Improve echo probe to recognize CUB+EL instead of BS+SPACE+BS. Issue 6878

Author: gnachman

sources/PTYSession.m

@@ -2603,10 +2603,6 @@ - (void)taskWasDeregistered {
 // This is run in PTYTask's thread. It parses the input here and then queues an async task to run
 // in the main thread to execute the parsed tokens.
 - (void)threadedReadTask:(char *)buffer length:(int)length {
-    @synchronized (self) {
-        [_echoProbe updateEchoProbeStateWithBuffer:buffer length:length];
-    }
-
     // Pass the input stream to the parser.
     [_terminal.parser putStreamData:buffer length:length];
 
@@ -2620,6 +2616,10 @@ - (void)threadedReadTask:(char *)buffer length:(int)length {
         return;
     }
 
+    @synchronized (self) {
+        [_echoProbe updateEchoProbeStateWithTokenCVector:&vector];
+    }
+
     // This limits the number of outstanding execution blocks to prevent the main thread from
     // getting bogged down.
     dispatch_semaphore_wait(_executionSemaphore, DISPATCH_TIME_FOREVER);

sources/iTermEchoProbe.h

@@ -6,6 +6,7 @@
 //
 
 #import <Foundation/Foundation.h>
+#import "CVector.h"
 
 NS_ASSUME_NONNULL_BEGIN
 
@@ -25,7 +26,7 @@ NS_ASSUME_NONNULL_BEGIN
 
 - (void)beginProbeWithBackspace:(NSData *)backspaceData
                        password:(NSString *)password;
-- (void)updateEchoProbeStateWithBuffer:(char *)buffer length:(int)length;
+- (void)updateEchoProbeStateWithTokenCVector:(CVector *)vector;
 - (void)enterPassword;
 
 @end

sources/iTermEchoProbe.m

@@ -8,6 +8,7 @@
 #import "iTermEchoProbe.h"
 
 #import "iTermAdvancedSettingsModel.h"
+#import "VT100Token.h"
 
 typedef NS_ENUM(NSUInteger, iTermEchoProbeState) {
     iTermEchoProbeOff = 0,
@@ -47,61 +48,64 @@ - (void)beginProbeWithBackspace:(NSData *)backspace
     }
 }
 
-- (void)updateEchoProbeStateWithBuffer:(char *)buffer length:(int)length {
+- (void)updateEchoProbeStateWithTokenCVector:(CVector *)vector {
     @synchronized(self) {
-        if (_state == iTermEchoProbeOff) {
+        if (_state == iTermEchoProbeOff || _state == iTermEchoProbeFailed) {
             return;
         }
-        for (int i = 0; i < length; i++) {
-            switch (_state) {
-                case iTermEchoProbeOff:
-                case iTermEchoProbeFailed:
-                    return;
-                    
-                case iTermEchoProbeWaiting:
-                    if (buffer[i] == '*') {
-                        _state = iTermEchoProbeOneAsterisk;
-                    } else {
-                        _state = iTermEchoProbeFailed;
-                        return;
-                    }
-                    break;
-                    
-                case iTermEchoProbeOneAsterisk:
-                    if (buffer[i] == '\b') {
-                        _state = iTermEchoProbeBackspaceOverAsterisk;
-                    } else {
-                        _state = iTermEchoProbeFailed;
-                        return;
-                    }
-                    break;
-                    
-                case iTermEchoProbeBackspaceOverAsterisk:
-                    if (buffer[i] == ' ') {
-                        _state = iTermEchoProbeSpaceOverAsterisk;
-                    } else {
-                        _state = iTermEchoProbeFailed;
-                        return;
-                    }
-                    break;
-                    
-                case iTermEchoProbeSpaceOverAsterisk:
-                    if (buffer[i] == '\b') {
-                        _state = iTermEchoProbeBackspaceOverSpace;
-                    } else {
-                        _state = iTermEchoProbeFailed;
-                        return;
-                    }
-                    break;
-                    
-                case iTermEchoProbeBackspaceOverSpace:
-                    _state = iTermEchoProbeFailed;
-                    return;
+        const int count = CVectorCount(vector);
+        for (int i = 0; i < count; i++) {
+            VT100Token *token = CVectorGetObject(vector, i);
+            _state = iTermEchoProbeGetNextState(_state, token);
+            if (_state == iTermEchoProbeOff || _state == iTermEchoProbeFailed) {
+                break;
             }
         }
     }
 }
 
+iTermEchoProbeState iTermEchoProbeGetNextState(iTermEchoProbeState state, VT100Token *token) {
+    switch (state) {
+        case iTermEchoProbeOff:
+        case iTermEchoProbeFailed:
+            return state;
+            
+        case iTermEchoProbeWaiting:
+            if (token->type == VT100_ASCIISTRING && [[token stringForAsciiData] isEqualToString:@"*"]) {
+                return iTermEchoProbeOneAsterisk;
+            } else {
+                return iTermEchoProbeFailed;
+            }
+            
+        case iTermEchoProbeOneAsterisk:
+            if (token->type == VT100CC_BS ||
+                (token->type == VT100CSI_CUB && token.csi->p[0] == 1)) {
+                return iTermEchoProbeBackspaceOverAsterisk;
+            } else {
+                return iTermEchoProbeFailed;
+            }
+    
+        case iTermEchoProbeBackspaceOverAsterisk:
+            if (token->type == VT100_ASCIISTRING && [[token stringForAsciiData] isEqualToString:@" "]) {
+                return iTermEchoProbeSpaceOverAsterisk;
+            } else if (token->type == VT100CSI_EL && token.csi->p[0] == 0) {
+                return iTermEchoProbeBackspaceOverSpace;
+            } else {
+                return iTermEchoProbeFailed;
+            }
+            
+        case iTermEchoProbeSpaceOverAsterisk:
+            if (token->type == VT100CC_BS) {
+                return iTermEchoProbeBackspaceOverSpace;
+            } else {
+                return iTermEchoProbeFailed;
+            }
+            
+        case iTermEchoProbeBackspaceOverSpace:
+            return iTermEchoProbeFailed;
+    }
+}
+
 - (void)enterPassword {
     [self.delegate echoProbeWriteString:_password];
     [self.delegate echoProbeWriteString:@"\n"];

tests/echo_probe_test.sh

@@ -0,0 +1,40 @@
+#!/bin/bash
+
+unset PASSWORD
+unset CHARCOUNT
+
+echo -n "Enter password: "
+
+stty -echo
+
+CHARCOUNT=0
+while IFS= read -p "$PROMPT" -r -s -n 1 CHAR
+do
+    # Enter - accept password
+    if [[ $CHAR == $'\0' ]] ; then
+        break
+    fi
+    # Backspace
+    if [[ $CHAR == $'\177' ]] ; then
+        if [ $CHARCOUNT -gt 0 ] ; then
+            CHARCOUNT=$((CHARCOUNT-1))
+            PROMPT=$'\b \b'
+# Alternate way of erasing a character that the echo probe understands:
+#            PROMPT=$''
+            PASSWORD="${PASSWORD%?}"
+        else
+            PROMPT=''
+        fi
+    else
+        CHARCOUNT=$((CHARCOUNT+1))
+        PROMPT='*'
+        PASSWORD+="$CHAR"
+    fi
+done
+
+stty echo
+
+echo ""
+echo Your password is:
+echo $PASSWORD
+