sftp: add support for ~/.ssh/config, fixes borgbackup#37

including support for configured IdentityFiles

pyproject.toml

@@ -23,7 +23,7 @@ classifiers = [
 license = {text="BSD"}
 requires-python = ">=3.9"
 dependencies = [
-    "paramiko",
+    "paramiko >= 1.9.1",  # 1.9.1+ supports multiple IdentityKey entries in .ssh/config
 ]
 
 [project.urls]

src/borgstore/backends/sftp.py

@@ -40,7 +40,20 @@ def __init__(self, hostname: str, path: str, port: int = 22, username: Optional[
     def _connect(self):
         ssh = paramiko.SSHClient()
         ssh.set_missing_host_key_policy(paramiko.AutoAddPolicy())
-        ssh.connect(hostname=self.hostname, username=self.username, port=self.port, allow_agent=True)
+        config_path = Path("~/.ssh/config").expanduser()
+        try:
+            sc = paramiko.SSHConfig.from_path(str(config_path))
+        except FileNotFoundError:
+            scd = paramiko.SSHConfigDict()  # empty dict
+        else:
+            scd = sc.lookup(self.hostname)
+        ssh.connect(
+            hostname=scd.get("hostname", self.hostname),
+            username=scd.get("user", self.username),
+            port=scd.as_int("port") if "port" in scd else self.port,
+            key_filename=scd.get("identityfile", None),  # list of keys
+            allow_agent=True,
+        )
         self.client = ssh.open_sftp()
 
     def _disconnect(self):

tests/test_backends.py

@@ -31,13 +31,23 @@ def posixfs_backend_created(tmp_path):
         be.destroy()
 
 
-def _get_sftp_backend():
+def _get_sftp_backend(local=False, remote_url=False, remote_config=True):
     # needs an authorized key loaded into the ssh agent. pytest works, tox doesn't:
-    # return Sftp(username="tw", hostname="localhost", path="/Users/tw/w/borgstore/temp-store")
+    if local:
+        return Sftp(username="tw", hostname="localhost", path="/Users/tw/w/borgstore/temp-store")
     # for tests with higher latency:
-    return Sftp(
-        username="twaldmann", hostname="shell.ipv4.thinkmo.de", port=2222, path="/home/twaldmann/borgstore/temp-store"
-    )
+    if remote_url:
+        return Sftp(
+            username="twaldmann",
+            hostname="shell.ipv4.thinkmo.de",
+            port=2222,
+            path="/home/twaldmann/borgstore/temp-store",
+        )
+    # same as previous, but loads config for host "shell" from ~/.ssh/config:
+    if remote_config:
+        return Sftp(hostname="shell", path="/home/twaldmann/borgstore/temp-store")
+
+    raise ValueError("check _get_sftp_backend() parameter defaults!")
 
 
 def check_sftp_available():