feat(client): Support body placeholder for SSH endpoints (#1286)

* feat(ssh): Add BODY placeholder support for SSH endpoints

- Modify ExecuteSSHCommand to capture stdout output
- Update SSH endpoint handling to use needsToReadBody() mechanism
- Add comprehensive test cases for SSH BODY functionality
- Support basic body content, pattern matching, JSONPath, and functions
- Maintain backward compatibility with existing SSH endpoints

* docs: Add SSH BODY placeholder examples to README

- Add [BODY] placeholder to supported SSH placeholders list
- Add comprehensive examples showing various SSH BODY conditions
- Include pattern matching, length checks, JSONPath expressions
- Demonstrate function wrappers (len, has, any) usage

* Revert "docs: Add SSH BODY placeholder examples to README"

This reverts commit ae93e38683.

* docs: Add [BODY] placeholder to SSH supported placeholders list

* test: remove SSH BODY placeholder test cases

* Update client/client.go

* Update client/client.go

* docs: Add minimal SSH BODY example

---------

Co-authored-by: TwiN <twin@linux.com>

README.md

@@ -3031,12 +3031,13 @@ endpoints:
       password: "password"
     body: |
       {
-        "command": "uptime"
+        "command": "echo '{\"memory\": {\"used\": 512}}'"
       }
     interval: 1m
     conditions:
       - "[CONNECTED] == true"
       - "[STATUS] == 0"
+      - "[BODY].memory.used > 500"
 ```
 
 you can also use no authentication to monitor the endpoint by not specifying the username
@@ -3059,6 +3060,7 @@ endpoints:
 The following placeholders are supported for endpoints of type SSH:
 - `[CONNECTED]` resolves to `true` if the SSH connection was successful, `false` otherwise
 - `[STATUS]` resolves the exit code of the command executed on the remote server (e.g. `0` for success)
+- `[BODY]` resolves to the stdout output of the command executed on the remote server
 - `[IP]` resolves to the IP address of the server
 - `[RESPONSE_TIME]` resolves to the time it took to establish the connection and execute the command
 

client/client.go

@@ -1,6 +1,7 @@
 package client
 
 import (
+	"bytes"
 	"context"
 	"crypto/tls"
 	"crypto/x509"
@@ -301,7 +302,7 @@ func CheckSSHBanner(address string, cfg *Config) (bool, int, error) {
 }
 
 // ExecuteSSHCommand executes a command to an address using the SSH protocol.
-func ExecuteSSHCommand(sshClient *ssh.Client, body string, config *Config) (bool, int, error) {
+func ExecuteSSHCommand(sshClient *ssh.Client, body string, config *Config) (bool, int, []byte, error) {
 	type Body struct {
 		Command string `json:"command"`
 	}
@@ -309,26 +310,30 @@ func ExecuteSSHCommand(sshClient *ssh.Client, body string, config *Config) (bool
 	var b Body
 	body = parseLocalAddressPlaceholder(body, sshClient.Conn.LocalAddr())
 	if err := json.Unmarshal([]byte(body), &b); err != nil {
-		return false, 0, err
+		return false, 0, nil, err
 	}
 	sess, err := sshClient.NewSession()
 	if err != nil {
-		return false, 0, err
+		return false, 0, nil, err
 	}
+	// Capture stdout
+	var stdout bytes.Buffer
+	sess.Stdout = &stdout
 	err = sess.Start(b.Command)
 	if err != nil {
-		return false, 0, err
+		return false, 0, nil, err
 	}
 	defer sess.Close()
 	err = sess.Wait()
+	output := stdout.Bytes()
 	if err == nil {
-		return true, 0, nil
+		return true, 0, output, nil
 	}
 	var exitErr *ssh.ExitError
 	if ok := errors.As(err, &exitErr); !ok {
-		return false, 0, err
+		return false, 0, nil, err
 	}
-	return true, exitErr.ExitStatus(), nil
+	return true, exitErr.ExitStatus(), output, nil
 }
 
 // Ping checks if an address can be pinged and returns the round-trip time if the address can be pinged

config/endpoint/endpoint.go

@@ -514,11 +514,16 @@ func (e *Endpoint) call(result *Result) {
 			result.AddError(err.Error())
 			return
 		}
-		result.Success, result.HTTPStatus, err = client.ExecuteSSHCommand(cli, e.getParsedBody(), e.ClientConfig)
+		var output []byte
+		result.Success, result.HTTPStatus, output, err = client.ExecuteSSHCommand(cli, e.getParsedBody(), e.ClientConfig)
 		if err != nil {
 			result.AddError(err.Error())
 			return
 		}
+		// Only store the output in result.Body if there's a condition that uses the BodyPlaceholder
+		if e.needsToReadBody() {
+			result.Body = output
+		}
 		result.Duration = time.Since(startTime)
 	} else {
 		response, err = client.GetHTTPClient(e.ClientConfig).Do(request)