From 7960ce842b4188fd49a87ddd39b7ab7549228e1d Mon Sep 17 00:00:00 2001
From: Michal Privoznik <mprivozn@redhat.com>
Date: Tue, 3 Apr 2012 14:59:06 +0200
Subject: [PATCH] virsh: Clarify escape sequence

Currently, we put no strains on escape sequence possibly leaving users
with console that cannot be terminated. However, not all ASCII
characters can be used as escape sequence. Only those falling in
@ - _ can be; implement and document this constraint.
---
 tools/console.c |  3 ++-
 tools/virsh.c   | 13 ++++++++++++-
 tools/virsh.pod |  3 ++-
 3 files changed, 16 insertions(+), 3 deletions(-)

diff --git a/tools/console.c b/tools/console.c
index ca226c3356..34fde05eb7 100644
--- a/tools/console.c
+++ b/tools/console.c
@@ -34,6 +34,7 @@
 # include <errno.h>
 # include <unistd.h>
 # include <signal.h>
+# include <c-ctype.h>
 
 # include "internal.h"
 # include "console.h"
@@ -292,7 +293,7 @@ static char
 vshGetEscapeChar(const char *s)
 {
     if (*s == '^')
-        return CONTROL(s[1]);
+        return CONTROL(c_toupper(s[1]));
 
     return *s;
 }
diff --git a/tools/virsh.c b/tools/virsh.c
index 1ed2ddaae6..cfdd040b5e 100644
--- a/tools/virsh.c
+++ b/tools/virsh.c
@@ -19879,6 +19879,16 @@ vshShowVersion(vshControl *ctl ATTRIBUTE_UNUSED)
     vshPrint(ctl, "\n");
 }
 
+static bool
+vshAllowedEscapeChar(char c)
+{
+    /* Allowed escape characters:
+     * a-z A-Z @ [ \ ] ^ _
+     */
+    return ('a' <= c && c <= 'z') ||
+        ('@' <= c && c <= '_');
+}
+
 /*
  * argv[]:  virsh [options] [command]
  *
@@ -19942,7 +19952,8 @@ vshParseArgv(vshControl *ctl, int argc, char **argv)
         case 'e':
             len = strlen(optarg);
 
-            if ((len == 2 && *optarg == '^') ||
+            if ((len == 2 && *optarg == '^' &&
+                 vshAllowedEscapeChar(optarg[1])) ||
                 (len == 1 && *optarg != '^')) {
                 ctl->escapeChar = optarg;
             } else {
diff --git a/tools/virsh.pod b/tools/virsh.pod
index d4971a32cb..a60e66770a 100644
--- a/tools/virsh.pod
+++ b/tools/virsh.pod
@@ -95,7 +95,8 @@ Output elapsed time information for each command.
 =item B<-e>, B<--escape> I<string>
 
 Set alternative escape sequence for I<console> command. By default,
-telnet's B<^]> is used.
+telnet's B<^]> is used. Allowed characters when using hat notation are:
+alphabetic character, @, [, ], \, ^, _.
 
 =back