cts128.c: add support for NIST "Ciphertext Stealing" proposal.

crypto/modes/cts128.c

@@ -23,8 +23,9 @@
  * deviates from mentioned RFCs. Most notably it allows input to be
  * of block length and it doesn't flip the order of the last two
  * blocks. CTS is being discussed even in ECB context, but it's not
- * adopted for any known application. This implementation complies
- * with mentioned RFCs and [as such] extends CBC mode.
+ * adopted for any known application. This implementation provides
+ * two interfaces: one compliant with above mentioned RFCs and one
+ * compliant with the NIST proposal, both extending CBC mode.
  */
 
 size_t CRYPTO_cts128_encrypt_block(const unsigned char *in, unsigned char *out,
@@ -54,6 +55,34 @@ size_t CRYPTO_cts128_encrypt_block(const unsigned char *in, unsigned char *out,
 	return len+residue;
 }
 
+size_t CRYPTO_nistcts128_encrypt_block(const unsigned char *in, unsigned char *out,
+			size_t len, const void *key,
+			unsigned char ivec[16], block128_f block)
+{	size_t residue, n;
+
+	assert (in && out && key && ivec);
+
+	if (len < 16) return 0;
+
+	residue=len%16;
+
+	len -= residue;
+
+	CRYPTO_cbc128_encrypt(in,out,len,key,ivec,block);
+
+	if (residue==0)	return len;
+
+	in  += len;
+	out += len;
+
+	for (n=0; n<residue; ++n)
+		ivec[n] ^= in[n];
+	(*block)(ivec,ivec,key);
+	memcpy(out-16+residue,ivec,16);
+
+	return len+residue;
+}
+
 size_t CRYPTO_cts128_encrypt(const unsigned char *in, unsigned char *out,
 			size_t len, const void *key,
 			unsigned char ivec[16], cbc128_f cbc)
@@ -90,6 +119,41 @@ size_t CRYPTO_cts128_encrypt(const unsigned char *in, unsigned char *out,
 	return len+residue;
 }
 
+size_t CRYPTO_nistcts128_encrypt(const unsigned char *in, unsigned char *out,
+			size_t len, const void *key,
+			unsigned char ivec[16], cbc128_f cbc)
+{	size_t residue;
+	union { size_t align; unsigned char c[16]; } tmp;
+
+	assert (in && out && key && ivec);
+
+	if (len < 16) return 0;
+
+	residue=len%16;
+
+	len -= residue;
+
+	(*cbc)(in,out,len,key,ivec,1);
+
+	if (residue==0) return len;
+
+	in  += len;
+	out += len;
+
+#if defined(CBC_HANDLES_TRUNCATED_IO)
+	(*cbc)(in,out-16+residue,residue,key,ivec,1);
+#else
+	{
+	size_t n;
+	for (n=0; n<16; n+=sizeof(size_t))
+		*(size_t *)(tmp.c+n) = 0;
+	memcpy(tmp.c,in,residue);
+	}
+	(*cbc)(tmp.c,out-16+residue,16,key,ivec,1);
+#endif
+	return len+residue;
+}
+
 size_t CRYPTO_cts128_decrypt_block(const unsigned char *in, unsigned char *out,
 			size_t len, const void *key,
 			unsigned char ivec[16], block128_f block)
@@ -125,7 +189,51 @@ size_t CRYPTO_cts128_decrypt_block(const unsigned char *in, unsigned char *out,
 	for(residue+=16; n<residue; ++n)
 		out[n] = tmp.c[n] ^ in[n];
 
-	return len+residue-16;
+	return 16+len+residue;
+}
+
+size_t CRYPTO_nistcts128_decrypt_block(const unsigned char *in, unsigned char *out,
+			size_t len, const void *key,
+			unsigned char ivec[16], block128_f block)
+{	size_t residue, n;
+	union { size_t align; unsigned char c[32]; } tmp;
+
+	assert (in && out && key && ivec);
+
+	if (len<16) return 0;
+
+	residue=len%16;
+
+	if (residue==0) {
+		CRYPTO_cbc128_decrypt(in,out,len,key,ivec,block);
+		return len;
+	}
+
+	len -= 16+residue;
+
+	if (len) {
+		CRYPTO_cbc128_decrypt(in,out,len,key,ivec,block);
+		in  += len;
+		out += len;
+	}
+
+	(*block)(in+residue,tmp.c+16,key);
+
+	for (n=0; n<16; n+=sizeof(size_t))
+		*(size_t *)(tmp.c+n) = *(size_t *)(tmp.c+16+n);
+	memcpy(tmp.c,in,residue);
+	(*block)(tmp.c,tmp.c,key);
+
+	for(n=0; n<16; ++n) {
+		unsigned char c = in[n];
+		out[n] = tmp.c[n] ^ ivec[n];
+		ivec[n] = in[n+residue];
+		tmp.c[n] = c;
+	}
+	for(residue+=16; n<residue; ++n)
+		out[n] = tmp.c[n] ^ tmp.c[n-16];
+
+	return 16+len+residue;
 }
 
 size_t CRYPTO_cts128_decrypt(const unsigned char *in, unsigned char *out,
@@ -160,7 +268,47 @@ size_t CRYPTO_cts128_decrypt(const unsigned char *in, unsigned char *out,
 	(*cbc)(tmp.c,tmp.c,32,key,ivec,0);
 	memcpy(out,tmp.c,16+residue);
 #endif
-	return len+residue;
+	return 16+len+residue;
+}
+
+size_t CRYPTO_nistcts128_decrypt(const unsigned char *in, unsigned char *out,
+			size_t len, const void *key,
+			unsigned char ivec[16], cbc128_f cbc)
+{	size_t residue, n;
+	union { size_t align; unsigned char c[32]; } tmp;
+
+	assert (in && out && key && ivec);
+
+	if (len<16) return 0;
+
+	residue=len%16;
+
+	if (residue==0) {
+		(*cbc)(in,out,len,key,ivec,0);
+		return len;
+	}
+
+	len -= 16+residue;
+
+	if (len) {
+		(*cbc)(in,out,len,key,ivec,0);
+		in  += len;
+		out += len;
+	}
+
+	for (n=16; n<32; n+=sizeof(size_t))
+		*(size_t *)(tmp.c+n) = 0;
+	/* this places in[16] at &tmp.c[16] and decrypted block at &tmp.c[0] */
+	(*cbc)(in+residue,tmp.c,16,key,tmp.c+16,0);
+
+	memcpy(tmp.c,in,residue);
+#if defined(CBC_HANDLES_TRUNCATED_IO)
+	(*cbc)(tmp.c,out,16+residue,key,ivec,0);
+#else
+	(*cbc)(tmp.c,tmp.c,32,key,ivec,0);
+	memcpy(out,tmp.c,16+residue);
+#endif
+	return 16+len+residue;
 }
 
 #if defined(SELFTEST)
@@ -200,9 +348,8 @@ static const unsigned char vector_64[64] =
 static AES_KEY encks, decks;
 
 void test_vector(const unsigned char *vector,size_t len)
-{	unsigned char cleartext[64];
-	unsigned char iv[sizeof(test_iv)];
-	unsigned char ciphertext[64];
+{	unsigned char iv[sizeof(test_iv)];
+	unsigned char cleartext[64],ciphertext[64];
 	size_t tail;
 
 	printf("vector_%d\n",len); fflush(stdout);
@@ -243,7 +390,57 @@ void test_vector(const unsigned char *vector,size_t len)
 		fprintf(stderr,"iv_%d mismatch\n",len), exit(4);
 }
 
-main()
+void test_nistvector(const unsigned char *vector,size_t len)
+{	unsigned char iv[sizeof(test_iv)];
+	unsigned char cleartext[64],ciphertext[64],nistvector[64];
+	size_t tail;
+
+	printf("nistvector_%d\n",len); fflush(stdout);
+
+	if ((tail=len%16) == 0) tail = 16;
+
+	len -= 16 + tail;
+	memcpy(nistvector,vector,len);
+	/* flip two last blocks */
+	memcpy(nistvector+len,vector+len+16,tail);
+	memcpy(nistvector+len+tail,vector+len,16);
+	len += 16 + tail;
+	tail = 16;
+
+	/* test block-based encryption */
+	memcpy(iv,test_iv,sizeof(test_iv));
+	CRYPTO_nistcts128_encrypt_block(test_input,ciphertext,len,&encks,iv,(block128_f)AES_encrypt);
+	if (memcmp(ciphertext,nistvector,len))
+		fprintf(stderr,"output_%d mismatch\n",len), exit(1);
+	if (memcmp(iv,nistvector+len-tail,sizeof(iv)))
+		fprintf(stderr,"iv_%d mismatch\n",len), exit(1);
+
+	/* test block-based decryption */
+	memcpy(iv,test_iv,sizeof(test_iv));
+	CRYPTO_nistcts128_decrypt_block(ciphertext,cleartext,len,&decks,iv,(block128_f)AES_decrypt);
+	if (memcmp(cleartext,test_input,len))
+		fprintf(stderr,"input_%d mismatch\n",len), exit(2);
+	if (memcmp(iv,nistvector+len-tail,sizeof(iv)))
+		fprintf(stderr,"iv_%d mismatch\n",len), exit(2);
+
+	/* test streamed encryption */
+	memcpy(iv,test_iv,sizeof(test_iv));
+	CRYPTO_nistcts128_encrypt(test_input,ciphertext,len,&encks,iv,(cbc128_f)AES_cbc_encrypt);
+	if (memcmp(ciphertext,nistvector,len))
+		fprintf(stderr,"output_%d mismatch\n",len), exit(3);
+	if (memcmp(iv,nistvector+len-tail,sizeof(iv)))
+		fprintf(stderr,"iv_%d mismatch\n",len), exit(3);
+
+	/* test streamed decryption */
+	memcpy(iv,test_iv,sizeof(test_iv));
+	CRYPTO_nistcts128_decrypt(ciphertext,cleartext,len,&decks,iv,(cbc128_f)AES_cbc_encrypt);
+	if (memcmp(cleartext,test_input,len))
+		fprintf(stderr,"input_%d mismatch\n",len), exit(4);
+	if (memcmp(iv,nistvector+len-tail,sizeof(iv)))
+		fprintf(stderr,"iv_%d mismatch\n",len), exit(4);
+}
+
+int main()
 {
 	AES_set_encrypt_key(test_key,128,&encks);
 	AES_set_decrypt_key(test_key,128,&decks);
@@ -254,6 +451,14 @@ main()
 	test_vector(vector_47,sizeof(vector_47));
 	test_vector(vector_48,sizeof(vector_48));
 	test_vector(vector_64,sizeof(vector_64));
-	exit(0);
+
+	test_nistvector(vector_17,sizeof(vector_17));
+	test_nistvector(vector_31,sizeof(vector_31));
+	test_nistvector(vector_32,sizeof(vector_32));
+	test_nistvector(vector_47,sizeof(vector_47));
+	test_nistvector(vector_48,sizeof(vector_48));
+	test_nistvector(vector_64,sizeof(vector_64));
+
+	return 0;
 }
 #endif

crypto/modes/modes.h

@@ -57,3 +57,16 @@ size_t CRYPTO_cts128_decrypt_block(const unsigned char *in, unsigned char *out,
 size_t CRYPTO_cts128_decrypt(const unsigned char *in, unsigned char *out,
 			size_t len, const void *key,
 			unsigned char ivec[16], cbc128_f cbc);
+
+size_t CRYPTO_nistcts128_encrypt_block(const unsigned char *in, unsigned char *out,
+			size_t len, const void *key,
+			unsigned char ivec[16], block128_f block);
+size_t CRYPTO_nistcts128_encrypt(const unsigned char *in, unsigned char *out,
+			size_t len, const void *key,
+			unsigned char ivec[16], cbc128_f cbc);
+size_t CRYPTO_nistcts128_decrypt_block(const unsigned char *in, unsigned char *out,
+			size_t len, const void *key,
+			unsigned char ivec[16], block128_f block);
+size_t CRYPTO_nistcts128_decrypt(const unsigned char *in, unsigned char *out,
+			size_t len, const void *key,
+			unsigned char ivec[16], cbc128_f cbc);