ML-KEM keygen Pairwise Consistency Test

crypto/fipsmodule/ml_kem/ml_kem_ref/kem.c

@@ -9,6 +9,21 @@
 #include "symmetric.h"
 #include "openssl/rand.h"
 
+// FIPS 203. Pair-wise Consistency Test (PCT) required per [FIPS 140-3 IG](https://csrc.nist.gov/csrc/media/Projects/cryptographic-module-validation-program/documents/fips%20140-3/FIPS%20140-3%20IG.pdf):
+// The PCT consists of applying the encapsulation key to encapsulate a shared
+// secret leading to ciphertext, and then applying decapsulation key to
+// retrieve the same shared secret. Returns 0 if the PCT passes, 1 otherwise.
+static int keygen_pct(ml_kem_params *params, const uint8_t *ek, const uint8_t *dk) {
+  uint8_t ct[KYBER_CIPHERTEXTBYTES_MAX];
+  uint8_t ss_enc[KYBER_SSBYTES];
+  uint8_t ss_dec[KYBER_SSBYTES];
+
+  crypto_kem_enc(params, ct, ss_enc, ek);
+  crypto_kem_dec(params, ss_dec, ct, dk);
+
+  return verify(ss_enc, ss_dec, KYBER_SSBYTES);
+}
+
 /*************************************************
 * Name:        crypto_kem_keypair_derand
 *
@@ -22,7 +37,7 @@
 *              - uint8_t *coins: pointer to input randomness
 *                (an already allocated array filled with 2*KYBER_SYMBYTES random bytes)
 **
-* Returns 0 (success)
+* Returns 0 on success, aborts on failure.
 **************************************************/
 int crypto_kem_keypair_derand(ml_kem_params *params,
                               uint8_t *pk,
@@ -34,6 +49,11 @@ int crypto_kem_keypair_derand(ml_kem_params *params,
   hash_h(sk+params->secret_key_bytes-2*KYBER_SYMBYTES, pk, params->public_key_bytes);
   /* Value z for pseudo-random output on reject */
   memcpy(sk+params->secret_key_bytes-KYBER_SYMBYTES, coins+KYBER_SYMBYTES, KYBER_SYMBYTES);
+
+  // Abort in case of PCT failure.
+  if (keygen_pct(params, pk, sk)) {
+    BORINGSSL_FIPS_abort();
+  }
   return 0;
 }
 
@@ -48,19 +68,20 @@ int crypto_kem_keypair_derand(ml_kem_params *params,
 *              - uint8_t *sk: pointer to output private key
 *                (an already allocated array of KYBER_SECRETKEYBYTES bytes)
 *
-* Returns 0 (success)
+* Returns 0 on success, aborts on failure.
 **************************************************/
 int crypto_kem_keypair(ml_kem_params *params,
                        uint8_t *pk,
                        uint8_t *sk)
 {
   uint8_t coins[2*KYBER_SYMBYTES];
   RAND_bytes(coins, 2*KYBER_SYMBYTES);
-  crypto_kem_keypair_derand(params, pk, sk, coins);
+  int res = crypto_kem_keypair_derand(params, pk, sk, coins);
 
   // FIPS 203. Section 3.3 Destruction of intermediate values.
   OPENSSL_cleanse(coins, sizeof(coins));
-  return 0;
+
+  return res;
 }
 
 // Converts a centered representative |in| which is an integer in