xof: Add helper to determine MGF1 XOF type from hash algorithm

src/libstrongswan/crypto/xofs/xof.c

@@ -1,4 +1,5 @@
 /*
+ * Copyright (C) 2017 Tobias Brunner
  * Copyright (C) 2016 Andreas Steffen
  * HSR Hochschule fuer Technik Rapperswil
  *
@@ -25,3 +26,31 @@ ENUM(ext_out_function_names, XOF_UNDEFINED, XOF_CHACHA20,
 	"XOF_CHACHA20"
 );
 
+/*
+ * Described in header
+ */
+ext_out_function_t xof_mgf1_from_hash_algorithm(hash_algorithm_t alg)
+{
+	switch (alg)
+	{
+		case HASH_SHA1:
+			return XOF_MGF1_SHA1;
+		case HASH_SHA256:
+			return XOF_MGF1_SHA256;
+		case HASH_SHA512:
+			return XOF_MGF1_SHA512;
+		case HASH_SHA224:
+		case HASH_SHA384:
+		case HASH_IDENTITY:
+		case HASH_UNKNOWN:
+		case HASH_MD2:
+		case HASH_MD4:
+		case HASH_MD5:
+		case HASH_SHA3_224:
+		case HASH_SHA3_256:
+		case HASH_SHA3_384:
+		case HASH_SHA3_512:
+			break;
+	}
+	return XOF_UNDEFINED;
+}

src/libstrongswan/crypto/xofs/xof.h

@@ -1,4 +1,5 @@
 /*
+ * Copyright (C) 2017 Tobias Brunner
  * Copyright (C) 2016 Andreas Steffen
  * HSR Hochschule fuer Technik Rapperswil
  *
@@ -111,4 +112,12 @@ struct xof_t {
 	void (*destroy)(xof_t *this);
 };
 
+/**
+ * Determine an MGF1 XOF type for the given hash algorithm.
+ *
+ * @param alg			hash algorithm to map
+ * @return				MGF1 XOF type if available, XOF_UNDEFINED otherwise
+ */
+ext_out_function_t xof_mgf1_from_hash_algorithm(hash_algorithm_t alg);
+
 #endif /** XOF_H_ @}*/