Mailing-List: contact securesoftware-help@list.cr.yp.to; run by ezmlm Delivered-To: mailing list securesoftware@list.cr.yp.to Received: (qmail 9712 invoked by uid 1017); 15 Dec 2004 08:10:44 -0000 Date: 15 Dec 2004 08:10:44 -0000 Message-ID: <20041215081044.9702.qmail@cr.yp.to> Mail-Followup-To: securesoftware@list.cr.yp.to, jeanmarcj@usa.net Automatic-Legal-Notices: See http://cr.yp.to/mailcopyright.html. From: "D. J. Bernstein" To: securesoftware@list.cr.yp.to, jeanmarcj@usa.net Subject: [remote] [control] LinPopUp 1.2.0 overflows sub_string buffer Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="4Ckj6UjgE2iN1+kY" Content-Disposition: inline --4Ckj6UjgE2iN1+kY Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Stephen Dranger, a student in my Fall 2004 UNIX Security Holes course, has discovered a remotely exploitable security hole in LinPopUp, an instant-messaging tool. I'm publishing this notice, but all the discovery credits should be assigned to Dranger. You are at risk if you use LinPopUp to reply to a message received from the network or any other source that could be controlled by an attacker. Whoever sent that message then has complete control over your account: he can read and modify your files, watch the programs you're running, etc. Proof of concept: On an x86 computer running FreeBSD 4.10, as root, type cd /usr/ports/net/linpopup make install to download and compile the LinPopUp program, version 1.2.0 (current FreeBSD ports version). Then, as any user, save the file 3.msg attached to this message, and type cat 3.msg >> /var/db/linpopup/messages.dat to simulate receipt of 3.msg from the network. Then type LinPopUp and click on Reply. Unauthorized result: a file named x is removed from the current directory. Here's the bug: In string.c, strexpand() uses strcpy() to copy from replace_string, which can have as many as 100 bytes, to a 50-byte sub_string array. ---D. J. 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