On Jan 6, 2017, at 11:29 AM, Jason A. Donenfeld <Jason@xxxxxxxxx> wrote: > > The "half md4" transform should not be used by any new code. And > fortunately, it's only used now by ext4. Since ext4 supports several > hashing methods, at some point it might be desirable to move to > something like SipHash. As an intermediate step, remove half md4 from > cryptohash.h and lib, and make it just a local function in ext4's > hash.c. There's precedent for doing this; the other function ext can use > for its hashes -- TEA -- is also implemented in the same place. Also, by > being a local function, this might allow gcc to perform some additional > optimizations. This is essentially a reversion of a patch applied in 2.6.11 to remove the half-MD4 code from ext3: ftp://ftp.kernel.org/pub/linux/kernel/people/akpm/patches/2.6/2.6.11-rc2/2.6.11-rc2-mm2/broken-out/random-pt4-kill-duplicate-halfmd4-in-ext3-htree.patch This _just_ predates Git history so there is no commit hash for it. A couple of trivial whitespace changes if patch is resubmitted, but it looks fine as-is. Reviewed-by: Andreas Dilger <adilger@xxxxxxxxx> > Signed-off-by: Jason A. Donenfeld <Jason@xxxxxxxxx> > Cc: Theodore Ts'o <tytso@xxxxxxx> > --- > fs/ext4/hash.c | 69 +++++++++++++++++++++++++++++++++++++++++++++- > include/linux/cryptohash.h | 2 -- > lib/Makefile | 2 +- > lib/halfmd4.c | 67 -------------------------------------------- > 4 files changed, 69 insertions(+), 71 deletions(-) > delete mode 100644 lib/halfmd4.c > > diff --git a/fs/ext4/hash.c b/fs/ext4/hash.c > index e026aa941fd5..4d743d8f72fd 100644 > --- a/fs/ext4/hash.c > +++ b/fs/ext4/hash.c > @@ -10,7 +10,8 @@ > */ > > #include <linux/fs.h> > -#include <linux/cryptohash.h> > +#include <linux/compiler.h> > +#include <linux/bitops.h> > #include "ext4.h" > > #define DELTA 0x9E3779B9 > @@ -32,6 +33,72 @@ static void TEA_transform(__u32 buf[4], __u32 const in[]) > buf[1] += b1; > } > > +/* F, G and H are basic MD4 functions: selection, majority, parity */ > +#define F(x, y, z) ((z) ^ ((x) & ((y) ^ (z)))) > +#define G(x, y, z) (((x) & (y)) + (((x) ^ (y)) & (z))) > +#define H(x, y, z) ((x) ^ (y) ^ (z)) (style) Would be nice to get an empty line here. > +/* > + * The generic round function. The application is so specific that > + * we don't bother protecting all the arguments with parens, as is generally > + * good macro practice, in favor of extra legibility. > + * Rotation is separate from addition to prevent recomputation > + */ > +#define ROUND(f, a, b, c, d, x, s) \ > + (a += f(b, c, d) + x, a = rol32(a, s)) > +#define K1 0 > +#define K2 013240474631UL > +#define K3 015666365641UL Blank line here too. > +/* > + * Basic cut-down MD4 transform. Returns only 32 bits of result. > + */ > +static __u32 half_md4_transform(__u32 buf[4], __u32 const in[8]) > +{ > + __u32 a = buf[0], b = buf[1], c = buf[2], d = buf[3]; > + > + /* Round 1 */ > + ROUND(F, a, b, c, d, in[0] + K1, 3); > + ROUND(F, d, a, b, c, in[1] + K1, 7); > + ROUND(F, c, d, a, b, in[2] + K1, 11); > + ROUND(F, b, c, d, a, in[3] + K1, 19); > + ROUND(F, a, b, c, d, in[4] + K1, 3); > + ROUND(F, d, a, b, c, in[5] + K1, 7); > + ROUND(F, c, d, a, b, in[6] + K1, 11); > + ROUND(F, b, c, d, a, in[7] + K1, 19); > + > + /* Round 2 */ > + ROUND(G, a, b, c, d, in[1] + K2, 3); > + ROUND(G, d, a, b, c, in[3] + K2, 5); > + ROUND(G, c, d, a, b, in[5] + K2, 9); > + ROUND(G, b, c, d, a, in[7] + K2, 13); > + ROUND(G, a, b, c, d, in[0] + K2, 3); > + ROUND(G, d, a, b, c, in[2] + K2, 5); > + ROUND(G, c, d, a, b, in[4] + K2, 9); > + ROUND(G, b, c, d, a, in[6] + K2, 13); > + > + /* Round 3 */ > + ROUND(H, a, b, c, d, in[3] + K3, 3); > + ROUND(H, d, a, b, c, in[7] + K3, 9); > + ROUND(H, c, d, a, b, in[2] + K3, 11); > + ROUND(H, b, c, d, a, in[6] + K3, 15); > + ROUND(H, a, b, c, d, in[1] + K3, 3); > + ROUND(H, d, a, b, c, in[5] + K3, 9); > + ROUND(H, c, d, a, b, in[0] + K3, 11); > + ROUND(H, b, c, d, a, in[4] + K3, 15); > + > + buf[0] += a; > + buf[1] += b; > + buf[2] += c; > + buf[3] += d; > + > + return buf[1]; /* "most hashed" word */ > +} > +#undef ROUND > +#undef K1 > +#undef K2 > +#undef K3 > +#undef F > +#undef G > +#undef H > > /* The old legacy hash */ > static __u32 dx_hack_hash_unsigned(const char *name, int len) > diff --git a/include/linux/cryptohash.h b/include/linux/cryptohash.h > index f4754282c9c2..3252799832cf 100644 > --- a/include/linux/cryptohash.h > +++ b/include/linux/cryptohash.h > @@ -15,6 +15,4 @@ void sha_transform(__u32 *digest, const char *data, __u32 *W); > > void md5_transform(__u32 *hash, __u32 const *in); > > -__u32 half_md4_transform(__u32 buf[4], __u32 const in[8]); > - > #endif > diff --git a/lib/Makefile b/lib/Makefile > index bc4073a8cd08..19ea76149a37 100644 > --- a/lib/Makefile > +++ b/lib/Makefile > @@ -31,7 +31,7 @@ lib-$(CONFIG_HAS_DMA) += dma-noop.o > lib-y += kobject.o klist.o > obj-y += lockref.o > > -obj-y += bcd.o div64.o sort.o parser.o halfmd4.o debug_locks.o random32.o \ > +obj-y += bcd.o div64.o sort.o parser.o debug_locks.o random32.o \ > bust_spinlocks.o kasprintf.o bitmap.o scatterlist.o \ > gcd.o lcm.o list_sort.o uuid.o flex_array.o iov_iter.o clz_ctz.o \ > bsearch.o find_bit.o llist.o memweight.o kfifo.o \ > diff --git a/lib/halfmd4.c b/lib/halfmd4.c > deleted file mode 100644 > index 137e861d9690..000000000000 > --- a/lib/halfmd4.c > +++ /dev/null > @@ -1,67 +0,0 @@ > -#include <linux/compiler.h> > -#include <linux/export.h> > -#include <linux/cryptohash.h> > -#include <linux/bitops.h> > - > -/* F, G and H are basic MD4 functions: selection, majority, parity */ > -#define F(x, y, z) ((z) ^ ((x) & ((y) ^ (z)))) > -#define G(x, y, z) (((x) & (y)) + (((x) ^ (y)) & (z))) > -#define H(x, y, z) ((x) ^ (y) ^ (z)) > - > -/* > - * The generic round function. The application is so specific that > - * we don't bother protecting all the arguments with parens, as is generally > - * good macro practice, in favor of extra legibility. > - * Rotation is separate from addition to prevent recomputation > - */ > -#define ROUND(f, a, b, c, d, x, s) \ > - (a += f(b, c, d) + x, a = rol32(a, s)) > -#define K1 0 > -#define K2 013240474631UL > -#define K3 015666365641UL > - > -/* > - * Basic cut-down MD4 transform. Returns only 32 bits of result. > - */ > -__u32 half_md4_transform(__u32 buf[4], __u32 const in[8]) > -{ > - __u32 a = buf[0], b = buf[1], c = buf[2], d = buf[3]; > - > - /* Round 1 */ > - ROUND(F, a, b, c, d, in[0] + K1, 3); > - ROUND(F, d, a, b, c, in[1] + K1, 7); > - ROUND(F, c, d, a, b, in[2] + K1, 11); > - ROUND(F, b, c, d, a, in[3] + K1, 19); > - ROUND(F, a, b, c, d, in[4] + K1, 3); > - ROUND(F, d, a, b, c, in[5] + K1, 7); > - ROUND(F, c, d, a, b, in[6] + K1, 11); > - ROUND(F, b, c, d, a, in[7] + K1, 19); > - > - /* Round 2 */ > - ROUND(G, a, b, c, d, in[1] + K2, 3); > - ROUND(G, d, a, b, c, in[3] + K2, 5); > - ROUND(G, c, d, a, b, in[5] + K2, 9); > - ROUND(G, b, c, d, a, in[7] + K2, 13); > - ROUND(G, a, b, c, d, in[0] + K2, 3); > - ROUND(G, d, a, b, c, in[2] + K2, 5); > - ROUND(G, c, d, a, b, in[4] + K2, 9); > - ROUND(G, b, c, d, a, in[6] + K2, 13); > - > - /* Round 3 */ > - ROUND(H, a, b, c, d, in[3] + K3, 3); > - ROUND(H, d, a, b, c, in[7] + K3, 9); > - ROUND(H, c, d, a, b, in[2] + K3, 11); > - ROUND(H, b, c, d, a, in[6] + K3, 15); > - ROUND(H, a, b, c, d, in[1] + K3, 3); > - ROUND(H, d, a, b, c, in[5] + K3, 9); > - ROUND(H, c, d, a, b, in[0] + K3, 11); > - ROUND(H, b, c, d, a, in[4] + K3, 15); > - > - buf[0] += a; > - buf[1] += b; > - buf[2] += c; > - buf[3] += d; > - > - return buf[1]; /* "most hashed" word */ > -} > -EXPORT_SYMBOL(half_md4_transform); > -- > 2.11.0 > Cheers, Andreas
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