diff options
Diffstat (limited to 'debian/patches/0070-video-readers-png-Drop-greyscale-support-to-fix-heap.patch')
| -rw-r--r-- | debian/patches/0070-video-readers-png-Drop-greyscale-support-to-fix-heap.patch | 168 |
1 files changed, 168 insertions, 0 deletions
diff --git a/debian/patches/0070-video-readers-png-Drop-greyscale-support-to-fix-heap.patch b/debian/patches/0070-video-readers-png-Drop-greyscale-support-to-fix-heap.patch new file mode 100644 index 0000000..08c33f8 --- /dev/null +++ b/debian/patches/0070-video-readers-png-Drop-greyscale-support-to-fix-heap.patch @@ -0,0 +1,168 @@ +From 558c69b5d36d14d55bff21e6570205fe73a02ca2 Mon Sep 17 00:00:00 2001 +From: Daniel Axtens <dja@axtens.net> +Date: Tue, 6 Jul 2021 18:51:35 +1000 +Subject: video/readers/png: Drop greyscale support to fix heap out-of-bounds + write + +A 16-bit greyscale PNG without alpha is processed in the following loop: + + for (i = 0; i < (data->image_width * data->image_height); + i++, d1 += 4, d2 += 2) + { + d1[R3] = d2[1]; + d1[G3] = d2[1]; + d1[B3] = d2[1]; + } + +The increment of d1 is wrong. d1 is incremented by 4 bytes per iteration, +but there are only 3 bytes allocated for storage. This means that image +data will overwrite somewhat-attacker-controlled parts of memory - 3 bytes +out of every 4 following the end of the image. + +This has existed since greyscale support was added in 2013 in commit +3ccf16dff98f (grub-core/video/readers/png.c: Support grayscale). + +Saving starfield.png as a 16-bit greyscale image without alpha in the gimp +and attempting to load it causes grub-emu to crash - I don't think this code +has ever worked. + +Delete all PNG greyscale support. + +Fixes: CVE-2021-3695 + +Signed-off-by: Daniel Axtens <dja@axtens.net> +Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com> +--- + grub-core/video/readers/png.c | 87 +++-------------------------------- + 1 file changed, 7 insertions(+), 80 deletions(-) + +diff --git a/grub-core/video/readers/png.c b/grub-core/video/readers/png.c +index 8955b8ecf..a3161e25b 100644 +--- a/grub-core/video/readers/png.c ++++ b/grub-core/video/readers/png.c +@@ -100,7 +100,7 @@ struct grub_png_data + + unsigned image_width, image_height; + int bpp, is_16bit; +- int raw_bytes, is_gray, is_alpha, is_palette; ++ int raw_bytes, is_alpha, is_palette; + int row_bytes, color_bits; + grub_uint8_t *image_data; + +@@ -296,13 +296,13 @@ grub_png_decode_image_header (struct grub_png_data *data) + data->bpp = 3; + else + { +- data->is_gray = 1; +- data->bpp = 1; ++ return grub_error (GRUB_ERR_BAD_FILE_TYPE, ++ "png: color type not supported"); + } + + if ((color_bits != 8) && (color_bits != 16) + && (color_bits != 4 +- || !(data->is_gray || data->is_palette))) ++ || !data->is_palette)) + return grub_error (GRUB_ERR_BAD_FILE_TYPE, + "png: bit depth must be 8 or 16"); + +@@ -331,7 +331,7 @@ grub_png_decode_image_header (struct grub_png_data *data) + } + + #ifndef GRUB_CPU_WORDS_BIGENDIAN +- if (data->is_16bit || data->is_gray || data->is_palette) ++ if (data->is_16bit || data->is_palette) + #endif + { + data->image_data = grub_calloc (data->image_height, data->row_bytes); +@@ -899,27 +899,8 @@ grub_png_convert_image (struct grub_png_data *data) + int shift; + int mask = (1 << data->color_bits) - 1; + unsigned j; +- if (data->is_gray) +- { +- /* Generic formula is +- (0xff * i) / ((1U << data->color_bits) - 1) +- but for allowed bit depth of 1, 2 and for it's +- equivalent to +- (0xff / ((1U << data->color_bits) - 1)) * i +- Precompute the multipliers to avoid division. +- */ +- +- const grub_uint8_t multipliers[5] = { 0xff, 0xff, 0x55, 0x24, 0x11 }; +- for (i = 0; i < (1U << data->color_bits); i++) +- { +- grub_uint8_t col = multipliers[data->color_bits] * i; +- palette[i][0] = col; +- palette[i][1] = col; +- palette[i][2] = col; +- } +- } +- else +- grub_memcpy (palette, data->palette, 3 << data->color_bits); ++ ++ grub_memcpy (palette, data->palette, 3 << data->color_bits); + d1c = d1; + d2c = d2; + for (j = 0; j < data->image_height; j++, d1c += data->image_width * 3, +@@ -956,60 +937,6 @@ grub_png_convert_image (struct grub_png_data *data) + } + return; + } +- +- if (data->is_gray) +- { +- switch (data->bpp) +- { +- case 4: +- /* 16-bit gray with alpha. */ +- for (i = 0; i < (data->image_width * data->image_height); +- i++, d1 += 4, d2 += 4) +- { +- d1[R4] = d2[3]; +- d1[G4] = d2[3]; +- d1[B4] = d2[3]; +- d1[A4] = d2[1]; +- } +- break; +- case 2: +- if (data->is_16bit) +- /* 16-bit gray without alpha. */ +- { +- for (i = 0; i < (data->image_width * data->image_height); +- i++, d1 += 4, d2 += 2) +- { +- d1[R3] = d2[1]; +- d1[G3] = d2[1]; +- d1[B3] = d2[1]; +- } +- } +- else +- /* 8-bit gray with alpha. */ +- { +- for (i = 0; i < (data->image_width * data->image_height); +- i++, d1 += 4, d2 += 2) +- { +- d1[R4] = d2[1]; +- d1[G4] = d2[1]; +- d1[B4] = d2[1]; +- d1[A4] = d2[0]; +- } +- } +- break; +- /* 8-bit gray without alpha. */ +- case 1: +- for (i = 0; i < (data->image_width * data->image_height); +- i++, d1 += 3, d2++) +- { +- d1[R3] = d2[0]; +- d1[G3] = d2[0]; +- d1[B3] = d2[0]; +- } +- break; +- } +- return; +- } + + { + /* Only copy the upper 8 bit. */ |