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a5496f4098
The RabbitMQ docs state ([1]):
RabbitMQ nodes and CLI tools (e.g. rabbitmqctl) use a cookie to
determine whether they are allowed to communicate with each
other. [...] The cookie is just a string of alphanumeric
characters up to 255 characters in size. It is usually stored in a
local file.
...and goes on to state (emphasis ours):
If the file does not exist, Erlang VM will try to create one with
a randomly generated value when the RabbitMQ server starts
up. Using such generated cookie files are **appropriate in
development environments only.**
The auto-generated cookie does not use cryptographic sources of
randomness, and generates 20 characters of `[A-Z]`. Because of a
semi-predictable seed, the entropy of this password is thus less than
the idealized 26^20 = 94 bits of entropy; in actuality, it is 36 bits
of entropy, or potentially as low as 20 if the performance of the
server is known.
These sizes are well within the scope of remote brute-force attacks.
On provision, install, and upgrade, replace the default insecure
20-character Erlang cookie with a cryptographically secure
255-character string (the max length allowed).
[1] https://www.rabbitmq.com/clustering.html#erlang-cookie
28 lines
891 B
Bash
Executable File
28 lines
891 B
Bash
Executable File
#!/usr/bin/env bash
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#
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# rabbitmq sets an insecure "magic cookie" which is used for auth;
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# reset it to be longer.
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set -eu
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cookiefile=/var/lib/rabbitmq/.erlang.cookie
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# If the RabbitMQ distribution cookie is insecure, reset it
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if [ ! -f "$cookiefile" ] || ! size="$(wc -c "$cookiefile")" || [ "${size%% *}" -le 20 ]; then
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running=0
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if service rabbitmq-server status >/dev/null; then
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running=1
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service rabbitmq-server stop
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fi
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echo "Setting a more secure RabbitMQ distribution magic cookie"
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cookie="$(LC_ALL=C tr -dc '[:alnum:]' </dev/urandom | head -c255)"
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[ "${#cookie}" -eq 255 ] # make sure tr wasn’t OOM-killed
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tmpfile="$(mktemp "$cookiefile.XXXXXXXXXX")"
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chown rabbitmq: "$tmpfile"
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printf '%s' "$cookie" >"$tmpfile"
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mv "$tmpfile" "$cookiefile"
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if [ "$running" == "1" ]; then
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service rabbitmq-server start
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fi
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fi
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