Improve code clarity on IsTimeGreaterThanEqual (#17178)

* Improve code clarity on IsTimeGreaterThanEqual

Existing code is very hard to validate given the complex boolean
expression.

Split the logic into clearer steps of comparing year, month,
day, hr, min, sec individually.

The code change should generally be a NOOP except code clarity.

* Update src/crypto/CHIPCryptoPALmbedTLS.cpp

Co-authored-by: Evgeny Margolis <[email protected]>

Co-authored-by: Evgeny Margolis <[email protected]>

Author: 2 people

src/crypto/CHIPCryptoPALmbedTLS.cpp

@@ -1351,27 +1351,28 @@ CHIP_ERROR ValidateCertificateChain(const uint8_t * rootCertificate, size_t root
 
 inline bool IsTimeGreaterThanEqual(const mbedtls_x509_time * const timeA, const mbedtls_x509_time * const timeB)
 {
-    return timeA->CHIP_CRYPTO_PAL_PRIVATE_X509(year) > timeB->CHIP_CRYPTO_PAL_PRIVATE_X509(year) ||
-        (timeA->CHIP_CRYPTO_PAL_PRIVATE_X509(year) == timeB->CHIP_CRYPTO_PAL_PRIVATE_X509(year) &&
-         timeA->CHIP_CRYPTO_PAL_PRIVATE_X509(mon) > timeB->CHIP_CRYPTO_PAL_PRIVATE_X509(mon)) ||
-        (timeA->CHIP_CRYPTO_PAL_PRIVATE_X509(year) == timeB->CHIP_CRYPTO_PAL_PRIVATE_X509(year) &&
-         timeA->CHIP_CRYPTO_PAL_PRIVATE_X509(mon) == timeB->CHIP_CRYPTO_PAL_PRIVATE_X509(mon) &&
-         timeA->CHIP_CRYPTO_PAL_PRIVATE_X509(day) > timeB->CHIP_CRYPTO_PAL_PRIVATE_X509(day)) ||
-        (timeA->CHIP_CRYPTO_PAL_PRIVATE_X509(year) == timeB->CHIP_CRYPTO_PAL_PRIVATE_X509(year) &&
-         timeA->CHIP_CRYPTO_PAL_PRIVATE_X509(mon) == timeB->CHIP_CRYPTO_PAL_PRIVATE_X509(mon) &&
-         timeA->CHIP_CRYPTO_PAL_PRIVATE_X509(day) == timeB->CHIP_CRYPTO_PAL_PRIVATE_X509(day) &&
-         timeA->CHIP_CRYPTO_PAL_PRIVATE_X509(hour) > timeB->CHIP_CRYPTO_PAL_PRIVATE_X509(hour)) ||
-        (timeA->CHIP_CRYPTO_PAL_PRIVATE_X509(year) == timeB->CHIP_CRYPTO_PAL_PRIVATE_X509(year) &&
-         timeA->CHIP_CRYPTO_PAL_PRIVATE_X509(mon) == timeB->CHIP_CRYPTO_PAL_PRIVATE_X509(mon) &&
-         timeA->CHIP_CRYPTO_PAL_PRIVATE_X509(day) == timeB->CHIP_CRYPTO_PAL_PRIVATE_X509(day) &&
-         timeA->CHIP_CRYPTO_PAL_PRIVATE_X509(hour) == timeB->CHIP_CRYPTO_PAL_PRIVATE_X509(hour) &&
-         timeA->CHIP_CRYPTO_PAL_PRIVATE_X509(min) > timeB->CHIP_CRYPTO_PAL_PRIVATE_X509(min)) ||
-        (timeA->CHIP_CRYPTO_PAL_PRIVATE_X509(year) == timeB->CHIP_CRYPTO_PAL_PRIVATE_X509(year) &&
-         timeA->CHIP_CRYPTO_PAL_PRIVATE_X509(mon) == timeB->CHIP_CRYPTO_PAL_PRIVATE_X509(mon) &&
-         timeA->CHIP_CRYPTO_PAL_PRIVATE_X509(day) == timeB->CHIP_CRYPTO_PAL_PRIVATE_X509(day) &&
-         timeA->CHIP_CRYPTO_PAL_PRIVATE_X509(hour) == timeB->CHIP_CRYPTO_PAL_PRIVATE_X509(hour) &&
-         timeA->CHIP_CRYPTO_PAL_PRIVATE_X509(min) == timeB->CHIP_CRYPTO_PAL_PRIVATE_X509(min) &&
-         timeA->CHIP_CRYPTO_PAL_PRIVATE_X509(sec) >= timeB->CHIP_CRYPTO_PAL_PRIVATE_X509(sec));
+
+    // checks if two values are different and if yes, then returns first > second.
+#define RETURN_STRICTLY_GREATER_IF_DIFFERENT(component)                                                                            \
+    {                                                                                                                              \
+        auto valueA = timeA->CHIP_CRYPTO_PAL_PRIVATE_X509(component);                                                              \
+        auto valueB = timeB->CHIP_CRYPTO_PAL_PRIVATE_X509(component);                                                              \
+                                                                                                                                   \
+        if (valueA != valueB)                                                                                                      \
+        {                                                                                                                          \
+            return valueA > valueB;                                                                                                \
+        }                                                                                                                          \
+    }
+
+    RETURN_STRICTLY_GREATER_IF_DIFFERENT(year);
+    RETURN_STRICTLY_GREATER_IF_DIFFERENT(mon);
+    RETURN_STRICTLY_GREATER_IF_DIFFERENT(day);
+    RETURN_STRICTLY_GREATER_IF_DIFFERENT(hour);
+    RETURN_STRICTLY_GREATER_IF_DIFFERENT(min);
+    RETURN_STRICTLY_GREATER_IF_DIFFERENT(sec);
+
+    // all above are equal
+    return true;
 }
 
 CHIP_ERROR IsCertificateValidAtIssuance(const ByteSpan & referenceCertificate, const ByteSpan & toBeEvaluatedCertificate)