1 files changed, 22 insertions, 4 deletions

diff --git a/libvpx/vp9/decoder/vp9_reader.c b/libvpx/vp9/decoder/vp9_reader.c
index fb44c8898..6bb4f9f73 100644
--- a/libvpx/vp9/decoder/vp9_reader.c
+++ b/libvpx/vp9/decoder/vp9_reader.c
@@ -18,7 +18,11 @@
 // Even relatively modest values like 100 would work fine.
 #define LOTS_OF_BITS 0x40000000
 
-int vp9_reader_init(vp9_reader *r, const uint8_t *buffer, size_t size) {
+int vp9_reader_init(vp9_reader *r,
+                    const uint8_t *buffer,
+                    size_t size,
+                    vpx_decrypt_cb decrypt_cb,
+                    void *decrypt_state) {
   if (size && !buffer) {
     return 1;
   } else {
@@ -27,6 +31,8 @@ int vp9_reader_init(vp9_reader *r, const uint8_t *buffer, size_t size) {
     r->value = 0;
     r->count = -8;
     r->range = 255;
+    r->decrypt_cb = decrypt_cb;
+    r->decrypt_state = decrypt_state;
     vp9_reader_fill(r);
     return vp9_read_bit(r) != 0;  // marker bit
   }
@@ -35,12 +41,21 @@ int vp9_reader_init(vp9_reader *r, const uint8_t *buffer, size_t size) {
 void vp9_reader_fill(vp9_reader *r) {
   const uint8_t *const buffer_end = r->buffer_end;
   const uint8_t *buffer = r->buffer;
+  const uint8_t *buffer_start = buffer;
   BD_VALUE value = r->value;
   int count = r->count;
   int shift = BD_VALUE_SIZE - CHAR_BIT - (count + CHAR_BIT);
   int loop_end = 0;
-  const int bits_left = (int)((buffer_end - buffer) * CHAR_BIT);
-  const int x = shift + CHAR_BIT - bits_left;
+  const size_t bytes_left = buffer_end - buffer;
+  const size_t bits_left = bytes_left * CHAR_BIT;
+  const int x = (int)(shift + CHAR_BIT - bits_left);
+
+  if (r->decrypt_cb) {
+    size_t n = MIN(sizeof(r->clear_buffer), bytes_left);
+    r->decrypt_cb(r->decrypt_state, buffer, r->clear_buffer, (int)n);
+    buffer = r->clear_buffer;
+    buffer_start = r->clear_buffer;
+  }
 
   if (x >= 0) {
     count += LOTS_OF_BITS;
@@ -55,7 +70,10 @@ void vp9_reader_fill(vp9_reader *r) {
     }
   }
 
-  r->buffer = buffer;
+  // NOTE: Variable 'buffer' may not relate to 'r->buffer' after decryption,
+  // so we increase 'r->buffer' by the amount that 'buffer' moved, rather than
+  // assign 'buffer' to 'r->buffer'.
+  r->buffer += buffer - buffer_start;
   r->value = value;
   r->count = count;
 }