From 1312c5426e7dd84e396ef2ff35aa09b64d92d382 Mon Sep 17 00:00:00 2001 From: Lumir Balhar 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