Add vault --file

vault_cli/cli.py

@@ -1,4 +1,5 @@
 import contextlib
+import json
 import logging
 import os
 import pathlib
@@ -414,11 +415,26 @@ def delete(client_obj: client.VaultClientBase, name: str, key: Optional[str]) ->
     formerly deprecated. See command help for details.
     """,
 )
+@click.option(
+    "--file",
+    multiple=True,
+    help="""
+    Write a secret from this path into a file on the filesystem. Expected format is
+    path/in/vault:key=/path/in/filesystem . This option is meant to be used when you are
+    your command can only read its inputs from a file and not from the environment (e.g.
+    secret keys, ...). It's highly recommended to only use the option when provided with
+    a secure private temporary filesystem. Writing to a physical disk should be avoided
+    when possible.
+    """,
+)
 @click.option(
     "-o",
     "--omit-single-key/--no-omit-single-key",
     default=False,
-    help="When the secret has only one key, don't use that key to build the name of the environment variable",
+    help="""
+    When the secret has only one key, don't use that key to build the name of the
+    environment variable. This option doesn't affect --file.
+    """,
 )
 @click.option(
     "-f",
@@ -432,6 +448,7 @@ def delete(client_obj: client.VaultClientBase, name: str, key: Optional[str]) ->
 def env(
     client_obj: client.VaultClientBase,
     envvar: Sequence[str],
+    file: Sequence[str],
     omit_single_key: bool,
     force: bool,
     command: Sequence[str],
@@ -462,6 +479,7 @@ def env(
     Using `--path a/b/c:username=FOO` will inject `FOO=me` in the environment.
     """
     envvars = list(envvar) or []
+    files = list(file) or []
 
     env_secrets = {}
 
@@ -483,6 +501,22 @@ def env(
 
         env_secrets.update(env_updates)
 
+    for file in files:
+        path, key, filesystem_path = get_env_parts(file)
+        if not (path and key and filesystem_path):
+            raise click.BadOptionUsage(
+                "file", "--file expected format is vault/path:key=filesystem/path"
+            )
+        secret_obj = client_obj.get_secret(path=path, key=key)
+
+        if isinstance(secret_obj, str):
+            secret = secret_obj
+        else:
+            secret = yaml.safe_dump(
+                secret_obj, default_flow_style=False, explicit_start=True
+            )
+        pathlib.Path(filesystem_path).write_text(secret + "\n")
+
     if bool(client_obj.errors) and not force:
         raise click.ClickException("There was an error while reading the secrets.")
     environment.exec_command(command=command, environment=env_secrets)