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Slim down dummy signing driver.

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This commit is contained in:
Henrik Ekblad
2015-02-19 11:22:36 +01:00
parent 8274188b43
commit 8550162235
2 changed files with 6 additions and 86 deletions
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libraries/MySensors/MySigningDriverDummy.cpp
+4 -77
View File
@@ -36,51 +36,17 @@ static void DEBUG_DUMMY_PRINTBUF(char* str, uint8_t* buf, uint8_t sz)
#endif
MySigningDriverDummy::MySigningDriverDummy() : MySigningDriver() {
verification_ongoing = false;
current_nonce = 0;
}
bool MySigningDriverDummy::getNonce(MyMessage &msg) {
uint8_t nonce_buf[2];
nonce_buf[0] = SIGNING_IDENTIFIER;
// This is normally a buffer but for our minimal driver we use a single byte
// We at least use a new nonce for every session
nonce_buf[1] = ++current_nonce;
msg.set(nonce_buf, 2);
verification_ongoing = true;
timestamp = millis(); // Set timestamp to determine when to purge nonce
// Be a little fancy to handle turnover (prolong the time allowed to timeout after turnover)
// Note that if message is "too" quick, and arrives before turnover, it will be rejected
// but this is consider such a rare case that it is accepted and rejects are 'safe'
if (timestamp + VERIFICATION_TIMEOUT_MS < millis()) timestamp = 0;
return true;
}
bool MySigningDriverDummy::checkTimer() {
if (verification_ongoing) {
if (millis() < timestamp || millis() > timestamp + VERIFICATION_TIMEOUT_MS) {
DEBUG_DUMMY_PRINTLN("Verification timeout");
// Purge nonce
current_nonce = 0; // purge nonce when used
verification_ongoing = false;
return false;
}
}
return true;
}
bool MySigningDriverDummy::putNonce(MyMessage &msg) {
if (mGetLength(msg) != 2) {
DEBUG_DUMMY_PRINTLN("Incoming nonce with incorrect size");
return false; // We require a signing identifier and a 1byte nonce
}
if (((uint8_t*)msg.getCustom())[0] != SIGNING_IDENTIFIER) {
DEBUG_DUMMY_PRINTLN("Incorrect signing identifier");
return false;
}
current_nonce = ((uint8_t*)msg.getCustom())[1];
return true;
}
@@ -90,54 +56,15 @@ bool MySigningDriverDummy::signMsg(MyMessage &msg) {
DEBUG_DUMMY_PRINTLN("Cannot fit any signature to this message");
return false;
}
// Calculate signature of message
mSetSigned(msg, 1); // make sure signing flag is set before signature is calculated
DEBUG_DUMMY_PRINTBUF("Message to sign:", (uint8_t*)&msg.data[1-HEADER_SIZE], MAX_MESSAGE_LENGTH-1-(MAX_PAYLOAD-mGetLength(msg)));
uint8_t signature = msg.data[0] ^ current_nonce;
msg.data[mGetLength(msg)] = SIGNING_IDENTIFIER; // Add signing identifier
msg.data[mGetLength(msg)+1] = signature;
current_nonce = 0; // purge nonce when used
return true;
}
bool MySigningDriverDummy::verifyMsg(MyMessage &msg) {
if (!verification_ongoing) {
DEBUG_DUMMY_PRINTLN("No active verification session");
return false;
} else {
// Make sure we have not expired
if (!checkTimer()) {
return false;
}
verification_ongoing = false;
if (msg.data[mGetLength(msg)] != SIGNING_IDENTIFIER) {
DEBUG_DUMMY_PRINTLN("Incorrect signing identifier");
return false;
}
DEBUG_DUMMY_PRINTBUF("Message to verify:", (uint8_t*)&msg.data[1-HEADER_SIZE], MAX_MESSAGE_LENGTH-1-(MAX_PAYLOAD-mGetLength(msg)));
DEBUG_DUMMY_PRINTBUF("Signature in message:", (uint8_t*)&msg.data[mGetLength(msg)], 2);
// The dummy signing is the nonce XOR the first payload byte,
// so we "verify" by redoing that calculation with the nonce we transmitted
// Message without a payload this implementation always accepts as signed and messages that cannot
// fit a signature are also accepted as signed
if (mGetLength(msg) && mGetLength(msg) < MAX_PAYLOAD-2) {
uint8_t signature = msg.data[0] ^ current_nonce;
if (msg.data[mGetLength(msg)+1] != signature) {
DEBUG_DUMMY_PRINTBUF("Signature bad. Calculated signature:", &signature, 1);
return false;
} else {
DEBUG_DUMMY_PRINTLN("Signature ok");
return true;
}
} else {
DEBUG_DUMMY_PRINTLN("No signature in message");
return false;
}
}
if (msg.data[mGetLength(msg)] != SIGNING_IDENTIFIER)
return false;
else
return true;
}
#endif
libraries/MySensors/MySigningDriverDummy.h
+2 -9
View File
@@ -10,11 +10,8 @@
#include "MySigningDriver.h"
#include <stdint.h>
// The dummy signing driver implements the most rudimentary form of signing
// No pre-shared key is used, nonce is simply incremeted each turn and signature
// is only calculated on the fist byte using data XOR nonce.
// This driver is intended for library debugging and sensor network integrity
// verification (signed messages will force the radio to transmit all 32 bytes of data).
// The dummy signing driver that can be used for nodes
// not requiring signing
// It does check SIGNING_IDENTIFIER byte to avoid illegal mixing of signing back-ends in
// the network (as seen by this node) and it does verify proper execution order on the API.
// The dummy driver rejects all other back-ends.
@@ -27,10 +24,6 @@ public:
bool putNonce(MyMessage &msg);
bool signMsg(MyMessage &msg);
bool verifyMsg(MyMessage &msg);
private:
unsigned long timestamp;
bool verification_ongoing;
uint8_t current_nonce;
};
#endif