mm_getpwnamallow(const char *username)
{
	Buffer m;
	struct passwd *pw;
	u_int len, i;
	ServerOptions *newopts;

	debug3("%s entering", __func__);

	buffer_init(&m);
	buffer_put_cstring(&m, username);

	mm_request_send(pmonitor->m_recvfd, MONITOR_REQ_PWNAM, &m);

	debug3("%s: waiting for MONITOR_ANS_PWNAM", __func__);
	mm_request_receive_expect(pmonitor->m_recvfd, MONITOR_ANS_PWNAM, &m);

	if (buffer_get_char(&m) == 0) {
		pw = NULL;
		goto out;
	}
	pw = buffer_get_string(&m, &len);
	if (len != sizeof(struct passwd))
		fatal("%s: struct passwd size mismatch", __func__);
	pw->pw_name = buffer_get_string(&m, NULL);
	pw->pw_passwd = buffer_get_string(&m, NULL);
#ifdef HAVE_STRUCT_PASSWD_PW_GECOS
	pw->pw_gecos = buffer_get_string(&m, NULL);
#endif
#ifdef HAVE_STRUCT_PASSWD_PW_CLASS
	pw->pw_class = buffer_get_string(&m, NULL);
#endif
	pw->pw_dir = buffer_get_string(&m, NULL);
	pw->pw_shell = buffer_get_string(&m, NULL);

out:
	/* copy options block as a Match directive may have changed some */
	newopts = buffer_get_string(&m, &len);
	if (len != sizeof(*newopts))
		fatal("%s: option block size mismatch", __func__);

#define M_CP_STROPT(x) do { \
		if (newopts->x != NULL) \
			newopts->x = buffer_get_string(&m, NULL); \
	} while (0)
#define M_CP_STRARRAYOPT(x, nx) do { \
		for (i = 0; i < newopts->nx; i++) \
			newopts->x[i] = buffer_get_string(&m, NULL); \
	} while (0)
	/* See comment in servconf.h */
	COPY_MATCH_STRING_OPTS();
#undef M_CP_STROPT
#undef M_CP_STRARRAYOPT

	copy_set_server_options(&options, newopts, 1);
	free(newopts);

	buffer_free(&m);

	return (pw);
}

The product receives input or data, but it does not validate or incorrectly validates that the input has the properties that are required to process the data safely and correctly.