[woff2] Fix SFNT table checks.

Also reduce number of SFNT table lookups.

Reported as

  https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=18065

* include/freetype/internal/wofftypes.h (WOFF2_InfoRec): Add fields
`glyf_table', `loca_table', and `head_table'.

* src/sfnt/sfwoff2.c (reconstruct_glyf): Update signature.
Use table pointers in `info' parameter.
(get_x_mins): Check `maxp_table'
Use table pointers in `info' parameter.
(reconstruct_font):  Use and set table pointers in `info' parameter.
Fix check for `glyf' and `loca' tables.
Update call to `reconstruct_glyf'.
(woff2_open_font): Updated.

1 files changed, 41 insertions, 28 deletions

diff --git a/include/freetype/internal/wofftypes.h b/include/freetype/internal/wofftypes.h
index 5741fbabb..7b1689d81 100644
--- a/include/freetype/internal/wofftypes.h
+++ b/include/freetype/internal/wofftypes.h
@@ -179,6 +179,34 @@ FT_BEGIN_HEADER
   /**************************************************************************
    *
    * @struct:
+   *   WOFF2_TableRec
+   *
+   * @description:
+   *   This structure describes a given table of a WOFF2 font.
+   *
+   * @fields:
+   *   See
+   *
+   *     https://www.w3.org/TR/WOFF2/#table_dir_format
+   */
+  typedef struct  WOFF2_TableRec_
+  {
+    FT_Byte   FlagByte;           /* table type and flags      */
+    FT_ULong  Tag;                /* table file offset         */
+    FT_ULong  dst_length;         /* uncompressed table length */
+    FT_ULong  TransformLength;    /* transformed length        */
+
+    FT_ULong  flags;              /* calculated flags          */
+    FT_ULong  src_offset;         /* compressed table offset   */
+    FT_ULong  src_length;         /* compressed table length   */
+    FT_ULong  dst_offset;         /* uncompressed table offset */
+
+  } WOFF2_TableRec, *WOFF2_Table;
+
+
+  /**************************************************************************
+   *
+   * @struct:
    *   WOFF2_InfoRec
    *
    * @description:
@@ -197,6 +225,15 @@ FT_BEGIN_HEADER
    *
    *   x_mins ::
    *     `xMin` values of glyph bounding box.
+   *
+   *   glyf_table ::
+   *     A pointer to the `glyf' table record.
+   *
+   *   loca_table ::
+   *     A pointer to the `loca' table record.
+   *
+   *   head_table ::
+   *     A pointer to the `head' table record.
    */
   typedef struct  WOFF2_InfoRec_
   {
@@ -205,35 +242,11 @@ FT_BEGIN_HEADER
     FT_UShort  num_hmetrics;
     FT_Short*  x_mins;
 
-  } WOFF2_InfoRec, *WOFF2_Info;
-
-
-  /**************************************************************************
-   *
-   * @struct:
-   *   WOFF2_TableRec
-   *
-   * @description:
-   *   This structure describes a given table of a WOFF2 font.
-   *
-   * @fields:
-   *   See
-   *
-   *     https://www.w3.org/TR/WOFF2/#table_dir_format
-   */
-  typedef struct  WOFF2_TableRec_
-  {
-    FT_Byte   FlagByte;           /* table type and flags      */
-    FT_ULong  Tag;                /* table file offset         */
-    FT_ULong  dst_length;         /* uncompressed table length */
-    FT_ULong  TransformLength;    /* transformed length        */
-
-    FT_ULong  flags;              /* calculated flags          */
-    FT_ULong  src_offset;         /* compressed table offset   */
-    FT_ULong  src_length;         /* compressed table length   */
-    FT_ULong  dst_offset;         /* uncompressed table offset */
+    WOFF2_Table  glyf_table;
+    WOFF2_Table  loca_table;
+    WOFF2_Table  head_table;
 
-  } WOFF2_TableRec, *WOFF2_Table;
+  } WOFF2_InfoRec, *WOFF2_Info;
 
 
   /**************************************************************************