Remove DEL characters from password input (#5837)

* Remove DEL characters from password input

iTerm password manager sends \x03\0x7f before sending a password
from its password manager to make sure the password is not being
echoed to the screen.  Unfortunately, vault login does not handle
the Space DEL sequence, causing the login to fail when using the
password manager.  This patch uses a simple method to delete the
sequence if present anywhere in the string, although it is strictly
only needed at the start of input.

* Simplify iTerm handling to only remove iTerm prefix

The logic now only removes the two byte prefix sent in by iTerm
instead of trying to remove all deletes in the string.

This has been tested to work with the iTerm password manager.

As a small correction, the byte sequence is \x20\x7f.  The
earlier commit message incorrectly stated it was \x03\x7f.

helper/password/password.go

@@ -8,6 +8,7 @@ import (
 	"io"
 	"os"
 	"os/signal"
+	"strings"
 )
 
 var ErrInterrupted = errors.New("interrupted")
@@ -34,7 +35,7 @@ func Read(f *os.File) (string, error) {
 	case <-ch:
 		return "", ErrInterrupted
 	case <-doneCh:
-		return result, resultErr
+		return removeiTermDelete(result), resultErr
 	}
 }
 
@@ -62,3 +63,7 @@ func readline(f *os.File) (string, error) {
 
 	return string(resultBuf), nil
 }
+
+func removeiTermDelete(input string) string {
+	return strings.TrimPrefix(input, "\x20\x7f")
+}

helper/password/password_test.go

@@ -0,0 +1,27 @@
+package password
+
+import "testing"
+
+type testCase struct {
+	name     string
+	input    string
+	expected string
+}
+
+func TestRemoveiTermDelete(t *testing.T) {
+	var tests = []testCase{
+		{"NoDelete", "TestingStuff", "TestingStuff"},
+		{"SingleDelete", "Testing\x7fStuff", "Testing\x7fStuff"},
+		{"DeleteFirst", "\x7fTestingStuff", "\x7fTestingStuff"},
+		{"DoubleDelete", "\x7f\x7fTestingStuff", "\x7f\x7fTestingStuff"},
+		{"SpaceFirst", "\x20TestingStuff", "\x20TestingStuff"},
+		{"iTermDelete", "\x20\x7fTestingStuff", "TestingStuff"},
+	}
+
+	for _, test := range tests {
+		result := removeiTermDelete(test.input)
+		if result != test.expected {
+			t.Errorf("Test %s failed, input: '%s', expected: '%s', output: '%s'", test.name, test.input, test.expected, result)
+		}
+	}
+}