mirror of
https://blitiri.com.ar/repos/chasquid
synced 2026-10-29 15:02:30 +00:00
Alberto Bertogli
6b64c9ccba
If chasquid runs out of file descriptors, that can cause problems accepting connections, writing to the queue, and even reloading configs. Some of those errors are fatal, as they should not happen under normal conditions. Since a remote client can open a lot of connections, this can end up consuming all file descriptors, and resulting in a denial of service. To reduce the impact of that kind of event, this patch makes chasquid limit the number of concurrent SMTP connections to half the maximum number of file descriptors. Connections over that limit will get closed immediately. The server will log (rate-limited) when such event happens, and new metrics make these events visible through monitoring too. This approach complements the previous patch, which made the server retry Accept errors, to reduce the impact of connection overloads. This mainly affects deployments with low file descriptor limits; most modern deployments have very high limits by default, so they are unlikely to experience this problem in the first place. Users who have to be very defensive can deploy OS-level safeguards (such as firewall rules to limit number of connections, etc.) which are more effective and tunable. Thanks to John JEAN <john@wargan.com> for finding and reporting this problem. The detailed report can be found in https://johnjean.io/advisories/chasquid-unauthenticated-remote-dos/.
37 lines
1002 B
Bash
Executable File
37 lines
1002 B
Bash
Executable File
#!/bin/bash
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set -e
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. "$(dirname "$0")/../util/lib.sh"
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init
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generate_certs_for testserver
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add_user user@testserver secretpassword
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# Note we run the server with minimal logging, to avoid generating very large
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# log files, which are not very useful anyway.
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mkdir -p .logs
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chasquid -v=-1 --logfile=.logs/chasquid.log --config_dir=config &
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wait_until_ready 1025
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echo "Peak RAM: $(chasquid_ram_peak)"
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# Set connection count to (connection limit) - (leeway).
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# chasquid limits incoming connections to half of its file descriptor limit.
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# Go raises the soft limit to (almost) the hard limit at startup, so we use
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# the hard limit, with some leeway; 20 should be enough for now.
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# Cap it to 2000, as otherwise it can be problematic due to port availability.
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COUNT=$(( $(ulimit -Hn) / 2 - 20 ))
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if [ $COUNT -gt 2000 ]; then
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COUNT=2000
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fi
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if ! conngen -logtime -addr=localhost:1025 -count=$COUNT; then
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tail -n 1 .logs/chasquid.log
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fail "conngen error"
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fi
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echo "Peak RAM: $(chasquid_ram_peak)"
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success
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