From 58baf40af641f8cbf597e508a292e85ae94688f1 Mon Sep 17 00:00:00 2001
From: Werner Koch <wk@gnupg.org>
Date: Mon, 2 Jul 2018 20:24:10 +0200
Subject: [PATCH] common: New function percent_data_escape.

* common/percent.c (percent_data_escape): New.
* common/t-percent.c (test_percent_data_escape): New.

Signed-off-by: Werner Koch <wk@gnupg.org>
---
 common/percent.c   | 44 +++++++++++++++++++++++++++++++++++++++
 common/t-percent.c | 51 +++++++++++++++++++++++++++++++++++++++++++++-
 common/util.h      |  1 +
 3 files changed, 95 insertions(+), 1 deletion(-)

diff --git a/common/percent.c b/common/percent.c
index 569c5fd99..eeb026fbe 100644
--- a/common/percent.c
+++ b/common/percent.c
@@ -87,6 +87,50 @@ percent_plus_escape (const char *string)
 }
 
 
+/* Create a newly alloced string from (DATA,DATALEN) with embedded
+ * Nuls quoted as %00.  The standard percent unescaping can be
+ * used to reverse this encoding.   */
+char *
+percent_data_escape (const void *data, size_t datalen)
+{
+  char *buffer, *p;
+  const char *s;
+  size_t n, length;
+
+  for (length=1, s=data, n=datalen; n; s++, n--)
+    {
+      if (!*s || *s == '%')
+        length += 3;
+      else
+        length++;
+    }
+
+  buffer = p = xtrymalloc (length);
+  if (!buffer)
+    return NULL;
+
+  for (s=data, n=datalen; n; s++, n--)
+    {
+      if (!*s)
+        {
+          memcpy (p, "%00", 3);
+          p += 3;
+        }
+      else if (*s == '%')
+        {
+          memcpy (p, "%25", 3);
+          p += 3;
+        }
+      else
+        *p++ = *s;
+    }
+  *p = 0;
+
+  return buffer;
+
+}
+
+
 /* Do the percent and plus/space unescaping from STRING to BUFFER and
    return the length of the valid buffer.  Plus unescaping is only
    done if WITHPLUS is true.  An escaped Nul character will be
diff --git a/common/t-percent.c b/common/t-percent.c
index 145a89bf3..94ece9249 100644
--- a/common/t-percent.c
+++ b/common/t-percent.c
@@ -99,6 +99,55 @@ test_percent_plus_escape (void)
 }
 
 
+static void
+test_percent_data_escape (void)
+{
+  static struct {
+    const char *data;
+    size_t datalen;
+    const char *expect;
+  } tbl[] = {
+    {
+      "", 0,
+      ""
+    }, {
+      "a", 1,
+      "a",
+    }, {
+      "%22", 3,
+      "%2522"
+    }, {
+      "%%", 3,
+      "%25%25%00"
+    }, {
+      "\n \0BC\t", 6,
+      "\n %00BC\t"
+    }, { NULL, 0, NULL }
+  };
+  char *buf;
+  int i;
+  size_t len;
+
+  for (i=0; tbl[i].data; i++)
+    {
+      buf = percent_data_escape (tbl[i].data, tbl[i].datalen);
+      if (!buf)
+        {
+          fprintf (stderr, "out of core: %s\n", strerror (errno));
+          exit (2);
+        }
+      if (strcmp (buf, tbl[i].expect))
+        fail (i);
+      len = percent_plus_unescape_inplace (buf, 0);
+      if (len != tbl[i].datalen)
+        fail (i);
+      else if (memcmp (buf, tbl[i].data, tbl[i].datalen))
+        fail (i);
+      xfree (buf);
+    }
+}
+
+
 
 int
 main (int argc, char **argv)
@@ -109,6 +158,6 @@ main (int argc, char **argv)
   /* FIXME: We escape_unescape is not tested - only
      percent_plus_unescape.  */
   test_percent_plus_escape ();
-
+  test_percent_data_escape ();
   return 0;
 }
diff --git a/common/util.h b/common/util.h
index 123d88079..682415d92 100644
--- a/common/util.h
+++ b/common/util.h
@@ -201,6 +201,7 @@ char *hex2str_alloc (const char *hexstring, size_t *r_count);
 
 /*-- percent.c --*/
 char *percent_plus_escape (const char *string);
+char *percent_data_escape (const void *data, size_t datalen);
 char *percent_plus_unescape (const char *string, int nulrepl);
 char *percent_unescape (const char *string, int nulrepl);