hotp: use sess_ctx instead of global variables

Resolve the issue of global variables in TA, which currently do not have
isolation when accessed by multiple CAs. It is suggested to attach the
variables to session_ctx for easy access when needed.

Signed-off-by: Shiqi Liu <erha_email@163.com>
Reviewed-by: Joakim Bech <joakim.bech@linaro.org>

Author: erhade

hotp/host/main.c

@@ -75,7 +75,12 @@ int main(void)
 	op.params[0].tmpref.buffer = K;
 	op.params[0].tmpref.size = sizeof(K);
 
-	fprintf(stdout, "Register the shared key: %s\n", K);
+	fprintf(stdout, "Register the shared key: ");
+	for (i = 0; i < sizeof(K); i++) {
+        	fprintf(stdout, "%02x ", K[i]);
+    	}
+	fprintf(stdout, "\n");
+
 	res = TEEC_InvokeCommand(&sess, TA_HOTP_CMD_REGISTER_SHARED_KEY,
 				 &op, &err_origin);
 	if (res != TEEC_SUCCESS) {

hotp/ta/hotp_ta.c

@@ -19,16 +19,21 @@
 /* Dynamic Binary Code 2 Modulo, which is 10^6 according to the spec. */
 #define DBC2_MODULO 1000000
 
+/* The size of a counter in bytes. */
+#define COUNTER_SIZE 8
+
 /*
  * Currently this only supports a single key, in the future this could be
  * updated to support multiple users, all with different unique keys (stored
  * using secure storage).
  */
-static uint8_t K[MAX_KEY_SIZE];
-static uint32_t K_len;
-
-/* The counter as defined by RFC4226. */
-static uint8_t counter[] = { 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0 };
+struct hotp_key
+{
+	uint8_t K[MAX_KEY_SIZE];
+	uint32_t K_len;
+	/* The counter as defined by RFC4226. */
+	uint8_t counter[COUNTER_SIZE];
+};
 
 /*
  *  HMAC a block of memory to produce the authentication tag
@@ -126,7 +131,8 @@ static void truncate(uint8_t *hmac_result, uint32_t *bin_code)
 	*bin_code %= DBC2_MODULO;
 }
 
-static TEE_Result register_shared_key(uint32_t param_types, TEE_Param params[4])
+static TEE_Result register_shared_key(struct hotp_key *state, 
+					uint32_t param_types, TEE_Param params[4])
 {
 	TEE_Result res = TEE_SUCCESS;
 
@@ -140,19 +146,20 @@ static TEE_Result register_shared_key(uint32_t param_types, TEE_Param params[4])
 		return TEE_ERROR_BAD_PARAMETERS;
 	}
 
-	if (params[0].memref.size > sizeof(K))
+	if (params[0].memref.size > sizeof(state->K))
 		return TEE_ERROR_BAD_PARAMETERS;
 
-	memset(K, 0, sizeof(K));
-	memcpy(K, params[0].memref.buffer, params[0].memref.size);
+	memset(state->K, 0, sizeof(state->K));
+	memcpy(state->K, params[0].memref.buffer, params[0].memref.size);
 
-	K_len = params[0].memref.size;
-	DMSG("Got shared key %s (%u bytes).", K, params[0].memref.size);
+	state->K_len = params[0].memref.size;
+	DMSG("Got shared key %s (%u bytes).", state->K, params[0].memref.size);
 
 	return res;
 }
 
-static TEE_Result get_hotp(uint32_t param_types, TEE_Param params[4])
+static TEE_Result get_hotp(struct hotp_key *state, 
+					uint32_t param_types, TEE_Param params[4])
 {
 	TEE_Result res = TEE_SUCCESS;
 	uint32_t hotp_val;
@@ -170,11 +177,12 @@ static TEE_Result get_hotp(uint32_t param_types, TEE_Param params[4])
 		return TEE_ERROR_BAD_PARAMETERS;
 	}
 
-	res = hmac_sha1(K, K_len, counter, sizeof(counter), mac, &mac_len);
+	res = hmac_sha1(state->K, state->K_len, state->counter, 
+			sizeof(state->counter), mac, &mac_len);
 
 	/* Increment the counter. */
-	for (i = sizeof(counter) - 1; i >= 0; i--) {
-		if (++counter[i])
+	for (i = sizeof(state->counter) - 1; i >= 0; i--) {
+		if (++(state->counter)[i])
 			break;
 	}
 
@@ -199,32 +207,45 @@ void TA_DestroyEntryPoint(void)
 
 TEE_Result TA_OpenSessionEntryPoint(uint32_t param_types,
 				    TEE_Param __unused params[4],
-				    void __unused **sess_ctx)
+				    void **sess_ctx)
 {
+	struct hotp_key *state = NULL;
+
 	uint32_t exp_param_types = TEE_PARAM_TYPES(TEE_PARAM_TYPE_NONE,
 						   TEE_PARAM_TYPE_NONE,
 						   TEE_PARAM_TYPE_NONE,
 						   TEE_PARAM_TYPE_NONE);
 	if (param_types != exp_param_types)
 		return TEE_ERROR_BAD_PARAMETERS;
 
+	/*
+	 * Allocate and init state for the session.
+	 */
+	state = TEE_Malloc(sizeof(*state), 0);
+	if (!state)
+		return TEE_ERROR_OUT_OF_MEMORY;
+
+	*sess_ctx = state;
+
 	return TEE_SUCCESS;
 }
 
-void TA_CloseSessionEntryPoint(void __unused *sess_ctx)
+void TA_CloseSessionEntryPoint(void *sess_ctx)
 {
+	TEE_Free(sess_ctx);
+	sess_ctx = NULL;
 }
 
-TEE_Result TA_InvokeCommandEntryPoint(void __unused *sess_ctx,
+TEE_Result TA_InvokeCommandEntryPoint(void *sess_ctx,
 				      uint32_t cmd_id,
 				      uint32_t param_types, TEE_Param params[4])
 {
 	switch (cmd_id) {
 	case TA_HOTP_CMD_REGISTER_SHARED_KEY:
-		return register_shared_key(param_types, params);
+		return register_shared_key(sess_ctx, param_types, params);
 
 	case TA_HOTP_CMD_GET_HOTP:
-		return get_hotp(param_types, params);
+		return get_hotp(sess_ctx, param_types, params);
 
 	default:
 		return TEE_ERROR_BAD_PARAMETERS;