Linux - SecurityThis forum is for all security related questions.
Questions, tips, system compromises, firewalls, etc. are all included here.
Welcome to LinuxQuestions.org, a friendly and active Linux Community.
You are currently viewing LQ as a guest. By joining our community you will have the ability to post topics, receive our newsletter, use the advanced search, subscribe to threads and access many other special features. Registration is quick, simple and absolutely free. Join our community today!
Note that registered members see fewer ads, and ContentLink is completely disabled once you log in.
AppArmor causing multiple (minor) problems - a cautionary tale
A while ago, I noticed that AppArmor was not enabled and, being prudent, I enabled it.
Meanwhile, I had been noticing some strange failures, where things worked before. Acrobat reader would not open files from my home directory (but would open files from web sites). I could no longer click on links in emails to open web pages. I could not connect to mysql on "localhost" (but could if I specified "127.0.0.1"). I could not save an email attachment to my Windows partition. I did not link any of these things to AppArmor. Indeed I didn't link them together at all!
Today, though, I noticed some entries in /var/log/messages of the form:
Jun 25 21:45:34 linux kernel: SubDomain: REJECTING w access to /var/lib/mysql/mysql.sock (httpd2-prefork(5766) profile /usr/sbin/httpd2-prefork active /usr/sbin/httpd2-prefork)
A google search showed that this entry was from AppArmor. The "linux kernel:SubDomain: REJECTING [letter] access to..." remains constant, while the endings of the entries refer to different files and programs. There were entries which would explain each of the effects I had noticed, and disabling AppArmor restored the functions.
While none of the effects was very serious, and some of them would increase security a little (at least for an incautious user), they were inconvenient. At present, I plan to learn a bit more about configuring AppArmor before enabling it again.
You can configure which applications AppArmour handles and which don't in the YaST configuration. There are a fixed number of applications that OpenSuSE configures automatically. I think that the commercial SuSE product includes support for the rest. You could turn off AppArmour for the applications that cause a problem until configuring them yourself. That way, for some core applications, you will still be protected in the meantime.