[freetype2] master f958c48: [psaux] Better protect `flex' handling.

[Werner LEMBERG]

branch: master
commit f958c48ee431bef8d4d466b40c9cb2d4dbcb7791
Author: Werner Lemberg <address@hidden>
Commit: Werner Lemberg <address@hidden>

    [psaux] Better protect `flex' handling.
    
    Reported as
    
      https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=935
    
    * src/psaux/t1decode.c (t1_decoder_parse_charstrings)
    <callothersubr>: Since there is not a single flex operator but a
    series of subroutine calls, malformed fonts can call arbitrary other
    operators after the start of a flex, possibly adding points.  For
    this reason we have to check the available number of points before
    inserting a point.
---
 ChangeLog            | 15 +++++++++++++++
 src/psaux/t1decode.c |  9 +++++++++
 2 files changed, 24 insertions(+)

diff --git a/ChangeLog b/ChangeLog
index a98267a..01e9a7b 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,20 @@
 2017-03-23  Werner Lemberg  <address@hidden>
 
+       [psaux] Better protect `flex' handling.
+
+       Reported as
+
+         https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=935
+
+       * src/psaux/t1decode.c (t1_decoder_parse_charstrings)
+       <callothersubr>: Since there is not a single flex operator but a
+       series of subroutine calls, malformed fonts can call arbitrary other
+       operators after the start of a flex, possibly adding points.  For
+       this reason we have to check the available number of points before
+       inserting a point.
+
+2017-03-23  Werner Lemberg  <address@hidden>
+
        [sfnt] Fix check for default named instance.
 
        * src/sfnt/sfobjs.c (sfnt_init_face): A `fixed' number needs four
diff --git a/src/psaux/t1decode.c b/src/psaux/t1decode.c
index af7b465..7dd4513 100644
--- a/src/psaux/t1decode.c
+++ b/src/psaux/t1decode.c
@@ -780,10 +780,19 @@
             /* point without adding any point to the outline    */
             idx = decoder->num_flex_vectors++;
             if ( idx > 0 && idx < 7 )
+            {
+              /* in malformed fonts it is possible to have other */
+              /* opcodes in the middle of a flex (which don't    */
+              /* increase `num_flex_vectors'); we thus have to   */
+              /* check whether we can add a point                */
+              if ( FT_SET_ERROR( t1_builder_check_points( builder, 1 ) ) )
+                goto Syntax_Error;
+
               t1_builder_add_point( builder,
                                     x,
                                     y,
                                     (FT_Byte)( idx == 3 || idx == 6 ) );
+            }
           }
           break;