1 files changed, 399 insertions, 0 deletions
diff --git a/src/method_aes128_gcm.c b/src/method_aes128_gcm.c
new file mode 100644
index 0000000..139276c
--- /dev/null
+++ b/src/method_aes128_gcm.c
@@ -0,0 +1,399 @@
+/*
+  Copyright (c) 2012, Matthias Schiffer <mschiffer@universe-factory.net>
+  All rights reserved.
+
+  Redistribution and use in source and binary forms, with or without
+  modification, are permitted provided that the following conditions are met:
+
+    1. Redistributions of source code must retain the above copyright notice,
+       this list of conditions and the following disclaimer.
+    2. Redistributions in binary form must reproduce the above copyright notice,
+       this list of conditions and the following disclaimer in the documentation
+       and/or other materials provided with the distribution.
+
+  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+  AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+  IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+  DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+  FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+  DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+  SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+  CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+  OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+  OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+*/
+
+
+#include "fastd.h"
+#include <crypto_stream_aes128ctr.h>
+
+
+#define NONCEBYTES 7
+#define BLOCKBYTES 16
+
+
+struct _fastd_method_session_state {
+	struct timespec valid_till;
+	struct timespec refresh_after;
+
+	uint8_t d[crypto_stream_aes128ctr_BEFORENMBYTES];
+	uint8_t H[BLOCKBYTES];
+
+	uint8_t send_nonce[NONCEBYTES];
+	uint8_t receive_nonce[NONCEBYTES];
+
+	struct timespec receive_last;
+	uint64_t receive_reorder_seen;
+};
+
+
+static inline void increment_nonce(uint8_t nonce[NONCEBYTES]) {
+	nonce[0] += 2;
+
+	if (nonce[0] == 0 || nonce[0] == 1) {
+		int i;
+		for (i = 1; i < NONCEBYTES; i++) {
+			nonce[i]++;
+			if (nonce[i] != 0)
+				break;
+		}
+	}
+}
+
+static inline bool is_nonce_valid(const uint8_t nonce[NONCEBYTES], const uint8_t old_nonce[NONCEBYTES], int64_t *age) {
+	if ((nonce[0] & 1) != (old_nonce[0] & 1))
+		return false;
+
+	int i;
+	*age = 0;
+
+	for (i = NONCEBYTES-1; i >= 0; i--) {
+		*age *= 256;
+		*age += old_nonce[i]-nonce[i];
+	}
+
+	*age /= 2;
+	return true;
+}
+
+static size_t method_max_packet_size(fastd_context *ctx) {
+	return (fastd_max_packet_size(ctx) + NONCEBYTES + BLOCKBYTES);
+}
+
+
+static size_t method_min_encrypt_head_space(fastd_context *ctx) {
+	return 0;
+}
+
+static size_t method_min_decrypt_head_space(fastd_context *ctx) {
+	return 0;
+}
+
+static fastd_method_session_state* method_session_init(fastd_context *ctx, uint8_t *secret, size_t length, bool initiator) {
+	int i;
+
+	if (length < crypto_stream_aes128ctr_KEYBYTES)
+		exit_bug(ctx, "aes128-gcm: tried to init with short secret");
+
+	fastd_method_session_state *session = malloc(sizeof(fastd_method_session_state));
+
+	session->valid_till = ctx->now;
+	session->valid_till.tv_sec += ctx->conf->key_valid;
+
+	session->refresh_after = ctx->now;
+	session->refresh_after.tv_sec += ctx->conf->key_refresh;
+
+	crypto_stream_aes128ctr_beforenm(session->d, secret);
+
+	uint8_t zerononce[crypto_stream_aes128ctr_NONCEBYTES];
+	memset(zerononce, 0, crypto_stream_aes128ctr_NONCEBYTES);
+	crypto_stream_aes128ctr_afternm(session->H, BLOCKBYTES, zerononce, session->d);
+
+	session->send_nonce[0] = initiator ? 3 : 2;
+	session->receive_nonce[0] = initiator ? 0 : 1;
+
+	for (i = 1; i < NONCEBYTES; i++) {
+		session->send_nonce[i] = 0;
+		session->receive_nonce[i] = 0;
+	}
+
+	return session;
+}
+
+static bool method_session_is_valid(fastd_context *ctx, fastd_method_session_state *session) {
+	return (session && timespec_after(&session->valid_till, &ctx->now));
+}
+
+static bool method_session_is_initiator(fastd_context *ctx, fastd_method_session_state *session) {
+	return (session->send_nonce[0] & 1);
+}
+
+static bool method_session_want_refresh(fastd_context *ctx, fastd_method_session_state *session) {
+	return timespec_after(&ctx->now, &session->refresh_after);
+}
+
+static void method_session_free(fastd_context *ctx, fastd_method_session_state *session) {
+	if(session) {
+		memset(session, 0, sizeof(fastd_method_session_state));
+		free(session);
+	}
+}
+
+static void sel(uint8_t *out, const uint8_t *r, const uint8_t *s, unsigned int l, unsigned int b) {
+        unsigned int j;
+        unsigned int t;
+        uint8_t bminus1;
+
+        bminus1 = b - 1;
+        for (j = 0; j < l; ++j) {
+                t = bminus1 & (r[j] ^ s[j]);
+                out[j] = s[j] ^ t;
+        }
+}
+
+static inline void xor(uint8_t *x, const uint8_t *a, const uint8_t *b, unsigned int l) {
+	int i;
+	for (i = 0; i < l; i++)
+		x[i] = a[i] ^ b[i];
+}
+
+static inline void shl1(uint8_t *x, unsigned int l) {
+	int i;
+	uint8_t c = 0;
+
+	for (i = 0; i < l; i++) {
+		uint8_t c2 = x[i] >> 7;
+		x[i] = (x[i] << 1) | c;
+		c = c2;
+	}
+}
+
+static inline void shr1(uint8_t *x, unsigned int l) {
+	int i;
+	uint8_t c = 0;
+
+	for (i = l-1; i >= 0; i--) {
+		uint8_t c2 = x[i] & 1;
+		x[i] = (x[i] >> 1) | (c << 7);
+		c = c2;
+	}
+}
+
+static const uint8_t p[BLOCKBYTES] = {0x87};
+
+static void mul(uint8_t out[BLOCKBYTES], const uint8_t a[BLOCKBYTES], const uint8_t b[BLOCKBYTES]) {
+	uint8_t out2[2*BLOCKBYTES];
+	uint8_t zero[2*BLOCKBYTES];
+	uint8_t a2[2*BLOCKBYTES];
+	uint8_t b2[BLOCKBYTES];
+
+	memset(out2, 0, 2*BLOCKBYTES);
+	memset(zero, 0, 2*BLOCKBYTES);
+
+	memcpy(a2, a, BLOCKBYTES);
+	memset(a2+BLOCKBYTES, 0, BLOCKBYTES);
+
+	memcpy(b2, b, BLOCKBYTES);
+
+	int i;
+	for (i = 0; i < 8*BLOCKBYTES; i++) {
+		uint8_t tmp[2*BLOCKBYTES];
+
+		sel(tmp, zero, a2, 2*BLOCKBYTES, b2[0]&1);
+		xor(out2, out2, tmp, 2*BLOCKBYTES);
+
+		shl1(a2, 2*BLOCKBYTES);
+		shr1(b2, BLOCKBYTES);
+	}
+
+	uint8_t out3[BLOCKBYTES+1];
+	memcpy(out3, out2, BLOCKBYTES);
+	out3[BLOCKBYTES] = 0;
+
+	uint8_t p2[BLOCKBYTES+1];
+	memcpy(p2, p, BLOCKBYTES);
+	p2[BLOCKBYTES] = 0;
+
+	for (i = 0; i < 8*BLOCKBYTES; i++) {
+		uint8_t tmp[BLOCKBYTES+1];
+
+		sel(tmp, zero, p2, BLOCKBYTES+1, out2[BLOCKBYTES]&1);
+		xor(out3, out3, tmp, BLOCKBYTES+1);
+
+		shl1(p2, BLOCKBYTES+1);
+		shr1(out2+BLOCKBYTES, BLOCKBYTES);
+	}
+
+	memcpy(out, out3, BLOCKBYTES);
+	memcpy(p2, p, BLOCKBYTES);
+
+	for (i = 0; i < 8; i++) {
+		uint8_t tmp[2];
+
+		sel(tmp, zero, p2, 2, out3[BLOCKBYTES]&1);
+		xor(out, out, tmp, 2);
+
+		shl1(p2, BLOCKBYTES);
+		out3[BLOCKBYTES] >>= 1;
+	}
+}
+
+#define BLOCKPTR(buf, i) (((uint8_t*)(buf))+i*BLOCKBYTES)
+
+static bool method_encrypt(fastd_context *ctx, fastd_peer *peer, fastd_method_session_state *session, fastd_buffer *out, fastd_buffer in) {
+	*out = fastd_buffer_alloc(in.len, NONCEBYTES+BLOCKBYTES, 0);
+	uint8_t *sig = ((uint8_t*)out->data) - BLOCKBYTES;
+
+	memset(sig, 0, BLOCKBYTES);
+
+	uint8_t nonce[crypto_stream_aes128ctr_NONCEBYTES];
+	memcpy(nonce, session->send_nonce, NONCEBYTES);
+	memset(nonce+NONCEBYTES, 0, crypto_stream_aes128ctr_NONCEBYTES-NONCEBYTES-1);
+	nonce[crypto_stream_aes128ctr_NONCEBYTES-1] = 1;
+
+	uint8_t stream[in.len+BLOCKBYTES];
+	crypto_stream_aes128ctr_afternm(stream, in.len+BLOCKBYTES, nonce, session->d);
+
+	int blocks = (in.len+BLOCKBYTES-1)/BLOCKBYTES;
+
+	int i;
+	for (i = 0; i < blocks; i++) {
+		int len = BLOCKBYTES;
+		if (i == blocks-1)
+			len = in.len - i*BLOCKBYTES;
+
+		xor(BLOCKPTR(out->data, i), BLOCKPTR(in.data, i), BLOCKPTR(stream, i+1), len);
+
+		xor(sig, sig, BLOCKPTR(out->data, i), len);
+		mul(sig, sig, session->H);
+	}
+
+	sig[BLOCKBYTES-8] ^= (in.len >> 53) & 0xff;
+	sig[BLOCKBYTES-7] ^= (in.len >> 45) & 0xff;
+	sig[BLOCKBYTES-6] ^= (in.len >> 37) & 0xff;
+	sig[BLOCKBYTES-5] ^= (in.len >> 29) & 0xff;
+	sig[BLOCKBYTES-4] ^= (in.len >> 21) & 0xff;
+	sig[BLOCKBYTES-3] ^= (in.len >> 13) & 0xff;
+	sig[BLOCKBYTES-2] ^= (in.len >> 5) & 0xff;
+	sig[BLOCKBYTES-1] ^= (in.len << 3) & 0xff;
+	mul(sig, sig, session->H);
+
+	xor(sig, sig, stream, BLOCKBYTES);
+
+	fastd_buffer_free(in);
+
+	fastd_buffer_pull_head(out, NONCEBYTES+BLOCKBYTES);
+	memcpy(out->data, session->send_nonce, NONCEBYTES);
+	increment_nonce(session->send_nonce);
+
+	return true;
+}
+
+static bool method_decrypt(fastd_context *ctx, fastd_peer *peer, fastd_method_session_state *session, fastd_buffer *out, fastd_buffer in) {
+	if (in.len < NONCEBYTES+BLOCKBYTES)
+		return false;
+
+	if (!method_session_is_valid(ctx, session))
+		return false;
+
+	uint8_t nonce[crypto_stream_aes128ctr_NONCEBYTES];
+	memcpy(nonce, in.data, NONCEBYTES);
+	memset(nonce+NONCEBYTES, 0, crypto_stream_aes128ctr_NONCEBYTES-NONCEBYTES-1);
+	nonce[crypto_stream_aes128ctr_NONCEBYTES-1] = 1;
+
+	int64_t age;
+	if (!is_nonce_valid(nonce, session->receive_nonce, &age))
+		return false;
+
+	if (age >= 0) {
+		if (timespec_diff(&ctx->now, &session->receive_last) > ctx->conf->reorder_time*1000)
+			return false;
+
+		if (age > ctx->conf->reorder_count)
+			return false;
+	}
+
+	fastd_buffer_push_head(&in, NONCEBYTES+BLOCKBYTES);
+
+	*out = fastd_buffer_alloc(in.len, 0, 0);
+
+	uint8_t sig[BLOCKBYTES];
+	memset(sig, 0, BLOCKBYTES);
+
+	uint8_t stream[in.len+BLOCKBYTES];
+	crypto_stream_aes128ctr_afternm(stream, in.len+BLOCKBYTES, nonce, session->d);
+
+	int blocks = (in.len+BLOCKBYTES-1)/BLOCKBYTES;
+
+	int i;
+	for (i = 0; i < blocks; i++) {
+		int len = BLOCKBYTES;
+		if (i == blocks-1)
+			len = in.len - i*BLOCKBYTES;
+
+		xor(BLOCKPTR(out->data, i), BLOCKPTR(in.data, i), BLOCKPTR(stream, i+1), len);
+
+		xor(sig, sig, BLOCKPTR(in.data, i), len);
+		mul(sig, sig, session->H);
+	}
+
+	sig[BLOCKBYTES-8] ^= (in.len >> 53) & 0xff;
+	sig[BLOCKBYTES-7] ^= (in.len >> 45) & 0xff;
+	sig[BLOCKBYTES-6] ^= (in.len >> 37) & 0xff;
+	sig[BLOCKBYTES-5] ^= (in.len >> 29) & 0xff;
+	sig[BLOCKBYTES-4] ^= (in.len >> 21) & 0xff;
+	sig[BLOCKBYTES-3] ^= (in.len >> 13) & 0xff;
+	sig[BLOCKBYTES-2] ^= (in.len >> 5) & 0xff;
+	sig[BLOCKBYTES-1] ^= (in.len << 3) & 0xff;
+	mul(sig, sig, session->H);
+
+	xor(sig, sig, stream, BLOCKBYTES);
+
+	fastd_buffer_pull_head(&in, BLOCKBYTES);
+
+	if (memcmp(sig, in.data, BLOCKBYTES) != 0) {
+		fastd_buffer_free(*out);
+
+		/* restore input buffer */
+		fastd_buffer_pull_head(&in, NONCEBYTES);
+
+		return false;
+	}
+
+	fastd_buffer_free(in);
+
+	if (age < 0) {
+		session->receive_reorder_seen >>= age;
+		session->receive_reorder_seen |= (1 >> (age+1));
+		memcpy(session->receive_nonce, nonce, NONCEBYTES);
+		session->receive_last = ctx->now;
+	}
+	else if (age == 0 || session->receive_reorder_seen & (1 << (age-1))) {
+		pr_debug(ctx, "dropping duplicate packet from %P (age %u)", peer, (unsigned)age);
+		fastd_buffer_free(*out);
+		*out = fastd_buffer_alloc(0, 0, 0);
+	}
+	else {
+		pr_debug(ctx, "accepting reordered packet from %P (age %u)", peer, (unsigned)age);
+		session->receive_reorder_seen |= (1 << (age-1));
+	}
+
+	return true;
+}
+
+const fastd_method fastd_method_aes128_gcm = {
+	.name = "aes128-gcm",
+
+	.max_packet_size = method_max_packet_size,
+	.min_encrypt_head_space = method_min_encrypt_head_space,
+	.min_decrypt_head_space = method_min_decrypt_head_space,
+
+	.session_init = method_session_init,
+	.session_is_valid = method_session_is_valid,
+	.session_is_initiator = method_session_is_initiator,
+	.session_want_refresh = method_session_want_refresh,
+	.session_free = method_session_free,
+
+	.encrypt = method_encrypt,
+	.decrypt = method_decrypt,
+};