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Use constant-time comparison for MAC verification #1656

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Use constant-time comparison for MAC verification #1656

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761f018
use constant-time comparison for MAC verification
weebl2000 Feb 11, 2026
83bbda0
Use secure_compare
weebl2000 Feb 16, 2026
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3 changes: 2 additions & 1 deletion src/Utils.cpp
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Original file line number Diff line number Diff line change
@@ -1,5 +1,6 @@
#include "Utils.h"
#include <AES.h>
#include <Crypto.h>
#include <SHA256.h>

#ifdef ARDUINO
Expand Down Expand Up @@ -81,7 +82,7 @@ int Utils::MACThenDecrypt(const uint8_t* shared_secret, uint8_t* dest, const uin
sha.update(src + CIPHER_MAC_SIZE, src_len - CIPHER_MAC_SIZE);
sha.finalizeHMAC(shared_secret, PUB_KEY_SIZE, hmac, CIPHER_MAC_SIZE);
}
if (memcmp(hmac, src, CIPHER_MAC_SIZE) == 0) {
if (secure_compare(hmac, src, CIPHER_MAC_SIZE)) {
return decrypt(shared_secret, dest, src + CIPHER_MAC_SIZE, src_len - CIPHER_MAC_SIZE);
}
return 0; // invalid HMAC
Expand Down