# SSH (22)

<details>

<summary>Protocol Information</summary>

SSH (Secure Shell) is a remote administration protocol that offers encryption and is the successor to Telnet. It is generally used for remote access to servers and systems.\
SSH authentication can be configured in two main ways: user/password, or with key.

</details>

## Port

<table data-header-hidden><thead><tr><th width="166">Port</th><th>Description</th></tr></thead><tbody><tr><td><mark style="color:green;"><strong>22</strong></mark><strong> TCP</strong></td><td>SSH</td></tr></tbody></table>

## Config File

* **Linux**: `/etc/ssh/sshd_config`
* **Windows**: `%ProgramData%\ssh\sshd_config`

## Interact

If **anonymous access** is enabled, it's possible log in with username `“Anonymous”` and password `“”`.

{% code overflow="wrap" %}

```bash
ssh <USER>@<IP>
```

{% endcode %}

{% code overflow="wrap" %}

```bash
ssh -i <KEY> <USER>@<IP>
```

{% endcode %}

### SSH Key

{% code overflow="wrap" %}

```bash
ssh-keygen
```

{% endcode %}

Move the public key in `~/.ssh/authorized_keys` target machine (append if it already exists).

{% code overflow="wrap" %}

```bash
cat id_rsa.pub >> authorized_keys
```

{% endcode %}

| Algorithm             | Private Key  | Public Key       |
| --------------------- | ------------ | ---------------- |
| RSA                   | `id_rsa`     | `id_rsa.pub`     |
| DSA (obsolete)        | `id_dsa`     | `id_dsa.pub`     |
| ECDSA                 | `id_ecdsa`   | `id_ecdsa.pub`   |
| Ed25519 (recommended) | `id_ed25519` | `id_ed25519.pub` |

### Upload Key on Server SSH

{% code overflow="wrap" %}

```bash
ssh-keygen -f ~/.ssh/id_rsa -N ""
ssh-copy-id -i ~/.ssh/id_rsa.pub <USER>@<IP>
```

{% endcode %}

### scp

```bash
scp [-r] [-O] <USER>@<IP>:/<REMOTE_FILE> /<TO_LOCAL>
scp [-r] [-O] /<LOCAL_FILE> <USER>@<IP>:/<TO_REMOTE>
```


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