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fca13a17b1
This applies to all of AES, SHA-1, SHA-256 and SHA-512. All those source files previously contained multiple implementations of the algorithm, enabled or disabled by ifdefs detecting whether they would work on a given compiler. And in order to get advanced machine instructions like AES-NI or NEON crypto into the output file when the compile flags hadn't enabled them, we had to do nasty stuff with compiler-specific pragmas or attributes. Now we can do the detection at cmake time, and enable advanced instructions in the more sensible way, by compile-time flags. So I've broken up each of these modules into lots of sub-pieces: a file called (e.g.) 'foo-common.c' containing common definitions across all implementations (such as round constants), one called 'foo-select.c' containing the top-level vtable(s), and a separate file for each implementation exporting just the vtable(s) for that implementation. One advantage of this is that it depends a lot less on compiler- specific bodgery. My particular least favourite part of the previous setup was the part where I had to _manually_ define some Arm ACLE feature macros before including <arm_neon.h>, so that it would define the intrinsics I wanted. Now I'm enabling interesting architecture features in the normal way, on the compiler command line, there's no need for that kind of trick: the right feature macros are already defined and <arm_neon.h> does the right thing. Another change in this reorganisation is that I've stopped assuming there's just one hardware implementation per platform. Previously, the accelerated vtables were called things like sha256_hw, and varied between FOO-NI and NEON depending on platform; and the selection code would simply ask 'is hw available? if so, use hw, else sw'. Now, each HW acceleration strategy names its vtable its own way, and the selection vtable has a whole list of possibilities to iterate over looking for a supported one. So if someone feels like writing a second accelerated implementation of something for a given platform - for example, I've heard you can use plain NEON to speed up AES somewhat even without the crypto extension - then it will now have somewhere to drop in alongside the existing ones.
106 lines
3.3 KiB
C
106 lines
3.3 KiB
C
/*
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* Definitions likely to be helpful to multiple SHA-256 implementations.
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*/
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/*
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* The 'extra' structure used by SHA-256 implementations is used to
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* include information about how to check if a given implementation is
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* available at run time, and whether we've already checked.
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*/
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struct sha256_extra_mutable;
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struct sha256_extra {
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/* Function to check availability. Might be expensive, so we don't
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* want to call it more than once. */
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bool (*check_available)(void);
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/* Point to a writable substructure. */
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struct sha256_extra_mutable *mut;
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};
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struct sha256_extra_mutable {
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bool checked_availability;
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bool is_available;
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};
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static inline bool check_availability(const struct sha256_extra *extra)
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{
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if (!extra->mut->checked_availability) {
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extra->mut->is_available = extra->check_available();
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extra->mut->checked_availability = true;
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}
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return extra->mut->is_available;
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}
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/*
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* Macro to define a SHA-256 vtable together with its 'extra'
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* structure.
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*/
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#define SHA256_VTABLE(impl_c, impl_display) \
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static struct sha256_extra_mutable sha256_ ## impl_c ## _extra_mut; \
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static const struct sha256_extra sha256_ ## impl_c ## _extra = { \
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.check_available = sha256_ ## impl_c ## _available, \
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.mut = &sha256_ ## impl_c ## _extra_mut, \
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}; \
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const ssh_hashalg ssh_sha256_ ## impl_c = { \
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.new = sha256_ ## impl_c ## _new, \
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.reset = sha256_ ## impl_c ## _reset, \
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.copyfrom = sha256_ ## impl_c ## _copyfrom, \
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.digest = sha256_ ## impl_c ## _digest, \
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.free = sha256_ ## impl_c ## _free, \
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.hlen = 32, \
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.blocklen = 64, \
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HASHALG_NAMES_ANNOTATED("SHA-256", impl_display), \
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.extra = &sha256_ ## impl_c ## _extra, \
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}
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extern const uint32_t sha256_initial_state[8];
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extern const uint32_t sha256_round_constants[64];
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#define SHA256_ROUNDS 64
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typedef struct sha256_block sha256_block;
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struct sha256_block {
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uint8_t block[64];
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size_t used;
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uint64_t len;
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};
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static inline void sha256_block_setup(sha256_block *blk)
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{
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blk->used = 0;
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blk->len = 0;
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}
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static inline bool sha256_block_write(
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sha256_block *blk, const void **vdata, size_t *len)
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{
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size_t blkleft = sizeof(blk->block) - blk->used;
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size_t chunk = *len < blkleft ? *len : blkleft;
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const uint8_t *p = *vdata;
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memcpy(blk->block + blk->used, p, chunk);
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*vdata = p + chunk;
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*len -= chunk;
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blk->used += chunk;
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blk->len += chunk;
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if (blk->used == sizeof(blk->block)) {
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blk->used = 0;
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return true;
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}
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return false;
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}
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static inline void sha256_block_pad(sha256_block *blk, BinarySink *bs)
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{
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uint64_t final_len = blk->len << 3;
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size_t pad = 1 + (63 & (55 - blk->used));
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put_byte(bs, 0x80);
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for (size_t i = 1; i < pad; i++)
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put_byte(bs, 0);
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put_uint64(bs, final_len);
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assert(blk->used == 0 && "Should have exactly hit a block boundary");
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}
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