+/* ask agent to sign data, returns -1 on error, 0 on success */
+int
+ssh_agent_sign(AuthenticationConnection *auth,
+ Key *key,
+ u_char **sigp, int *lenp,
+ u_char *data, int datalen)
+{
+ extern int datafellows;
+ Buffer msg;
+ u_char *blob;
+ u_int blen;
+ int type, flags = 0;
+ int ret = -1;
+
+ if (key_to_blob(key, &blob, &blen) == 0)
+ return -1;
+
+ if (datafellows & SSH_BUG_SIGBLOB)
+ flags = SSH_AGENT_OLD_SIGNATURE;
+
+ buffer_init(&msg);
+ buffer_put_char(&msg, SSH2_AGENTC_SIGN_REQUEST);
+ buffer_put_string(&msg, blob, blen);
+ buffer_put_string(&msg, data, datalen);
+ buffer_put_int(&msg, flags);
+ xfree(blob);
+
+ if (ssh_request_reply(auth, &msg, &msg) == 0) {
+ buffer_free(&msg);
+ return -1;
+ }
+ type = buffer_get_char(&msg);
+ if (agent_failed(type)) {
+ log("Agent admitted failure to sign using the key.");
+ } else if (type != SSH2_AGENT_SIGN_RESPONSE) {
+ fatal("Bad authentication response: %d", type);
+ } else {
+ ret = 0;
+ *sigp = buffer_get_string(&msg, lenp);
+ }
+ buffer_free(&msg);
+ return ret;
+}
+