X-Git-Url: https://www.flypig.org.uk/git/?p=libcontrac.git;a=blobdiff_plain;f=src%2Frpi.c;fp=src%2Frpi.c;h=7523ba4c6e4d31b139b6258f07f5a661bad245a5;hp=0000000000000000000000000000000000000000;hb=8515bbba069347de07a452586d7e49a2e8bdf151;hpb=79942abab927241b65a29a8a30d71b8efe6b6d94

diff --git a/src/rpi.c b/src/rpi.c
new file mode 100644
index 0000000..7523ba4
--- /dev/null
+++ b/src/rpi.c
@@ -0,0 +1,141 @@
+/** \ingroup contrac
+ * @file
+ * @author	David Llewellyn-Jones
+ * @version	$(VERSION)
+ *
+ * @section LICENSE
+ *
+ *
+ *
+ * @brief
+ * @section DESCRIPTION
+ *
+ *
+ *
+ */
+
+// Includes
+
+#include <stdlib.h>
+#include <string.h>
+#include <stddef.h>
+#include <stdint.h>
+
+#include <openssl/crypto.h>
+#include <openssl/hmac.h>
+#include <openssl/err.h>
+
+#include "contrac/contrac.h"
+#include "contrac/utils.h"
+#include "contrac/log.h"
+
+#include "contrac/rpi.h"
+
+// Defines
+
+#define RPI_INFO_PREFIX "CT-RPI"
+
+// Structures
+
+struct _Rpi {
+	// Rolling proximity identifier
+	unsigned char rpi[RPI_SIZE];
+	uint8_t time_interval_number;
+};
+
+// Function prototypes
+
+// Function definitions
+
+Rpi * rpi_new() {
+	Rpi * data;
+	
+	data = calloc(sizeof(Rpi), 1);
+
+	return data;
+}
+
+void rpi_delete(Rpi * data) {
+	if (data) {
+		// Clear the data for security
+		memset(data, 0, sizeof(Rpi));
+
+		free(data);
+	}
+}
+
+bool rpi_generate_proximity_id(Rpi * data, Dtk const * dtk, uint8_t time_interval_number) {
+	int result = 1;
+	unsigned char encode[sizeof(RPI_INFO_PREFIX) + sizeof(uint16_t)];
+	unsigned char output[EVP_MAX_MD_SIZE];
+	unsigned int out_length = 0;
+	unsigned int pos;
+	unsigned int min;
+	unsigned char const * daily_key;
+
+	// RPI_{i, j} <- Truncate(HMAC(dkt_i, (UTF8("CT-RPI") || TIN_j)), 16)
+
+	if (result > 0) {
+		// Produce Info sequence UTF8("CT-DTK") || D_i)
+		// From the spec it's not clear whether this is string or byte concatenation.
+		// Here we use byte, but it might have to be changed
+		memcpy(encode, RPI_INFO_PREFIX, sizeof(RPI_INFO_PREFIX));
+		((uint8_t *)(encode + sizeof(RPI_INFO_PREFIX)))[0] = time_interval_number;
+		out_length = sizeof(output);
+
+		daily_key = dtk_get_daily_key(dtk);
+		HMAC(EVP_sha256(), daily_key, DTK_SIZE, encode, sizeof(encode), output, &out_length);
+
+		_Static_assert ((EVP_MAX_MD_SIZE >= 16), "HMAC buffer size too small");
+
+		// Truncate and copy the result
+		min = MIN(out_length, 16);
+		for (pos = 0; pos < min; ++pos) {
+			data->rpi[pos] = output[pos];
+		}
+		// Zero out padding if there is any
+		for (pos = min; pos < 16; ++pos) {
+			data->rpi[pos] = 0;
+		}
+	}
+	
+	if (result > 0) {
+		data->time_interval_number = time_interval_number;
+	}
+
+	if (result <= 0) {
+		LOG(LOG_ERR, "Error generating rolling proximity id: %lu\n", ERR_get_error());
+	}
+
+	return (result > 0);
+}
+
+const unsigned char * rpi_get_proximity_id(Rpi const * data) {
+	return data->rpi;
+}
+
+uint8_t rpi_get_time_interval_number(Rpi const * data) {
+	return data->time_interval_number;
+}
+
+
+void rpi_assign(Rpi * data, unsigned char const * rpi_bytes, uint8_t time_interval_number) {
+	memcpy(data->rpi, rpi_bytes, RPI_SIZE);
+	data->time_interval_number = time_interval_number;
+}
+
+bool rpi_compare(Rpi const * data, Rpi const * comparitor) {
+	unsigned char left[RPI_SIZE_BASE64 + 1];
+	unsigned char right[RPI_SIZE_BASE64 + 1];
+	size_t size;
+
+	size = RPI_SIZE_BASE64 + 1;
+	base64_encode_binary_to_base64(data->rpi, RPI_SIZE, left, &size);
+
+	size = RPI_SIZE_BASE64 + 1;
+	base64_encode_binary_to_base64(comparitor->rpi, RPI_SIZE, right, &size);
+
+	return (memcmp(data, comparitor, RPI_SIZE) == 0);
+}
+
+