drafted header encryption

header_encryption.c

@@ -0,0 +1,104 @@
+#include <stdio.h>
+#include <stdint.h>
+
+// #include "n2n_wire.h"	// n2n_community_t
+#include "n2n.h"
+#include "speck.h"
+#include "portable_endian.h"
+
+
+uint32_t decryt_packet_header (uint8_t packet[], uint8_t packet_len,
+			       char * community_name, speck_ctx * ctx) {
+
+	// assemble IV
+	// the last four are ASCII "n2n!" and do not get overwritten
+	uint8_t iv[16] = { 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+			   0x00, 0x00, 0x00, 0x00, 0x6E, 0x32, 0x6E, 0x21 };
+	// the first 96 bits of the packet are used padded with ASCII "n2n!"
+	// to full 128 bit IV
+	memcopy (iv, packet, 12);
+
+	// alternatively, consider: pearson_hash_128 (iv, packet, 12)
+
+	// try community name as possible key and check for magic bytes
+	uint32_t magic = 0x6E326E00; // ="n2n_"
+	uint32_t test_magic;
+	// check for magic bytes and resonable value in header len field
+	speck_he ((uint8_t*)&test_magic, &packet[12], 4, iv, ctx);
+	test_magic = be32toh (test_magic);
+	if ( ((test_magic <<  8) == magic)
+	  && ((test_magic >> 24) <= packet_len) // (test_masgic >> 24) is header_len
+	   ) {
+		speck_he (&packet[12], &packet[12], (test_magic >> 24) - 12, iv, ctx);
+		// restore original packet order
+		memcpy (&packet[0], &packet[16], 4);
+		memcpy (&packet[4], community_name, N2N_COMMUNITY_SIZE);
+		return (1); // successful
+	} else
+		return (0); // unsuccessful
+}
+
+
+int32_t decryt_packet_header_if_required (uint8_t packet[], uint16_t packet_len,
+					   struct sn_community *communities) {
+
+	if (packet_len < 20)
+		return (-1);
+
+	// first, check if header is unenrypted to put it into the fast-lane then
+
+	// the following check is around 99.99962 percent reliable
+	// it heavily relies on the structure of packet's common part
+	// changes to wire.c:encode/decode_common need to go together with this code
+	if ( (packet[19] == (uint8_t)0x00)	// null terminated community name
+	  && (packet[00] == N2N_PKT_VERSION)	// correct packet version
+//	  && (packet[01] <= N2N_DEFAULT_TTL) 	// reasonable TTL -- might interfere with hole-punching-related or cli passed higher values ?!
+	  && ((be16toh (*(uint16_t*)&(packet[02])) & N2N_FLAGS_TYPE_MASK ) <= MSG_TYPE_MAX_TYPE  ) // message type
+	  && ( be16toh (*(uint16_t*)&(packet[02])) < N2N_FLAGS_OPTIONS)	// flags
+	   ) {
+
+		// most probably unencrypted
+		return (1);
+
+	} else {
+
+		// most probably encrypted
+		// cycle through the known communities (as keys) to eventually decrypt
+		int32_t ret;
+		struct sn_community *c, *tmp;
+		HASH_ITER (hh, communities, c, tmp) {
+			// check if this is an encrypted community
+			if ( ret = decrypt_packet_header (packet, packet_len, c->community, c-> ctx) ) {
+				// no upgrade from unencrypted to encrypted
+				if (c->header_encryption == 1)
+					return (-2);
+				// set to 'encrypted'
+				 c->header_encryption = 2;
+				// no need to test any further
+				return (2);
+			}
+		}
+		// no match
+		return (-3);
+	}
+}
+
+
+int32_t encryt_packet_header (uint8_t packet[], uint8_t header_len, speck_ctx * ctx) {
+
+	if (header_len < 20)
+		return (-1);
+
+	memcpy (&packet[16], &packet[00], 4);
+
+	uint8_t iv[16];
+	((uint64_t*)iv)[0] = n2n_rand ();
+	((uint64_t*)iv)[1] = n2n_rand ();
+
+	const uint32_t magic = 0x006E326E;
+	((uint32_t*)iv)[3] = htobe32 (magic);
+
+	iv[12] = header_len;
+
+	speck_he (&packet[12], &packet[12], header_len - 12, iv, ctx);
+}

speck.c

@@ -1,4 +1,4 @@
-// cipher SPECK -- 128 bit block size -- 256 bit key size
+// cipher SPECK -- 128 bit block size -- 256 bit key size -- CTR mode
 // taken from (and modified: removed pure crypto-stream generation and seperated key expansion)
 // https://github.com/nsacyber/simon-speck-supercop/blob/master/crypto_stream/speck128256ctr/
 
@@ -565,9 +565,9 @@ int speck_expand_key (const unsigned char *k, speck_context_t *ctx) {
 #else 		// plain C ----------------------------------------------------------------
 
 
-#define ROR64(x,r) (((x)>>(r))|((x)<<(64-(r))))
+#define ROR(x,r) (((x)>>(r))|((x)<<(64-(r))))
-#define ROL64(x,r) (((x)<<(r))|((x)>>(64-(r))))
+#define ROL(x,r) (((x)<<(r))|((x)>>(64-(r))))
-#define R(x,y,k) (x=ROR64(x,8), x+=y, x^=k, y=ROL64(y,3), y^=x)
+#define R(x,y,k) (x=ROR(x,8), x+=y, x^=k, y=ROL(y,3), y^=x)
 
 
 static int speck_encrypt (u64 *u, u64 *v, speck_context_t *ctx) {
@@ -642,6 +642,85 @@ int speck_expand_key (const unsigned char *k, speck_context_t *ctx) {
 #endif		// AVX, SSE, NEON, plain C ------------------------------------------------
 
 
+// cipher SPECK -- 128 bit block size -- 128 bit key size -- CTR mode
+// used for header encryption, thus the prefix 'he_'
+// for now: just plain C -- AVX, SSE, NEON might follow
+
+#define ROR64(x,r) (((x)>>(r))|((x)<<(64-(r))))
+#define ROL64(x,r) (((x)<<(r))|((x)>>(64-(r))))
+#define R64(x,y,k) (x=ROR64(x,8), x+=y, x^=k, y=ROL64(y,3), y^=x)
+
+
+static int speck_encrypt_he (u64 *u, u64 *v, speck_context_t *ctx) {
+
+  u64 i, x=*u, y=*v;
+
+  for (i = 0; i < 32; i++)
+    R64 (x, y, ctx->key[i]);
+
+  *u = x; *v = y;
+
+  return 0;
+}
+
+
+int speck_he (unsigned char *out, const unsigned char *in, unsigned long long inlen,
+	      const unsigned char *n, speck_context_t *ctx) {
+
+  u64 i, nonce[2], x, y, t;
+  unsigned char *block = malloc(16);
+
+  if (!inlen) {
+    free (block);
+    return 0;
+  }
+  nonce[0] = htole64 ( ((u64*)n)[0] );
+  nonce[1] = htole64 ( ((u64*)n)[1] );
+
+  t = 0;
+  while (inlen >= 16) {
+    x = nonce[1]; y = nonce[0]; nonce[0]++;
+    speck_encrypt_he (&x, &y, ctx);
+    ((u64 *)out)[1+t] = htole64 (x ^ ((u64 *)in)[1+t]);
+    ((u64 *)out)[0+t] = htole64 (y ^ ((u64 *)in)[0+t]);
+    t += 2;
+    inlen -= 16;
+  }
+
+  if (inlen > 0) {
+    x = nonce[1]; y = nonce[0];
+    speck_encrypt_he (&x, &y, ctx);
+    ((u64 *)block)[1] = htole64 (x); ((u64 *)block)[0] = htole64 (y);
+    for (i = 0; i < inlen; i++)
+      out[i+8*t] = block[i] ^ in[i+8*t];
+  }
+
+  free(block);
+  return 0;
+}
+
+
+int speck_expand_key_he (const unsigned char *k, speck_context_t *ctx) {
+
+  u64 A, B;
+  u64 i;
+
+  A = htole64 ( ((u64 *)k)[0] );
+  B = htole64 ( ((u64 *)k)[1] );
+
+  for (i = 0; i < 32; i ++) {
+    ctx->key[i] = A;
+    R64 ( B, A, i);
+  }
+  return 1;
+}
+
+
+// code for testing -- to be removed when finished
+/*
+#include <stdio.h> // for testing
+#include <string.h>
+
 int speck_test () {
 
   uint8_t key[32] = { 0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07,
@@ -649,16 +728,23 @@ int speck_test () {
 		      0x10, 0x11, 0x12, 0x13, 0x14, 0x15, 0x16, 0x17,
 		      0x18, 0x19, 0x1A, 0x1B, 0x1C, 0x1D, 0x1E, 0x1F };
 
-
   uint8_t iv[16]  = { 0x70, 0x6f, 0x6f, 0x6e, 0x65, 0x72, 0x2e, 0x20,
 		      0x49, 0x6e, 0x20, 0x74, 0x68, 0x6f, 0x73, 0x65 };
 
+  uint8_t xv[16]  = { 0x20, 0x6d, 0x61, 0x64, 0x65, 0x20, 0x69, 0x74,
+		      0x20, 0x65, 0x71, 0x75, 0x69, 0x76, 0x61, 0x6c };
+
+
   uint8_t pt[16]  = { 0x00 };
 
   // expected outcome (according to pp. 35 & 36 of Implementation Guide)
   uint8_t ct[16]  = { 0x43, 0x8f, 0x18, 0x9c, 0x8d, 0xb4, 0xee, 0x4e,
 		      0x3e, 0xf5, 0xc0, 0x05, 0x04, 0x01, 0x09, 0x41 };
 
+  uint8_t xt[16]  = { 0x18, 0x0d, 0x57, 0x5c, 0xdf, 0xfe, 0x60, 0x78,
+		      0x65, 0x32, 0x78, 0x79, 0x51, 0x98, 0x5d, 0xa6 };
+
+
   speck_context_t ctx;
 
   speck_expand_key (key, &ctx);
@@ -667,24 +753,35 @@ int speck_test () {
 #else
   speck_ctr (pt, pt, 16, iv, &ctx);
 #endif
+
   u64 i;
-  // fprintf (stderr, "rk00: %016llx\n",  ctx.key[0]);
+   fprintf (stderr, "rk00: %016llx\n",  ctx.key[0]);
-  // fprintf (stderr, "rk33: %016llx\n",  ctx.key[33]);
+   fprintf (stderr, "rk33: %016llx\n",  ctx.key[33]);
-  // fprintf (stderr, "out : %016lx\n", *(uint64_t*)pt);
+   fprintf (stderr, "out : %016lx\n", *(uint64_t*)pt);
-  // fprintf (stderr, "mem : " ); for (i=0; i < 16; i++) fprintf (stderr, "%02x ", pt[i]); fprintf (stderr, "\n");
+   fprintf (stderr, "mem : " ); for (i=0; i < 16; i++) fprintf (stderr, "%02x ", pt[i]); fprintf (stderr, "\n");
 
   int ret = 1;
   for (i=0; i < 16; i++)
     if (pt[i] != ct[i]) ret = 0;
 
+  memset (pt, 0, 16);
+  speck_expand_key_he (key, &ctx);
+  speck_he (pt, pt, 16, xv, &ctx);
+
+   fprintf (stderr, "rk00: %016llx\n",  ctx.key[0]);
+   fprintf (stderr, "rk31: %016llx\n",  ctx.key[31]);
+   fprintf (stderr, "out : %016lx\n", *(uint64_t*)pt);
+   fprintf (stderr, "mem : " ); for (i=0; i < 16; i++) fprintf (stderr, "%02x ", pt[i]); fprintf (stderr, "\n");
+
+  for (i=0; i < 16; i++)
+    if (pt[i] != xt[i]) ret = 0;
+
   return (ret);
 }
 
-/*
-#include <stdio.h> // for testing
 
-  int main (int argc, char* argv[]) {
+int main (int argc, char* argv[]) {
 
   fprintf (stdout, "SPECK SELF TEST RESULT: %u\n", speck_test (0,NULL));
-  }
+}
 */

speck.h

@@ -54,3 +54,10 @@ speck_context_t *ctx);
 
 
 int speck_expand_key (const unsigned char *k, speck_context_t *ctx);
+
+
+int speck_he (unsigned char *out, const unsigned char *in, unsigned long long inlen,
+              const unsigned char *n, speck_context_t *ctx);
+
+
+int speck_expand_key_he (const unsigned char *k, speck_context_t *ctx);