Move all the intelligence into the new file address_translation.go.
That the calculations were spread out too much became apparent when adding
the file header. This should make the code much easier to modify in the
future.
Format: [ "Version" uint16 big endian ] [ "Id" 16 random bytes ]
Quoting SECURITY.md:
* Every file has a header that contains a 16-byte random *file id*
* Each block uses the file id and its block number as GCM *authentication data*
* This means the position of the blocks is protected as well. The blocks
can not be reordered or copied between different files without
causing an decryption error.
The old implementation of counting up from a random starting
point had the problem that is allowed an attacker to find out
the write order of the blocks.
This fixes relative symlinks:
$ tar xf linux-4.2.tar.gz
tar: linux-4.2/tools/testing/selftests/powerpc/vphn/vphn.h: Cannot utime: No such file or directory
tar: linux-4.2/tools/testing/selftests/powerpc/vphn/vphn.c: Cannot utime: No such file or directory
tar: linux-4.2/tools/testing/selftests/powerpc/stringloops/memcmp_64.S: Cannot utime: No such file or directory
tar: linux-4.2/tools/testing/selftests/powerpc/primitives/word-at-a-time.h: Cannot utime: No such file or directory
tar: linux-4.2/tools/testing/selftests/powerpc/primitives/asm/asm-compat.h: Cannot utime: No such file or directory
tar: linux-4.2/tools/testing/selftests/powerpc/copyloops/memcpy_power7.S: Cannot utime: No such file or directory
tar: linux-4.2/tools/testing/selftests/powerpc/copyloops/memcpy_64.S: Cannot utime: No such file or directory
tar: linux-4.2/tools/testing/selftests/powerpc/copyloops/copyuser_power7.S: Cannot utime: No such file or directory
tar: linux-4.2/tools/testing/selftests/powerpc/copyloops/copyuser_64.S: Cannot utime: No such file or directory
tar: linux-4.2/arch/powerpc/boot/dts/include/dt-bindings: Cannot utime: No such file or directory
tar: linux-4.2/arch/mips/boot/dts/include/dt-bindings: Cannot utime: No such file or directory
tar: linux-4.2/arch/metag/boot/dts/include/dt-bindings: Cannot utime: No such file or directory
tar: linux-4.2/arch/arm64/boot/dts/include/dt-bindings: Cannot utime: No such file or directory
tar: linux-4.2/arch/arm/boot/dts/include/dt-bindings: Cannot utime: No such file or directory
tar: Exiting with failure status due to previous errors
The too-large reported value broke mmap
(applications saw appended zero bytes)
Also
* Add locking for all fd operations
* Add "--debug" command line switch
