Gentoo: pptpd Remote buffer overflow
Summary
- - --------------------------------------------------------------------- GENTOO LINUX SECURITY ANNOUNCEMENT 200304-08 - - ---------------------------------------------------------------------
- - ---------------------------------------------------------------------
- From advisory:
"PPTP packet header contain 16bit length which specifies the full size of the packet:
bytes_this = read(clientFd, packet + bytes_ttl, 2 - bytes_ttl); // ... bytes_ttl += bytes_this; // ... length = htons(*(u_int16_t *) packet); if (length > PPTP_MAX_CTRL_PCKT_SIZE) { // abort }
Looks good so far, except:
bytes_this = read(clientFd, packet + bytes_ttl, length - bytes_ttl);
If given length was 0 or 1, the "length - bytes_ttl" result is -1 or -2, which means that it reads unlimited amount of data from client into "packet", which is a buffer located in stack.
The exploitability only depends on if libc allows the size parameter to be larger than SSIZE_MAX bytes. GLIBC does, Solaris and *BSD don't."
Read the full advisory at: http://marc.theaimsgroup.com/?l=bugtraq&m=104994375011406&w=2
SOLUTION
It is recommended that all Gentoo Linux users who are running net-dialup/pptpd upgrade to pptpd-1.1.3.20030409 as follows:
emerge sync emerge pptpd emerge clean