From: Jon Trulson Date: Sun, 12 Jan 2020 02:30:51 +0000 (-0700) Subject: dtsession, DtSvc: fix CVE-2020-2696/VU#308289 X-Git-Url: https://git.librecmc.org/?a=commitdiff_plain;h=6b32246d06ab16fd7897dc344db69d0957f3ae08;p=oweals%2Fcde.git dtsession, DtSvc: fix CVE-2020-2696/VU#308289 Marco Ivaldi has identified 3 vulnerabilities in CDE. Two of them could affect our CDE (open-source version), while the 3rd (sdtcm_convert) is Solaris specific. The two vulnerabilities, both of which affect dtsession could allow a local privilege escalation to root. A POC exists for Solaris. The POC will not function on our CDE for two main reasons: - the POC is Solaris specific - The overflowed variables in question are allocated on the heap, whereas in Solaris these variables are located on the stack. The first vulnerability allows an extra long palette name to be used to cause a crash via insufficient validation in SrvPalette.c:CheckMonitor(). The second, which has not yet been assigned a CERT CVE resides in SmCreateDirs.c:_DtCreateDtDirs() in libDtSvc. Due to insufficient bounds checking, a crash or corruption can be achieved by using a very long DISPLAY name. This one is considered difficult to exploit, and no POC code is available at this time. CDE 2.x code-bases are also listed as not vulnerable, however some work has been done anyway to do some proper bounds checking in this function. The following text portions are copied from the relevant advisories, which have not been released as of this writing. NOTE: Oracle CDE does NOT use CDE 2.3.0a or earlier as mentioned below. They are completely different code-bases): Regarding CVE-2020-2692: A buffer overflow in the CheckMonitor() function in the Common Desktop Environment 2.3.0a and earlier, as distributed with Oracle Solaris 10 1/13 (Update 11) and earlier, allows local users to gain root privileges via a long palette name passed to dtsession in a malicious .Xdefaults file. Note that Oracle Solaris CDE is based on the original CDE 1.x train, which is different from the CDE 2.x codebase that was later open sourced. Most notably, the vulnerable buffer in the Oracle Solaris CDE is stack-based, while in the open source version it is heap-based. Regarding the DtSvc bug, which does not currently have a CERT CVE: A difficult to exploit stack-based buffer overflow in the _DtCreateDtDirs() function in the Common Desktop Environment version distributed with Oracle Solaris 10 1/13 (Update 11) and earlier may allow local users to corrupt memory and potentially execute arbitrary code in order to escalate privileges via a long X11 display name. The vulnerable function is located in the libDtSvc library and can be reached by executing the setuid program dtsession. The open source version of CDE (based on the CDE 2.x codebase) is not affected. --- diff --git a/cde/lib/DtSvc/DtUtil1/SmUtil.c b/cde/lib/DtSvc/DtUtil1/SmUtil.c index 3fa75b7c..af4a83b2 100644 --- a/cde/lib/DtSvc/DtUtil1/SmUtil.c +++ b/cde/lib/DtSvc/DtUtil1/SmUtil.c @@ -176,10 +176,23 @@ getSessionPath( /* * NOTE: it is assumed that _DtCreateDtDirs() returns a buffer of - * size MAXPATHLEN+1. This allows us to avoid a extra alloc + * size MAXPATHLEN. This allows us to avoid a extra alloc * and copy -- at the expense of code maintainability. + * + * JET - 2020. This is stupid. At least account for the strings + * you are adding further on down... This "solution" isn't great + * either. Real fix would be to have all callers pass in bufptr + * and len all the way down the chain instead of tmpPath. */ - if ((strlen(tmpPath) + 1 + strlen(property)) > MAXPATHLEN) goto abort; + if ((strlen(tmpPath) + + 1 /* "/" */ + + strlen(property) + + 1 /* "/" */ + + ((*saveFile == NULL) ? strlen("dtXXXXXX") + 1 : strlen(*saveFile)) + ) >= MAXPATHLEN) + { + goto abort; + } /* * parse the property string and create directory if needed diff --git a/cde/lib/DtSvc/DtUtil2/SmCreateDirs.c b/cde/lib/DtSvc/DtUtil2/SmCreateDirs.c index 81308c42..4e8c0b11 100644 --- a/cde/lib/DtSvc/DtUtil2/SmCreateDirs.c +++ b/cde/lib/DtSvc/DtUtil2/SmCreateDirs.c @@ -83,33 +83,32 @@ char * _DtCreateDtDirs( Display *display ) { - char *tmpPath; + char *tmpPath = NULL; Boolean needSessionsDir = False; Boolean useOldSession = False; struct stat buf; int status; - char *home; - char *sessionDir; - char *displayName; + char *home = NULL; + char *sessionDir = NULL; + char *displayName = NULL; /* * Sanity check - make sure there's an existing display */ if(!display) return(NULL); - - if ((home =getenv("HOME")) == NULL) + + if ((home = getenv("HOME")) == NULL) home = ""; - - tmpPath = XtCalloc(1, MAXPATHLEN + 1); + + tmpPath = XtCalloc(1, MAXPATHLEN); if(tmpPath == NULL) return(NULL); /* * If the $HOME/.dt directory does not exist, create it */ - strncpy(tmpPath, home, MAXPATHLEN); - strncat(tmpPath, "/" DtPERSONAL_CONFIG_DIRECTORY, MAXPATHLEN); + snprintf(tmpPath, MAXPATHLEN, "%s/%s", home, DtPERSONAL_CONFIG_DIRECTORY); status = stat(tmpPath, &buf); if (status == -1) { @@ -122,11 +121,10 @@ _DtCreateDtDirs( } /* - * Create the personal DB directory if it does not exist. + * Create the personal DB directory if it does not exist. */ - strncpy(tmpPath, home, MAXPATHLEN); - strncat(tmpPath, "/" DtPERSONAL_DB_DIRECTORY, MAXPATHLEN); - + snprintf(tmpPath, MAXPATHLEN, "%s/%s", home, DtPERSONAL_DB_DIRECTORY); + if ((status = stat (tmpPath, &buf)) == -1) { if ((status = mkdir (tmpPath, 0000)) != -1) (void) chmod (tmpPath, 0755); @@ -135,8 +133,7 @@ _DtCreateDtDirs( /* * Create the personal tmp dir if it does not exist. */ - strncpy(tmpPath, home, MAXPATHLEN); - strncat(tmpPath, "/" DtPERSONAL_TMP_DIRECTORY, MAXPATHLEN); + snprintf(tmpPath, MAXPATHLEN, "%s/%s", home, DtPERSONAL_TMP_DIRECTORY); if ((status = stat (tmpPath, &buf)) == -1) { if ((status = mkdir (tmpPath, 0000)) != -1) @@ -173,12 +170,13 @@ _DtCreateDtDirs( */ if ((displayName = GetDisplayName (display)) != NULL) { - strncpy (tmpPath, home, MAXPATHLEN); - strncat (tmpPath, "/" DtPERSONAL_CONFIG_DIRECTORY, MAXPATHLEN); - strncat (tmpPath, "/", MAXPATHLEN); - strncat (tmpPath, displayName, MAXPATHLEN); + snprintf(tmpPath, MAXPATHLEN, "%s/%s/%s", + home, + DtPERSONAL_CONFIG_DIRECTORY, + displayName); free(displayName); /* CDExc22771 */ + displayName = NULL; if ((status = stat (tmpPath, &buf)) == -1) { if ((status = mkdir (tmpPath, 0000)) != -1) @@ -215,12 +213,13 @@ _DtCreateDtDirs( */ if ((displayName = GetDisplayName (display)) != NULL) { - strncpy (tmpPath, home, MAXPATHLEN); - strncat (tmpPath, "/" DtPERSONAL_CONFIG_DIRECTORY, MAXPATHLEN); - strncat (tmpPath, "/", MAXPATHLEN); - strncat (tmpPath, displayName, MAXPATHLEN); + snprintf(tmpPath, MAXPATHLEN, "%s/%s/%s", + home, + DtPERSONAL_CONFIG_DIRECTORY, + displayName); free(displayName); /* CDExc22771 */ + displayName = NULL; if ((status = stat(tmpPath, &buf)) != 0) /* @@ -238,9 +237,10 @@ _DtCreateDtDirs( * If we don't have an old style directory - we check for a sessions * directory, and create it if it doesn't exist */ - strncpy (tmpPath, home, MAXPATHLEN); - strncat (tmpPath, "/" DtPERSONAL_CONFIG_DIRECTORY, MAXPATHLEN); - strncat (tmpPath, "/" DtSM_SESSION_DIRECTORY, MAXPATHLEN); + snprintf(tmpPath, MAXPATHLEN, "%s/%s/%s", + home, + DtPERSONAL_CONFIG_DIRECTORY, + DtSM_SESSION_DIRECTORY); if ((status = stat(tmpPath, &buf)) == -1) { if ((status = mkdir(tmpPath, 0000)) == -1) { diff --git a/cde/programs/dtsession/SrvPalette.c b/cde/programs/dtsession/SrvPalette.c index b967c7ee..55b722c9 100644 --- a/cde/programs/dtsession/SrvPalette.c +++ b/cde/programs/dtsession/SrvPalette.c @@ -501,10 +501,10 @@ CheckMonitor( int n, screen_number, result; Arg args[4]; char screenStr[5], cust_msg[24]; - char *tmpStr; - char tmpPalette[SRVBUFSIZE]; - char *token1; - char *xrdb_string; + char *tmpStr = NULL; + char tmpPalette[SRVBUFSIZE]; + char *token1 = NULL; + char *xrdb_string = NULL; Widget mainShell; XtAppContext app_context; @@ -541,7 +541,7 @@ CheckMonitor( /* cycle through each screen */ for(screen_number=0;screen_number != colorSrv.NumOfScreens;screen_number++) { - sprintf(screenStr,"%d",screen_number); + snprintf(screenStr, sizeof(screenStr), "%d", screen_number); n = 0; XtSetArg(args[n], XmNbackground, BlackPixelOfScreen(DefaultScreenOfDisplay(dpy))); n++; @@ -559,7 +559,8 @@ CheckMonitor( XtRealizeWidget(shell[screen_number]); - sprintf(cust_msg,"%s%d", XmSCUSTOMIZE_DATA, screen_number); + snprintf(cust_msg, sizeof(cust_msg), "%s%d", + XmSCUSTOMIZE_DATA, screen_number); colorSrv.XA_CUSTOMIZE[screen_number] = XInternAtom(dpy, cust_msg, FALSE); @@ -574,11 +575,16 @@ CheckMonitor( /* * Don't forget to add length for the extra characters. */ - tmpStr = (char *)SRV_MALLOC(strlen(MSG1) + 25 + 5 + 1 + 1); - sprintf(tmpStr,"%s colorSrv.XA_CUSTOMIZE[%d].\n", - MSG1, screen_number); - _DtSimpleError(XmSCOLOR_SRV_NAME, DtWarning, NULL, tmpStr, NULL); - SRV_FREE(tmpStr); + int len = strlen(MSG1) + 25 + 5 + 1 + 1; + tmpStr = (char *)SRV_MALLOC(len); + if (tmpStr) + { + snprintf(tmpStr, len, "%s colorSrv.XA_CUSTOMIZE[%d].\n", + MSG1, screen_number); + _DtSimpleError(XmSCOLOR_SRV_NAME, DtWarning, NULL, tmpStr, NULL); + SRV_FREE(tmpStr); + tmpStr = NULL; + } return(-1); } @@ -608,15 +614,19 @@ CheckMonitor( (struct _palette *) SRV_MALLOC( sizeof(struct _palette) + 1 ); /* allocate enough space for the name */ - strcpy(tmpPalette, pColorSrvRsrc.MonochromePalette); - for (token1=tmpPalette; *token1; token1++); - while (token1!=tmpPalette && *token1!='.') token1--; - if (!strcmp(token1,PALETTE_SUFFIX)) *token1 = '\0'; + snprintf(tmpPalette, SRVBUFSIZE, "%s", + pColorSrvRsrc.MonochromePalette); + for (token1=tmpPalette; *token1; token1++) + ; + while (token1 != tmpPalette && *token1 != '.') + token1--; + if (!strcmp(token1, PALETTE_SUFFIX)) + *token1 = '\0'; colorSrv.pCurrentPalette[screen_number]->name = (char *)SRV_MALLOC(strlen(tmpPalette) + 1); strcpy(colorSrv.pCurrentPalette[screen_number]->name, (char *) tmpPalette); - colorSrv.pCurrentPalette[screen_number]->converted=NULL; + colorSrv.pCurrentPalette[screen_number]->converted = NULL; } if (colorSrv.pCurrentPalette[screen_number] == (struct _palette *) NULL) @@ -627,19 +637,21 @@ CheckMonitor( /* write out the color or monochrome palette resource for the screen */ xrdb_string = XtMalloc(BUFSIZ); + if (!xrdb_string) + return -1; if (colorSrv.TypeOfMonitor[0] == XmCO_HIGH_COLOR || colorSrv.TypeOfMonitor[0] == XmCO_MEDIUM_COLOR || colorSrv.TypeOfMonitor[0] == XmCO_LOW_COLOR) { - sprintf(xrdb_string, "*%d*ColorPalette: %s%s\n", + snprintf(xrdb_string, BUFSIZ, "*%d*ColorPalette: %s%s\n", screen_number, colorSrv.pCurrentPalette[screen_number]->name, PALETTE_SUFFIX); } else /* XmCO_BLACK_WHITE */ { - sprintf(xrdb_string, "*%d*MonochromePalette: %s%s\n", + snprintf(xrdb_string, BUFSIZ, "*%d*MonochromePalette: %s%s\n", screen_number, colorSrv.pCurrentPalette[screen_number]->name, PALETTE_SUFFIX); @@ -647,7 +659,7 @@ CheckMonitor( _DtAddToResource(dpy, xrdb_string); XtFree(xrdb_string); - + } /* for each screen */ return(0); }