mbedtls: enable support of hkdf

Adds the support of key derivation using
the scheme hkdf.

Reviewed-by: Raymond Mao <raymond.mao@linaro.org>
Signed-off-by: Philippe Reynes <philippe.reynes@softathome.com>

lib/mbedtls/Kconfig

@@ -297,6 +297,13 @@ config MD5_MBEDTLS
 	  This option enables support of hashing using MD5 algorithm
 	  with MbedTLS crypto library.
 
+config HKDF_MBEDTLS
+	bool "Enable HKDF support with MbedTLS crypto library"
+	depends on MBEDTLS_LIB_CRYPTO
+	help
+	  This option enables support of key derivation using HKDF algorithm
+	  with MbedTLS crypto library.
+
 if SPL
 
 config SPL_SHA1_MBEDTLS
@@ -335,6 +342,13 @@ config SPL_MD5_MBEDTLS
 	  This option enables support of hashing using MD5 algorithm
 	  with MbedTLS crypto library.
 
+config SPL_HKDF_MBEDTLS
+	bool "Enable HKDF support in SPL with MbedTLS crypto library"
+	depends on MBEDTLS_LIB_CRYPTO
+	help
+	  This option enables support of key derivation using HKDF algorithm
+	  with MbedTLS crypto library.
+
 endif # SPL
 
 endif # MBEDTLS_LIB_CRYPTO

lib/mbedtls/Makefile

@@ -33,6 +33,8 @@ mbedtls_lib_crypto-$(CONFIG_$(SPL_)SHA256_MBEDTLS) += \
 	$(MBEDTLS_LIB_DIR)/sha256.o
 mbedtls_lib_crypto-$(CONFIG_$(SPL_)SHA512_MBEDTLS) += \
 	$(MBEDTLS_LIB_DIR)/sha512.o
+mbedtls_lib_crypto-$(CONFIG_$(SPL_)HKDF_MBEDTLS) += \
+	$(MBEDTLS_LIB_DIR)/hkdf.o
 
 # MbedTLS X509 library
 obj-$(CONFIG_MBEDTLS_LIB_X509) += mbedtls_lib_x509.o

lib/mbedtls/mbedtls_def_config.h

@@ -56,6 +56,10 @@
 #endif
 #endif
 
+#if CONFIG_IS_ENABLED(HKDF_MBEDTLS)
+#define MBEDTLS_HKDF_C
+#endif
+
 #if defined CONFIG_MBEDTLS_LIB_X509
 
 #if CONFIG_IS_ENABLED(X509_CERTIFICATE_PARSER)