From 536e20571a077db11b82b646ab0199ebf34cb99c Mon Sep 17 00:00:00 2001
From: Gilles Peskine <Gilles.Peskine@arm.com>
Date: Mon, 13 May 2019 12:51:03 +0200
Subject: [PATCH] New macro to get the bit size of an elliptic curve

---
 include/psa/crypto_sizes.h                    | 41 +++++++++++++++++++
 .../test_suite_psa_crypto_metadata.function   |  4 +-
 2 files changed, 42 insertions(+), 3 deletions(-)

diff --git a/include/psa/crypto_sizes.h b/include/psa/crypto_sizes.h
index 34664fc10..3cb0c73ab 100644
--- a/include/psa/crypto_sizes.h
+++ b/include/psa/crypto_sizes.h
@@ -187,6 +187,47 @@
 #define PSA_VENDOR_ECC_MAX_CURVE_BITS 0
 #endif
 
+/** Bit size associated with an elliptic curve.
+ *
+ * \param curve     An elliptic curve (value of type #psa_ecc_curve_t).
+ *
+ * \return          The size associated with \p curve, in bits.
+ *                  This may be 0 if the implementation does not support
+ *                  the specified curve.
+ */
+#define PSA_ECC_CURVE_BITS(curve)               \
+    ((curve) == PSA_ECC_CURVE_SECT163K1        ? 163 : \
+     (curve) == PSA_ECC_CURVE_SECT163R1        ? 163 : \
+     (curve) == PSA_ECC_CURVE_SECT163R2        ? 163 : \
+     (curve) == PSA_ECC_CURVE_SECT193R1        ? 193 : \
+     (curve) == PSA_ECC_CURVE_SECT193R2        ? 193 : \
+     (curve) == PSA_ECC_CURVE_SECT233K1        ? 233 : \
+     (curve) == PSA_ECC_CURVE_SECT233R1        ? 233 : \
+     (curve) == PSA_ECC_CURVE_SECT239K1        ? 239 : \
+     (curve) == PSA_ECC_CURVE_SECT283K1        ? 283 : \
+     (curve) == PSA_ECC_CURVE_SECT283R1        ? 283 : \
+     (curve) == PSA_ECC_CURVE_SECT409K1        ? 409 : \
+     (curve) == PSA_ECC_CURVE_SECT409R1        ? 409 : \
+     (curve) == PSA_ECC_CURVE_SECT571K1        ? 571 : \
+     (curve) == PSA_ECC_CURVE_SECT571R1        ? 571 : \
+     (curve) == PSA_ECC_CURVE_SECP160K1        ? 160 : \
+     (curve) == PSA_ECC_CURVE_SECP160R1        ? 160 : \
+     (curve) == PSA_ECC_CURVE_SECP160R2        ? 160 : \
+     (curve) == PSA_ECC_CURVE_SECP192K1        ? 192 : \
+     (curve) == PSA_ECC_CURVE_SECP192R1        ? 192 : \
+     (curve) == PSA_ECC_CURVE_SECP224K1        ? 224 : \
+     (curve) == PSA_ECC_CURVE_SECP224R1        ? 224 : \
+     (curve) == PSA_ECC_CURVE_SECP256K1        ? 256 : \
+     (curve) == PSA_ECC_CURVE_SECP256R1        ? 256 : \
+     (curve) == PSA_ECC_CURVE_SECP384R1        ? 384 : \
+     (curve) == PSA_ECC_CURVE_SECP521R1        ? 521 : \
+     (curve) == PSA_ECC_CURVE_BRAINPOOL_P256R1 ? 256 : \
+     (curve) == PSA_ECC_CURVE_BRAINPOOL_P384R1 ? 384 : \
+     (curve) == PSA_ECC_CURVE_BRAINPOOL_P512R1 ? 512 : \
+     (curve) == PSA_ECC_CURVE_CURVE25519       ? 255 : \
+     (curve) == PSA_ECC_CURVE_CURVE448         ? 448 : \
+     0)
+
 /** \def PSA_ALG_TLS12_PSK_TO_MS_MAX_PSK_LEN
  *
  * This macro returns the maximum length of the PSK supported
diff --git a/tests/suites/test_suite_psa_crypto_metadata.function b/tests/suites/test_suite_psa_crypto_metadata.function
index 01c8628ce..4686bfa3f 100644
--- a/tests/suites/test_suite_psa_crypto_metadata.function
+++ b/tests/suites/test_suite_psa_crypto_metadata.function
@@ -477,9 +477,7 @@ void ecc_key_types( int curve_arg, int curve_bits_arg )
     TEST_EQUAL( PSA_KEY_TYPE_GET_CURVE( public_type ), curve );
     TEST_EQUAL( PSA_KEY_TYPE_GET_CURVE( pair_type ), curve );
 
-    /* Validate that the bit size is less than the maximum ECC bit size
-     * in this implementation. There's no parameter that should be equal
-     * to curve_bits and can be validated without creating a key. */
+    TEST_EQUAL( curve_bits, PSA_ECC_CURVE_BITS( curve ) );
     TEST_ASSERT( curve_bits <= PSA_VENDOR_ECC_MAX_CURVE_BITS );
 }
 /* END_CASE */