Users of Skype for Linux have just found out that it reads the files /etc/passwd, firefox profile, plugins, addons, etc, and many other unnecessary files in /etc. This fact was originally discovered by using AppArmor, but others have confirmed this fact using strace on versions 22.214.171.124 and 126.96.36.199. What is going on? This probably shows how important it is to use AppArmor in any closed-source application in Linux to restrict any undue access to your files."
Seems like people don't understand unix at all, when they post to security lists...
Just checking your own identity in unix requires a call to getpwnam, getpwent or their equivalent, which means that a function call in glibc has to read the password file. Practically every unix program does that... It reads in the whole file in memory and looks for you, unless you're using the db source, yp, nis+ or an external module: nss_ldap, nss_mysql, nss_pgsql. It's doing that to find YOU out... That's normal, system-wide behaviour, and not sinister at all(that's also why there's a nscd daemon to cache those results, to prevent your machine from grinding to a halt if you have 200k+ entries in that file.
Now unless the legacy api gets redesigned to NOT do a line by line scan, anyone using strace/ltrace/dtrace/tusc needs to filter out these internal "housekeeping" calls, which are perfectly normal, needing to find out if _you_ can open up your own log file...
The /etc/passwd /etc/group files are public files precisely because they are referred to in this manner. That's why shadow passwords are so necessary.
[Reactie gewijzigd door MyKel op 27 augustus 2007 00:35]