cr50: move FIPS DRBG initialization check into fips_drbg_init()

To drop dependency on internal rand_state.drbg_initialized in functions
located in other sources, slightly change fips_drbg_init() logic to
avoid initialization if already initialized.

Also update 0/1 to false/true as rand_state.drbg_initialized is bool.

BUG=none
TEST=make BOARD=cr50 CRYPTO_TEST=1; test/tpm_tests

Signed-off-by: Vadim Sukhomlinov <sukhomlinov@google.com>
Change-Id: Ia541266c36793c65dffce27a60a20ae25e10f92c
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/ec/+/3179316
Reviewed-by: Vadim Sukhomlinov <sukhomlinov@chromium.org>
Reviewed-by: Andrey Pronin <apronin@chromium.org>
Tested-by: Vadim Sukhomlinov <sukhomlinov@chromium.org>
Commit-Queue: Vadim Sukhomlinov <sukhomlinov@chromium.org>

1 files changed, 9 insertions, 8 deletions

diff --git a/board/cr50/dcrypto/fips_rand.c b/board/cr50/dcrypto/fips_rand.c
index e3dcf4d298..3c3b4bbfb6 100644
--- a/board/cr50/dcrypto/fips_rand.c
+++ b/board/cr50/dcrypto/fips_rand.c
@@ -248,6 +248,8 @@ bool fips_drbg_init(void)
 	if (!fips_crypto_allowed())
 		return false;
 
+	if (rand_state.drbg_initialized)
+		return true;
 	/**
 	 * initialize DRBG with 440 bits of entropy as required
 	 * by NIST SP 800-90A 10.1. Includes entropy and nonce,
@@ -270,7 +272,7 @@ bool fips_drbg_init(void)
 		       0);
 
 	set_fast_random_seed((uint32_t)fips_trng32(0));
-	rand_state.drbg_initialized = 1;
+	rand_state.drbg_initialized = true;
 	return true;
 }
 
@@ -278,7 +280,7 @@ bool fips_drbg_init(void)
 void fips_drbg_clear(void)
 {
 	drbg_exit(&fips_drbg);
-	rand_state.drbg_initialized = 0;
+	rand_state.drbg_initialized = false;
 }
 
 static bool fips_drbg_reseed_with_entropy(struct drbg_ctx *ctx)
@@ -310,13 +312,13 @@ enum hmac_result fips_hmac_drbg_generate_reseed(struct drbg_ctx *ctx, void *out,
 
 bool fips_rand_bytes(void *buffer, size_t len)
 {
-	if (!fips_crypto_allowed())
-		return false;
 	/**
 	 * make sure cr50 DRBG is initialized after power-on or resume,
 	 * but do it on first use to minimize latency of board_init()
+	 *
+	 * fips_drbg_init() also checks for fips_crypto_allowed().
 	 */
-	if (!rand_state.drbg_initialized && !fips_drbg_init())
+	if (!fips_drbg_init())
 		return false;
 
 	/* HMAC_DRBG can only return up to 7500 bits in a single request */
@@ -354,10 +356,9 @@ enum hmac_result fips_p256_hmac_drbg_generate(struct drbg_ctx *drbg,
 int fips_p256_ecdsa_sign(const p256_int *key, const p256_int *message,
 			 p256_int *r, p256_int *s)
 {
-	if (!fips_crypto_allowed())
+	/* Also check for fips_crypto_allowed(). */
+	if (!fips_drbg_init())
 		return 0;
-	if (!rand_state.drbg_initialized && !fips_drbg_init())
-		return false;
 
 	return dcrypto_p256_fips_sign_internal(&fips_drbg, key, message, r, s);
 }