From 9b1ca569db3e698c3a901720ae6989c876a9e6ee Mon Sep 17 00:00:00 2001 From: Sandeep Patil Date: Mon, 21 Aug 2017 12:17:19 -0700 Subject: [PATCH] libc: Add support to allow library calls to find appropriate shell executable for a process Library calls like system() and popen() invoke the shell executable pointed to by '_PATH_BSHELL' in order to run the command passed into the function. The _PATH_BSHELL points to /system/bin/sh by default and thus breaks any vendor process trying to use system() / popen(), as they are denied access to system shell by selinux. This CL make necessary changes, so the implmentations of system() and popen() can use the appropriate shell (e.g. /vendor/bin/sh for processes running out of /vendor partition). Also, changes the implementation of system() and popen(). Bug: 64832610 Test: Manual, Using a test program running from /system/bin and /vendor/bin to ensure correct shell is being used. Change-Id: Ie7168d69decb1ae98284446ae7db34dec930dc33 Merged-In: Ie7168d69decb1ae98284446ae7db34dec930dc33 Signed-off-by: Sandeep Patil (cherry picked from commit aa3e32422cc7089b9b15976f2651a58840d95e4f) --- libc/Android.bp | 1 + libc/bionic/__bionic_get_shell_path.cpp | 51 +++++++++++++++++++ libc/include/paths.h | 2 + .../android/include/netbsd-compat.h | 4 ++ .../android/include/openbsd-compat.h | 4 ++ 5 files changed, 62 insertions(+) create mode 100644 libc/bionic/__bionic_get_shell_path.cpp diff --git a/libc/Android.bp b/libc/Android.bp index 42d091456..be45f40ed 100644 --- a/libc/Android.bp +++ b/libc/Android.bp @@ -1385,6 +1385,7 @@ cc_library_static { defaults: ["libc_defaults"], srcs: [ "bionic/NetdClientDispatch.cpp", + "bionic/__bionic_get_shell_path.cpp", "bionic/__cmsg_nxthdr.cpp", "bionic/__errno.cpp", "bionic/__gnu_basename.cpp", diff --git a/libc/bionic/__bionic_get_shell_path.cpp b/libc/bionic/__bionic_get_shell_path.cpp new file mode 100644 index 000000000..477fa4a1b --- /dev/null +++ b/libc/bionic/__bionic_get_shell_path.cpp @@ -0,0 +1,51 @@ +/* + * Copyright (C) 2017 The Android Open Source Project + * All rights reserved. + * + * Redistribution and use in source and binary forms, with or without + * modification, are permitted provided that the following conditions + * are met: + * * Redistributions of source code must retain the above copyright + * notice, this list of conditions and the following disclaimer. + * * Redistributions in binary form must reproduce the above copyright + * notice, this list of conditions and the following disclaimer in + * the documentation and/or other materials provided with the + * distribution. + * + * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS + * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT + * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS + * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE + * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, + * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, + * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS + * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED + * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, + * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT + * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF + * SUCH DAMAGE. + */ + +#include +#include +#include +#include + +__LIBC_HIDDEN__ static const char* __libc_system_sh = "/system/bin/sh"; +__LIBC_HIDDEN__ static const char* __libc_vendor_sh = "/vendor/bin/sh"; + +static const char* init_sh_path() { + /* look for /system or /vendor prefix */ + char exe_path[7]; + ssize_t len = readlink("/proc/self/exe", exe_path, sizeof(exe_path)); + if (len != -1 && !strncmp(exe_path, __libc_vendor_sh, sizeof(exe_path))) { + return __libc_vendor_sh; + } + + return __libc_system_sh; +} + +__LIBC_HIDDEN__ extern "C" const char* __bionic_get_shell_path() { + static const char* sh_path = init_sh_path(); + return sh_path; +} diff --git a/libc/include/paths.h b/libc/include/paths.h index b76d0454a..d2c5956a8 100644 --- a/libc/include/paths.h +++ b/libc/include/paths.h @@ -34,7 +34,9 @@ #include +#ifndef _PATH_BSHELL #define _PATH_BSHELL "/system/bin/sh" +#endif #define _PATH_CONSOLE "/dev/console" #define _PATH_DEFPATH "/sbin:/system/sbin:/system/bin:/system/xbin:/vendor/bin:/vendor/xbin" #define _PATH_DEV "/dev/" diff --git a/libc/upstream-netbsd/android/include/netbsd-compat.h b/libc/upstream-netbsd/android/include/netbsd-compat.h index 45b974a6f..af5ae2927 100644 --- a/libc/upstream-netbsd/android/include/netbsd-compat.h +++ b/libc/upstream-netbsd/android/include/netbsd-compat.h @@ -44,4 +44,8 @@ #include int reallocarr(void*, size_t, size_t); +/* Use appropriate shell depending on process's executable. */ +__LIBC_HIDDEN__ extern const char* __bionic_get_shell_path(); +#define _PATH_BSHELL __bionic_get_shell_path() + #endif diff --git a/libc/upstream-openbsd/android/include/openbsd-compat.h b/libc/upstream-openbsd/android/include/openbsd-compat.h index baf505723..d83143583 100644 --- a/libc/upstream-openbsd/android/include/openbsd-compat.h +++ b/libc/upstream-openbsd/android/include/openbsd-compat.h @@ -71,6 +71,10 @@ extern const char* __progname; */ #define _PATH_TMP "/data/local/tmp/" +/* Use appropriate shell depending on process's executable. */ +__LIBC_HIDDEN__ extern const char* __bionic_get_shell_path(); +#define _PATH_BSHELL __bionic_get_shell_path() + /* We have OpenBSD's getentropy_linux.c, but we don't mention getentropy in any header. */ __LIBC_HIDDEN__ extern int getentropy(void*, size_t);