//@(#) Mordred Labs advisory 0x0007
Release data: 26/08/02
Name: Remote DoS condition in PostgreSQL
Versions affected: all versions
Conditions: entry in a pg_hba.conf file that matches attacker's host.
Risk: average
---[ Description:
Upon connecting to a database, postmaster will fork a new process.
After that, a child process will call a
src/backend/postmaster/postmaster.c:DoBackend() routine,
which after processing a startup packet (see src/include/libpq/pqcomm.h),
will invoke a src/backend/libpq/auth.c:ClientAuthentication() routine to
perform client authentication.
If there is an entry in pg_hba.conf file, that matches an attacker's host,
an attacker could trigger
invocation of src/backend/libpq/auth.c:recv_and_check_password0(), which
fails to detect a DoS condition.
---[ Details:
Consider this snip of code from src/backend/libpq/auth.c:
[snip]
static int recv_and_check_password0(Port *port) {int32 len;char *buf;if (pq_getint(&len, 4) == EOF) return
STATUS_EOF;len-= 4;buf = palloc(len); /* len is taken from a packet */
[snip]
Note, that the size of palloced memory is taken from the user's input,
which is stupid if you ask me.
--[ How to reproduce:
I dont want to provide any tools to illustrate this vulnerability.
--[ Solution
Disable network access for untrusted users.
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