pocket_archive/ext/monocypher/lua_monocypher.c

#include <stdlib.h>
#include <stdbool.h>
#include <lua.h>
#include <lauxlib.h>
#include "monocypher.h"


static int new_blake2b (lua_State *L) {
    // Initialize an incremental blake2b hashing function.
    // lua api:  blake2b_init([hash_size]) return iterator
    // hash_size: the optional length of the digest to be computed 
    //    (between 1 and 64) - default value is 64
    // iterator: opaque handle to be passed to blake2b_update().
    int hash_size = luaL_optinteger (L, 1, 64);
    if ((hash_size < 1)||(hash_size > 64))
        return luaL_error (L, "Bad digest size");

    crypto_blake2b_ctx *ctx = lua_newuserdatauv (L, sizeof (*ctx), 1);
    luaL_getmetatable (L, "monocypher.B2Context");
    lua_setmetatable (L, -2);

    crypto_blake2b_init (ctx, hash_size);

    return 1;
}

static int l_blake2b_update (lua_State *L) {
    // Update a blake2b hash.
    //
    // This function can be used to feed message data into a hash incrementally
    // in a streaming fashion.
    //
    // lua api: blake2b_update(it, m)
    // it: iterator handle obtained with blake2b_init().
    // m: the string to be hashed.
    size_t msg_size;
    crypto_blake2b_ctx *ctx = luaL_checkudata (L, 1, "monocypher.B2Context");
    const char *m = luaL_checklstring (L, 2, &msg_size);

    crypto_blake2b_update (ctx, m, msg_size);

    return 0;
}


static int l_blake2b_final (lua_State *L) {
    // Finalize a blake2b incremental hash and return the checksum.
    // lua_api blake2b_final(it) return digest
    // it: iterator handle obtained with blake2b_init().
    // digest: BLAKE2 hash.
    crypto_blake2b_ctx *ctx = luaL_checkudata (L, 1, "monocypher.B2Context");
    bool convert_hex = lua_toboolean (L, 2);
    printf ("Convert to hex: %d\n", convert_hex);

    unsigned char digest[64];
    size_t hash_size = ctx->hash_size;

    crypto_blake2b_final (ctx, digest);

    char *hex_hash;
    if (convert_hex) {
        size_t hash_hex_size = 2 * hash_size + 1;
        hex_hash = calloc (hash_hex_size, sizeof (*hex_hash));
        if (!hex_hash) return luaL_error (L, "Allocation error");
        for (size_t i = 0; i < hash_size; i++)
            sprintf (hex_hash + 2 * i, "%02x", digest[i]);
        lua_pushstring (L, hex_hash);
    } else lua_pushlstring (L, digest, hash_size);

    return 1;
}


static const luaL_Reg mc_lib_fn [] = {
    {"new_blake2b", new_blake2b},

    {NULL}
};


int luaopen_pocket_archive_monocypher (lua_State *L)
{
    luaL_newmetatable (L, "monocypher");

    luaL_newmetatable (L, "monocypher.B2Context");
    lua_pushvalue (L, -1);
    lua_setfield (L, -2, "__index");
    lua_pushcfunction (L, l_blake2b_update);
    lua_setfield (L, -2, "update");
    lua_pushcfunction (L, l_blake2b_final);
    lua_setfield (L, -2, "final");

    luaL_newlib (L, mc_lib_fn);

    return 1;
}