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adding an event for disallowed_ssh_connection_non_standard_port #144

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Apr 23, 2024
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39 changes: 39 additions & 0 deletions events/syscall/disallowed_ssh_connection_non_standard_port.go
Original file line number Diff line number Diff line change
@@ -0,0 +1,39 @@
// SPDX-License-Identifier: Apache-2.0
/*
Copyright (C) 2024 The Falco Authors.
Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at
http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/

package syscall

import (
"github.com/falcosecurity/event-generator/events"
"os/exec"
)

var _ = events.Register(DisallowedSSHConnectionNonStandardPort)

func DisallowedSSHConnectionNonStandardPort(h events.Helper) error {
path, err := exec.LookPath("ssh")
if err != nil {
// If we don't have an SSH, just bail
return &events.ErrSkipped{
Reason: "ssh utility not found in path",
}
}
// non_standard_port : 443
cmd := exec.Command("timeout", "1s", path, "[email protected]", "-p", "443")
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@h4l0gen

Generally speaking, it is good practice to use example domains.

Just a doubt: will it work with localhost as well? 🤔

If so, it would be preferable, to avoid outbound traffic. Otherwise, it's ok as-is now.

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@leogr let me check..

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@leogr Its not working on localhost :)
image

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@FedeDP what do you think about using example.net ?

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@FedeDP FedeDP Apr 22, 2024

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I think localhost should work just fine; in your case it is not working because you are actually succeeding in logging in (ie: you have an ssh daemon on port 443(?))
I'd try to connect to localhost to a different port, like 4444, and see if that triggers the rule.

See https://github.com/falcosecurity/rules/blob/main/rules/falco_rules.yaml#L1207 for the ports that can be used.

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Uh nope, the rule triggers only for outbound connections, therefore it won't fire for localhost. See: https://github.com/falcosecurity/rules/blob/main/rules/falco_rules.yaml#L1223C5-L1223C13

I guess it's ok then.

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@h4l0gen h4l0gen Apr 22, 2024

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Yes, @FedeDP, if everything seems good, then we are good to proceed with this PR and this one?

err = cmd.Run()
if err != nil {
return err
}
return nil
}
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