From b4f4f5600298436c63b89f289c318d777300c499 Mon Sep 17 00:00:00 2001
From: Jeroen Wijenbergh <jeroen.wijenbergh@geant.org>
Date: Wed, 13 Aug 2025 14:06:28 +0200
Subject: Exports: Attempt to fix ARM MTE crash

---
 exports/exports.go | 44 +++++++++++++++++++++++++++++++-------------
 1 file changed, 31 insertions(+), 13 deletions(-)

(limited to 'exports')

diff --git a/exports/exports.go b/exports/exports.go
index 880101a..47b9f14 100644
--- a/exports/exports.go
+++ b/exports/exports.go
@@ -33,6 +33,24 @@ import (
 	"codeberg.org/eduVPN/eduvpn-common/util"
 )
 
+// goString copies a null-terminated *C.char to a Go string.
+// the default C.GoString doesn't play well with ARM MTE
+// see: https://github.com/golang/go/issues/27610#issuecomment-2381919857
+// see also: https://codeberg.org/eduVPN/android/issues/31
+// this was changed from: https://github.com/ebitengine/purego/blob/77ed15346fbb448af291a0509e024e06252a428f/internal/strings/strings.go#L25C1-L40C2
+// License: https://github.com/ebitengine/purego/blob/77ed15346fbb448af291a0509e024e06252a428f/LICENSE
+func goString(c *C.char) string {
+	ptr := unsafe.Pointer(c)
+	if ptr == nil {
+		return ""
+	}
+	length := 0
+	for *(*byte)(unsafe.Add(ptr, uintptr(length))) != '\x00' {
+		length++
+	}
+	return C.GoStringN(c, C.int(length))
+}
+
 // VPNState is the current state of the library
 var VPNState *client.Client
 
@@ -144,9 +162,9 @@ func Register(
 		return getCError(i18nerr.NewInternal("failed to register, a VPN state is already present"))
 	}
 	c, err := client.New(
-		C.GoString(name),
-		C.GoString(version),
-		C.GoString(configDirectory),
+		goString(name),
+		goString(version),
+		goString(configDirectory),
 		func(oldState client.FSMStateID, newState client.FSMStateID, data interface{}) bool {
 			return stateCallback(cb, oldState, newState, data)
 		},
@@ -297,7 +315,7 @@ func AddServer(c C.uintptr_t, _type C.int, id *C.char, ot *C.longlong) *C.char {
 		got := int64(*ot)
 		auth = &got
 	}
-	err = state.AddServer(v, C.GoString(id), srvtypes.Type(_type), auth)
+	err = state.AddServer(v, goString(id), srvtypes.Type(_type), auth)
 	return getCError(err)
 }
 
@@ -331,7 +349,7 @@ func RemoveServer(_type C.int, id *C.char) *C.char {
 	if stateErr != nil {
 		return getCError(stateErr)
 	}
-	err := state.RemoveServer(C.GoString(id), srvtypes.Type(_type))
+	err := state.RemoveServer(goString(id), srvtypes.Type(_type))
 	return getCError(err)
 }
 
@@ -547,7 +565,7 @@ func GetConfig(c C.uintptr_t, _type C.int, id *C.char, pTCP C.int, startup C.int
 	}
 	preferTCPBool := pTCP != 0
 	startupBool := startup != 0
-	cfg, err := state.GetConfig(ck, C.GoString(id), srvtypes.Type(_type), preferTCPBool, startupBool)
+	cfg, err := state.GetConfig(ck, goString(id), srvtypes.Type(_type), preferTCPBool, startupBool)
 	if cfg != nil && err == nil {
 		d, err := getReturnData(cfg)
 		if err == nil {
@@ -581,7 +599,7 @@ func SetProfileID(data *C.char) *C.char {
 	if stateErr != nil {
 		return getCError(stateErr)
 	}
-	profileErr := state.SetProfileID(C.GoString(data))
+	profileErr := state.SetProfileID(goString(data))
 	return getCError(profileErr)
 }
 
@@ -610,7 +628,7 @@ func SetSecureLocation(orgID *C.char, cc *C.char) *C.char {
 	if stateErr != nil {
 		return getCError(stateErr)
 	}
-	locationErr := state.SetSecureLocation(C.GoString(orgID), C.GoString(cc))
+	locationErr := state.SetSecureLocation(goString(orgID), goString(cc))
 	return getCError(locationErr)
 }
 
@@ -669,7 +687,7 @@ func DiscoServers(c C.uintptr_t, search *C.char) (*C.char, *C.char) {
 	if err != nil {
 		return nil, getCError(err)
 	}
-	servers, err := state.DiscoServers(ck, C.GoString(search))
+	servers, err := state.DiscoServers(ck, goString(search))
 	if servers == nil && err != nil {
 		return nil, getCError(err)
 	}
@@ -744,7 +762,7 @@ func DiscoOrganizations(c C.uintptr_t, search *C.char) (*C.char, *C.char) {
 	if err != nil {
 		return nil, getCError(err)
 	}
-	orgs, err := state.DiscoOrganizations(ck, C.GoString(search))
+	orgs, err := state.DiscoOrganizations(ck, goString(search))
 	if orgs == nil && err != nil {
 		return nil, getCError(err)
 	}
@@ -846,7 +864,7 @@ func StartFailover(c C.uintptr_t, gateway *C.char, mtu C.int, readRxBytes C.Read
 	if err != nil {
 		return C.int(0), getCError(err)
 	}
-	dropped, droppedErr := state.StartFailover(ck, C.GoString(gateway), int(mtu), func() (int64, error) {
+	dropped, droppedErr := state.StartFailover(ck, goString(gateway), int(mtu), func() (int64, error) {
 		rxBytes := int64(C.get_read_rx_bytes(readRxBytes))
 		if rxBytes < 0 {
 			return 0, i18nerr.NewInternal("client gave an invalid rx bytes value")
@@ -1035,7 +1053,7 @@ func SetTokenHandler(getter C.TokenGetter, setter C.TokenSetter) *C.char {
 //
 //export CalculateGateway
 func CalculateGateway(subnet *C.char) (*C.char, *C.char) {
-	gw, err := util.CalculateGateway(C.GoString(subnet))
+	gw, err := util.CalculateGateway(goString(subnet))
 	if err != nil {
 		return nil, getCError(err)
 	}
@@ -1076,7 +1094,7 @@ func CookieReply(c C.uintptr_t, data *C.char) *C.char {
 	if err != nil {
 		return getCError(err)
 	}
-	err = v.Send(C.GoString(data))
+	err = v.Send(goString(data))
 	return getCError(err)
 }
 
-- 
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