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SSH audit events and contexts #28

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Jun 29, 2023
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SSH audit events and contexts #28

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SSH audit events and contexts
beldmit Jun 27, 2023
1937966
fixup! SSH audit events and contexts
beldmit Jun 28, 2023
a04e720
fixup! SSH audit events and contexts
beldmit Jun 28, 2023
2d1c2db
fixup! fixup! SSH audit events and contexts
beldmit Jun 28, 2023
1da8a08
fixup! fixup! SSH audit events and contexts
beldmit Jun 28, 2023
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fixup! fixup! fixup! SSH audit events and contexts
beldmit Jun 29, 2023
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fixup! fixup! fixup! SSH audit events and contexts
beldmit Jun 29, 2023
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fixup! fixup! fixup! fixup! SSH audit events and contexts
beldmit Jun 29, 2023
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39 changes: 39 additions & 0 deletions docs/logging-format.md
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Expand Up @@ -228,6 +228,45 @@ and TLS probe points.
| `tls::key_exchange_algorithm` | uint16 | Key exchange mode: ECDHE(0), DHE(1), PSK(2), ECDHE-PSK(3), DHE-PSK(4) |
| `tls::group` | uint16 | Groups used in the handshake (as in IANA [registry][iana-tls-supported-groups]) |

##### SSH context names

| name | description |
|------------------------|----------------------------------------|
| `ssh::handshake_client`| SSH handshake for client |
| `ssh::handshake_server`| SSH handshake for server |
| `ssh::client_key` | SSH client key signature/verification |
| `ssh::server_key` | SSH server key signature/verification |
| `ssh::key_exchange` | SSH key exchange |

Example of SSH context tree:

- `ssh::handshake_client`
- `ssh::ident_string` = `SSH-2.0-OpenSSH_8.8`
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- `ssh::client key`
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underscore instead of space

Suggested change
- `ssh::client key`
- `ssh::client_key`

I assume the events should come in order they happen during the ssh session so the client key operation should happen only after the key_exchange is finished.

The hostkey verification happens as part of the key exchange though so it is a question whether it should be part of that context or somehow separately.

In any case, this is a context so it should have again some events attached for example:

Suggested change
- `ssh::client key`
- `ssh::client_key`
- `ssh::key_algorithm` = `rsa-sha2-256`
- `ssh::rsa_bits` = `2048`

- `ssh::key_exchange`
- `ssh::kex_algorithm` = `curve25519-sha256`
- `ssh::c2s_cipher` = `[email protected]`
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##### SSH keys

All the keys except `rsa_bits` have `string` type.
We distinguish server and client values by the context we are in. We log all relevant events in both contexts.

| key | description | example |
|---------------------------------|--------------------------------------------------|----------------------------|
| `ssh::ident_string` | Software identification string | `SSH-2.0-OpenSSH_8.8` |
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| `ssh::key_algorithm` | Key used in handshake | `ssh-ed25519` |
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| `ssh::rsa_bits` | Key bits (RSA only) | 2048 |
| `ssh::cert_signature_algorithm` | If cert is used, signature algorithm of the cert | `ecdsa-sha2-nistp521` |
| `ssh::kex_algorithm` | Negotiated key exchange algorithm | `curve25519-sha256` |
| `ssh::kex_group` | Group used for key exchange | moduli+bits or group name. |
| `ssh::c2s_cipher` | Data cipher algorithm | `[email protected]` |
| `ssh::s2c_cipher` | | |
| `ssh::c2s_mac` | Data integrity algorithm | Omitted for "implicit" |
| `ssh::s2c_mac` | | |
| `ssh::c2s_compression` | Data compression algorithm | Omitted for "none" |
| `ssh::s2c_compression` | | |
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### CBOR based logging format definition

The recommended format of storing events is to use a sequence of
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