"
-#define MEMFD_LNKNAME "/memfd:" MEMFD_COMMENT " (deleted)"
-
-/* Use our own wrapper for memfd_create. */
-#if !defined(SYS_memfd_create) && defined(__NR_memfd_create)
-#  define SYS_memfd_create __NR_memfd_create
-#endif
-#ifndef SYS_memfd_create
-#  error "memfd_create(2) syscall not supported by this glibc version"
-#endif
-int memfd_create(const char *name, unsigned int flags)
-{
-	return syscall(SYS_memfd_create, name, flags);
-}
-
-/* This comes directly from <linux/fcntl.h>. */
-#ifndef F_LINUX_SPECIFIC_BASE
-# define F_LINUX_SPECIFIC_BASE 1024
-#endif
-#ifndef F_ADD_SEALS
-# define F_ADD_SEALS (F_LINUX_SPECIFIC_BASE + 9)
-# define F_GET_SEALS (F_LINUX_SPECIFIC_BASE + 10)
-#endif
-#ifndef F_SEAL_SEAL
-# define F_SEAL_SEAL   0x0001	/* prevent further seals from being set */
-# define F_SEAL_SHRINK 0x0002	/* prevent file from shrinking */
-# define F_SEAL_GROW   0x0004	/* prevent file from growing */
-# define F_SEAL_WRITE  0x0008	/* prevent writes */
-#endif
-
-/*
- * Verify whether we are currently in a self-cloned program. It's not really
- * possible to trivially identify a memfd compared to a regular tmpfs file, so
- * the best we can do is to check whether the readlink(2) looks okay and that
- * it is on a tmpfs.
- */
-static int is_self_cloned(void)
-{
-	struct statfs statfsbuf = {0};
-	char linkname[PATH_MAX + 1] = {0};
-
-	if (statfs("/proc/self/exe", &statfsbuf) < 0)
-		return -1;
-	if (readlink("/proc/self/exe", linkname, PATH_MAX) < 0)
-		return -1;
-
-	return statfsbuf.f_type == TMPFS_MAGIC &&
-		!strncmp(linkname, MEMFD_LNKNAME, PATH_MAX);
-}
-
-/*
- * Basic wrapper around mmap(2) that gives you the file length so you can
- * safely treat it as an ordinary buffer. Only gives you read access.
- */
-static char *read_file(char *path, size_t *length)
-{
-	int fd;
-	char buf[4096], *copy = NULL;
-
-	if (!length)
-		goto err;
-	*length = 0;
-
-	fd = open(path, O_RDONLY|O_CLOEXEC);
-	if (fd < 0)
-		goto err_free;
-
-	for (;;) {
-		int n;
-		char *old = copy;
-
-		n = read(fd, buf, sizeof(buf));
-		if (n < 0)
-			goto err_fd;
-		if (!n)
-			break;
-
-		do {
-			copy = realloc(old, (*length + n) * sizeof(*old));
-		} while(!copy);
-
-		memcpy(copy + *length, buf, n);
-		*length += n;
-	}
-	close(fd);
-	return copy;
-
-err_fd:
-	close(fd);
-err_free:
-	free(copy);
-err:
-	return NULL;
-}
-
-/*
- * A poor-man's version of "xargs -0". Basically parses a given block of
- * NUL-delimited data, within the given length and adds a pointer to each entry
- * to the array of pointers.
- */
-static int parse_xargs(char *data, int data_length, char ***output)
-{
-	int num = 0;
-	char *cur = data;
-
-	if (!data || *output)
-		return -1;
-
-	do {
-		*output = malloc(sizeof(**output));
-	} while (!*output);
-
-	while (cur < data + data_length) {
-		char **old = *output;
-
-		num++;
-		do {
-			*output = realloc(old, (num + 1) * sizeof(*old));
-		} while (!*output);
-
-		(*output)[num - 1] = cur;
-		cur += strlen(cur) + 1;
-	}
-	(*output)[num] = NULL;
-	return num;
-}
-
-/*
- * "Parse" out argv and envp from /proc/self/cmdline and /proc/self/environ.
- * This is necessary because we are running in a context where we don't have a
- * main() that we can just get the arguments from.
- */
-static int fetchve(char ***argv, char ***envp)
-{
-	char *cmdline, *environ;
-	size_t cmdline_size, environ_size;
-
-	cmdline = read_file("/proc/self/cmdline", &cmdline_size);
-	if (!cmdline)
-		goto err;
-	environ = read_file("/proc/self/environ", &environ_size);
-	if (!environ)
-		goto err_free;
-
-	if (parse_xargs(cmdline, cmdline_size, argv) <= 0)
-		goto err_free_both;
-	if (parse_xargs(environ, environ_size, envp) <= 0)
-		goto err_free_both;
-
-	return 0;
-
-err_free_both:
-	free(environ);
-err_free:
-	free(cmdline);
-err:
-	return -1;
-}
-
-static int clone_binary(void)
-{
-	int binfd, memfd, err;
-	ssize_t sent = 0;
-	struct stat statbuf = {0};
-
-	binfd = open("/proc/self/exe", O_RDONLY|O_CLOEXEC);
-	if (binfd < 0)
-		goto err;
-	if (fstat(binfd, &statbuf) < 0)
-		goto err_binfd;
-
-	memfd = memfd_create(MEMFD_COMMENT, MFD_CLOEXEC|MFD_ALLOW_SEALING);
-	if (memfd < 0)
-		goto err_binfd;
-
-	while (sent < statbuf.st_size) {
-		ssize_t n = sendfile(memfd, binfd, NULL, statbuf.st_size - sent);
-		if (n < 0)
-			goto err_memfd;
-		sent += n;
-	}
-
-	err = fcntl(memfd, F_ADD_SEALS, F_SEAL_SHRINK|F_SEAL_GROW|F_SEAL_WRITE|F_SEAL_SEAL);
-	if (err < 0)
-		goto err_memfd;
-
-	close(binfd);
-	return memfd;
-
-err_memfd:
-	close(memfd);
-err_binfd:
-	close(binfd);
-err:
-	return -1;
-}
-
-int ensure_cloned_binary(void)
-{
-	int execfd;
-	char **argv = NULL, **envp = NULL;
-
-	/* Check that we're not self-cloned, and if we are then bail. */
-	int cloned = is_self_cloned();
-	if (cloned != 0)
-		return cloned;
-
-	if (fetchve(&argv, &envp) < 0)
-		return -1;
-
-	execfd = clone_binary();
-	if (execfd < 0)
-		return -1;
-
-	fexecve(execfd, argv, envp);
-	return -1;
-}
diff --git a/libcontainer/nsenter/nsexec.c b/libcontainer/nsenter/nsexec.c
index 75211c8..0ad6883 100644
--- a/libcontainer/nsenter/nsexec.c
+++ b/libcontainer/nsenter/nsexec.c
@@ -432,9 +432,6 @@ void join_namespaces(char *nslist)
 	free(namespaces);
 }
 
-/* Defined in cloned_binary.c. */
-int ensure_cloned_binary(void);
-
 void nsexec(void)
 {
 	int pipenum;
@@ -450,14 +447,6 @@ void nsexec(void)
 	if (pipenum == -1)
 		return;
 
-	/*
-	 * We need to re-exec if we are not in a cloned binary. This is necessary
-	 * to ensure that containers won't be able to access the host binary
-	 * through /proc/self/exe. See CVE-2019-5736.
-	 */
-	if (ensure_cloned_binary() < 0)
-		bail("could not ensure we are a cloned binary");
-
 	/* Parse all of the netlink configuration. */
 	nl_parse(pipenum, &config);
 
-- 
2.7.4.3

