Ensure methods called by global funcs are init'd

If a hypothetical calling application does something really stupid and
changes cinfo->data_precision after calling jpeg_start_*compress(), then
the precision-specific methods called by jpeg_write_scanlines(),
jpeg_write_raw_data(), jpeg_finish_compress(), jpeg_read_scanlines(),
jpeg_read_raw_data(), or jpeg_start_output() may not be initialized.

Ensure that the first precision-specific method (which will always be
cinfo->main->process_data*(), cinfo->coef->compress_data*(), or
cinfo->coef->decompress_data()) called by any global function that may
be called after jpeg_start_*compress() is initialized and non-NULL.
This increases the likelihood (but does not guarantee) that a
hypothetical stupid calling application will fail gracefully rather than
segfault if it changes cinfo->data_precision after calling
jpeg_start_*compress().  A hypothetical stupid calling application can
still bork itself by changing cinfo->data_precision after initializing
the source manager but before calling jpeg_start_compress(), or after
initializing the destination manager but before calling
jpeg_start_decompress().

ChangeLog.md

@@ -19,6 +19,11 @@ was previously enabled in a libjpeg or TurboJPEG instance.
 instance, and setting `TJPARAM_LOSSLESS`/`TJ.PARAM_LOSSLESS` to `0` now
 disables lossless JPEG compression in a TurboJPEG instance.
 
+4. Hardened the libjpeg API against hypothetical calling applications that may
+erroneously change the value of the `data_precision` field in
+`jpeg_compress_struct` or `jpeg_decompress_struct` after calling
+`jpeg_start_compress()` or `jpeg_start_decompress()`.
+
 
 3.0.4
 =====

jcapimin.c

@@ -5,7 +5,7 @@
  * Copyright (C) 1994-1998, Thomas G. Lane.
  * Modified 2003-2010 by Guido Vollbeding.
  * libjpeg-turbo Modifications:
- * Copyright (C) 2022, D. R. Commander.
+ * Copyright (C) 2022, 2024, D. R. Commander.
  * For conditions of distribution and use, see the accompanying README.ijg
  * file.
  *
@@ -196,15 +196,21 @@ jpeg_finish_compress(j_compress_ptr cinfo)
        */
       if (cinfo->data_precision == 16) {
 #ifdef C_LOSSLESS_SUPPORTED
+        if (cinfo->coef->compress_data_16 == NULL)
+          ERREXIT1(cinfo, JERR_BAD_PRECISION, cinfo->data_precision);
         if (!(*cinfo->coef->compress_data_16) (cinfo, (J16SAMPIMAGE)NULL))
           ERREXIT(cinfo, JERR_CANT_SUSPEND);
 #else
         ERREXIT1(cinfo, JERR_BAD_PRECISION, cinfo->data_precision);
 #endif
       } else if (cinfo->data_precision == 12) {
+        if (cinfo->coef->compress_data_12 == NULL)
+          ERREXIT1(cinfo, JERR_BAD_PRECISION, cinfo->data_precision);
         if (!(*cinfo->coef->compress_data_12) (cinfo, (J12SAMPIMAGE)NULL))
           ERREXIT(cinfo, JERR_CANT_SUSPEND);
       } else {
+        if (cinfo->coef->compress_data == NULL)
+          ERREXIT1(cinfo, JERR_BAD_PRECISION, cinfo->data_precision);
         if (!(*cinfo->coef->compress_data) (cinfo, (JSAMPIMAGE)NULL))
           ERREXIT(cinfo, JERR_CANT_SUSPEND);
       }

jcapistd.c

@@ -4,7 +4,7 @@
  * This file was part of the Independent JPEG Group's software:
  * Copyright (C) 1994-1996, Thomas G. Lane.
  * libjpeg-turbo Modifications:
- * Copyright (C) 2022, D. R. Commander.
+ * Copyright (C) 2022, 2024, D. R. Commander.
  * For conditions of distribution and use, see the accompanying README.ijg
  * file.
  *
@@ -117,6 +117,8 @@ _jpeg_write_scanlines(j_compress_ptr cinfo, _JSAMPARRAY scanlines,
     num_lines = rows_left;
 
   row_ctr = 0;
+  if (cinfo->main->_process_data == NULL)
+    ERREXIT1(cinfo, JERR_BAD_PRECISION, cinfo->data_precision);
   (*cinfo->main->_process_data) (cinfo, scanlines, &row_ctr, num_lines);
   cinfo->next_scanline += row_ctr;
   return row_ctr;
@@ -174,6 +176,8 @@ _jpeg_write_raw_data(j_compress_ptr cinfo, _JSAMPIMAGE data,
     ERREXIT(cinfo, JERR_BUFFER_SIZE);
 
   /* Directly compress the row. */
+  if (cinfo->coef->_compress_data == NULL)
+    ERREXIT1(cinfo, JERR_BAD_PRECISION, cinfo->data_precision);
   if (!(*cinfo->coef->_compress_data) (cinfo, data)) {
     /* If compressor did not consume the whole row, suspend processing. */
     return 0;

jccoefct.c

@@ -4,7 +4,7 @@
  * This file was part of the Independent JPEG Group's software:
  * Copyright (C) 1994-1997, Thomas G. Lane.
  * libjpeg-turbo Modifications:
- * Copyright (C) 2022, D. R. Commander.
+ * Copyright (C) 2022, 2024, D. R. Commander.
  * For conditions of distribution and use, see the accompanying README.ijg
  * file.
  *
@@ -414,6 +414,7 @@ _jinit_c_coef_controller(j_compress_ptr cinfo, boolean need_full_buffer)
   coef = (my_coef_ptr)
     (*cinfo->mem->alloc_small) ((j_common_ptr)cinfo, JPOOL_IMAGE,
                                 sizeof(my_coef_controller));
+  memset(coef, 0, sizeof(my_coef_controller));
   cinfo->coef = (struct jpeg_c_coef_controller *)coef;
   coef->pub.start_pass = start_pass_coef;
 

jcmainct.c

@@ -6,7 +6,7 @@
  * Lossless JPEG Modifications:
  * Copyright (C) 1999, Ken Murchison.
  * libjpeg-turbo Modifications:
- * Copyright (C) 2022, D. R. Commander.
+ * Copyright (C) 2022, 2024, D. R. Commander.
  * For conditions of distribution and use, see the accompanying README.ijg
  * file.
  *
@@ -146,6 +146,7 @@ _jinit_c_main_controller(j_compress_ptr cinfo, boolean need_full_buffer)
   main_ptr = (my_main_ptr)
     (*cinfo->mem->alloc_small) ((j_common_ptr)cinfo, JPOOL_IMAGE,
                                 sizeof(my_main_controller));
+  memset(main_ptr, 0, sizeof(my_main_controller));
   cinfo->main = (struct jpeg_c_main_controller *)main_ptr;
   main_ptr->pub.start_pass = start_pass_main;
 

jdapistd.c

@@ -128,20 +128,28 @@ output_pass_setup(j_decompress_ptr cinfo)
       }
       /* Process some data */
       last_scanline = cinfo->output_scanline;
+      if (cinfo->data_precision == 16) {
 #ifdef D_LOSSLESS_SUPPORTED
-      if (cinfo->data_precision == 16)
+        if (cinfo->main->process_data_16 == NULL)
+          ERREXIT1(cinfo, JERR_BAD_PRECISION, cinfo->data_precision);
         (*cinfo->main->process_data_16) (cinfo, (J16SAMPARRAY)NULL,
                                          &cinfo->output_scanline,
                                          (JDIMENSION)0);
-      else
+#else
+        ERREXIT1(cinfo, JERR_BAD_PRECISION, cinfo->data_precision);
 #endif
-      if (cinfo->data_precision == 12)
+      } else if (cinfo->data_precision == 12) {
+        if (cinfo->main->process_data_12 == NULL)
+          ERREXIT1(cinfo, JERR_BAD_PRECISION, cinfo->data_precision);
         (*cinfo->main->process_data_12) (cinfo, (J12SAMPARRAY)NULL,
                                          &cinfo->output_scanline,
                                          (JDIMENSION)0);
-      else
+      } else {
+        if (cinfo->main->process_data == NULL)
+          ERREXIT1(cinfo, JERR_BAD_PRECISION, cinfo->data_precision);
         (*cinfo->main->process_data) (cinfo, (JSAMPARRAY)NULL,
                                       &cinfo->output_scanline, (JDIMENSION)0);
+      }
       if (cinfo->output_scanline == last_scanline)
         return FALSE;           /* No progress made, must suspend */
     }
@@ -333,6 +341,8 @@ _jpeg_read_scanlines(j_decompress_ptr cinfo, _JSAMPARRAY scanlines,
 
   /* Process some data */
   row_ctr = 0;
+  if (cinfo->main->_process_data == NULL)
+    ERREXIT1(cinfo, JERR_BAD_PRECISION, cinfo->data_precision);
   (*cinfo->main->_process_data) (cinfo, scanlines, &row_ctr, max_lines);
   cinfo->output_scanline += row_ctr;
   return row_ctr;
@@ -679,6 +689,8 @@ _jpeg_read_raw_data(j_decompress_ptr cinfo, _JSAMPIMAGE data,
     ERREXIT(cinfo, JERR_BUFFER_SIZE);
 
   /* Decompress directly into user's buffer. */
+  if (cinfo->coef->_decompress_data == NULL)
+    ERREXIT1(cinfo, JERR_BAD_PRECISION, cinfo->data_precision);
   if (!(*cinfo->coef->_decompress_data) (cinfo, data))
     return 0;                   /* suspension forced, can do nothing more */
 

jdcoefct.c

@@ -5,7 +5,7 @@
  * Copyright (C) 1994-1997, Thomas G. Lane.
  * libjpeg-turbo Modifications:
  * Copyright 2009 Pierre Ossman <ossman@cendio.se> for Cendio AB
- * Copyright (C) 2010, 2015-2016, 2019-2020, 2022-2023, D. R. Commander.
+ * Copyright (C) 2010, 2015-2016, 2019-2020, 2022-2024, D. R. Commander.
  * Copyright (C) 2015, 2020, Google, Inc.
  * For conditions of distribution and use, see the accompanying README.ijg
  * file.
@@ -824,6 +824,7 @@ _jinit_d_coef_controller(j_decompress_ptr cinfo, boolean need_full_buffer)
   coef = (my_coef_ptr)
     (*cinfo->mem->alloc_small) ((j_common_ptr)cinfo, JPOOL_IMAGE,
                                 sizeof(my_coef_controller));
+  memset(coef, 0, sizeof(my_coef_controller));
   cinfo->coef = (struct jpeg_d_coef_controller *)coef;
   coef->pub.start_input_pass = start_input_pass;
   coef->pub.start_output_pass = start_output_pass;

jdmainct.c

@@ -4,7 +4,7 @@
  * This file was part of the Independent JPEG Group's software:
  * Copyright (C) 1994-1996, Thomas G. Lane.
  * libjpeg-turbo Modifications:
- * Copyright (C) 2010, 2016, 2022, D. R. Commander.
+ * Copyright (C) 2010, 2016, 2022, 2024, D. R. Commander.
  * For conditions of distribution and use, see the accompanying README.ijg
  * file.
  *
@@ -437,6 +437,7 @@ _jinit_d_main_controller(j_decompress_ptr cinfo, boolean need_full_buffer)
   main_ptr = (my_main_ptr)
     (*cinfo->mem->alloc_small) ((j_common_ptr)cinfo, JPOOL_IMAGE,
                                 sizeof(my_main_controller));
+  memset(main_ptr, 0, sizeof(my_main_controller));
   cinfo->main = (struct jpeg_d_main_controller *)main_ptr;
   main_ptr->pub.start_pass = start_pass_main;