fix: clear RemoteCommand on every non-interactive path

lua/sshfs/lib/ssh.lua

@@ -48,6 +48,10 @@ local function get_ssh_options(auth_type)
   local Config = require("sshfs.config")
   local options = {}
 
+  -- A config RemoteCommand cannot coexist with the command these paths append,
+  -- and sftp needs a plain session, so it is cleared for everything but a shell.
+  if auth_type == "batch" or auth_type == "socket" then table.insert(options, "RemoteCommand=none") end
+
   -- Add ControlMaster options
   local control_opts = Config.get_control_master_options()
   if auth_type == "batch" then
@@ -94,8 +98,11 @@ local function append_host_options(cmd, host)
   table.insert(cmd, host.name)
 end
 
-local function build_with_options(host, auth_type)
+local function build_with_options(host, auth_type, extra_options)
   local cmd = { "ssh" }
+  for _, opt in ipairs(extra_options or {}) do
+    vim.list_extend(cmd, { "-o", opt })
+  end
   for _, opt in ipairs(get_ssh_options(auth_type)) do
     vim.list_extend(cmd, { "-o", opt })
   end
@@ -147,7 +154,7 @@ end
 ---@param host table|string Host object or SSH host name
 ---@return table SSH command array
 function Ssh.build_auth_command(host)
-  local cmd = { "ssh" }
+  local cmd = { "ssh", "-o", "RemoteCommand=none" }
   for _, opt in ipairs(get_ssh_options(nil)) do
     if opt:match("^ControlMaster=") then opt = "ControlMaster=yes" end
     vim.list_extend(cmd, { "-o", opt })
@@ -207,10 +214,12 @@ end
 ---@param remote_path string|nil Optional remote path to cd into
 ---@return table SSH command as array (safer than string to avoid shell injection)
 function Ssh.build_command(host, remote_path)
-  local cmd = build_with_options(host, nil)
+  local has_remote_path = remote_path ~= nil and remote_path ~= ""
+  -- Only a bare session keeps a config RemoteCommand; a cd would collide with it.
+  local cmd = build_with_options(host, nil, has_remote_path and { "RemoteCommand=none" } or nil)
 
   -- If remote_path specified, cd into it and start a login shell
-  if remote_path and remote_path ~= "" then
+  if has_remote_path then
     table.insert(cmd, "-t")
     local cd_command = build_cd_command(remote_path)
     table.insert(cmd, cd_command .. " && exec $SHELL -l")

tests/remote_command_spec.lua

@@ -0,0 +1,59 @@
+-- tests/remote_command_spec.lua
+-- A `RemoteCommand` in ssh_config makes a mount impossible: OpenSSH refuses to
+-- run both it and a command line, and sftp needs a plain session. Every
+-- non-interactive path clears it; a bare terminal keeps it.
+
+local SOCKET_DIR = "/home/tester/.ssh/sockets"
+
+local function load_ssh()
+  stub.reload()
+  require("sshfs.config").setup({ connections = { socket_dir = SOCKET_DIR, control_persist = "10m" } })
+  return require("sshfs.lib.ssh")
+end
+
+--- Index of an "-o <value>" pair in a command list, or nil
+local function option_index(cmd, value)
+  for index, argument in ipairs(cmd) do
+    if argument == "-o" and cmd[index + 1] == value then return index end
+  end
+  return nil
+end
+
+local function clears_remote_command(cmd)
+  return option_index(cmd, "RemoteCommand=none") ~= nil
+end
+
+describe("RemoteCommand handling", function()
+  it("clears it on every command that appends a remote command", function()
+    local Ssh = load_ssh()
+
+    expect.truthy(clears_remote_command(Ssh.build_batch_command("example.com")), "batch runs exit")
+    expect.truthy(clears_remote_command(Ssh.build_home_command("example.com")), "home runs readlink")
+    expect.truthy(clears_remote_command(Ssh.build_auth_command("example.com")), "auth runs exit")
+  end)
+
+  it("clears it for the ssh command sshfs runs", function()
+    local Ssh = load_ssh()
+    expect.contains(Ssh.build_command_string("socket"), "-o RemoteCommand=none")
+  end)
+
+  it("clears it on the control command", function()
+    local Ssh = load_ssh()
+    expect.truthy(clears_remote_command(Ssh.build_control_command("example.com", "exit")))
+  end)
+
+  it("clears it for a terminal that cds into a remote path", function()
+    local Ssh = load_ssh()
+    local cmd = Ssh.build_command("example.com", "/srv/app")
+
+    expect.truthy(clears_remote_command(cmd), "the cd would collide with a RemoteCommand")
+    expect.truthy(option_index(cmd, "RemoteCommand=none") < #cmd, "options must precede the host")
+  end)
+
+  it("keeps it for a bare terminal session", function()
+    local Ssh = load_ssh()
+    local cmd = Ssh.build_command("example.com")
+
+    expect.is_nil(option_index(cmd, "RemoteCommand=none"), "a plain shell is what RemoteCommand is for")
+  end)
+end)

tests/ssh_spec.lua

@@ -11,9 +11,9 @@ local function load_ssh()
 end
 
 describe("Ssh.build_command_string", function()
-  it("passes only the control path when reusing a socket", function()
+  it("passes the control path and clears any RemoteCommand when reusing a socket", function()
     local Ssh = load_ssh()
-    expect.eq(Ssh.build_command_string("socket"), "ssh -o " .. CONTROL_PATH)
+    expect.eq(Ssh.build_command_string("socket"), "ssh -o RemoteCommand=none -o " .. CONTROL_PATH)
   end)
 
   it("forces a master and disables prompts for batch connections", function()