/*-
* Copyright © 2011, 2014, 2015, 2021
* mirabilos <m@mirbsd.org>
*
* Provided that these terms and disclaimer and all copyright notices
* are retained or reproduced in an accompanying document, permission
* is granted to deal in this work without restriction, including un‐
* limited rights to use, publicly perform, distribute, sell, modify,
* merge, give away, or sublicence.
*
* This work is provided “AS IS” and WITHOUT WARRANTY of any kind, to
* the utmost extent permitted by applicable law, neither express nor
* implied; without malicious intent or gross negligence. In no event
* may a licensor, author or contributor be held liable for indirect,
* direct, other damage, loss, or other issues arising in any way out
* of dealing in the work, even if advised of the possibility of such
* damage or existence of a defect, except proven that it results out
* of said person’s immediate fault when using the work as intended.
*-
* This file provides BAFH (Better Avalanche for the Jenkins Hash) as
* inline macro bodies that operate on “register uint32_t” variables,
* with variants that use their local intermediate registers.
*
* Usage note for BAFH with entropy distribution: input up to 4 bytes
* is best combined into a 32-bit unsigned integer, which is then run
* through BAFHFinish_reg for mixing and then used as context instead
* of 0. Longer input should be handled the same: take the first four
* bytes as IV after mixing then add subsequent bytes the same way.
* This needs counting input bytes and is endian-dependent, thus not,
* for speed reasons, specified for the regular stable hash, but very
* much recommended if the actual output value may differ across runs
* (so is using a random value instead of 0 for the IV).
*-
* Little quote gem:
* We are looking into it. Changing the core
* hash function in PHP isn't a trivial change
* and will take us some time.
* -- Rasmus Lerdorf
*/
#ifndef SYSKERN_MIRHASH_H
#define SYSKERN_MIRHASH_H 1
#define SYSKERN_MIRHASH_BAFH
#include <sys/types.h>
__RCSID("$MirOS: src/bin/mksh/mirhash.h,v 1.9 2021/07/31 19:56:33 tg Exp $");
/*-
* BAFH itself is defined by the following primitives:
*
* • BAFHInit(ctx) initialises the hash context, which consists of a
* sole 32-bit unsigned integer (ideally in a register), to 0.
* It is possible to use any initial value out of [0; 2³²[ – which
* is, in fact, recommended if using BAFH for entropy distribution
* – but for a regular stable hash, the IV 0 is needed.
*
* • BAFHUpdateOctet(ctx,val) compresses the unsigned 8-bit quantity
* into the hash context. The algorithm used is Jenkins’ one-at-a-
* time, except that an additional constant 1 is added so that, if
* the context is (still) zero, adding a NUL byte is not ignored.
*
* • BAFHror(eax,cl) evaluates to the unsigned 32-bit integer “eax”,
* rotated right by “cl” ∈ [1; 31] (no casting, be careful!) where
* “eax” must be uint32_t and “cl” an in-range integer.
*
* • BAFHFinish(ctx) avalanches the context around so every sub-byte
* depends on all input octets; afterwards, the context variable’s
* value is the hash output. BAFH does not use any padding, nor is
* the input length added; this is due to the common use case (for
* quick entropy distribution and use with a hashtable).
* Warning: BAFHFinish uses the MixColumn algorithm of AES – which
* is reversible (to avoid introducing funnels and reducing entro‐
* py), so blinding may need to be employed for some uses, e.g. in
* mksh, after a fork.
*
* The BAFHUpdateOctet and BAFHFinish are available in two flavours:
* suffixed with _reg (assumes the context is in a register) or _mem
* (which doesn’t).
*
* The following high-level macros (with _reg and _mem variants) are
* available:
*
* • BAFHUpdateMem(ctx,buf,len) adds a memory block to a context.
* • BAFHUpdateStr(ctx,buf) is equivalent to using len=strlen(buf).
*
* All macros may use ctx multiple times in their expansion, but all
* other arguments are always evaluated at most once except BAFHror.
*
* To stay portable, encode numbers using ULEB128, or better and for
* sortability, VLQ (same unsigned but big endian), normal or Git’s.
*/
#define BAFHInit(h) do { \
(h) = 0; \
} while (/* CONSTCOND */ 0)
#define BAFHUpdateOctet_reg(h,b) do { \
(h) += (unsigned char)(b); \
++(h); \
(h) += (h) << 10; \
(h) ^= (h) >> 6; \
} while (/* CONSTCOND */ 0)
#define BAFHUpdateOctet_mem(m,b) do { \
register uint32_t BAFH_h = (m); \
\
BAFHUpdateOctet_reg(BAFH_h, (b)); \
(m) = BAFH_h; \
} while (/* CONSTCOND */ 0)
#define BAFHror(eax,cl) (((eax) >> (cl)) | ((eax) << (32 - (cl))))
#define BAFHFinish_reg(h) do { \
register uint32_t BAFHFinish_v; \
\
BAFHFinish_v = ((h) >> 7) & 0x01010101U; \
BAFHFinish_v += BAFHFinish_v << 1; \
BAFHFinish_v += BAFHFinish_v << 3; \
BAFHFinish_v ^= ((h) << 1) & 0xFEFEFEFEU; \
\
BAFHFinish_v ^= BAFHror(BAFHFinish_v, 8); \
BAFHFinish_v ^= ((h) = BAFHror((h), 8)); \
BAFHFinish_v ^= ((h) = BAFHror((h), 8)); \
(h) = BAFHror((h), 8) ^ BAFHFinish_v; \
} while (/* CONSTCOND */ 0)
#define BAFHFinish_mem(m) do { \
register uint32_t BAFHFinish_v, BAFH_h = (m); \
\
BAFHFinish_v = (BAFH_h >> 7) & 0x01010101U; \
BAFHFinish_v += BAFHFinish_v << 1; \
BAFHFinish_v += BAFHFinish_v << 3; \
BAFHFinish_v ^= (BAFH_h << 1) & 0xFEFEFEFEU; \
\
BAFHFinish_v ^= BAFHror(BAFHFinish_v, 8); \
BAFHFinish_v ^= (BAFH_h = BAFHror(BAFH_h, 8)); \
BAFHFinish_v ^= (BAFH_h = BAFHror(BAFH_h, 8)); \
(m) = BAFHror(BAFH_h, 8) ^ BAFHFinish_v; \
} while (/* CONSTCOND */ 0)
#define BAFHUpdateMem_reg(h,p,z) do { \
register const unsigned char *BAFHUpdate_p; \
register size_t BAFHUpdate_z = (z); \
\
BAFHUpdate_p = (const void *)(p); \
while (BAFHUpdate_z--) \
BAFHUpdateOctet_reg((h), *BAFHUpdate_p++); \
} while (/* CONSTCOND */ 0)
/* meh should have named them _r/m but that’s not valid C */
#define BAFHUpdateMem_mem(m,p,z) do { \
register uint32_t BAFH_h = (m); \
\
BAFHUpdateMem_reg(BAFH_h, (p), (z)); \
(m) = BAFH_h; \
} while (/* CONSTCOND */ 0)
#define BAFHUpdateStr_reg(h,s) do { \
register const unsigned char *BAFHUpdate_s; \
register unsigned char BAFHUpdate_c; \
\
BAFHUpdate_s = (const void *)(s); \
while ((BAFHUpdate_c = *BAFHUpdate_s++) != 0) \
BAFHUpdateOctet_reg((h), BAFHUpdate_c); \
} while (/* CONSTCOND */ 0)
#define BAFHUpdateStr_mem(m,s) do { \
register uint32_t BAFH_h = (m); \
\
BAFHUpdateStr_reg(BAFH_h, (s)); \
(m) = BAFH_h; \
} while (/* CONSTCOND */ 0)
#endif