SSH Configuration Validation

This document describes the validation rules for SSH configuration options in the persistent-ssh-agent package.

Connection Settings

Port

Valid range: 1-65535
Example: Port 22

Hostname

Any valid hostname or IP address
Example: Hostname github.com

User

Any valid username
Example: User git

IdentityFile

Valid file path
Can have multiple entries
Example: IdentityFile ~/.ssh/id_rsa

Security Settings

StrictHostKeyChecking

Valid options: yes, no, accept-new, off, ask
Example: StrictHostKeyChecking yes

BatchMode

Valid options: yes, no
Example: BatchMode yes

PasswordAuthentication

Valid options: yes, no
Example: PasswordAuthentication no

PubkeyAuthentication

Valid options: yes, no
Example: PubkeyAuthentication yes

Connection Optimization

Compression

Valid options: yes, no
Example: Compression yes

ConnectTimeout

Non-negative integer
Example: ConnectTimeout 30

ServerAliveInterval

Non-negative integer
Example: ServerAliveInterval 60

ServerAliveCountMax

Non-negative integer
Example: ServerAliveCountMax 3

Proxy and Forwarding

ProxyCommand

Any valid command string
Example: ProxyCommand ssh -W %h:%p jumphost

ForwardAgent

Valid options: yes, no
Example: ForwardAgent yes

ForwardX11

Valid options: yes, no
Example: ForwardX11 no

Environment Settings

RequestTTY

Valid options: yes, no, force, auto
Example: RequestTTY auto

SendEnv

Any valid environment variable pattern
Can have multiple entries
Example: SendEnv LANG LC_*

Multiplexing

ControlMaster

Valid options: yes, no, ask, auto, autoask
Example: ControlMaster auto

ControlPath

Valid file path
Example: ControlPath ~/.ssh/cm-%r@%h:%p

ControlPersist

Valid options: yes, no, or time duration in seconds
Example: ControlPersist 1h

Canonicalization

CanonicalizeHostname

Valid options: yes, no, always
Example: CanonicalizeHostname yes

CanonicalizeMaxDots

Non-negative integer
Example: CanonicalizeMaxDots 1

CanonicalizeDomains

List of domain names
Example: CanonicalizeDomains example.com example.net

Error Handling

The configuration parser will:

Skip invalid configuration keys
Log warnings for invalid values
Use default values when invalid values are provided
Validate all values before applying them

Best Practices

Always use the most restrictive security settings appropriate for your use case
Set appropriate timeouts to prevent hanging connections
Use multiplexing when making multiple connections to the same host
Enable compression for slow connections
Use canonical hostnames when working with complex network setups