[UNIX] Drcatd Multiple Buffer Overflows
From: SecuriTeam (support_at_securiteam.com)
To: firstname.lastname@example.org Date: 28 Jun 2004 18:37:03 +0200
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Drcatd Multiple Buffer Overflows
<http://www.joltedweb.com/drcat/ > Dave's Remote Cat concatenates a file
on a remote Linux host that is running the Dr.Cat daemon (drcatd) to
stdout in the clients terminal. It authenticates users versus the standard
shadow password authentication facility and spawns a process with that
users permission to attempt to access the requested file.
Multiple local buffer overflows and a remotely triggered buffer overflow
have been found in the remote cat daemon. The remote overflow is triggered
once an overly long filename string of a file that does not exist is
passed to the server.
* Drcatd version 0.5.0-beta
When a filename is passed to the server remotely, after a user has
authenticated it is possible to pass an overly long filename string. If
the file specified does not exist, the server logs the error. However,
this is handled by a sprintf() function call without any bounds checking,
leading to a remotely exploitable buffer overflow. An excerpt from the
vulnerable code is presented below:
sprintf(fdne_msg, "%s - File Does Not Exist", buf);
sprintf(fd_msg, "%s - File Does Not Exist\n", buf);
len = sizeof(fd_msg);
local_send(new_fd, fd_msg, len);
Note: Due to the exit system call it is not possible to exploit the
overflow on the 80x86 architecture.
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