Per "man 5 cpio", the namesize in the cpio header includes the trailing
NUL byte of the pathname and the pathname is followed by NUL bytes, but
the current implementation ignores the trailing NUL byte when making
the newc header. Although make_header() tries to pad the pathname string,
the padding won't happen when strlen(name) + sizeof(struct newc_head)
is a multiple of 4, and the non-NULL-terminated pathname may lead to
unexpected results.
Assume that a file is created with 'echo -n aaaa > /boot/test12' and
loaded by grub2:
linux /boot/vmlinuz
initrd newc:test12:/boot/test12 /boot/initrd
The initrd command eventually invoked grub_initrd_load() and sent
't''e''s''t''1''2' to make_header() to generate the header:
00000070 30 37 30 37 30 31 33 30 31 43 41 30 44 45 30 30 |070701301CA0DE00|
00000080 30 30 38 31 41 34 30 30 30 30 30 33 45 38 30 30 |0081A4000003E800|
00000090 30 30 30 30 36 34 30 30 30 30 30 30 30 31 36 33 |0000640000000163|
000000a0 37 36 45 34 35 32 30 30 30 30 30 30 30 34 30 30 |76E4520000000400|
000000b0 30 30 30 30 30 38 30 30 30 30 30 30 31 33 30 30 |0000080000001300|
000000c0 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 |0000000000000000|
000000d0 30 30 30 30 30 36 30 30 30 30 30 30 30 30 74 65 |00000600000000te|
^namesize
000000e0 73 74 31 32 61 61 61 61 30 37 30 37 30 31 30 30 |st12aaaa07070100|
^^ end of the pathname
Since strlen("test12") + sizeof(struct newc_head) is 116 = 29 * 4,
make_header() didn't pad the pathname, and the file content followed
"test12" immediately. This violates the cpio format and may trigger such
error during linux boot:
Initramfs unpacking failed: ZSTD-compressed data is trunc
To avoid the potential problems, this commit counts the trailing NUL byte
in when calling make_header() and adjusts the initrd size accordingly.
Now the header becomes
00000070 30 37 30 37 30 31 33 30 31 43 41 30 44 45 30 30 |070701301CA0DE00|
00000080 30 30 38 31 41 34 30 30 30 30 30 33 45 38 30 30 |0081A4000003E800|
00000090 30 30 30 30 36 34 30 30 30 30 30 30 30 31 36 33 |0000640000000163|
000000a0 37 36 45 34 35 32 30 30 30 30 30 30 30 34 30 30 |76E4520000000400|
000000b0 30 30 30 30 30 38 30 30 30 30 30 30 31 33 30 30 |0000080000001300|
000000c0 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 |0000000000000000|
000000d0 30 30 30 30 30 37 30 30 30 30 30 30 30 30 74 65 |00000700000000te|
^namesize
000000e0 73 74 31 32 00 00 00 00 61 61 61 61 30 37 30 37 |st12....aaaa0707|
^^ end of the pathname
Besides the trailing NUL byte, make_header() pads 3 more NUL bytes, and
the user can safely read the pathname without a further check.
To conform to the cpio format, the headers for "TRAILER!!!" are also
adjusted to include the trailing NUL byte, not ignore it.
Signed-off-by: Gary Lin <glin@suse.com>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
In the case of an error grub_initrd_load() uses argv[] to print the
filename that caused the error. It is also possible to obtain the
filename from the file handles and there is no need to duplicate that
information in argv[], so let's drop it.
Signed-off-by: Nikita Ermakov <arei@altlinux.org>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
These could be triggered by a crafted filesystem with very large files.
Fixes: CVE-2020-15707
Signed-off-by: Colin Watson <cjwatson@debian.org>
Reviewed-by: Jan Setje-Eilers <jan.setjeeilers@oracle.com>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
Let's provide file type info to the I/O layer. This way verifiers
framework and its users will be able to differentiate files and verify
only required ones.
This is preparatory patch.
Signed-off-by: Vladimir Serbinenko <phcoder@gmail.com>
Signed-off-by: Daniel Kiper <daniel.kiper@oracle.com>
Reviewed-by: Ross Philipson <ross.philipson@oracle.com>
Regression from commit:
loader/linux: do not pad initrd with zeroes at the end
a8c473288d3f0a5e17a903a5121dea1a695dda3b
Wimboot fails since the change above because it expects the "trailer"
initrd element on an aligned address.
This issue shows only when newc_name is used and the last initrd
entry has a not aligned size.
Syslinux memdisk is using initrd image and needs to know uncompressed
size in advance. For gzip uncompressed size is at the end of compressed
stream. Grub padded each input file to 4 bytes at the end, which means
syslinux got wrong size.
Linux initramfs loader apparently does not care about trailing alignment.
So change code to align beginning of each file instead which atomatically
gives us the correct size for single file.
Reported-By: David Shaw <dshaw@jabberwocky.com>
