Add 'run-as' command implementation as set-uid program. (1f4d9529) · Commits · e / os / android_system_core

include/private/android_filesystem_config.h

+4 −1

Original line number	Diff line number	Diff line
		@@ -169,7 +169,7 @@ static struct fs_path_config android_files[] = {
		* Do not change. */
		{ 02755, AID_ROOT, AID_NET_RAW, "system/bin/ping" },
		{ 02750, AID_ROOT, AID_INET, "system/bin/netcfg" },
		/* the following four files are INTENTIONALLY set-uid, but they
		/* the following five files are INTENTIONALLY set-uid, but they
		* are NOT included on user builds. */
		{ 06755, AID_ROOT, AID_ROOT, "system/xbin/su" },
		{ 06755, AID_ROOT, AID_ROOT, "system/xbin/librank" },
		@@ -177,6 +177,9 @@ static struct fs_path_config android_files[] = {
		{ 06755, AID_ROOT, AID_ROOT, "system/xbin/procmem" },
		{ 06755, AID_ROOT, AID_ROOT, "system/xbin/tcpdump" },
		{ 04770, AID_ROOT, AID_RADIO, "system/bin/pppd-ril" },
		/* the following file is INTENTIONALLY set-uid, and IS included
		* in user builds. */
		{ 06750, AID_ROOT, AID_SHELL, "system/bin/run-as" },
		{ 00755, AID_ROOT, AID_SHELL, "system/bin/*" },
		{ 00755, AID_ROOT, AID_SHELL, "system/xbin/*" },
		{ 00750, AID_ROOT, AID_SHELL, "sbin/*" },

run-as/Android.mk

0 → 100644

+12 −0

Original line number	Diff line number	Diff line
		LOCAL_PATH:= $(call my-dir)
		include $(CLEAR_VARS)

		LOCAL_SRC_FILES:= run-as.c package.c

		LOCAL_MODULE:= run-as

		LOCAL_FORCE_STATIC_EXECUTABLE := true

		LOCAL_STATIC_LIBRARIES := libc

		include $(BUILD_EXECUTABLE)

run-as/NOTICE

0 → 100644

+190 −0

Original line number	Diff line number	Diff line

		Copyright (c) 2005-2008, The Android Open Source Project

		Licensed under the Apache License, Version 2.0 (the "License");
		you may not use this file except in compliance with the License.

		Unless required by applicable law or agreed to in writing, software
		distributed under the License is distributed on an "AS IS" BASIS,
		WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
		See the License for the specific language governing permissions and
		limitations under the License.


		Apache License
		Version 2.0, January 2004
		http://www.apache.org/licenses/

		TERMS AND CONDITIONS FOR USE, REPRODUCTION, AND DISTRIBUTION

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		form, that is based on (or derived from) the Work and for which the
		editorial revisions, annotations, elaborations, or other modifications
		represent, as a whole, an original work of authorship. For the purposes
		of this License, Derivative Works shall not include works that remain
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		"Contribution" shall mean any work of authorship, including
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		of the NOTICE file are for informational purposes only and
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		may provide additional or different license terms and conditions
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		the conditions stated in this License.

		5. Submission of Contributions. Unless You explicitly state otherwise,
		any Contribution intentionally submitted for inclusion in the Work
		by You to the Licensor shall be under the terms and conditions of
		this License, without any additional terms or conditions.
		Notwithstanding the above, nothing herein shall supersede or modify
		the terms of any separate license agreement you may have executed
		with Licensor regarding such Contributions.

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run-as/package.c

0 → 100644

+471 −0

Original line number	Diff line number	Diff line
		/*
		**
		** Copyright 2010, The Android Open Source Project
		**
		** Licensed under the Apache License, Version 2.0 (the "License");
		** you may not use this file except in compliance with the License.
		** You may obtain a copy of the License at
		**
		** http://www.apache.org/licenses/LICENSE-2.0
		**
		** Unless required by applicable law or agreed to in writing, software
		** distributed under the License is distributed on an "AS IS" BASIS,
		** WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
		** See the License for the specific language governing permissions and
		** limitations under the License.
		*/
		#include <errno.h>
		#include <fcntl.h>
		#include <unistd.h>
		#include <sys/stat.h>
		#include <private/android_filesystem_config.h>
		#include "package.h"

		/*
		* WARNING WARNING WARNING WARNING
		*
		* The following code runs as root on production devices, before
		* the run-as command has dropped the uid/gid. Hence be very
		* conservative and keep in mind the following:
		*
		* - Performance does not matter here, clarity and safety of the code
		* does however. Documentation is a must.
		*
		* - Avoid calling C library functions with complex implementations
		* like malloc() and printf(). You want to depend on simple system
		* calls instead, which behaviour is not going to be altered in
		* unpredictible ways by environment variables or system properties.
		*
		* - Do not trust user input and/or the filesystem whenever possible.
		*
		*/

		/* The file containing the list of installed packages on the system */
		#define PACKAGES_LIST_FILE "/data/system/packages.list"

		/* This should be large enough to hold the content of the package database file */
		#define PACKAGES_LIST_BUFFER_SIZE 8192

		/* Copy 'srclen' string bytes from 'src' into buffer 'dst' of size 'dstlen'
		* This function always zero-terminate the destination buffer unless
		* 'dstlen' is 0, even in case of overflow.
		*/
		static void
		string_copy(char* dst, size_t dstlen, const char* src, size_t srclen)
		{
		const char* srcend = src + srclen;
		const char* dstend = dst + dstlen;

		if (dstlen == 0)
		return;

		dstend--; /* make room for terminating zero */

		while (dst < dstend && src < srcend && *src != '\0')
		dst++ = src++;

		dst = '\0'; / zero-terminate result */
		}

		/* Read up to 'buffsize' bytes into 'buff' from the file
		* named 'filename'. Return byte length on success, or -1
		* on error.
		*/
		static int
		read_file(const char* filename, char* buff, size_t buffsize)
		{
		int fd, len, old_errno;

		/* check the input buffer size */
		if (buffsize >= INT_MAX) {
		errno = EINVAL;
		return -1;
		}

		/* open the file for reading */
		do {
		fd = open(filename, O_RDONLY);
		} while (fd < 0 && errno == EINTR);

		if (fd < 0)
		return -1;

		/* read the content */
		do {
		len = read(fd, buff, buffsize);
		} while (len < 0 && errno == EINTR);

		/* close the file, preserve old errno for better diagnostics */
		old_errno = errno;
		close(fd);
		errno = old_errno;

		return len;
		}

		/* Check that a given directory:
		* - exists
		* - is owned by a given uid/gid
		* - is a real directory, not a symlink
		* - isn't readable or writable by others
		*
		* Return 0 on success, or -1 on error.
		* errno is set to EINVAL in case of failed check.
		*/
		static int
		check_directory_ownership(const char* path, uid_t uid)
		{
		int ret;
		struct stat st;

		do {
		ret = lstat(path, &st);
		} while (ret < 0 && errno == EINTR);

		if (ret < 0)
		return -1;

		/* must be a real directory, not a symlink */
		if (!S_ISDIR(st.st_mode))
		goto BAD;

		/* must be owned by specific uid/gid */
		if (st.st_uid != uid \|\| st.st_gid != uid)
		goto BAD;

		/* must not be readable or writable by others */
		if ((st.st_mode & (S_IROTH\|S_IWOTH)) != 0)
		goto BAD;

		/* everything ok */
		return 0;

		BAD:
		errno = EINVAL;
		return -1;
		}

		/* This function is used to check the data directory path for safety.
		* We check that every sub-directory is owned by the 'system' user
		* and exists and is not a symlink. We also check that the full directory
		* path is properly owned by the user ID.
		*
		* Return 0 on success, -1 on error.
		*/
		int
		check_data_path(const char* dataPath, uid_t uid)
		{
		int nn;

		/* the path should be absolute */
		if (dataPath[0] != '/') {
		errno = EINVAL;
		return -1;
		}

		/* look for all sub-paths, we do that by finding
		* directory separators in the input path and
		* checking each sub-path independently
		*/
		for (nn = 1; dataPath[nn] != '\0'; nn++)
		{
		char subpath[PATH_MAX];

		/* skip non-separator characters */
		if (dataPath[nn] != '/')
		continue;

		/* handle trailing separator case */
		if (dataPath[nn+1] == '\0') {
		break;
		}

		/* found a separator, check that dataPath is not too long. */
		if (nn >= (int)(sizeof subpath)) {
		errno = EINVAL;
		return -1;
		}

		/* reject any '..' subpath */
		if (nn >= 3 &&
		dataPath[nn-3] == '/' &&
		dataPath[nn-2] == '.' &&
		dataPath[nn-1] == '.') {
		errno = EINVAL;
		return -1;
		}

		/* copy to 'subpath', then check ownership */
		memcpy(subpath, dataPath, nn);
		subpath[nn] = '\0';

		if (check_directory_ownership(subpath, AID_SYSTEM) < 0)
		return -1;
		}

		/* All sub-paths were checked, now verify that the full data
		* directory is owned by the application uid
		*/
		if (check_directory_ownership(dataPath, uid) < 0)
		return -1;

		/* all clear */
		return 0;
		}

		/* Return TRUE iff a character is a space or tab */
		static inline int
		is_space(char c)
		{
		return (c == ' ' \|\| c == '\t');
		}

		/* Skip any space or tab character from 'p' until 'end' is reached.
		* Return new position.
		*/
		static const char*
		skip_spaces(const char* p, const char* end)
		{
		while (p < end && is_space(*p))
		p++;

		return p;
		}

		/* Skip any non-space and non-tab character from 'p' until 'end'.
		* Return new position.
		*/
		static const char*
		skip_non_spaces(const char* p, const char* end)
		{
		while (p < end && !is_space(*p))
		p++;

		return p;
		}

		/* Find the first occurence of 'ch' between 'p' and 'end'
		* Return its position, or 'end' if none is found.
		*/
		static const char*
		find_first(const char* p, const char* end, char ch)
		{
		while (p < end && *p != ch)
		p++;

		return p;
		}

		/* Check that the non-space string starting at 'p' and eventually
		* ending at 'end' equals 'name'. Return new position (after name)
		* on success, or NULL on failure.
		*
		* This function fails is 'name' is NULL, empty or contains any space.
		*/
		static const char*
		compare_name(const char* p, const char* end, const char* name)
		{
		/* 'name' must not be NULL or empty */
		if (name == NULL \|\| name[0] == '\0' \|\| p == end)
		return NULL;

		/* compare characters to those in 'name', excluding spaces */
		while (*name) {
		/* note, we don't check for *p == '\0' since
		* it will be caught in the next conditional.
		*/
		if (p >= end \|\| is_space(*p))
		goto BAD;

		if (p != name)
		goto BAD;

		p++;
		name++;
		}

		/* must be followed by end of line or space */
		if (p < end && !is_space(*p))
		goto BAD;

		return p;

		BAD:
		return NULL;
		}

		/* Parse one or more whitespace characters starting from '*pp'
		* until 'end' is reached. Updates '*pp' on exit.
		*
		* Return 0 on success, -1 on failure.
		*/
		static int
		parse_spaces(const char** pp, const char* end)
		{
		const char* p = *pp;

		if (p >= end \|\| !is_space(*p)) {
		errno = EINVAL;
		return -1;
		}
		p = skip_spaces(p, end);
		*pp = p;
		return 0;
		}

		/* Parse a positive decimal number starting from '*pp' until 'end'
		* is reached. Adjust '*pp' on exit. Return decimal value or -1
		* in case of error.
		*
		* If the value is larger than INT_MAX, -1 will be returned,
		* and errno set to EOVERFLOW.
		*
		* If '*pp' does not start with a decimal digit, -1 is returned
		* and errno set to EINVAL.
		*/
		static int
		parse_positive_decimal(const char** pp, const char* end)
		{
		const char* p = *pp;
		int value = 0;
		int overflow = 0;

		if (p >= end \|\| p < '0' \|\| p > '9') {
		errno = EINVAL;
		return -1;
		}

		while (p < end) {
		int ch = *p;
		unsigned d = (unsigned)(ch - '0');
		int val2;

		if (d >= 10U) /* d is unsigned, no lower bound check */
		break;

		val2 = value*10 + (int)d;
		if (val2 < value)
		overflow = 1;
		value = val2;
		p++;
		}
		*pp = p;

		if (overflow) {
		errno = EOVERFLOW;
		value = -1;
		}
		return value;

		BAD:
		*pp = p;
		return -1;
		}

		/* Read the system's package database and extract information about
		* 'pkgname'. Return 0 in case of success, or -1 in case of error.
		*
		* If the package is unknown, return -1 and set errno to ENOENT
		* If the package database is corrupted, return -1 and set errno to EINVAL
		*/
		int
		get_package_info(const char* pkgName, PackageInfo *info)
		{
		static char buffer[PACKAGES_LIST_BUFFER_SIZE];
		int buffer_len;
		const char* p;
		const char* buffer_end;
		int result;

		info->uid = 0;
		info->isDebuggable = 0;
		info->dataDir[0] = '\0';

		buffer_len = read_file(PACKAGES_LIST_FILE, buffer, sizeof buffer);
		if (buffer_len < 0)
		return -1;

		p = buffer;
		buffer_end = buffer + buffer_len;

		/* expect the following format on each line of the control file:
		*
		* <pkgName> <uid> <debugFlag> <dataDir>
		*
		* where:
		* <pkgName> is the package's name
		* <uid> is the application-specific user Id (decimal)
		* <debugFlag> is 1 if the package is debuggable, or 0 otherwise
		* <dataDir> is the path to the package's data directory (e.g. /data/data/com.example.foo)
		*
		* The file is generated in com.android.server.PackageManagerService.Settings.writeLP()
		*/

		while (p < buffer_end) {
		/* find end of current line and start of next one */
		const char* end = find_first(p, buffer_end, '\n');
		const char* next = (end < buffer_end) ? end + 1 : buffer_end;
		const char* q;
		int uid, debugFlag;

		/* first field is the package name */
		p = compare_name(p, end, pkgName);
		if (p == NULL)
		goto NEXT_LINE;

		/* skip spaces */
		if (parse_spaces(&p, end) < 0)
		goto BAD_FORMAT;

		/* second field is the pid */
		uid = parse_positive_decimal(&p, end);
		if (uid < 0)
		return -1;

		info->uid = (uid_t) uid;

		/* skip spaces */
		if (parse_spaces(&p, end) < 0)
		goto BAD_FORMAT;

		/* third field is debug flag (0 or 1) */
		debugFlag = parse_positive_decimal(&p, end);
		switch (debugFlag) {
		case 0:
		info->isDebuggable = 0;
		break;
		case 1:
		info->isDebuggable = 1;
		break;
		default:
		goto BAD_FORMAT;
		}

		/* skip spaces */
		if (parse_spaces(&p, end) < 0)
		goto BAD_FORMAT;

		/* fourth field is data directory path and must not contain
		* spaces.
		*/
		q = skip_non_spaces(p, end);
		if (q == p)
		goto BAD_FORMAT;

		string_copy(info->dataDir, sizeof info->dataDir, p, q - p);

		/* Ignore the rest */
		return 0;

		NEXT_LINE:
		p = next;
		}

		/* the package is unknown */
		errno = ENOENT;
		return -1;

		BAD_FORMAT:
		errno = EINVAL;
		return -1;
		}

run-as/package.h

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Preview size limit exceeded, changes collapsed.