systemd-resolve: allow easy querying of openpgp keys

$ systemd-resolve --openpgp zbyszek@fedoraproject.org
d08ee310438ca124a6149ea5cc21b6313b390dce485576eff96f8722._openpgpkey.fedoraproject.org. IN OPENPGPKEY
        mQINBFBHPMsBEACeInGYJCb+7TurKfb6wGyTottCDtiSJB310i37/6ZYoeIay/5soJjlM
        yfMFQ9T2XNT/0LM6gTa0MpC1st9LnzYTMsT6tzRly1D1UbVI6xw0g0vE5y2Cjk3xUwAyn
        ...

1 files changed, 29 insertions, 0 deletions

diff --git a/src/shared/gcrypt-util.c b/src/shared/gcrypt-util.c
index 3bbc161ef2..b887243849 100644
--- a/src/shared/gcrypt-util.c
+++ b/src/shared/gcrypt-util.c
@@ -38,3 +38,32 @@ void initialize_libgcrypt(bool secmem) {
                 gcry_control(GCRYCTL_DISABLE_SECMEM);
         gcry_control(GCRYCTL_INITIALIZATION_FINISHED, 0);
 }
+
+int string_hashsum(const char *s, size_t len, int md_algorithm, char **out) {
+        gcry_md_hd_t md = NULL;
+        size_t hash_size;
+        void *hash;
+        char *enc;
+
+        initialize_libgcrypt(false);
+
+        hash_size = gcry_md_get_algo_dlen(md_algorithm);
+        assert(hash_size > 0);
+
+        gcry_md_open(&md, md_algorithm, 0);
+        if (!md)
+                return -EIO;
+
+        gcry_md_write(md, s, len);
+
+        hash = gcry_md_read(md, 0);
+        if (!hash)
+                return -EIO;
+
+        enc = hexmem(hash, hash_size);
+        if (!enc)
+                return -ENOMEM;
+
+        *out = enc;
+        return 0;
+}