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67 lines
3.9 KiB
Markdown
67 lines
3.9 KiB
Markdown
# Defender
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The built-in `defender` allows you to configure an auto-blocking policy for SFTPGo and thus helps to prevent DoS (Denial of Service) and brute force password guessing.
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If enabled it will protect SFTP, FTP and WebDAV services and it will automatically block hosts (IP addresses) that continually fail to log in or attempt to connect.
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You can configure a score for the following events:
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- `score_valid`, defines the score for valid login attempts, eg. user accounts that exist. Default `1`.
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- `score_invalid`, defines the score for invalid login attempts, eg. non-existent user accounts or client disconnected for inactivity without authentication attempts. Default `2`.
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- `score_limit_exceeded`, defines the score for hosts that exceeded the configured rate limits or the configured max connections per host. Default `3`.
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And then you can configure:
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- `observation_time`, defines the time window, in minutes, for tracking client errors.
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- `threshold`, defines the threshold value before banning a host.
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- `ban_time`, defines the time to ban a client, as minutes
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So a host is banned, for `ban_time` minutes, if the sum of the scores has exceeded the defined threshold during the last observation time minutes.
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By defining the scores, each type of event can be weighted. Let's see an example: if `score_invalid` is 3 and `threshold` is 8, a host will be banned after 3 login attempts with an non-existent user within the configured `observation_time`.
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A banned IP has no score, it makes no sense to accumulate host events in memory for an already banned IP address.
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If an already banned client tries to log in again, its ban time will be incremented according the `ban_time_increment` configuration.
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The `ban_time_increment` is calculated as percentage of `ban_time`, so if `ban_time` is 30 minutes and `ban_time_increment` is 50 the host will be banned for additionally 15 minutes. You can also specify values greater than 100 for `ban_time_increment` if you want to increase the penalty for already banned hosts.
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SFTPGo can store host scores and banned hosts in memory or within the configured data provider according to the `driver` set in the `defender` configuration section. The available drivers are `memory` and `provider`.
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The `provider` driver is useful if you want to share the defender data across multiple SFTPGo instances and it requires a shared or distributed data provider: `MySQL`, `PostgreSQL` and `CockroachDB` are supported.
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If you set the `provider` driver, the defender implementation may do many database queries (at least one query every time a new client connects to check if it is banned), if you have a single SFTPGo instance the `memory` driver is recommended.
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For the `memory` driver, you can limit the memory usage using the `entries_soft_limit` and `entries_hard_limit` configuration keys.
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The `provider` driver will periodically clean up expired hosts and events.
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Using the REST API you can:
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- list hosts within the defender's lists
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- remove hosts from the defender's lists
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The `defender` can also load a permanent block list and/or a safe list of ip addresses/networks from a file:
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- `safelist_file`, defines the path to a file containing a list of ip addresses and/or networks to never ban.
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- `blocklist_file`, defines the path to a file containing a list of ip addresses and/or networks to always ban.
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These list must be stored as JSON conforming to the following schema:
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- `addresses`, list of strings. Each string must be a valid IPv4/IPv6 address.
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- `networks`, list of strings. Each string must be a valid IPv4/IPv6 CIDR address.
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Here is a small example:
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```json
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{
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"addresses":[
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"192.0.2.1",
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"2001:db8::68"
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],
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"networks":[
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"192.0.3.0/24",
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"2001:db8:1234::/48"
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]
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}
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```
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These list will be always loaded in memory (even if you use the `provider` driver) for faster lookups. The REST API queries "live" data and not these lists.
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