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List:       kde-commits
Subject:    KDE/kdebase/workspace/kdm/backend
From:       Oswald Buddenhagen <ossi () kde ! org>
Date:       2010-02-28 20:37:07
Message-ID: 1267389427.735981.31243.nullmailer () svn ! kde ! org
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SVN commit 1097263 by ossi:

even more random temp file names

this makes temp file names yet more resilient against local DoS - not
that it would be a particularly useful attack vector ...

 M  +21 -29    auth.c  
 M  +1 -0      dm.h  
 M  +15 -0     util.c  


--- trunk/KDE/kdebase/workspace/kdm/backend/auth.c #1097262:1097263
@@ -319,15 +319,29 @@
 }
 
 
+static FILE *
+mkTempFile( char *nambuf, int namelen )
+{
+	FILE *f;
+	int r;
+
+	for (r = 0; r < 100; r++) {
+		randomStr( nambuf + namelen );
+		if ((f = fdOpenW( open( nambuf, O_WRONLY | O_CREAT | O_EXCL, 0600 ) )))
+			return f;
+		if (errno != EEXIST)
+			break;
+	}
+	return 0;
+}
+
 #define NAMELEN 255
 
 static FILE *
 makeServerAuthFile( struct display *d )
 {
 	FILE *f;
-#ifndef HAVE_MKSTEMP
-	int r;
-#endif
+	int i;
 	char cleanname[NAMELEN], nambuf[NAMELEN+128];
 
 	/*
@@ -339,22 +353,11 @@
 	if (mkdir( authDir, 0755 ) < 0  &&  errno != EEXIST)
 		return 0;
 	cleanUpFileName( d->name, cleanname, NAMELEN - 8 );
-#ifdef HAVE_MKSTEMP
-	sprintf( nambuf, "%s/A%s-XXXXXX", authDir, cleanname );
-	if ((f = fdOpenW( mkstemp( nambuf ) ))) {
+	i = sprintf( nambuf, "%s/A%s-", authDir, cleanname );
+	if ((f = mkTempFile( nambuf, i ))) {
 		strDup( &d->authFile, nambuf );
 		return f;
 	}
-#else
-	for (r = 0; r < 100; r++) {
-		sprintf( nambuf, "%s/A%s-XXXXXX", authDir, cleanname );
-		(void)mktemp( nambuf );
-		if ((f = fdOpenW( open( nambuf, O_WRONLY | O_CREAT | O_EXCL, 0600 ) ))) {
-			strDup( &d->authFile, nambuf );
-			return f;
-		}
-	}
-#endif
 	return 0;
 }
 
@@ -1203,19 +1206,8 @@
 			 * temporary - we can assume that we are the only ones
 			 * knowing about this file anyway.
 			 */
-#ifdef HAVE_MKSTEMP
-			sprintf( name_buf, "%s/.XauthXXXXXX", d->userAuthDir );
-			new = fdOpenW( mkstemp( name_buf ) );
-#else
-			for (i = 0; i < 100; i++) {
-				sprintf( name_buf, "%s/.XauthXXXXXX", d->userAuthDir );
-				(void)mktemp( name_buf );
-				if ((new =
-				     fdOpenW( open( name_buf, O_WRONLY | O_CREAT | O_EXCL,
-				                    0600 ) )))
-					break;
-			}
-#endif
+			i = sprintf( name_buf, "%s/.Xauth", d->userAuthDir );
+			new = mkTempFile( name_buf, i );
 			if (!new) {
 				logError( "Cannot create authorization file in %s: %m\n",
 				          d->userAuthDir );
--- trunk/KDE/kdebase/workspace/kdm/backend/dm.h #1097262:1097263
@@ -560,6 +560,7 @@
 int writer( int fd, const void *buf, int len );
 int fGets( char *buf, int max, FILE *f );
 time_t mTime( const char *fn );
+void randomStr( char *s );
 int hexToBinary( char *out, const char *in );
 void listSessions( int flags, struct display *d, void *ctx,
                    void (*emitXSess)( struct display *, struct display *, void * ),
--- trunk/KDE/kdebase/workspace/kdm/backend/util.c #1097262:1097263
@@ -35,6 +35,7 @@
  */
 
 #include "dm.h"
+#include "dm_auth.h"
 #include "dm_error.h"
 
 #include <string.h>
@@ -570,6 +571,20 @@
 		return st.st_mtime;
 }
 
+void
+randomStr( char *s )
+{
+	static const char letters[] =
+		"abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";
+	unsigned i, rn = secureRandom();
+
+	for (i = 0; i < 6; i++) {
+		*s++ = letters[rn % 62];
+		rn /= 62;
+	}
+	*s = 0;
+}
+
 static int
 strNChrCnt( const char *s, int slen, char c )
 {
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