From f284a40385422465bb91fe0a313317f74844b338 Mon Sep 17 00:00:00 2001
From: Campbell Barton <ideasman42@gmail.com>
Date: Thu, 12 Nov 2020 12:19:12 +1100
Subject: ImBuf: pass the number of bytes read to 'is_a' callbacks

Previously the header was a fixed size and assumed to be zeroed.
Now read in bytes up to `HEADER_SIZE`, pass the number or bytes
read to the callback which must not read past those bytes.
---
 source/blender/imbuf/intern/util.c | 58 +++++++++++++++-----------------------
 1 file changed, 22 insertions(+), 36 deletions(-)

diff --git a/source/blender/imbuf/intern/util.c b/source/blender/imbuf/intern/util.c
index 1741d3f20b7..5b9aa9ed88a 100644
--- a/source/blender/imbuf/intern/util.c
+++ b/source/blender/imbuf/intern/util.c
@@ -120,8 +120,8 @@ const char *imb_ext_audio[] = {
 /* Increased from 32 to 64 because of the bitmaps header size. */
 #define HEADER_SIZE 64
 
-static bool imb_ispic_read_header_from_filepath(const char *filepath,
-                                                unsigned char buf[HEADER_SIZE])
+static ssize_t imb_ispic_read_header_from_filepath(const char *filepath,
+                                                   unsigned char buf[HEADER_SIZE])
 {
   BLI_stat_t st;
   int fp;
@@ -133,43 +133,27 @@ static bool imb_ispic_read_header_from_filepath(const char *filepath,
   }
 
   if (BLI_stat(filepath, &st) == -1) {
-    return false;
+    return -1;
   }
   if (((st.st_mode) & S_IFMT) != S_IFREG) {
-    return false;
+    return -1;
   }
 
   if ((fp = BLI_open(filepath, O_BINARY | O_RDONLY, 0)) == -1) {
-    return false;
+    return -1;
   }
 
-  memset(buf, 0, HEADER_SIZE);
-  if (read(fp, buf, HEADER_SIZE) <= 0) {
-    close(fp);
-    return false;
-  }
+  const ssize_t size = read(fp, buf, HEADER_SIZE);
 
   close(fp);
-  return true;
+  return size;
 }
 
-int IMB_ispic_type_from_memory(const unsigned char *mem, const size_t mem_size)
+int IMB_ispic_type_from_memory(const unsigned char *buf, const size_t buf_size)
 {
-  unsigned char buf_static[HEADER_SIZE];
-  const unsigned char *buf;
-
-  if (mem_size >= HEADER_SIZE) {
-    buf = buf_static;
-  }
-  else {
-    memset(buf_static, 0, HEADER_SIZE);
-    memcpy(buf_static, mem, mem_size);
-    buf = buf_static;
-  }
-
   for (const ImFileType *type = IMB_FILE_TYPES; type < IMB_FILE_TYPES_LAST; type++) {
     if (type->is_a != NULL) {
-      if (type->is_a(buf, HEADER_SIZE)) {
+      if (type->is_a(buf, buf_size)) {
         return type->filetype;
       }
     }
@@ -181,17 +165,19 @@ int IMB_ispic_type_from_memory(const unsigned char *mem, const size_t mem_size)
 int IMB_ispic_type(const char *filepath)
 {
   unsigned char buf[HEADER_SIZE];
-  if (!imb_ispic_read_header_from_filepath(filepath, buf)) {
+  const ssize_t buf_size = imb_ispic_read_header_from_filepath(filepath, buf);
+  if (buf_size <= 0) {
     return 0;
   }
-  return IMB_ispic_type_from_memory(buf, HEADER_SIZE);
+  return IMB_ispic_type_from_memory(buf, (size_t)buf_size);
 }
 
 bool IMB_ispic_type_matches(const char *filepath, int filetype)
 {
   unsigned char buf[HEADER_SIZE];
-  if (!imb_ispic_read_header_from_filepath(filepath, buf)) {
-    return 0;
+  const ssize_t buf_size = imb_ispic_read_header_from_filepath(filepath, buf);
+  if (buf_size <= 0) {
+    return false;
   }
 
   for (const ImFileType *type = IMB_FILE_TYPES; type < IMB_FILE_TYPES_LAST; type++) {
@@ -200,11 +186,11 @@ bool IMB_ispic_type_matches(const char *filepath, int filetype)
        * Keep the check for developers. */
       BLI_assert(type->is_a != NULL);
       if (type->is_a != NULL) {
-        return type->is_a(buf, HEADER_SIZE);
+        return type->is_a(buf, (size_t)buf_size);
       }
     }
   }
-  return 0;
+  return false;
 }
 
 #undef HEADER_SIZE
@@ -360,7 +346,6 @@ static int isffmpeg(const char *filepath)
 
 int imb_get_anim_type(const char *filepath)
 {
-  int type;
   BLI_stat_t st;
 
   BLI_assert(!BLI_path_is_rel(filepath));
@@ -390,7 +375,7 @@ int imb_get_anim_type(const char *filepath)
   if (ismovie(filepath)) {
     return ANIM_MOVIE;
   }
-#else
+#else /* !_WIN32 */
   if (BLI_stat(filepath, &st) == -1) {
     return 0;
   }
@@ -410,9 +395,10 @@ int imb_get_anim_type(const char *filepath)
   if (isavi(filepath)) {
     return ANIM_AVI;
   }
-#endif
-  type = IMB_ispic(filepath);
-  if (type) {
+#endif /* !_WIN32 */
+
+  /* Assume a single image is part of an image sequence. */
+  if (IMB_ispic(filepath)) {
     return ANIM_SEQUENCE;
   }
 
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