cipher/chacha20: buffer the full input block
The final implementation is simpler, at the cost of doing work in chacha20_x_final.
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5bd46fffa6
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@ -42,7 +42,7 @@ chacha20_x_init_from(void *arg, const uint8_t *key, size_t keylen,
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ctx->c = counter;
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for (i = 0; i < CHACHA20_NONCE_WORDS; i++)
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ctx->n[i] = load32le(&iv[i * 4]);
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ctx->blen = 0;
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ctx->mlen = 0;
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return 1;
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}
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@ -59,50 +59,42 @@ chacha20_x_update(void *arg, uint8_t *out, size_t *outlen, const uint8_t *in,
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size_t inlen)
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{
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struct chacha20_ctx *ctx = arg;
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size_t i, blocks;
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uint32_t h;
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uint8_t s[4];
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size_t i, blocks, off, pad;
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*outlen = 0;
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if (inlen > SIZE_MAX - (CHACHA20_CHUNK - 1) - ctx->blen)
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if (inlen > SIZE_MAX - (CHACHA20_CHUNK - 1) - ctx->mlen)
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return 0;
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blocks = inlen + ctx->blen + CHACHA20_CHUNK - 1;
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if (blocks / CHACHA20_CHUNK + ctx->c > CHACHA20_CTRMAX)
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blocks = (inlen + ctx->mlen + CHACHA20_CHUNK - 1) / CHACHA20_CHUNK;
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if (blocks + ctx->c > CHACHA20_CTRMAX)
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return 0;
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if (out == NULL) {
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*outlen = inlen;
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*outlen = (ctx->mlen + inlen) / CHACHA20_CHUNK * CHACHA20_CHUNK;
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if (out == NULL)
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return 1;
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for (i = 0; i + ctx->mlen < CHACHA20_CHUNK && i < inlen; i++)
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ctx->m[i + ctx->mlen] = in[i];
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ctx->mlen += i;
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in += i;
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inlen -= i;
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if (ctx->mlen == CHACHA20_CHUNK) {
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chacha20_block(ctx);
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ctx->c++;
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for (i = 0; i < CHACHA20_CHUNK_WORDS; i++) {
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h = load32le(&ctx->m[i * 4]);
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h ^= ctx->s[i];
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store32le(&out[i * 4], h);
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}
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out += CHACHA20_CHUNK;
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ctx->mlen = 0;
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}
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*outlen = inlen;
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if (inlen == 0)
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return 1;
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if (ctx->blen == 0)
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goto fullblock;
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off = ctx->blen % 4;
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if (off != 0) {
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store32le(s, ctx->s[ctx->blen / 4]);
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for (i = 0; i + off < 4 && i < inlen; i++)
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out[i] = in[i] ^ s[i + off];
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ctx->blen += i;
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out += i;
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in += i;
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inlen -= i;
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}
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pad = inlen % 4;
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for (i = 0; i + ctx->blen < CHACHA20_CHUNK && i < inlen - pad; i += 4) {
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h = load32le(&in[i * 4]);
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h ^= ctx->s[(i + ctx->blen) / 4];
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store32le(&out[i * 4], h);
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}
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ctx->blen += i * 4;
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out += i * 4;
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in += i * 4;
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inlen -= i * 4;
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fullblock:
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while (inlen >= CHACHA20_CHUNK) {
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chacha20_block(ctx);
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ctx->c++;
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@ -117,23 +109,9 @@ chacha20_x_update(void *arg, uint8_t *out, size_t *outlen, const uint8_t *in,
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inlen -= CHACHA20_CHUNK;
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}
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chacha20_block(ctx);
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ctx->c++;
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ctx->blen = inlen;
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pad = inlen % 4;
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for (i = 0; i < (inlen - pad) / 4; i++) {
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h = load32le(&in[i * 4]);
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h ^= ctx->s[i];
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store32le(&out[i * 4], h);
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}
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out += i * 4;
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in += i * 4;
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inlen -= i * 4;
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store32le(s, ctx->s[i]);
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for (i = 0; i < pad; i++)
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out[i] = in[i] ^ s[i];
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for (i = 0; i < inlen; i++)
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ctx->m[i] = in[i];
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ctx->mlen = inlen;
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return 1;
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}
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@ -142,8 +120,30 @@ int
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chacha20_x_final(void *arg, uint8_t *out, size_t *outlen)
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{
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struct chacha20_ctx *ctx = arg;
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size_t i, off;
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uint32_t h;
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uint8_t s[4];
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*outlen = ctx->mlen;
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if (out == NULL)
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return 1;
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if (ctx->mlen > 0)
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chacha20_block(ctx);
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for (i = 0; i < ctx->mlen / 4; i++) {
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h = load32le(&ctx->m[i * 4]);
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h ^= ctx->s[i];
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store32le(&out[i * 4], h);
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}
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off = i * 4;
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ctx->mlen -= off;
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out += off;
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store32le(&s[0], ctx->s[i]);
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for (i = 0; i < ctx->mlen; i++)
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out[i] = ctx->m[i + off] ^ s[i];
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*outlen = 0;
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lc_scrub(ctx, sizeof(*ctx));
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return 1;
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@ -33,7 +33,8 @@ struct chacha20_ctx {
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uint32_t k[CHACHA20_KEY_WORDS];
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uint32_t c;
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uint32_t n[CHACHA20_NONCE_WORDS];
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size_t blen;
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size_t mlen;
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uint8_t m[CHACHA20_CHUNK];
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};
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