port string_hashsum from libgcrypt to openssl^gcrypt

This allows resolved and importd to be built without libgcrypt.

Note that we now say either 'cryptographic library' or 'cryptolib'.

Co-authored-by: Zbigniew Jędrzejewski-Szmek <zbyszek@in.waw.pl>

src/shared/openssl-util.c

@@ -2,6 +2,7 @@
 
 #include "openssl-util.h"
 #include "alloc-util.h"
+#include "hexdecoct.h"
 
 #if HAVE_OPENSSL
 int openssl_hash(const EVP_MD *alg,
@@ -107,4 +108,33 @@ int rsa_pkey_to_suitable_key_size(
         *ret_suitable_key_size = suitable_key_size;
         return 0;
 }
+
+#  if PREFER_OPENSSL
+int string_hashsum(
+                const char *s,
+                size_t len,
+                const EVP_MD *md_algorithm,
+                char **ret) {
+
+        uint8_t hash[EVP_MAX_MD_SIZE];
+        size_t hash_size;
+        char *enc;
+        int r;
+
+        hash_size = EVP_MD_size(md_algorithm);
+        assert(hash_size > 0);
+
+        r = openssl_hash(md_algorithm, s, len, hash, NULL);
+        if (r < 0)
+                return r;
+
+        enc = hexmem(hash, hash_size);
+        if (!enc)
+                return -ENOMEM;
+
+        *ret = enc;
+        return 0;
+
+}
+#  endif
 #endif

src/shared/openssl-util.h

@@ -62,3 +62,15 @@ typedef const char* elliptic_curve_t;
 typedef gcry_md_hd_t hash_context_t;
 #  define OPENSSL_OR_GCRYPT(a, b) (b)
 #endif
+
+#if PREFER_OPENSSL
+int string_hashsum(const char *s, size_t len, hash_algorithm_t md_algorithm, char **ret);
+
+static inline int string_hashsum_sha224(const char *s, size_t len, char **ret) {
+        return string_hashsum(s, len, EVP_sha224(), ret);
+}
+
+static inline int string_hashsum_sha256(const char *s, size_t len, char **ret) {
+        return string_hashsum(s, len, EVP_sha256(), ret);
+}
+#endif