Added base16 encoding/decoding, as well as a wrapper around SHA256

Makefile

@@ -3,7 +3,7 @@ DEBUG = true
 export DEBUG
 
 OBJS = crypto/rsa.o crypto/encoding/base58.o crypto/encoding/base64.o \
-	crypto/encoding/x509.o thirdparty/mbedtls/*.o
+	crypto/encoding/x509.o thirdparty/mbedtls/*.o crypto/encoding/base16.o
 
 
 compile: 

crypto/encoding/Makefile

@@ -2,8 +2,8 @@ CC = gcc
 CFLAGS = -O0 -I../../include -g3
 LFLAGS =
 DEPS = ../../include/libp2p/crypto/encoding/base58.h ../../include/libp2p/crypto/encoding/base64.h \
-	../../include/libp2p/crypto/encoding/x509.h
-OBJS = base58.o base64.o x509.o
+	../../include/libp2p/crypto/encoding/x509.h ../../include/libp2p/crypto/encoding/base16.h
+OBJS = base58.o base64.o x509.o base16.o
 
 %.o: %.c $(DEPS)
 	$(CC) -c -o $@ $< $(CFLAGS)

crypto/encoding/base16.c

@@ -0,0 +1,76 @@
+#include <string.h>
+#include <stdio.h>
+
+#include "libp2p/crypto/encoding/base16.h"
+
+/**
+ * Encode in Base16 format
+ * @param incoming the incoming bytes
+ * @param incoming_length the length of the incoming bytes
+ * @param results where to put the results
+ * @param results_length the size of the buffer, and returns the actual length used
+ * @returns true(1) on success
+ */
+int libp2p_crypto_encoding_base16_encode(const unsigned char* incoming, size_t incoming_length, unsigned char* results, size_t* results_length) {
+	// the size will be 2x the size of incoming, so check that
+	if (*results_length < incoming_length * 2)
+		return 0;
+
+	// clear out the results variable
+	memset(results, 0, *results_length);
+
+	*results_length = 0;
+	for(int i = 0; i < incoming_length; i++) {
+		unsigned char buf[3];
+		sprintf(buf, "%02x", incoming[i]);
+		results[i * 2] = buf[0];
+		results[i * 2 + 1] = buf[1];
+		*results_length += 2;
+	}
+
+	return 1;
+}
+
+/**
+ * Calculate the size of the buffer necessary to encode
+ * @param incoming_length the length of the incoming value
+ * @returns the size of the buffer necessary to hold the encoded bytes
+ */
+int libp2p_crypto_encoding_base16_encode_size(size_t incoming_length) {
+	return incoming_length * 2;
+}
+
+/**
+ * Decode from Base16 format
+ * @param incoming the incoming base16 encoded string
+ * @param incoming_length the length of the incoming string (no need to include null)
+ * @param results where to put the results
+ * @param results_length the size of the buffer, and returns the actual length used
+ * @returns true(1) on success
+ */
+int libp2p_crypto_encoding_base16_decode(const unsigned char* incoming, size_t incoming_length, unsigned char* results, size_t* results_length) {
+
+	// buffer too small
+	if (*results_length < incoming_length / 2)
+		return 0;
+
+	memset(results, 0, *results_length);
+
+	unsigned char* pos = (char*)incoming;
+
+	for(int i = 0; i < incoming_length / 2; i++) {
+		sscanf(pos, "%2hhx", &results[i]);
+		pos += 2;
+	}
+	return 1;
+}
+
+/**
+ * Calculate the size of the buffer necessary to decode
+ * @param incoming_length the length of the incoming value
+ * @returns the size of the buffer necessary to hold the decoded bytes
+ */
+int libp2p_crypto_encoding_base16_decode_size(size_t incoming_length) {
+	return incoming_length / 2;
+}
+

crypto/encoding/base58.c

@@ -170,32 +170,27 @@ int libp2p_crypto_encoding_base58_encode(const unsigned char* data, size_t binsz
 	return 1;
 }
 
-/***
- * calculate the size of the binary results based on an incoming base58 string
- * @param base58_string the string
- * @returns the size in bytes had the string been decoded
+/**
+ * calculate the max length in bytes of an encoding of n source bytes
+ * @param encoded_size the size of the encoded string
+ * @returns the maximum size in bytes had the string been decoded
  */
-size_t libp2p_crypto_encoding_base58_decode_size(const unsigned char* base58_string) {
-	size_t string_length = strlen((char*)base58_string);
-	size_t decoded_length = 0;
+size_t libp2p_crypto_encoding_base58_decode_size(size_t encoded_size) {
 	size_t radix = strlen(b58digits_ordered);
-	double bits_per_digit = log2(radix);
+	double bits_per_digit = log2(radix); // each char represents about 6 bits
 	
-	decoded_length = floor(string_length * bits_per_digit / 8);
-	return decoded_length;
+	return ceil(encoded_size * bits_per_digit / 8);
 }
 
 /**
- * calculate the max length in bytes of an encoding of n source bits
- * @param base58_string the string
- * @returns the maximum size in bytes had the string been decoded
+ * calculate the max length in bytes of a decoding of n source bytes
+ * @param decoded_size the size of the incoming string to be encoded
+ * @returns the maximum size in bytes had the string been encoded
  */
-size_t libp2p_crypto_encoding_base58_decode_max_size(const unsigned char* base58_string) {
-	size_t string_length = strlen((char*)base58_string);
-	size_t decoded_length = 0;
+size_t libp2p_crypto_encoding_base58_encode_size(size_t decoded_size) {
 	size_t radix = strlen(b58digits_ordered);
 	double bits_per_digit = log2(radix);
+	// each character
 	
-	decoded_length = ceil(string_length * bits_per_digit / 8);
-	return decoded_length;
+	return ceil( 8 / bits_per_digit * decoded_size);
 }

crypto/encoding/base64.c

@@ -7,6 +7,8 @@
 //
 
 #include <stdio.h>
+#include <math.h>
+
 #include "mbedtls/base64.h"
 
 /**
@@ -23,12 +25,6 @@ int libp2p_crypto_encoding_base64_encode(const unsigned char* input_data, size_t
 	return retVal == 0;
 }
 
-size_t libp2p_crypto_encoding_base64_encode_length(const unsigned char* input_data, size_t input_length) {
-	size_t req_bytes;
-	mbedtls_base64_encode(NULL, 0, &req_bytes, input_data, input_length);
-	return req_bytes;
-}
-
 /**
  * decode something that was encoded as base64
  * @param input_data the data to decode
@@ -43,8 +39,27 @@ int libp2p_crypto_encoding_base64_decode(const unsigned char* input_data, size_t
 	return retVal == 0;
 }
 
-size_t libp2p_crypto_encoding_base64_decode_length(const unsigned char* input_data, size_t input_length) {
-	size_t req_bytes;
-	mbedtls_base64_decode(NULL, 0, &req_bytes, input_data, input_length);
-	return req_bytes;
+/**
+ * calculate the max length in bytes of an encoding of n source bytes
+ * @param encoded_size the size of the encoded string
+ * @returns the maximum size in bytes had the string been decoded
+ */
+size_t libp2p_crypto_encoding_base64_decode_size(size_t encoded_size) {
+	size_t radix = 64;
+	double bits_per_digit = log2(radix); // each char represents about 6 bits
+
+	return ceil(encoded_size * bits_per_digit / 8);
 }
+
+/**
+ * calculate the max length in bytes of a decoding of n source bytes
+ * @param decoded_size the size of the incoming string to be encoded
+ * @returns the maximum size in bytes had the string been encoded
+ */
+size_t libp2p_crypto_encoding_base64_encode_size(size_t decoded_size) {
+	size_t radix = 64;
+	double bits_per_digit = log2(radix);
+
+	return ceil( 8 / bits_per_digit * decoded_size);
+}
+

include/libp2p/crypto/encoding/base16.h

@@ -0,0 +1,35 @@
+#include <stddef.h>
+
+/**
+ * Encode in Base16 format
+ * @param incoming the incoming bytes
+ * @param incoming_length the length of the incoming bytes
+ * @param results where to put the results
+ * @param results_length the size of the buffer, and returns the actual length used
+ * @returns true(1) on success
+ */
+int libp2p_crypto_encoding_base16_encode(const unsigned char* incoming, size_t incoming_length, unsigned char* results, size_t* results_length);
+
+/**
+ * Calculate the size of the buffer necessary to encode
+ * @param incoming_length the length of the incoming value
+ * @returns the size of the buffer necessary to hold the encoded bytes
+ */
+int libp2p_crypto_encoding_base16_encode_size(size_t incoming_length);
+
+/**
+ * Decode from Base16 format
+ * @param incoming the incoming base16 encoded string
+ * @param incoming_length the length of the incoming string (no need to include null)
+ * @param results where to put the results
+ * @param results_length the size of the buffer, and returns the actual length used
+ * @returns true(1) on success
+ */
+int libp2p_crypto_encoding_base16_decode(const unsigned char* incoming, size_t incoming_length, unsigned char* results, size_t* results_length);
+
+/**
+ * Calculate the size of the buffer necessary to decode
+ * @param incoming_length the length of the incoming value
+ * @returns the size of the buffer necessary to hold the decoded bytes
+ */
+int libp2p_crypto_encoding_base16_decode_size(size_t incoming_length);

include/libp2p/crypto/encoding/base58.h

@@ -30,18 +30,18 @@ int libp2p_crypto_encoding_base58_decode(const unsigned char* base58, size_t bas
 int libp2p_crypto_encoding_base58_encode(const unsigned char* binary_data, size_t binary_data_size, unsigned char** base58, size_t* base58_size);
 
 /***
- * calculate the size of the binary results based on an incoming base58 string with no initial padding
- * @param base58_string the string
- * @returns the size in bytes had the string been decoded
+ * calculate the size of the results based on an incoming string
+ * @param decoded_length the length of the string to be encoded
+ * @returns the size in bytes had the string been encoded
  */
-size_t libp2p_crypto_encoding_base58_decode_size(const unsigned char* base58_string);
+size_t libp2p_crypto_encoding_base58_encode_size(size_t decoded_length);
 
 /**
- * calculate the max length in bytes of an encoding of n source bits
- * @param base58_string the string
+ * calculate the max length in bytes of an encoding of n source bytes
+ * @param encoded_length the length of the string to be decoded
  * @returns the maximum size in bytes had the string been decoded
  */
-size_t libp2p_crypto_encoding_base58_decode_max_size(const unsigned char* base58_string);
+size_t libp2p_crypto_encoding_base58_decode_size(size_t encoded_length);
 
 
 #endif /* base58_h */

include/libp2p/crypto/encoding/base64.h

@@ -22,7 +22,12 @@
  */
 int libp2p_crypto_encoding_base64_encode(const unsigned char* input_data, size_t input_length, unsigned char* output_data, size_t max_output_length, size_t* bytes_written);
 
-size_t base64_encode_length(const unsigned char* input_data, size_t input_length);
+/**
+ * calculate the max length in bytes of an encoding of n source bytes
+ * @param encoded_size the size of the encoded string
+ * @returns the maximum size in bytes had the string been decoded
+ */
+size_t libp2p_crypto_encoding_base64_encode_size(size_t input_length);
 
 /**
  * decode something that was encoded as base64
@@ -35,6 +40,11 @@ size_t base64_encode_length(const unsigned char* input_data, size_t input_length
  */
 int libp2p_crypto_encoding_base64_decode(const unsigned char* input_data, size_t input_length, unsigned char* output_data, size_t max_output_length, size_t* bytes_written);
 
-size_t libp2p_crypto_encoding_base64_decode_length(const unsigned char* input_data, size_t input_length);
+/**
+ * calculate the max length in bytes of a decoding of n source bytes
+ * @param decoded_size the size of the incoming string to be encoded
+ * @returns the maximum size in bytes had the string been encoded
+ */
+size_t libp2p_crypto_encoding_base64_decode_size(size_t input_length);
 
 #endif /* base64_h */

include/libp2p/crypto/hashing/sha256.h

@@ -0,0 +1,18 @@
+#ifndef __CRYPTO_HASHING_SHA256_H__
+#define __CRYPTO_HASHING_SHA256_H__
+
+#include "mbedtls/sha256.h"
+
+/***
+ * hash a string using SHA256
+ * @param input the input string
+ * @param input_length the length of the input string
+ * @param output where to place the results
+ * @returns 1
+ */
+int libp2p_crypto_hashing_sha256(const unsigned char* input, size_t input_length, unsigned char output[32]) {
+	mbedtls_sha256(input, input_length, output, 0);
+	return 1;
+}
+
+#endif

test/Makefile

@@ -6,7 +6,7 @@ CFLAGS += -g3
 endif
 
 LFLAGS = -L../
-DEPS = crypto/test_base58.h crypto/test_rsa.h
+DEPS = crypto/test_base58.h crypto/test_rsa.h test_mbedtls.h
 OBJS = testit.o 
 
 %.o: %.c $(DEPS)

test/crypto/test_base58.h

@@ -43,30 +43,34 @@ int test_base58_encode_decode() {
 }
 
 int test_base58_size() {
-	unsigned char* unencoded = (unsigned char*)"Hello, World!";
+	unsigned char* unencoded = (unsigned char*)"Hello, World!"; // 13 chars + 1 null
 	size_t string_length = strlen((char*)unencoded) + 1;
 	
-	size_t encoded_length = 100;
-	unsigned char encoded[encoded_length];
+	size_t encoded_length = libp2p_crypto_encoding_base58_encode_size(string_length);
+
+	if (encoded_length != 20)
+		return 0;
+
+	size_t encoded_max_length = 100;
+	unsigned char encoded[encoded_max_length];
 	unsigned char* ptr = encoded;
 	
 	// now encode it
-	libp2p_crypto_encoding_base58_encode(unencoded, string_length, &ptr, &encoded_length);
+	libp2p_crypto_encoding_base58_encode(unencoded, string_length, &ptr, &encoded_max_length);
 	
-	size_t size_enc = libp2p_crypto_encoding_base58_decode_size(ptr);
-	size_t max_size_enc = libp2p_crypto_encoding_base58_decode_max_size(ptr);
-	
-	if (size_enc <= string_length && max_size_enc >= string_length)
-		return 1;
+	size_t decoded_length = libp2p_crypto_encoding_base58_decode_size(encoded_max_length);
 	
+	if (decoded_length != string_length)
 		return 0;
 	
+	return 1;
+	
 }
 
 int test_base58_max_size() {
 	unsigned char hash[5] = {'S', 'D', 'Y', 'h', 'd' };
 	
-	size_t results = libp2p_crypto_encoding_base58_decode_max_size(hash);
+	size_t results = libp2p_crypto_encoding_base58_decode_size(5);
 	if (results != 4)
 		return 0;
 	
@@ -76,7 +80,7 @@ int test_base58_max_size() {
 int test_base58_peer_address() {
 	char* x_data = "QmPZ9gcCEpqKTo6aq61g2nXGUhM4iCL3ewB6LDXZCtioEB";
 	size_t x_data_length = strlen(x_data);
-	size_t result_buffer_length = libp2p_crypto_encoding_base58_decode_max_size(x_data);
+	size_t result_buffer_length = libp2p_crypto_encoding_base58_decode_size(x_data_length);
 	unsigned char result_buffer[result_buffer_length];
 	unsigned char* ptr_to_result = result_buffer;
 	memset(result_buffer, 0, result_buffer_length);

test/crypto/test_rsa.h

@@ -41,7 +41,7 @@ int test_crypto_rsa_private_key_der() {
 int test_crypto_x509_der_to_private2() {
 	// this is an example private key. The type is not added. Therefore, it is not compatible with the go version
 	char* der = "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";
-	size_t b64_length = libp2p_crypto_encoding_base64_decode_length((unsigned char*)der, strlen(der));
+	size_t b64_length = libp2p_crypto_encoding_base64_decode_size(strlen(der));
 	unsigned char buffer[b64_length];
 	unsigned char* b = buffer;
 	size_t ultimate_length;
@@ -59,7 +59,7 @@ int test_crypto_x509_der_to_private2() {
 int test_crypto_x509_der_to_private() {
 	// this is a base64 encoded string from the go version of ipfs
 	char* der = "CAASpwkwggSjAgEAAoIBAQDTDJBWjDzS/HxDNOHazvzH2bu9CPMVHUrrvKRdBUM5ansL6/CC3MVZ6HVm4O6QHRapN6EF2CbrTgI4KBOXIL125Xo8MlROnyfXYk3O5q2tgwL/MbW8kXjtkyCfBak7MUoLOdLU7Svg0gkl3l+uDAiDcCLnwJVcFfq9ch6z4wMOhYJqE5dtx0uXxn6IuKWl1B69FTvBXCc0thw8Rw54b941FDcsBH5ttV9mRNCJym3poZ5qalNgXlxoIIB+PUx5QD+aq7KMJdpAX8HkapBntCOahP/QUceRmma0grlZLeYkH6/oi/hIrM6se3KUZ+F6tBuDFys8UAZy/X2BCUbKjbxtAgMBAAECggEANWfQfpYuLhXGPBt9q6kFPm1SnJtPJ+CpvM2XqhJS2IyhZnrl+bd0GTRBwS7aL42s1lVFYf04nAK5fQxnKK8YQqX/MIxr2RldM5ukpN6qxGWKtJkXrAgD2dqJPrRoBpqKahzPxSHfIJ0Fw5dqDtjsrpYJvyt0oEDPmnDuZAbmFx4sJqnesPNhKxtRMBx1+yxGVuRVJjHcqAgqPqwNiuoMEaYMY+G9yzT6vza8ovCpbX7BBIgM5fAT9PD8TBG//Vu9THvj/ZomiVG2qv6RL0qQyVb+DUzPZz1amBsSvahtXCl72jA3JwAZ943RxSR66P934S0ashkVwLUi46z/EAbJ4QKBgQDojGIO07BEVL2+7VxlGL9XGZQp4Y3qlhh2zDDQGwkCq/KQ+BdNYWitPwqRl9GqFLgpmeQIhyHTOa/IThx+AXGKVQ24ROH+skUs4IbO6R3qY7BKtb5lkZE/Yln09x70BBngUYAzh/rtnsXO3cl1x2XDDqUbCwlGcDAs8Jh/6UnvQwKBgQDoVSQs7Uq9MJCGIUM2bixX89tHzSxq5mn9wMD3/XRVfT5Ua8YkYBuzcmlcT39N7L5BwuyFqX3Vi7lv/Ya/qaQP6XkrZ8W1OAaTlYewfE5ZgknJqSpXcNWhABKeNmqndvqyQ/8HNCv/j8AdraGB2DGO57Xso5J0CQ43W/U9+QIyjwKBgHLL2hw3o+wXaRO3WMUPUmVM2zdRgR0suybp5a7Vqb0H5NZrohUw4NulIzJ8H6Q2VjMzJL6Q9sGu2HepF6ecTtBa7ErqtiVlG4Dr1aCOs5XhYEWBMlwxX+JKSt4Cn+UVoTB7Cy5lEhn7JurX0Xuy0ylXMWoIKKv89cs5eg6quzTBAoGAaq9eEztLjKCWXOE9SetBdYnG8aunb9cqaJlwgu/h0bfXPVDYBbAUSEyLURY4MQI7Q1tM3Pu9iqfEmUZj7/LoIV5mg6X9RX/alT6etk3+dF+9nlqN1OU9U9cCtZ/rTcb2y5EptJcidRH/eCFY/pTV/PcttOJPx/S4kHcroC+N8MUCgYEA6DA5QHxHfNN6Nxv+pEzy2DIxFe9RrBxS+KPBsra1C8jgdeMf4EmfU0Nox92V0q0bRrD5ztqQwSONI0hSRb1iiMWR6MuFnAFajUJfASjjIlZ6nIQjQslI7vjlvYyyHS/p/Codxap+yJlTLWwVEOXp2D9pWwiMq1xEyf0TH1BosvM=";
-	size_t b64_length = libp2p_crypto_encoding_base64_decode_length((unsigned char*)der, strlen(der));
+	size_t b64_length = libp2p_crypto_encoding_base64_decode_size(strlen(der));
 	unsigned char buffer[b64_length];
 	unsigned char* b = buffer;
 	size_t ultimate_length;

test/test_mbedtls.h

@@ -0,0 +1,89 @@
+/**
+ * A playground for testing mbedtls functions
+ */
+
+#include "mbedtls/bignum.h"
+
+int convertToString(unsigned char* string, int len) {
+	// load up the mpi
+	mbedtls_mpi mpi;
+	mbedtls_mpi_init(&mpi);
+	int retVal = mbedtls_mpi_read_binary(&mpi, string, len);
+	if (retVal < 0) {
+		mbedtls_mpi_free(&mpi);
+		return 0;
+	}
+
+	// put it in string form so we can see it
+	size_t buffer_len = 50;
+	size_t output_len = 0;
+	char buffer[buffer_len];
+	retVal = mbedtls_mpi_write_string(&mpi, 10, buffer, buffer_len, &output_len);
+	if (retVal < 0) {
+		mbedtls_mpi_free(&mpi);
+		return 0;
+	}
+	for(int i = 0; i < output_len; i++) {
+		printf("%02x", buffer[i]);
+	}
+	printf("\n");
+	mbedtls_mpi_free(&mpi);
+	return 1;
+}
+
+int test_mbedtls_varint_128_binary() {
+	// the values I'm working with 0x08, 0x00, 0x18, 0xa7, 0x09
+	unsigned char starting_val[5] = { 0x08, 0x00, 0x18, 0x87, 0x09 };
+	size_t starting_len = 5;
+
+	for(int i = 0; i < 5; i++) {
+		if (convertToString(&starting_val[i], 5 - i) != 1)
+			return 0;
+	}
+
+	printf(" 3 and 4\n");
+	if (convertToString(&starting_val[2], 2) != 1) {
+		return 0;
+	}
+
+	printf("And now the other way...\n");
+
+	for(int i = 1; i <= 5; i--) {
+		if (convertToString(starting_val, i) != 1)
+			return 0;
+	}
+
+
+	return 1;
+}
+
+int test_mbedtls_varint_128_string() {
+	// go from string to uint_128 and back again
+	char* bigint_string = "47942806932686753431";
+
+	mbedtls_mpi mpi;
+
+	mbedtls_mpi_init(&mpi);
+
+	int retVal = mbedtls_mpi_read_string( &mpi, 10, bigint_string );
+	if (retVal < 0) {
+		mbedtls_mpi_free(&mpi);
+		return 0;
+	}
+
+	// now go back again
+	size_t buffer_len = 50;
+	size_t output_len = 0;
+	char buffer[buffer_len];
+	retVal = mbedtls_mpi_write_string(&mpi, 10, buffer, buffer_len, &output_len);
+	if (retVal < 0) {
+		mbedtls_mpi_free(&mpi);
+		return 0;
+	}
+	if (strcmp(buffer, bigint_string) != 0) {
+		mbedtls_mpi_free(&mpi);
+		return 0;
+	}
+	mbedtls_mpi_free(&mpi);
+	return 1;
+}

test/testit.c

@@ -2,9 +2,8 @@
 #include <stdio.h>
 
 #include "crypto/test_rsa.h"
-//#include "multihash/test_multihash.h"
 #include "crypto/test_base58.h"
-//#include "crypto/test_mbedtls.h"
+#include "test_mbedtls.h"
 
 int testit(const char* name, int (*func)(void)) {
 	printf("Testing %s...\n", name);
@@ -17,6 +16,8 @@ int testit(const char* name, int (*func)(void)) {
 }
 
 int main(int argc, char** argv) {
+	testit("test_mbedtls_varint_128_binary", test_mbedtls_varint_128_binary);
+	testit("test_mbedtls_varint_128_string", test_mbedtls_varint_128_string);
 	testit("test_crypto_rsa_private_key_der", test_crypto_rsa_private_key_der);
 	//testit("test_crypto_x509_private_to_der", test_crypto_x509_private_to_der);
 	testit("test_crypto_x509_der_to_private2", test_crypto_x509_der_to_private2);