(Fix): fixed unsafe.Slice using &r (pointer-to-pointer) as the backing array instead of r (the calloc'd response array), which wrote password bytes into random

CHANGELOG.md

@@ -27,6 +27,10 @@ first public release
 - **utmpx time field portability** — replaced hardcoded `C.__uint32_t` / `C.__int32_t` casts with a C helper function (`auth/utmpx_time.h`) that lets the compiler handle type conversion. fixes build failure on systems where `ut_tv` uses `struct timeval` instead of the 32/64 compat struct
 - **cgo pointer safety for pam** — replaced `unsafe.Pointer(&h)` (Go stack pointer passed to C) with `storeHandle`/`loadHandle` helpers that keep the `cgo.Handle` in C-heap memory. fixes `cgo argument has Go pointer to unpinned Go pointer` panic on Go 1.22+
 - **pam conversation callback** — fixed `unsafe.Slice` using `&r` (pointer-to-pointer) as the backing array instead of `r` (the calloc'd response array), which wrote password bytes into random stack memory. also now only responds to `PAM_PROMPT_ECHO_OFF`/`PAM_PROMPT_ECHO_ON` messages — info and error messages get nil. fixes `pam_unix: auth could not identify password`
+- **cgo handle lifecycle** — moved `cgo.Handle` and its C-heap backing from `Validate` (where they were `defer`-freed on return) into the `Credentials` struct so they stay alive through `OpenSession` and until `CloseSession`. fixes `misuse of an invalid Handle` panic
+- **session spawning** — replaced the broken `ForkExec` (which relaunched the same binary with made-up flags) with a direct `session.Spawn` call that drops privileges and runs the desktop in-process. fixes `flag provided but not defined: -user`
+- **renamed extra/ files** — `lemurs.pam` → `latchd.pam`, `lemurs.service` → `latchd.service`
+- **readme credits** — added a credits section acknowledging lemurs for the `extra/` directory structure and session scanning approach
 - **makefile `enable` and `update` targets** — `make enable` stops any running DM, disables the aliased display-manager, and enables latchd. `make update` runs uninstall → git pull → reinstall in one command
 - **missing `extra/` directory** — added `extra/config.toml`, `extra/xsetup.sh`, `extra/lemurs.pam`, and `extra/lemurs.service` so `make install` can find them
 - **makefile `deps` target** — added `make deps` to automatically install `libpam0g-dev` and `build-essential`, and verify go is present

README.md

@@ -182,3 +182,7 @@ src/
 ## license
 
 MIT or Apache-2.0
+
+## credits
+
+the `extra/` directory structure and the session scanning / pam delegation approach are adapted from [lemurs](https://github.com/coastalwhite/lemurs), a rust display manager.

extra/lemurs.pam

@@ -1,5 +0,0 @@
-#%PAM-1.0
-auth        include    login
-account     include    login
-session     include    login
-password    include    login

extra/lemurs.service

@@ -1,15 +0,0 @@
-[Unit]
-Description=latchd display manager
-After=systemd-user-sessions.service plymouth-quit-wait.service getty@tty2.service
-Conflicts=getty@tty2.service
-
-[Service]
-ExecStart=/usr/bin/latchd
-StandardInput=tty
-TTYPath=/dev/tty2
-TTYReset=yes
-TTYVHangup=yes
-Type=idle
-
-[Install]
-Alias=display-manager.service

src/auth/pam.go

@@ -67,6 +67,8 @@ type Credentials struct {
 	HomeDir    string
 	Shell      string
 	pamHandle  *C.pam_handle_t
+	pamData    unsafe.Pointer
+	pamCB      cgo.Handle
 }
 
 //export latchd_pam_conv
@@ -110,16 +112,16 @@ func Validate(user, pass, service string) (*Credentials, error) {
 	defer C.free(unsafe.Pointer(cUser))
 
 	h := cgo.NewHandle(pass)
-	defer h.Delete()
 
 	cData := C.storeHandle(C.uintptr_t(h))
-	defer C.free(cData)
 
 	conv := C.makePAMConv(cData)
 
 	var pamh *C.pam_handle_t
 	ret := C.pam_start(cSvc, cUser, &conv, &pamh)
 	if ret != C.PAM_SUCCESS {
+		h.Delete()
+		C.free(cData)
 		return nil, &AuthError{ErrPAMService, fmt.Sprintf("pam_start: %s", pamErr(pamh, ret))}
 	}
 
@@ -127,6 +129,8 @@ func Validate(user, pass, service string) (*Credentials, error) {
 	if ret != C.PAM_SUCCESS {
 		msg := fmt.Sprintf("auth failed: %s", pamErr(pamh, ret))
 		C.pam_end(pamh, ret)
+		h.Delete()
+		C.free(cData)
 		return nil, &AuthError{ErrAccountValidation, msg}
 	}
 
@@ -134,12 +138,16 @@ func Validate(user, pass, service string) (*Credentials, error) {
 	if ret != C.PAM_SUCCESS {
 		msg := fmt.Sprintf("account: %s", pamErr(pamh, ret))
 		C.pam_end(pamh, ret)
+		h.Delete()
+		C.free(cData)
 		return nil, &AuthError{ErrAccountValidation, msg}
 	}
 
 	u, err := ouser.Lookup(user)
 	if err != nil {
 		C.pam_end(pamh, ret)
+		h.Delete()
+		C.free(cData)
 		return nil, &AuthError{ErrUsernameNotFound, fmt.Sprintf("lookup %s: %v", user, err)}
 	}
 
@@ -163,6 +171,8 @@ func Validate(user, pass, service string) (*Credentials, error) {
 		HomeDir:    u.HomeDir,
 		Shell:      "/bin/sh",
 		pamHandle:  pamh,
+		pamData:    cData,
+		pamCB:      h,
 	}, nil
 }
 
@@ -180,6 +190,11 @@ func (c *Credentials) CloseSession() {
 		C.pam_end(c.pamHandle, 0)
 		c.pamHandle = nil
 	}
+	if c.pamData != nil {
+		C.free(c.pamData)
+		c.pamData = nil
+	}
+	c.pamCB.Delete()
 }
 
 func pamErr(h *C.pam_handle_t, e C.int) string {