pgsql: Fix low-risk potential denial of service against RADIUS login.

Fix low-risk potential denial of service against RADIUS login.

Corrupt RADIUS responses were treated as errors and not ignored
(which the RFC2865 states they should be). This meant that a
user with unfiltered access to the network of the PostgreSQL
or RADIUS server could send a spoofed RADIUS response
to the PostgreSQL server causing it to reject a valid login,
provided the attacker could also guess (or brute-force) the
correct port number.

Fix is to simply retry the receive in a loop until the timeout
has expired or a valid (signed by the correct RADIUS server)
packet arrives.

Reported by Alan DeKok in bug #5687.

Branch
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master

Details
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http://git.postgresql.org/gitweb?p=postgresql.git;a=commitdiff;h=0e7f7071e893bb171150e53271404b0819a40669

Modified Files
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src/backend/libpq/auth.c | 220 ++++++++++++++++++++++++++--------------------
1 files changed, 126 insertions(+), 94 deletions(-)