ssh: provide our own types for host key lengths

Instead of using the libssh2 defines, provide our own, which eases usage
as we do not need to check whether libgit2 was built with libssh2 or not.

include/git2/transport.h

@@ -21,6 +21,16 @@
 GIT_BEGIN_DECL
 
 /**
+ * Type of SSH host fingerprint
+ */
+typedef enum {
+	/** MD5, 16 bytes */
+	GIT_CERT_SSH_MD5,
+	/** SHA-1, 20 bytes */
+	GIT_CERT_SSH_SHA1,
+} git_cert_ssh_type ;
+
+/**
  * Hostkey information taken from libssh2
  */
 typedef struct {
@@ -31,9 +41,9 @@ typedef struct {
 	git_cert_t cert_type;
         /**
          * A hostkey type from libssh2, either
-         * `LIBSSH2_HOSTKEY_HASH_MD5` or `LIBSSH2_HOSTKEY_HASH_SHA1`
+         * `GIT_CERT_SSH_MD5` or `GIT_CERT_SSH_SHA1`
          */
-        int type;
+	git_cert_ssh_type type;
         /**
          * Hostkey hash. If the type is MD5, only the first 16 bytes
          * will be set.

src/transports/ssh.c

@@ -480,23 +480,21 @@ static int _git_ssh_setup_conn(
 		goto on_error;
 
 	if (t->owner->certificate_check_cb != NULL) {
-		git_cert_hostkey cert;
+		git_cert_hostkey cert = { 0 };
 		const char *key;
-		size_t certlen;
 
 		cert.cert_type = GIT_CERT_HOSTKEY_LIBSSH2;
 
-		cert.type = LIBSSH2_HOSTKEY_HASH_SHA1;
 		key = libssh2_hostkey_hash(session, LIBSSH2_HOSTKEY_HASH_SHA1);
 		if (key != NULL) {
-			certlen = 20;
-			memcpy(&cert.hash, key, certlen);
+			cert.type = GIT_CERT_SSH_SHA1;
+			memcpy(&cert.hash, key, 20);
 		} else {
-			cert.type = LIBSSH2_HOSTKEY_HASH_MD5;
 			key = libssh2_hostkey_hash(session, LIBSSH2_HOSTKEY_HASH_MD5);
-			certlen = 16;
-			if (key != NULL)
-				memcpy(&cert.hash, key, certlen);
+			if (key != NULL) {
+				cert.type = GIT_CERT_SSH_MD5;
+				memcpy(&cert.hash, key, 16);
+			}
 		}
 
 		if (key == NULL) {

tests/online/clone.c

@@ -492,6 +492,8 @@ int ssh_certificate_check(git_cert *cert, int valid, void *payload)
 	key = (git_cert_hostkey *) cert;
 	git_oid_fromraw(&actual, key->hash);
 
+	cl_assert_equal_i(GIT_CERT_SSH_SHA1, key->type);
+
 	cl_assert(git_oid_equal(&expected, &actual));
 
 	return GIT_EUSER;