feat: SSH-Agent Support (#306)

* chore: add agent configuration bool

* feat: add ssh-agent authentication mechanism for linux

* chore: make sure ssh-agent auth is only executed on linux

* chore: add ssh user override

* chore: add ssh configuration block, check ssh config during VirtualEnvironmentClient creation

* fix: handle case of empty ssh config block

* chore: add ssh password auth fallback logic

* fix: remove not needed runtime

* fix linter errors & re-format

* allow ssh agent on all POSIX systems

* add `agent_socket` parameter

* update docs and examples

---------

Co-authored-by: zoop <zoop@zoop.li>
Co-authored-by: Pavel Boldyrev <627562+bpg@users.noreply.github.com>

docs/index.md

@@ -67,6 +67,35 @@ export PROXMOX_VE_PASSWORD="a-strong-password"
 terraform plan
 ```
 
+### SSH connection
+
+The Proxmox provider can connect to a Proxmox node via SSH. This is used in
+the `proxmox_virtual_environment_vm` or `proxmox_virtual_environment_file`
+resource to execute commands on the node to perform actions that are not
+supported by Proxmox API. For example, to import VM disks, or to uploading
+certain type of resources, such as snippets.
+
+The SSH connection configuration is provided via the optional `ssh` block in
+the `provider` block:
+
+```terraform
+provider "proxmox" {
+  endpoint = "https://10.0.0.2:8006/"
+  username = "username@realm"
+  password = "a-strong-password"
+  insecure = true
+  ssh {
+    agent = true
+  }
+}
+```
+
+If no `ssh` block is provided, the provider will attempt to connect to the
+target node using the credentials provided in the `username` and `password` fields.
+Note that the target node is identified by the `node` argument in the resource,
+and may be different from the Proxmox API endpoint. Please refer to the
+section below for all the available arguments in the `ssh` block.
+
 ## Argument Reference
 
 In addition
@@ -85,5 +114,20 @@ Proxmox `provider` block:
 - `password` - (Required) The password for the Proxmox Virtual Environment
   API (can also be sourced from `PROXMOX_VE_PASSWORD`).
 - `username` - (Required) The username and realm for the Proxmox Virtual
-  Environment API (can also be sourced from `PROXMOX_VE_USERNAME`). For 
+  Environment API (can also be sourced from `PROXMOX_VE_USERNAME`). For
   example, `root@pam`.
+- `ssh` - (Optional) The SSH connection configuration to a Proxmox node. This is
+  a
+  block, whose fields are documented below.
+    - `username` - (Optional) The username to use for the SSH connection.
+      Defaults to the username used for the Proxmox API connection. Can also be
+      sourced from `PROXMOX_VE_SSH_USERNAME`.
+    - `password` - (Optional) The password to use for the SSH connection.
+      Defaults to the password used for the Proxmox API connection. Can also be
+      sourced from `PROXMOX_VE_SSH_PASSWORD`.
+    - `agent` - (Optional) Whether to use the SSH agent for the SSH
+      authentication. Defaults to `false`. Can also be sourced
+      from `PROXMOX_VE_SSH_AGENT`.
+    - `agent_socket` - (Optional) The path to the SSH agent socket.
+      Defaults to the value of the `SSH_AUTH_SOCK` environment variable. Can
+      also be sourced from `PROXMOX_VE_SSH_AUTH_SOCK`.

example/main.tf

@@ -3,4 +3,7 @@ provider "proxmox" {
   username = var.virtual_environment_username
   password = var.virtual_environment_password
   insecure = true
+  ssh {
+    agent = true
+  }
 }

proxmox/virtual_environment_client.go

@@ -1,6 +1,8 @@
-/* This Source Code Form is subject to the terms of the Mozilla Public
+/*
+ * This Source Code Form is subject to the terms of the Mozilla Public
  * License, v. 2.0. If a copy of the MPL was not distributed with this
- * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/.
+ */
 
 package proxmox
 
@@ -14,6 +16,7 @@ import (
 	"io"
 	"net/http"
 	"net/url"
+	"runtime"
 	"strings"
 
 	"github.com/google/go-querystring/query"
@@ -24,7 +27,7 @@ import (
 // NewVirtualEnvironmentClient creates and initializes a VirtualEnvironmentClient instance.
 func NewVirtualEnvironmentClient(
 	endpoint, username, password, otp string,
-	insecure bool,
+	insecure bool, sshUsername string, sshPassword string, sshAgent bool, sshAgentSocket string,
 ) (*VirtualEnvironmentClient, error) {
 	u, err := url.ParseRequestURI(endpoint)
 	if err != nil {
@@ -51,6 +54,12 @@ func NewVirtualEnvironmentClient(
 		)
 	}
 
+	if !strings.Contains(username, "@") {
+		return nil, errors.New(
+			"make sure the username for the Proxmox Virtual Environment API ends in '@pve or @pam'",
+		)
+	}
+
 	var pOTP *string
 
 	if otp != "" {
@@ -68,13 +77,32 @@ func NewVirtualEnvironmentClient(
 
 	httpClient := &http.Client{Transport: transport}
 
+	if sshUsername == "" {
+		sshUsername = strings.Split(username, "@")[0]
+	}
+
+	if sshPassword == "" {
+		sshPassword = password
+	}
+
+	if sshAgent && runtime.GOOS != "linux" && runtime.GOOS != "darwin" && runtime.GOOS != "freebsd" {
+		return nil, errors.New(
+			"the ssh agent flag is only supported on POSIX systems, please set it to 'false'" +
+				" or remove it from your provider configuration",
+		)
+	}
+
 	return &VirtualEnvironmentClient{
-		Endpoint:   strings.TrimRight(u.String(), "/"),
-		Insecure:   insecure,
-		OTP:        pOTP,
-		Password:   password,
-		Username:   username,
-		httpClient: httpClient,
+		Endpoint:       strings.TrimRight(u.String(), "/"),
+		Insecure:       insecure,
+		OTP:            pOTP,
+		Password:       password,
+		Username:       username,
+		SSHUsername:    sshUsername,
+		SSHPassword:    sshPassword,
+		SSHAgent:       sshAgent,
+		SSHAgentSocket: sshAgentSocket,
+		httpClient:     httpClient,
 	}, nil
 }
 

proxmox/virtual_environment_client_types.go

@@ -1,6 +1,8 @@
-/* This Source Code Form is subject to the terms of the Mozilla Public
+/*
+ * This Source Code Form is subject to the terms of the Mozilla Public
  * License, v. 2.0. If a copy of the MPL was not distributed with this
- * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/.
+ */
 
 package proxmox
 
@@ -19,11 +21,15 @@ const (
 
 // VirtualEnvironmentClient implements an API client for the Proxmox Virtual Environment API.
 type VirtualEnvironmentClient struct {
-	Endpoint string
-	Insecure bool
-	OTP      *string
-	Password string
-	Username string
+	Endpoint       string
+	Insecure       bool
+	OTP            *string
+	Password       string
+	Username       string
+	SSHUsername    string
+	SSHPassword    string
+	SSHAgent       bool
+	SSHAgentSocket string
 
 	authenticationData *VirtualEnvironmentAuthenticationResponseData
 	httpClient         *http.Client

proxmox/virtual_environment_nodes.go

@@ -1,6 +1,8 @@
-/* This Source Code Form is subject to the terms of the Mozilla Public
+/*
+ * This Source Code Form is subject to the terms of the Mozilla Public
  * License, v. 2.0. If a copy of the MPL was not distributed with this
- * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/.
+ */
 
 package proxmox
 
@@ -21,6 +23,7 @@ import (
 	"github.com/skeema/knownhosts"
 
 	"golang.org/x/crypto/ssh"
+	"golang.org/x/crypto/ssh/agent"
 )
 
 // ExecuteNodeCommands executes commands on a given node.
@@ -193,8 +196,6 @@ func (c *VirtualEnvironmentClient) OpenNodeShell(
 		return nil, err
 	}
 
-	ur := strings.Split(c.Username, "@")
-
 	homeDir, err := os.UserHomeDir()
 	if err != nil {
 		return nil, fmt.Errorf("failed to determine the home directory: %w", err)
@@ -246,8 +247,61 @@ func (c *VirtualEnvironmentClient) OpenNodeShell(
 	})
 
 	sshConfig := &ssh.ClientConfig{
-		User:              ur[0],
-		Auth:              []ssh.AuthMethod{ssh.Password(c.Password)},
+		User:              c.SSHUsername,
+		Auth:              []ssh.AuthMethod{ssh.Password(c.SSHPassword)},
+		HostKeyCallback:   cb,
+		HostKeyAlgorithms: kh.HostKeyAlgorithms(sshHost),
+	}
+
+	tflog.Info(ctx, fmt.Sprintf("Agent is set to %t", c.SSHAgent))
+
+	if c.SSHAgent {
+		sshClient, err := c.CreateSSHClientAgent(ctx, cb, kh, sshHost)
+		if err != nil {
+			tflog.Error(ctx, "Failed ssh connection through agent, "+
+				"falling back to password authentication",
+				map[string]interface{}{
+					"error": err,
+				})
+		} else {
+			return sshClient, nil
+		}
+	}
+
+	sshClient, err := ssh.Dial("tcp", sshHost, sshConfig)
+	if err != nil {
+		return nil, fmt.Errorf("failed to dial %s: %w", sshHost, err)
+	}
+
+	tflog.Debug(ctx, "SSH connection established", map[string]interface{}{
+		"host": sshHost,
+		"user": c.SSHUsername,
+	})
+	return sshClient, nil
+}
+
+// CreateSSHClientAgent establishes an ssh connection through the agent authentication mechanism
+func (c *VirtualEnvironmentClient) CreateSSHClientAgent(
+	ctx context.Context,
+	cb ssh.HostKeyCallback,
+	kh knownhosts.HostKeyCallback,
+	sshHost string,
+) (*ssh.Client, error) {
+	if c.SSHAgentSocket == "" {
+		return nil, errors.New("failed connecting to SSH agent socket: the socket file is not defined, " +
+			"authentication will fall back to password")
+	}
+
+	conn, err := net.Dial("unix", c.SSHAgentSocket)
+	if err != nil {
+		return nil, fmt.Errorf("failed connecting to SSH auth socket '%s': %w", c.SSHAgentSocket, err)
+	}
+
+	ag := agent.NewClient(conn)
+
+	sshConfig := &ssh.ClientConfig{
+		User:              c.SSHUsername,
+		Auth:              []ssh.AuthMethod{ssh.PublicKeysCallback(ag.Signers), ssh.Password(c.SSHPassword)},
 		HostKeyCallback:   cb,
 		HostKeyAlgorithms: kh.HostKeyAlgorithms(sshHost),
 	}
@@ -259,7 +313,7 @@ func (c *VirtualEnvironmentClient) OpenNodeShell(
 
 	tflog.Debug(ctx, "SSH connection established", map[string]interface{}{
 		"host": sshHost,
-		"user": ur[0],
+		"user": c.SSHUsername,
 	})
 	return sshClient, nil
 }

proxmoxtf/provider/provider.go

@@ -17,14 +17,18 @@ import (
 )
 
 const (
-	dvProviderOTP = ""
-
+	dvProviderOTP                = ""
 	mkProviderVirtualEnvironment = "virtual_environment"
 	mkProviderEndpoint           = "endpoint"
 	mkProviderInsecure           = "insecure"
 	mkProviderOTP                = "otp"
 	mkProviderPassword           = "password"
 	mkProviderUsername           = "username"
+	mkProviderSSH                = "ssh"
+	mkProviderSSHUsername        = "username"
+	mkProviderSSHPassword        = "password"
+	mkProviderSSHAgent           = "agent"
+	mkProviderSSHAgentSocket     = "agent_socket"
 )
 
 // ProxmoxVirtualEnvironment returns the object for this provider.
@@ -41,26 +45,46 @@ func providerConfigure(_ context.Context, d *schema.ResourceData) (interface{},
 	var err error
 	var veClient *proxmox.VirtualEnvironmentClient
 
-	// Initialize the client for the Virtual Environment, if required.
+	// Legacy configuration, wrapped in the deprecated `virtual_environment` block
 	veConfigBlock := d.Get(mkProviderVirtualEnvironment).([]interface{})
-
 	if len(veConfigBlock) > 0 {
 		veConfig := veConfigBlock[0].(map[string]interface{})
+		veSSHConfig := veConfig[mkProviderSSH].(map[string]interface{})
 
 		veClient, err = proxmox.NewVirtualEnvironmentClient(
 			veConfig[mkProviderEndpoint].(string),
 			veConfig[mkProviderUsername].(string),
+			veConfig[mkProviderSSH].(map[string]interface{})[mkProviderSSHUsername].(string),
 			veConfig[mkProviderPassword].(string),
-			veConfig[mkProviderOTP].(string),
 			veConfig[mkProviderInsecure].(bool),
+			veSSHConfig[mkProviderSSHUsername].(string),
+			veSSHConfig[mkProviderSSHPassword].(string),
+			veSSHConfig[mkProviderSSHAgent].(bool),
+			veSSHConfig[mkProviderSSHAgentSocket].(string),
 		)
 	} else {
+		sshconf := map[string]interface{}{
+			mkProviderSSHUsername:    "",
+			mkProviderSSHPassword:    "",
+			mkProviderSSHAgent:       false,
+			mkProviderSSHAgentSocket: "",
+		}
+
+		sshBlock, sshSet := d.GetOk(mkProviderSSH)
+		if sshSet {
+			sshconf = sshBlock.(*schema.Set).List()[0].(map[string]interface{})
+		}
+
 		veClient, err = proxmox.NewVirtualEnvironmentClient(
 			d.Get(mkProviderEndpoint).(string),
 			d.Get(mkProviderUsername).(string),
 			d.Get(mkProviderPassword).(string),
 			d.Get(mkProviderOTP).(string),
 			d.Get(mkProviderInsecure).(bool),
+			sshconf[mkProviderSSHUsername].(string),
+			sshconf[mkProviderSSHPassword].(string),
+			sshconf[mkProviderSSHAgent].(bool),
+			sshconf[mkProviderSSHAgentSocket].(string),
 		)
 	}