tests: fix privdrop test's client key paths

sshd_privdrop_fail_test.sh runs from apps/wolfsshd/test and handed the
example clients relative key paths, but the clients call
ChangeToWolfSshRoot() before parsing arguments. Every client died at
"Error setting private key" and the test blamed the privilege drop.

- Anchor the key, payload and client paths at the script's own directory.
- Rename the saved directory to TESTDIR so a later cd cannot clobber it.
- Report "no fork at all" separately in the timeout diagnostic.
- Print the client's own output at every failure exit, so a client that
  never connects cannot be read as a daemon fault.
- Keep the client logs like log.txt, gitignored and removed on success.

.gitignore

@@ -70,6 +70,7 @@ apps/wolfssh/wolfssh
 apps/wolfsshd/wolfsshd
 apps/wolfsshd/test/test_configuration
 apps/wolfsshd/test/sshd_privdrop_preload.so
+apps/wolfsshd/test/privdrop_client_*.log
 apps/wolfsshd/test/log.txt
 apps/wolfsshd/test/sshd_config_*
 apps/wolfsshd/test/authorized_keys_test

apps/wolfsshd/test/sshd_privdrop_fail_test.sh

@@ -12,7 +12,9 @@ if [ -z "$1" ] || [ -z "$2" ]; then
     exit 1
 fi
 
-PWD=`pwd`
+# Not PWD: that is bash's own variable and the shell rewrites it on every cd,
+# so a saved copy is gone by the time it is read.
+TESTDIR=`pwd`
 USER=`whoami`
 TEST_HOST="$1"
 
@@ -46,15 +48,24 @@ if [ -f ./log.txt ]; then
 fi
 touch log.txt
 
-TEST_CLIENT="../../../examples/client/client"
-SFTP_CLIENT="../../../examples/sftpclient/wolfsftp"
-SCP_CLIENT="../../../examples/scpclient/wolfscp"
-PRIVATE_KEY="../../../keys/hansel-key-ecc.der"
-PUBLIC_KEY="../../../keys/hansel-key-ecc.pub"
+ROOT="$TESTDIR/../../.."
+TEST_CLIENT="$ROOT/examples/client/client"
+SFTP_CLIENT="$ROOT/examples/sftpclient/wolfsftp"
+SCP_CLIENT="$ROOT/examples/scpclient/wolfscp"
+
+# Absolute, and that matters. Unlike the other sshd tests this one runs from
+# its own directory rather than the repository root, and the example clients
+# call ChangeToWolfSshRoot() before parsing anything, so every path they are
+# handed is resolved from the repository root instead of here. Relative paths
+# were read as <root>/../../../keys/... and the clients died at "Error setting
+# private key" without ever opening a socket.
+PRIVATE_KEY="$ROOT/keys/hansel-key-ecc.der"
+PUBLIC_KEY="$ROOT/keys/hansel-key-ecc.pub"
 
 # Small payload for the sftp/scp transfers. The connection dies at the failed
-# drop long before any data moves, so the contents do not matter.
-PAYLOAD="privdrop_payload.txt"
+# drop long before any data moves, so the contents do not matter. Absolute for
+# the same reason: the sftp client reads it after the chdir above.
+PAYLOAD="$TESTDIR/privdrop_payload.txt"
 echo "privdrop" > "$PAYLOAD"
 
 source ./start_sshd.sh
@@ -68,8 +79,8 @@ PasswordAuthentication yes
 PermitEmptyPasswords no
 UsePrivilegeSeparation no
 UseDNS no
-HostKey $PWD/../../../keys/server-key.pem
-AuthorizedKeysFile $PWD/authorized_keys_test
+HostKey $ROOT/keys/server-key.pem
+AuthorizedKeysFile $TESTDIR/authorized_keys_test
 EOF
 
 # Preload and arm the interposer via SSHD_ENV (start_sshd.sh passes it through
@@ -77,7 +88,8 @@ EOF
 SSHD_ENV="LD_PRELOAD=$PRELOAD_LIB WOLFSSHD_FAULT_PRIVDROP=1"
 export SSHD_BIN SSHD_ENV
 
-# Teardown on every exit path; log.txt is kept for debugging like the other tests.
+# Teardown on every exit path; log.txt and the client logs are kept for
+# debugging like the other tests, and removed on the success path below.
 cleanup() {
     stop_wolfsshd
     rm -f sshd_config_test_privdrop "$PAYLOAD" "$PRELOAD_LIB"
@@ -94,6 +106,12 @@ fi
 
 DEADLINE=30
 
+# Every failure below is ambiguous without the client's own output.
+client_said() {
+    echo "  client said: `tail -n 3 "$CLIENT_LOG" | tr '\n' '|'`"
+    echo "  full client output in $CLIENT_LOG"
+}
+
 # Drives one client; the connection dies, so its exit status is not checked.
 # Counts are per-call deltas since all three subsystems share the one log.
 check_subsystem() {
@@ -104,7 +122,11 @@ check_subsystem() {
     BEFORE_CLOSE=`grep -c "Attempting to close down connection" log.txt`
     BEFORE_SPAWN=`grep -c "Spawned new process" log.txt`
 
-    "$@" > /dev/null 2>&1 &
+    # Keep the client's output. Its exit status is meaningless here (the
+    # connection is killed under it), but if it dies before opening a socket
+    # the daemon-side counters below stay flat and look like a daemon fault.
+    CLIENT_LOG="$TESTDIR/privdrop_client_$LABEL.log"
+    "$@" > "$CLIENT_LOG" 2>&1 &
     CLIENT_PID=$!
 
     # Wait for the connection child to fork and hit the failed drop, then take
@@ -128,7 +150,12 @@ check_subsystem() {
     wait $CLIENT_PID > /dev/null 2>&1
 
     if [ -z "$CHILD" ]; then
-        echo "FAIL: $LABEL never reached the privilege drop"
+        if [ "$AFTER_SPAWN" -eq "$BEFORE_SPAWN" ]; then
+            echo "FAIL: $LABEL daemon never forked a connection process"
+        else
+            echo "FAIL: $LABEL never reached the privilege drop"
+        fi
+        client_said
         exit 1
     fi
 
@@ -141,6 +168,7 @@ check_subsystem() {
     done
     if ps -p "$CHILD" > /dev/null 2>&1; then
         echo "FAIL: $LABEL connection process still running after ${DEADLINE}s"
+        client_said
         exit 1
     fi
 
@@ -149,6 +177,7 @@ check_subsystem() {
     AFTER_CLOSE=`grep -c "Attempting to close down connection" log.txt`
     if [ "$AFTER_CLOSE" -gt "$BEFORE_CLOSE" ]; then
         echo "FAIL: $LABEL handler continued after a failed privilege drop"
+        client_said
         exit 1
     fi
 
@@ -170,7 +199,9 @@ check_subsystem "sftp" \
 # SCP_Subsystem.
 check_subsystem "scp" \
     "$SCP_CLIENT" -u "$USER" -i "$PRIVATE_KEY" -j "$PUBLIC_KEY" \
-    -S"$PWD/$PAYLOAD:." -H "$TEST_HOST" -p "$TEST_PORT"
+    -S"$PAYLOAD:." -H "$TEST_HOST" -p "$TEST_PORT"
+
+rm -f "$TESTDIR"/privdrop_client_*.log
 
 echo "PASS: all subsystems terminate on privilege-drop failure"
 exit 0