Use base64 URL safe alphabet for message id generation.

The character '/' from base64 alphabet breaks web redirectors if the
message-id from an email is used as part of the URL for redirectors and/
or automatic pointers to an email.

Use the URL safe alphabet from RFC4648 section 5 for message id
generation.

Signed-off-by: Sebastian Andrzej Siewior <sebastian@breakpoint.cc>

1 files changed, 23 insertions, 10 deletions

diff --git a/base64.c b/base64.c
index 290f384e..5757b785 100644
--- a/base64.c
+++ b/base64.c
@@ -56,16 +56,15 @@ void mutt_buffer_to_base64 (BUFFER *out, const unsigned char *in, size_t len)
   mutt_buffer_fix_dptr (out);
 }
 
-/* raw bytes to null-terminated base 64 string */
-void mutt_to_base64 (unsigned char *out, const unsigned char *in, size_t len,
-		     size_t olen)
+static void to_base64 (unsigned char *out, const unsigned char *in, size_t len,
+		     size_t olen, const char *dict)
 {
   while (len >= 3 && olen > 4)
   {
-    *out++ = B64Chars[in[0] >> 2];
-    *out++ = B64Chars[((in[0] << 4) & 0x30) | (in[1] >> 4)];
-    *out++ = B64Chars[((in[1] << 2) & 0x3c) | (in[2] >> 6)];
-    *out++ = B64Chars[in[2] & 0x3f];
+    *out++ = dict[in[0] >> 2];
+    *out++ = dict[((in[0] << 4) & 0x30) | (in[1] >> 4)];
+    *out++ = dict[((in[1] << 2) & 0x3c) | (in[2] >> 6)];
+    *out++ = dict[in[2] & 0x3f];
     olen  -= 4;
     len   -= 3;
     in    += 3;
@@ -76,15 +75,29 @@ void mutt_to_base64 (unsigned char *out, const unsigned char *in, size_t len,
   {
     unsigned char fragment;
 
-    *out++ = B64Chars[in[0] >> 2];
+    *out++ = dict[in[0] >> 2];
     fragment = (in[0] << 4) & 0x30;
     if (len > 1)
       fragment |= in[1] >> 4;
-    *out++ = B64Chars[fragment];
-    *out++ = (len < 2) ? '=' : B64Chars[(in[1] << 2) & 0x3c];
+    *out++ = dict[fragment];
+    *out++ = (len < 2) ? '=' : dict[(in[1] << 2) & 0x3c];
     *out++ = '=';
   }
   *out = '\0';
+
+}
+
+/* raw bytes to null-terminated base 64 string */
+void mutt_to_base64 (unsigned char *out, const unsigned char *in, size_t len,
+		     size_t olen)
+{
+  to_base64 (out, in, len, olen, B64Chars);
+}
+
+void mutt_to_base64_safeurl (unsigned char *out, const unsigned char *in,
+			     size_t len, size_t olen)
+{
+  to_base64 (out, in, len, olen, B64Chars_urlsafe);
 }
 
 int mutt_buffer_from_base64 (BUFFER *out, const char *in)