1 files changed, 318 insertions, 0 deletions
diff --git a/third_party/bearssl/src/gcm.c b/third_party/bearssl/src/gcm.c
new file mode 100644
index 0000000..ede5f08
--- /dev/null
+++ b/third_party/bearssl/src/gcm.c
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+/*
+ * Copyright (c) 2017 Thomas Pornin <[email protected]>
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining 
+ * a copy of this software and associated documentation files (the
+ * "Software"), to deal in the Software without restriction, including
+ * without limitation the rights to use, copy, modify, merge, publish,
+ * distribute, sublicense, and/or sell copies of the Software, and to
+ * permit persons to whom the Software is furnished to do so, subject to
+ * the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be 
+ * included in all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, 
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND 
+ * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
+ * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
+ * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+ * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+#include "inner.h"
+
+/*
+ * Implementation Notes
+ * ====================
+ *
+ * Since CTR and GHASH implementations can handle only full blocks, a
+ * 16-byte buffer (buf[]) is maintained in the context:
+ *
+ *  - When processing AAD, buf[] contains the 0-15 unprocessed bytes.
+ *
+ *  - When doing CTR encryption / decryption, buf[] contains the AES output
+ *    for the last partial block, to be used with the next few bytes of
+ *    data, as well as the already encrypted bytes. For instance, if the
+ *    processed data length so far is 21 bytes, then buf[0..4] contains
+ *    the five last encrypted bytes, and buf[5..15] contains the next 11
+ *    AES output bytes to be XORed with the next 11 bytes of input.
+ *
+ *    The recorded AES output bytes are used to complete the block when
+ *    the corresponding bytes are obtained. Note that buf[] always
+ *    contains the _encrypted_ bytes, whether we apply encryption or
+ *    decryption: these bytes are used as input to GHASH when the block
+ *    is complete.
+ *
+ * In both cases, the low bits of the data length counters (count_aad,
+ * count_ctr) are used to work out the current situation.
+ */
+
+/* see bearssl_aead.h */
+void
+br_gcm_init(br_gcm_context *ctx, const br_block_ctr_class **bctx, br_ghash gh)
+{
+	unsigned char iv[12];
+
+	ctx->vtable = &br_gcm_vtable;
+	ctx->bctx = bctx;
+	ctx->gh = gh;
+
+	/*
+	 * The GHASH key h[] is the raw encryption of the all-zero
+	 * block. Since we only have a CTR implementation, we use it
+	 * with an all-zero IV and a zero counter, to CTR-encrypt an
+	 * all-zero block.
+	 */
+	memset(ctx->h, 0, sizeof ctx->h);
+	memset(iv, 0, sizeof iv);
+	(*bctx)->run(bctx, iv, 0, ctx->h, sizeof ctx->h);
+}
+
+/* see bearssl_aead.h */
+void
+br_gcm_reset(br_gcm_context *ctx, const void *iv, size_t len)
+{
+	/*
+	 * If the provided nonce is 12 bytes, then this is the initial
+	 * IV for CTR mode; it will be used with a counter that starts
+	 * at 2 (value 1 is for encrypting the GHASH output into the tag).
+	 *
+	 * If the provided nonce has any other length, then it is hashed
+	 * (with GHASH) into a 16-byte value that will be the IV for CTR
+	 * (both 12-byte IV and 32-bit counter).
+	 */
+	if (len == 12) {
+		memcpy(ctx->j0_1, iv, 12);
+		ctx->j0_2 = 1;
+	} else {
+		unsigned char ty[16], tmp[16];
+
+		memset(ty, 0, sizeof ty);
+		ctx->gh(ty, ctx->h, iv, len);
+		memset(tmp, 0, 8);
+		br_enc64be(tmp + 8, (uint64_t)len << 3);
+		ctx->gh(ty, ctx->h, tmp, 16);
+		memcpy(ctx->j0_1, ty, 12);
+		ctx->j0_2 = br_dec32be(ty + 12);
+	}
+	ctx->jc = ctx->j0_2 + 1;
+	memset(ctx->y, 0, sizeof ctx->y);
+	ctx->count_aad = 0;
+	ctx->count_ctr = 0;
+}
+
+/* see bearssl_aead.h */
+void
+br_gcm_aad_inject(br_gcm_context *ctx, const void *data, size_t len)
+{
+	size_t ptr, dlen;
+
+	ptr = (size_t)ctx->count_aad & (size_t)15;
+	if (ptr != 0) {
+		/*
+		 * If there is a partial block, then we first try to
+		 * complete it.
+		 */
+		size_t clen;
+
+		clen = 16 - ptr;
+		if (len < clen) {
+			memcpy(ctx->buf + ptr, data, len);
+			ctx->count_aad += (uint64_t)len;
+			return;
+		}
+		memcpy(ctx->buf + ptr, data, clen);
+		ctx->gh(ctx->y, ctx->h, ctx->buf, 16);
+		data = (const unsigned char *)data + clen;
+		len -= clen;
+		ctx->count_aad += (uint64_t)clen;
+	}
+
+	/*
+	 * Now AAD is aligned on a 16-byte block (with regards to GHASH).
+	 * We process all complete blocks, and save the last partial
+	 * block.
+	 */
+	dlen = len & ~(size_t)15;
+	ctx->gh(ctx->y, ctx->h, data, dlen);
+	memcpy(ctx->buf, (const unsigned char *)data + dlen, len - dlen);
+	ctx->count_aad += (uint64_t)len;
+}
+
+/* see bearssl_aead.h */
+void
+br_gcm_flip(br_gcm_context *ctx)
+{
+	/*
+	 * We complete the GHASH computation if there is a partial block.
+	 * The GHASH implementation automatically applies padding with
+	 * zeros.
+	 */
+	size_t ptr;
+
+	ptr = (size_t)ctx->count_aad & (size_t)15;
+	if (ptr != 0) {
+		ctx->gh(ctx->y, ctx->h, ctx->buf, ptr);
+	}
+}
+
+/* see bearssl_aead.h */
+void
+br_gcm_run(br_gcm_context *ctx, int encrypt, void *data, size_t len)
+{
+	unsigned char *buf;
+	size_t ptr, dlen;
+
+	buf = data;
+	ptr = (size_t)ctx->count_ctr & (size_t)15;
+	if (ptr != 0) {
+		/*
+		 * If we have a partial block, then we try to complete it.
+		 */
+		size_t u, clen;
+
+		clen = 16 - ptr;
+		if (len < clen) {
+			clen = len;
+		}
+		for (u = 0; u < clen; u ++) {
+			unsigned x, y;
+
+			x = buf[u];
+			y = x ^ ctx->buf[ptr + u];
+			ctx->buf[ptr + u] = encrypt ? y : x;
+			buf[u] = y;
+		}
+		ctx->count_ctr += (uint64_t)clen;
+		buf += clen;
+		len -= clen;
+		if (ptr + clen < 16) {
+			return;
+		}
+		ctx->gh(ctx->y, ctx->h, ctx->buf, 16);
+	}
+
+	/*
+	 * Process full blocks.
+	 */
+	dlen = len & ~(size_t)15;
+	if (!encrypt) {
+		ctx->gh(ctx->y, ctx->h, buf, dlen);
+	}
+	ctx->jc = (*ctx->bctx)->run(ctx->bctx, ctx->j0_1, ctx->jc, buf, dlen);
+	if (encrypt) {
+		ctx->gh(ctx->y, ctx->h, buf, dlen);
+	}
+	buf += dlen;
+	len -= dlen;
+	ctx->count_ctr += (uint64_t)dlen;
+
+	if (len > 0) {
+		/*
+		 * There is a partial block.
+		 */
+		size_t u;
+
+		memset(ctx->buf, 0, sizeof ctx->buf);
+		ctx->jc = (*ctx->bctx)->run(ctx->bctx, ctx->j0_1,
+			ctx->jc, ctx->buf, 16);
+		for (u = 0; u < len; u ++) {
+			unsigned x, y;
+
+			x = buf[u];
+			y = x ^ ctx->buf[u];
+			ctx->buf[u] = encrypt ? y : x;
+			buf[u] = y;
+		}
+		ctx->count_ctr += (uint64_t)len;
+	}
+}
+
+/* see bearssl_aead.h */
+void
+br_gcm_get_tag(br_gcm_context *ctx, void *tag)
+{
+	size_t ptr;
+	unsigned char tmp[16];
+
+	ptr = (size_t)ctx->count_ctr & (size_t)15;
+	if (ptr > 0) {
+		/*
+		 * There is a partial block: encrypted/decrypted data has
+		 * been produced, but the encrypted bytes must still be
+		 * processed by GHASH.
+		 */
+		ctx->gh(ctx->y, ctx->h, ctx->buf, ptr);
+	}
+
+	/*
+	 * Final block for GHASH: the AAD and plaintext lengths (in bits).
+	 */
+	br_enc64be(tmp, ctx->count_aad << 3);
+	br_enc64be(tmp + 8, ctx->count_ctr << 3);
+	ctx->gh(ctx->y, ctx->h, tmp, 16);
+
+	/*
+	 * Tag is the GHASH output XORed with the encryption of the
+	 * nonce with the initial counter value.
+	 */
+	memcpy(tag, ctx->y, 16);
+	(*ctx->bctx)->run(ctx->bctx, ctx->j0_1, ctx->j0_2, tag, 16);
+}
+
+/* see bearssl_aead.h */
+void
+br_gcm_get_tag_trunc(br_gcm_context *ctx, void *tag, size_t len)
+{
+	unsigned char tmp[16];
+
+	br_gcm_get_tag(ctx, tmp);
+	memcpy(tag, tmp, len);
+}
+
+/* see bearssl_aead.h */
+uint32_t
+br_gcm_check_tag_trunc(br_gcm_context *ctx, const void *tag, size_t len)
+{
+	unsigned char tmp[16];
+	size_t u;
+	int x;
+
+	br_gcm_get_tag(ctx, tmp);
+	x = 0;
+	for (u = 0; u < len; u ++) {
+		x |= tmp[u] ^ ((const unsigned char *)tag)[u];
+	}
+	return EQ0(x);
+}
+
+/* see bearssl_aead.h */
+uint32_t
+br_gcm_check_tag(br_gcm_context *ctx, const void *tag)
+{
+	return br_gcm_check_tag_trunc(ctx, tag, 16);
+}
+
+/* see bearssl_aead.h */
+const br_aead_class br_gcm_vtable = {
+	16,
+	(void (*)(const br_aead_class **, const void *, size_t))
+		&br_gcm_reset,
+	(void (*)(const br_aead_class **, const void *, size_t))
+		&br_gcm_aad_inject,
+	(void (*)(const br_aead_class **))
+		&br_gcm_flip,
+	(void (*)(const br_aead_class **, int, void *, size_t))
+		&br_gcm_run,
+	(void (*)(const br_aead_class **, void *))
+		&br_gcm_get_tag,
+	(uint32_t (*)(const br_aead_class **, const void *))
+		&br_gcm_check_tag,
+	(void (*)(const br_aead_class **, void *, size_t))
+		&br_gcm_get_tag_trunc,
+	(uint32_t (*)(const br_aead_class **, const void *, size_t))
+		&br_gcm_check_tag_trunc
+};