254 lines
10 KiB
Plaintext
254 lines
10 KiB
Plaintext
---
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page_title: Provisioner Connection Settings
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description: >-
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The connection block allows you to manage provisioner connection defaults for
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SSH and WinRM.
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---
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# Provisioner Connection Settings
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Most provisioners require access to the remote resource via SSH or WinRM, and
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expect a nested `connection` block with details about how to connect.
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-> **Note:** Provisioners should only be used as a last resort. For most
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common situations there are better alternatives. Refer to
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[Declaring Provisioners](/language/resources/provisioners/syntax) for more details.
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## Connection Block
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Connection blocks don't take a block label, and can be nested within either a
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`resource` or a `provisioner`.
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* A `connection` block nested directly within a `resource` affects all of
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that resource's provisioners.
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* A `connection` block nested in a `provisioner` block only affects that
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provisioner, and overrides any resource-level connection settings.
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One use case for providing multiple connections is to have an initial
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provisioner connect as the `root` user to set up user accounts, and have
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subsequent provisioners connect as a user with more limited permissions.
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Since the SSH connection type is most often used with
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newly-created remote resources, validation of SSH host keys is disabled by
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default. In scenarios where this is not acceptable, a separate mechanism for
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key distribution could be established and the `host_key` directive documented
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below explicitly set to verify against a specific key or signing CA.
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-> **Note:** In Terraform 0.11 and earlier, providers could set default values
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for some connection settings, so that `connection` blocks could sometimes be
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omitted. This feature was removed in 0.12 in order to make Terraform's behavior
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more predictable.
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## Example usage
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```hcl
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# Copies the file as the root user using SSH
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provisioner "file" {
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source = "conf/myapp.conf"
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destination = "/etc/myapp.conf"
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connection {
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type = "ssh"
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user = "root"
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password = "${var.root_password}"
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host = "${var.host}"
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}
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}
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# Copies the file as the Administrator user using WinRM
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provisioner "file" {
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source = "conf/myapp.conf"
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destination = "C:/App/myapp.conf"
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connection {
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type = "winrm"
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user = "Administrator"
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password = "${var.admin_password}"
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host = "${var.host}"
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}
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}
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```
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## The `self` Object
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Expressions in `connection` blocks cannot refer to their parent resource by
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name. Instead, they can use the special `self` object.
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The `self` object represents the connection's parent resource, and has all of
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that resource's attributes. For example, use `self.public_ip` to reference an
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`aws_instance`'s `public_ip` attribute.
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-> **Technical note:** Resource references are restricted here because
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references create dependencies. Referring to a resource by name within its own
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block would create a dependency cycle.
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## Argument Reference
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**The following arguments are supported by all connection types:**
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* `type` - The connection type that should be used. Valid types are `ssh` and `winrm`.
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Defaults to `ssh`.
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* `user` - The user that we should use for the connection.
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Defaults to `root` when using type `ssh` and defaults to `Administrator` when using type `winrm`.
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* `password` - The password we should use for the connection. In some cases this is
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specified by the provider.
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* `host` - (Required) The address of the resource to connect to.
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* `port` - The port to connect to.
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Defaults to `22` when using type `ssh` and defaults to `5985` when using type `winrm`.
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* `timeout` - The timeout to wait for the connection to become available. Should be provided as a string like `30s` or `5m`.
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Defaults to 5 minutes.
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* `script_path` - The path used to copy scripts meant for remote execution.
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For more information, see
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[How Provisioners Execute Remote Scripts](#how-provisioners-execute-remote-scripts)
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below.
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**Additional arguments only supported by the `ssh` connection type:**
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* `private_key` - The contents of an SSH key to use for the connection. These can
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be loaded from a file on disk using
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[the `file` function](/language/functions/file). This takes
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preference over the password if provided.
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* `certificate` - The contents of a signed CA Certificate. The certificate argument must be
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used in conjunction with a `private_key`. These can
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be loaded from a file on disk using the [the `file` function](/language/functions/file).
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* `agent` - Set to `false` to disable using `ssh-agent` to authenticate. On Windows the
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only supported SSH authentication agent is
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[Pageant](http://the.earth.li/\~sgtatham/putty/0.66/htmldoc/Chapter9.html#pageant).
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* `agent_identity` - The preferred identity from the ssh agent for authentication.
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* `host_key` - The public key from the remote host or the signing CA, used to
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verify the connection.
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* `target_platform` - The target platform to connect to. Valid values are `"windows"` and `"unix"`. Defaults to `"unix"` if not set.
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**Additional arguments only supported by the `winrm` connection type:**
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* `https` - Set to `true` to connect using HTTPS instead of HTTP.
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* `insecure` - Set to `true` to not validate the HTTPS certificate chain.
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* `use_ntlm` - Set to `true` to use NTLM authentication, rather than default (basic authentication), removing the requirement for basic authentication to be enabled within the target guest. Further reading for remote connection authentication can be found [here](https://docs.microsoft.com/en-us/windows/win32/winrm/authentication-for-remote-connections?redirectedfrom=MSDN).
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* `cacert` - The CA certificate to validate against.
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Provisioners typically assume that the remote system runs Microsoft Windows
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when using the `winrm` connection type. Behaviors which would vary based on
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the `target_platform` option if using SSH will instead force the
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Windows-specific behavior when using WinRM, unless otherwise specified.
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<a id="bastion"></a>
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## Connecting through a Bastion Host with SSH
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The `ssh` connection also supports the following fields to facilitate connnections via a
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[bastion host](https://en.wikipedia.org/wiki/Bastion_host).
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* `bastion_host` - Setting this enables the bastion Host connection. This host
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will be connected to first, and then the `host` connection will be made from there.
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* `bastion_host_key` - The public key from the remote host or the signing CA,
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used to verify the host connection.
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* `bastion_port` - The port to use connect to the bastion host. Defaults to the
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value of the `port` field.
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* `bastion_user` - The user for the connection to the bastion host. Defaults to
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the value of the `user` field.
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* `bastion_password` - The password we should use for the bastion host.
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Defaults to the value of the `password` field.
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* `bastion_private_key` - The contents of an SSH key file to use for the bastion
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host. These can be loaded from a file on disk using
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[the `file` function](/language/functions/file).
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Defaults to the value of the `private_key` field.
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* `bastion_certificate` - The contents of a signed CA Certificate. The certificate argument
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must be used in conjunction with a `bastion_private_key`. These can be loaded from
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a file on disk using the [the `file` function](/language/functions/file).
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## How Provisioners Execute Remote Scripts
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Provisioners which execute commands on a remote system via a protocol such as
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SSH typically achieve that by uploading a script file to the remote system
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and then asking the default shell to execute it. Provisioners use this strategy
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because it then allows you to use all of the typical scripting techniques
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supported by that shell, including preserving environment variable values
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and other context between script statements.
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However, this approach does have some consequences which can be relevant in
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some unusual situations, even though this is just an implementation detail
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for typical use.
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Most importantly, there must be a suitable location in the remote filesystem
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where the provisioner can create the script file. By default, Terraform
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chooses a path containing a random number using the following patterns
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depending on how `target_platform` is set:
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* `"unix"`: `/tmp/terraform_%RAND%.sh`
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* `"windows"`: `C:/windows/temp/terraform_%RAND%.cmd`
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In both cases above, the provisioner replaces the sequence `%RAND%` with
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some randomly-chosen decimal digits.
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Provisioners cannot react directly to remote environment variables such as
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`TMPDIR` or use functions like `mktemp` because they run on the system where
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Terraform is running, not on the remote system. Therefore if your remote
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system doesn't use the filesystem layout expected by these default paths
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then you can override it using the `script_path` option in your `connection`
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block:
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```hcl
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connection {
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# ...
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script_path = "H:/terraform-temp/script_%RAND%.sh"
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}
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```
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As with the default patterns, provisioners will replace the sequence `%RAND%`
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with randomly-selected decimal digits, to reduce the likelihood of collisions
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between multiple provisioners running concurrently.
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If your target system is running Windows, we recommend uses forward slashes
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instead of backslashes, despite the typical convention on Windows, because
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the Terraform language uses backslash as the quoted string escape character.
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### Executing Scripts using SSH/SCP
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When using the SSH protocol, provisioners upload their script files using
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the Secure Copy Protocol (SCP), which requires that the remote system have
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the `scp` service program installed to act as the server for that protocol.
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Provisioners will pass the chosen script path (after `%RAND%`
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expansion) directly to the remote `scp` process, which is responsible for
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interpreting it. With the default configuration of `scp` as distributed with
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OpenSSH, you can place temporary scripts in the home directory of the remote
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user by specifying a relative path:
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```hcl
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connection {
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type = "ssh"
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# ...
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script_path = "terraform_provisioner_%RAND%.sh"
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}
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```
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-> **Warning:** In Terraform v1.0 and earlier, the built-in provisioners
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incorrectly passed the `script_path` value to `scp` through a remote shell and
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thus allowed it to be subject to arbitrary shell expansion, and thus created an
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unintended opportunity for remote code execution. Terraform v1.1 and later
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will now correctly quote and escape the script path to ensure that the
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remote `scp` process can always interpret it literally. For modules that will
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be used with Terraform v1.0 and earlier, avoid using untrusted external
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values as part of the `script_path` argument.
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