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Enable SSH host key verification when gateway provides fingerprint #4

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Merged
persimmon16 merged 1 commit into from
Apr 1, 2026
Merged

Enable SSH host key verification when gateway provides fingerprint #4

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62 changes: 46 additions & 16 deletions crates/openshell-cli/src/ssh.rs
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -59,6 +59,7 @@ struct SshSessionConfig {
sandbox_id: String,
gateway_url: String,
token: String,
host_key_fingerprint: String,
}

async fn ssh_session_config(
Expand Down Expand Up @@ -127,22 +128,51 @@ async fn ssh_session_config(
sandbox_id: session.sandbox_id.clone(),
gateway_url,
token: session.token,
host_key_fingerprint: session.host_key_fingerprint,
})
}

fn ssh_base_command(proxy_command: &str) -> Command {
fn ssh_base_command(proxy_command: &str, host_key_fingerprint: &str) -> Command {
let mut command = Command::new("ssh");
command
.arg("-o")
.arg(format!("ProxyCommand={proxy_command}"))
.arg("-o")
.arg("StrictHostKeyChecking=no")
.arg("-o")
.arg("UserKnownHostsFile=/dev/null")
.arg("-o")
.arg("GlobalKnownHostsFile=/dev/null")
.arg("-o")
.arg("LogLevel=ERROR");
.arg(format!("ProxyCommand={proxy_command}"));
if host_key_fingerprint.is_empty() {
command
.arg("-o")
.arg("StrictHostKeyChecking=no")
.arg("-o")
.arg("UserKnownHostsFile=/dev/null")
.arg("-o")
.arg("GlobalKnownHostsFile=/dev/null");
} else {
// Write a temporary known_hosts with the gateway-provided fingerprint
// and enable strict host key checking to detect MITM attacks.
let known_hosts = format!("[sandbox]:2222 {host_key_fingerprint}");
let applied = (|| -> Option<()> {
let dir = tempfile::tempdir().ok()?;
let path = dir.into_path().join("known_hosts");
std::fs::write(&path, &known_hosts).ok()?;
command
.arg("-o")
.arg("StrictHostKeyChecking=yes")
.arg("-o")
.arg(format!("UserKnownHostsFile={}", path.display()))
.arg("-o")
.arg("GlobalKnownHostsFile=/dev/null");
Some(())
})();
if applied.is_none() {
command
.arg("-o")
.arg("StrictHostKeyChecking=no")
.arg("-o")
.arg("UserKnownHostsFile=/dev/null")
.arg("-o")
.arg("GlobalKnownHostsFile=/dev/null");
}
}
command.arg("-o").arg("LogLevel=ERROR");
command
}

Expand Down Expand Up @@ -236,7 +266,7 @@ async fn sandbox_connect_with_mode(
) -> Result<()> {
let session = ssh_session_config(server, name, tls).await?;

let mut command = ssh_base_command(&session.proxy_command);
let mut command = ssh_base_command(&session.proxy_command, &session.host_key_fingerprint);
command
.arg("-tt")
.arg("-o")
Expand Down Expand Up @@ -315,7 +345,7 @@ pub async fn sandbox_forward(

let session = ssh_session_config(server, name, tls).await?;

let mut command = TokioCommand::from(ssh_base_command(&session.proxy_command));
let mut command = TokioCommand::from(ssh_base_command(&session.proxy_command, &session.host_key_fingerprint));
command
.arg("-N")
.arg("-o")
Expand Down Expand Up @@ -395,7 +425,7 @@ async fn sandbox_exec_with_mode(
}

let session = ssh_session_config(server, name, tls).await?;
let mut ssh = ssh_base_command(&session.proxy_command);
let mut ssh = ssh_base_command(&session.proxy_command, &session.host_key_fingerprint);

if tty {
ssh.arg("-tt")
Expand Down Expand Up @@ -465,7 +495,7 @@ pub async fn sandbox_sync_up_files(

let session = ssh_session_config(server, name, tls).await?;

let mut ssh = ssh_base_command(&session.proxy_command);
let mut ssh = ssh_base_command(&session.proxy_command, &session.host_key_fingerprint);
ssh.arg("-T")
.arg("-o")
.arg("RequestTTY=no")
Expand Down Expand Up @@ -534,7 +564,7 @@ pub async fn sandbox_sync_up(
) -> Result<()> {
let session = ssh_session_config(server, name, tls).await?;

let mut ssh = ssh_base_command(&session.proxy_command);
let mut ssh = ssh_base_command(&session.proxy_command, &session.host_key_fingerprint);
ssh.arg("-T")
.arg("-o")
.arg("RequestTTY=no")
Expand Down Expand Up @@ -627,7 +657,7 @@ pub async fn sandbox_sync_down(
),
);

let mut ssh = ssh_base_command(&session.proxy_command);
let mut ssh = ssh_base_command(&session.proxy_command, &session.host_key_fingerprint);
ssh.arg("-T")
.arg("-o")
.arg("RequestTTY=no")
Expand Down
1 change: 1 addition & 0 deletions crates/openshell-tui/Cargo.toml
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -26,6 +26,7 @@ miette = { workspace = true }
owo-colors = { workspace = true }
serde = { workspace = true }
tracing = { workspace = true }
tempfile = "3"
url = { workspace = true }

[lints]
Expand Down
69 changes: 47 additions & 22 deletions crates/openshell-tui/src/lib.rs
View file
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Original file line number Diff line number Diff line change
Expand Up @@ -778,6 +778,44 @@ async fn fetch_sandbox_detail(app: &mut App) {
// Shell connect (suspend TUI, launch SSH, resume)
// ---------------------------------------------------------------------------

/// Apply SSH host key verification arguments to an SSH command.
///
/// When the gateway provides a host key fingerprint, a temporary `known_hosts` file
/// is written and strict checking is enabled. Otherwise, host key checking is
/// disabled (current behavior until the gateway populates the fingerprint field).
fn apply_host_key_args(cmd: &mut std::process::Command, host_key_fingerprint: &str) {
if host_key_fingerprint.is_empty() {
cmd.arg("-o")
.arg("StrictHostKeyChecking=no")
.arg("-o")
.arg("UserKnownHostsFile=/dev/null")
.arg("-o")
.arg("GlobalKnownHostsFile=/dev/null");
} else {
let known_hosts = format!("[sandbox]:2222 {host_key_fingerprint}");
let applied = (|| -> Option<()> {
let dir = tempfile::tempdir().ok()?;
let path = dir.into_path().join("known_hosts");
std::fs::write(&path, &known_hosts).ok()?;
cmd.arg("-o")
.arg("StrictHostKeyChecking=yes")
.arg("-o")
.arg(format!("UserKnownHostsFile={}", path.display()))
.arg("-o")
.arg("GlobalKnownHostsFile=/dev/null");
Some(())
})();
if applied.is_none() {
cmd.arg("-o")
.arg("StrictHostKeyChecking=no")
.arg("-o")
.arg("UserKnownHostsFile=/dev/null")
.arg("-o")
.arg("GlobalKnownHostsFile=/dev/null");
}
}
}

/// Suspend the TUI, launch an interactive SSH shell to the sandbox, resume on exit.
///
/// This replicates the `openshell sandbox connect` flow but uses `Command::status()`
Expand Down Expand Up @@ -863,13 +901,9 @@ async fn handle_shell_connect(
let mut command = std::process::Command::new("ssh");
command
.arg("-o")
.arg(format!("ProxyCommand={proxy_command}"))
.arg("-o")
.arg("StrictHostKeyChecking=no")
.arg("-o")
.arg("UserKnownHostsFile=/dev/null")
.arg("-o")
.arg("GlobalKnownHostsFile=/dev/null")
.arg(format!("ProxyCommand={proxy_command}"));
apply_host_key_args(&mut command, &session.host_key_fingerprint);
command
.arg("-o")
.arg("LogLevel=ERROR")
.arg("-tt")
Expand Down Expand Up @@ -1012,14 +1046,9 @@ async fn handle_exec_command(
.join(" ");
let mut ssh = std::process::Command::new("ssh");
ssh.arg("-o")
.arg(format!("ProxyCommand={proxy_command}"))
.arg("-o")
.arg("StrictHostKeyChecking=no")
.arg("-o")
.arg("UserKnownHostsFile=/dev/null")
.arg("-o")
.arg("GlobalKnownHostsFile=/dev/null")
.arg("-o")
.arg(format!("ProxyCommand={proxy_command}"));
apply_host_key_args(&mut ssh, &session.host_key_fingerprint);
ssh.arg("-o")
.arg("LogLevel=ERROR")
.arg("-tt")
.arg("-o")
Expand Down Expand Up @@ -1434,13 +1463,9 @@ async fn start_port_forwards(
let mut command = std::process::Command::new("ssh");
command
.arg("-o")
.arg(format!("ProxyCommand={proxy_command}"))
.arg("-o")
.arg("StrictHostKeyChecking=no")
.arg("-o")
.arg("UserKnownHostsFile=/dev/null")
.arg("-o")
.arg("GlobalKnownHostsFile=/dev/null")
.arg(format!("ProxyCommand={proxy_command}"));
apply_host_key_args(&mut command, &session.host_key_fingerprint);
command
.arg("-o")
.arg("LogLevel=ERROR")
.arg("-o")
Expand Down
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