(decode_coding_utf_8): Reject overlong sequences.

1 files changed, 20 insertions, 4 deletions

diff --git a/src/coding.c b/src/coding.c
index a4ad9c6a542..1fc59a02bb1 100644
--- a/src/coding.c
+++ b/src/coding.c
@@ -1078,6 +1078,7 @@ detect_coding_utf_8 (coding, mask)
 }
 
 
+/* Fixme: deal with surrogates?  */
 static void
 decode_coding_utf_8 (coding)
      struct coding_system *coding;
@@ -1126,23 +1127,38 @@ decode_coding_utf_8 (coding)
           if (! UTF_8_EXTRA_OCTET_P (c2))
             goto invalid_code;
           if (UTF_8_2_OCTET_LEADING_P (c1))
-            c = ((c1 & 0x1F) << 6) | (c2 & 0x3F);
+            {
+              c = ((c1 & 0x1F) << 6) | (c2 & 0x3F);
+              /* Reject overlong sequences here and below.  Encoders
+                 producing them are incorrect, they can be misleading,
+                 and they mess up read/write invariance.  */
+              if (c < 128)
+                goto invalid_code;
+            }
           else
             {
               ONE_MORE_BYTE (c3);
               if (! UTF_8_EXTRA_OCTET_P (c3))
                 goto invalid_code;
               if (UTF_8_3_OCTET_LEADING_P (c1))
-                c = (((c1 & 0xF) << 12)
-                     | ((c2 & 0x3F) << 6) | (c3 & 0x3F));
+                {
+                  c = (((c1 & 0xF) << 12)
+                       | ((c2 & 0x3F) << 6) | (c3 & 0x3F));
+                  if (c < 0x800)
+                    goto invalid_code;
+                }
               else
                 {
                   ONE_MORE_BYTE (c4);
                   if (! UTF_8_EXTRA_OCTET_P (c4))
                     goto invalid_code;
                   if (UTF_8_4_OCTET_LEADING_P (c1))
+                    {
                     c = (((c1 & 0x7) << 18) | ((c2 & 0x3F) << 12)
                          | ((c3 & 0x3F) << 6) | (c4 & 0x3F));
+                    if (c < 0x10000)
+                      goto invalid_code;
+                    }
                   else
                     {
                       ONE_MORE_BYTE (c5);
@@ -1153,7 +1169,7 @@ decode_coding_utf_8 (coding)
                           c = (((c1 & 0x3) << 24) | ((c2 & 0x3F) << 18)
                                | ((c3 & 0x3F) << 12) | ((c4 & 0x3F) << 6)
                                | (c5 & 0x3F));
-                          if (c > MAX_CHAR)
+                          if ((c > MAX_CHAR) || (c < 0x200000))
                             goto invalid_code;
                         }
                       else