python-pillow/SOURCES/CVE-2021-25293.patch

From 1312c5426e7dd84e396ef2ff35aa09b64d92d382 Mon Sep 17 00:00:00 2001
From: Lumir Balhar <lbalhar@redhat.com>
Date: Fri, 9 Apr 2021 19:33:55 +0200
Subject: [PATCH 3/4] CVE-2021-25293

---
 src/libImaging/SgiRleDecode.c | 88 +++++++++++++++++++++++++++++------
 1 file changed, 75 insertions(+), 13 deletions(-)

diff --git a/src/libImaging/SgiRleDecode.c b/src/libImaging/SgiRleDecode.c
index 2259159..85af456 100644
--- a/src/libImaging/SgiRleDecode.c
+++ b/src/libImaging/SgiRleDecode.c
@@ -25,13 +25,60 @@ static void read4B(UINT32* dest, UINT8* buf)
     *dest = (UINT32)((buf[0] << 24) | (buf[1] << 16) | (buf[2] << 8) | buf[3]);
 }
 
-static int expandrow(UINT8* dest, UINT8* src, int n, int z, int xsize)
+/*
+   SgiRleDecoding is done in a single channel row oriented set of RLE chunks.
+
+   * The file is arranged as
+     - SGI Header
+     - Rle Offset Table
+     - Rle Length Table
+     - Scanline Data
+
+   * Each RLE atom is c->bpc bytes wide (1 or 2)
+
+   * Each RLE Chunk is [specifier atom] [ 1 or n data atoms ]
+
+   * Copy Atoms are a byte with the high bit set, and the low 7 are
+     the number of bytes to copy from the source to the
+     destination. e.g.
+
+         CBBBBBBBB or 0CHLHLHLHLHLHL   (B=byte, H/L = Hi low bytes)
+
+   * Run atoms do not have the high bit set, and the low 7 bits are
+     the number of copies of the next atom to copy to the
+     destination. e.g.:
+
+         RB -> BBBBB or RHL -> HLHLHLHLHL
+
+   The upshot of this is, there is no way to determine the required
+   length of the input buffer from reloffset and rlelength without
+   going through the data at that scan line.
+
+   Furthermore, there's no requirement that individual scan lines
+   pointed to from the rleoffset table are in any sort of order or
+   used only once, or even disjoint. There's also no requirement that
+   all of the data in the scan line area of the image file be used
+
+ */
+
+static int expandrow(UINT8* dest, UINT8* src, int n, int z, int xsize, UINT8 *end_of_buffer)
 {
+    /*
+     * n here is the number of rlechunks
+     * z is the number of channels, for calculating the interleave
+     *   offset to go to RGBA style pixels
+     * xsize is the row width
+     * end_of_buffer is the address of the end of the input buffer
+     */
+
     UINT8 pixel, count;
     int x = 0;
 
     for (;n > 0; n--)
     {
+        if (src > end_of_buffer) {
+            return -1;
+        }
         pixel = *src++;
         if (n == 1 && pixel != 0)
             return n;
@@ -43,6 +90,9 @@ static int expandrow(UINT8* dest, UINT8* src, int n, int z, int xsize)
         }
         x += count;
         if (pixel & RLE_COPY_FLAG) {
+            if (src + count > end_of_buffer) {
+                return -1;
+            }
             while(count--) {
                 *dest = *src++;
                 dest += z;
@@ -50,6 +100,9 @@ static int expandrow(UINT8* dest, UINT8* src, int n, int z, int xsize)
 
         }
         else {
+            if (src > end_of_buffer) {
+                return -1;
+            }
             pixel = *src++;
             while (count--) {
                 *dest = pixel;
@@ -61,7 +114,7 @@ static int expandrow(UINT8* dest, UINT8* src, int n, int z, int xsize)
     return 0;
 }
 
-static int expandrow2(UINT16* dest, UINT16* src, int n, int z, int xsize)
+static int expandrow2(UINT16* dest, UINT16* src, int n, int z, int xsize, UINT8 *end_of_buffer)
 {
     UINT8 pixel, count;
 
@@ -69,6 +122,9 @@ static int expandrow2(UINT16* dest, UINT16* src, int n, int z, int xsize)
 
     for (;n > 0; n--)
     {
+        if (src + 1 > end_of_buffer) {
+            return -1;
+        }
         pixel = ((UINT8*)src)[1];
         ++src;
         if (n == 1 && pixel != 0)
@@ -81,12 +137,18 @@ static int expandrow2(UINT16* dest, UINT16* src, int n, int z, int xsize)
         }
         x += count;
         if (pixel & RLE_COPY_FLAG) {
+            if (src + 2 * count > end_of_buffer) {
+                return -1;
+            }
             while(count--) {
                 *dest = *src++;
                 dest += z;
             }
         }
         else {
+            if (src + 2 > end_of_buffer) {
+                return -1;
+            }
             while (count--) {
                 *dest = *src;
                 dest += z;
@@ -136,8 +198,10 @@ ImagingSgiRleDecode(Imaging im, ImagingCodecState state,
         return -1;
     }
     _imaging_seek_pyFd(state->fd, SGI_HEADER_SIZE, SEEK_SET);
-    _imaging_read_pyFd(state->fd, (char*)ptr, c->bufsize);
-
+    if (_imaging_read_pyFd(state->fd, (char *)ptr, c->bufsize) != c->bufsize) {
+        state->errcode = IMAGING_CODEC_UNKNOWN;
+        return -1;
+    }
 
     /* decoder initialization */
     state->count = 0;
@@ -168,8 +232,6 @@ ImagingSgiRleDecode(Imaging im, ImagingCodecState state,
     for (c->tabindex = 0, c->bufindex = c->tablen * sizeof(UINT32); c->tabindex < c->tablen; c->tabindex++, c->bufindex+=4)
         read4B(&c->lengthtab[c->tabindex], &ptr[c->bufindex]);
 
-    state->count += c->tablen * sizeof(UINT32) * 2;
-
     /* read compressed rows */
     for (c->rowno = 0; c->rowno < im->ysize; c->rowno++, state->y += state->ystep)
     {
@@ -177,19 +239,21 @@ ImagingSgiRleDecode(Imaging im, ImagingCodecState state,
         {
             c->rleoffset = c->starttab[c->rowno + c->channo * im->ysize];
             c->rlelength = c->lengthtab[c->rowno + c->channo * im->ysize];
-            c->rleoffset -= SGI_HEADER_SIZE;
 
-            if (c->rleoffset + c->rlelength > c->bufsize) {
+            // Check for underflow of rleoffset-SGI_HEADER_SIZE
+            if (c->rleoffset < SGI_HEADER_SIZE) {
                 state->errcode = IMAGING_CODEC_OVERRUN;
                 goto sgi_finish_decode;
             }
 
+            c->rleoffset -= SGI_HEADER_SIZE;
+
             /* row decompression */
             if (c->bpc ==1) {
-                status = expandrow(&state->buffer[c->channo], &ptr[c->rleoffset], c->rlelength, im->bands, im->xsize);
+                status = expandrow(&state->buffer[c->channo], &ptr[c->rleoffset], c->rlelength, im->bands, im->xsize, &ptr[c->bufsize-1]);
             }
             else {
-                status = expandrow2(&state->buffer[c->channo * 2], &ptr[c->rleoffset], c->rlelength, im->bands, im->xsize);
+                status = expandrow2(&state->buffer[c->channo * 2], &ptr[c->rleoffset], c->rlelength, im->bands, im->xsize, &ptr[c->bufsize-1]);
             }
             if (status == -1) {
                 state->errcode = IMAGING_CODEC_OVERRUN;
@@ -198,7 +262,6 @@ ImagingSgiRleDecode(Imaging im, ImagingCodecState state,
                 goto sgi_finish_decode;
             }
 
-            state->count += c->rlelength;
         }
 
         /* store decompressed data in image */
@@ -206,7 +269,6 @@ ImagingSgiRleDecode(Imaging im, ImagingCodecState state,
 
     }
 
-    c->bufsize++;
 
 sgi_finish_decode: ;
 
@@ -217,5 +279,5 @@ sgi_finish_decode: ;
         state->errcode=err;
         return -1;
     }
-    return state->count - c->bufsize;
+    return 0;
 }
-- 
2.30.2