transaction: Use cgo.Handle to pass callback data to PAM

Go provides a nicer way to handle Go structs lifetime when they
are passed to C now, so use this instead of a custom
implementation that requires to store them in a map

callback.go

@@ -1,39 +0,0 @@
-package pam
-
-import "sync"
-
-var cb struct {
-	sync.Mutex
-	m map[int]interface{}
-	c int
-}
-
-func init() {
-	cb.m = make(map[int]interface{})
-}
-
-func cbAdd(v interface{}) int {
-	cb.Lock()
-	defer cb.Unlock()
-	cb.c++
-	cb.m[cb.c] = v
-	return cb.c
-}
-
-func cbGet(c int) interface{} {
-	cb.Lock()
-	defer cb.Unlock()
-	if v, ok := cb.m[c]; ok {
-		return v
-	}
-	panic("Callback pointer not found")
-}
-
-func cbDelete(c int) {
-	cb.Lock()
-	defer cb.Unlock()
-	if _, ok := cb.m[c]; !ok {
-		panic("Callback pointer not found")
-	}
-	delete(cb.m, c)
-}

callback_test.go

@@ -1,33 +0,0 @@
-package pam
-
-import (
-	"reflect"
-	"testing"
-)
-
-func TestCallback_001(t *testing.T) {
-	c := cbAdd(TestCallback_001)
-	v := cbGet(c)
-	if reflect.TypeOf(v) != reflect.TypeOf(TestCallback_001) {
-		t.Error("Received unexpected value")
-	}
-	cbDelete(c)
-}
-
-func TestCallback_002(t *testing.T) {
-	defer func() {
-		recover()
-	}()
-	c := cbAdd(TestCallback_002)
-	cbGet(c + 1)
-	t.Error("Expected a panic")
-}
-
-func TestCallback_003(t *testing.T) {
-	defer func() {
-		recover()
-	}()
-	c := cbAdd(TestCallback_003)
-	cbDelete(c + 1)
-	t.Error("Expected a panic")
-}

transaction.c

@@ -1,5 +1,6 @@
 #include "_cgo_export.h"
 #include <security/pam_appl.h>
+#include <stdint.h>
 #include <string.h>
 
 #ifdef __sun
@@ -25,7 +26,7 @@ int cb_pam_conv(
 		struct cbPAMConv_return result = cbPAMConv(
 				msg[i]->msg_style,
 				(char *)msg[i]->msg,
-				(long)appdata_ptr);
+				(uintptr_t)appdata_ptr);
 		if (result.r1 != PAM_SUCCESS) {
 			goto error;
 		}
@@ -45,10 +46,10 @@ error:
 	return PAM_CONV_ERR;
 }
 
-void init_pam_conv(struct pam_conv *conv, long c)
+void init_pam_conv(struct pam_conv *conv, uintptr_t appdata)
 {
 	conv->conv = cb_pam_conv;
-	conv->appdata_ptr = (void *)c;
+	conv->appdata_ptr = (void *)appdata;
 }
 
 // pam_start_confdir is a recent PAM api to declare a confdir (mostly for tests)

transaction.go

@@ -3,9 +3,10 @@ package pam
 
 //#include <security/pam_appl.h>
 //#include <stdlib.h>
+//#include <stdint.h>
 //#cgo CFLAGS: -Wall -std=c99
 //#cgo LDFLAGS: -lpam
-//void init_pam_conv(struct pam_conv *conv, long c);
+//void init_pam_conv(struct pam_conv *conv, uintptr_t);
 //int pam_start_confdir(const char *service_name, const char *user, const struct pam_conv *pam_conversation, const char *confdir, pam_handle_t **pamh) __attribute__ ((weak));
 //int check_pam_start_confdir(void);
 import "C"
@@ -13,6 +14,7 @@ import "C"
 import (
 	"errors"
 	"runtime"
+	"runtime/cgo"
 	"strings"
 	"unsafe"
 )
@@ -56,10 +58,10 @@ func (f ConversationFunc) RespondPAM(s Style, msg string) (string, error) {
 
 // cbPAMConv is a wrapper for the conversation callback function.
 //export cbPAMConv
-func cbPAMConv(s C.int, msg *C.char, c int) (*C.char, C.int) {
+func cbPAMConv(s C.int, msg *C.char, c C.uintptr_t) (*C.char, C.int) {
 	var r string
 	var err error
-	v := cbGet(c)
+	v := cgo.Handle(c).Value()
 	switch cb := v.(type) {
 	case ConversationHandler:
 		r, err = cb.RespondPAM(Style(s), C.GoString(msg))
@@ -75,14 +77,14 @@ type Transaction struct {
 	handle *C.pam_handle_t
 	conv   *C.struct_pam_conv
 	status C.int
-	c      int
+	c      cgo.Handle
 }
 
 // transactionFinalizer cleans up the PAM handle and deletes the callback
 // function.
 func transactionFinalizer(t *Transaction) {
 	C.pam_end(t.handle, t.status)
-	cbDelete(t.c)
+	t.c.Delete()
 }
 
 // Start initiates a new PAM transaction. Service is treated identically to
@@ -117,9 +119,9 @@ func StartConfDir(service, user string, handler ConversationHandler, confDir str
 func start(service, user string, handler ConversationHandler, confDir string) (*Transaction, error) {
 	t := &Transaction{
 		conv: &C.struct_pam_conv{},
-		c:    cbAdd(handler),
+		c:    cgo.NewHandle(handler),
 	}
-	C.init_pam_conv(t.conv, C.long(t.c))
+	C.init_pam_conv(t.conv, C.uintptr_t(t.c))
 	runtime.SetFinalizer(t, transactionFinalizer)
 	s := C.CString(service)
 	defer C.free(unsafe.Pointer(s))