Initial commit

This code hasn't been tested. My next step is to write Kyua-based unit
tests.
Signed-off-by: Shawn Webb <shawn.webb@hardenedbsd.org>

Makefile

+SHLIB=		lattutil
+SHLIB_MAJOR=	0
+SRCS=		config.c
+INCS=		liblattutil.h
+
+.PATH: ${.CURDIR}/src
+.PATH: ${.CURDIR}/include
+
+CFLAGS+=	-I${.CURDIR}/include
+CFLAGS+=	-I/usr/local/include
+LDFLAGS+=	-L/usr/local/lib
+
+LDADD+=		-lucl
+
+.if defined(PREFIX)
+INCLUDEDIR=	${PREFIX}/include
+LIBDIR=		${PREFIX}/lib
+.endif
+
+.include <bsd.lib.mk>

include/liblattutil.h

+/*-
+ * Copyright (c) 2021 Shawn Webb <shawn.webb@hardenedbsd.org>
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
+ * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+ * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
+ * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
+ * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
+ * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#ifndef _LIBLATTUTIL_H
+#define	_LIBLATTUTIL_H
+
+#include <stdbool.h>
+#include <sys/queue.h>
+#include <sys/stat.h>
+
+#include <ucl.h>
+
+#define	EXPORTED_SYM	__attribute__((visibility("default")))
+
+/*
+ * Though we export the underlying data structure, using the API is
+ * preferred over directly accessing the ABI.
+ */
+typedef struct _llconfig {
+	struct stat		 l_sb;
+	char			*l_path;
+	int			 l_fd;
+	struct ucl_parser	*l_parser;
+	const ucl_object_t	*l_rootobj;
+} lattutil_config_path_t;
+
+/**
+ * Find a configuration file in a set of given paths
+ *
+ * This function iterates through the set of paths, looking for the
+ * passed-in configuration file name. If the configuration file is
+ * found, a UCL parser instance is created and the file is loaded by
+ * UCL.
+ *
+ * @param Set of paths
+ * @param Number of paths in set
+ * @param Configuration file name
+ * @return Pointer to struct that contains information about the
+ * 	config file on success, NULL on error.
+ */
+lattutil_config_path_t *lattutil_find_config(const char **, size_t, const char *,
+    int);
+
+/**
+ * Free a given lattutil_config_path_t object
+ *
+ * In order to prevent UAF vulnerabilities, the structure is zeroed
+ * after all its members have been freed. Additionally, the pointer to
+ * the structure is set to NULL.
+ *
+ * @param A pointer to the to-be-freed object
+ */
+void lattutil_free_config_path(lattutil_config_path_t **);
+
+/**
+ * Return the fully-qualified path of the config file
+ *
+ * @param A pointer to the lattutil_config_path_t object
+ * @return The path of the config file
+ */
+char *lattutil_config_path_path(lattutil_config_path_t *);
+
+/**
+ * Return the file descriptor of the opened config
+ *
+ * @param A pointer to the lattutil_config_path_t object
+ * @return The file descriptor
+ */
+int lattutil_config_path_fd(lattutil_config_path_t *);
+
+/**
+ * Look for a string-typed variable in a UCL configuration tree.
+ *
+ * @param UCL object root
+ * @param Path within the UCL object root
+ * @param Default value to set if path is not found
+ * @return The value if found, default value or zero-length string on
+ * error.
+ */
+char *lattutil_find_config_string(const ucl_object_t *, const char *,
+    const char *);
+
+/**
+ * Look for an integer-typed variable in a UCL configuration tree.
+ *
+ * @param UCL object root
+ * @param Path within the UCL object root
+ * @param Default value to set if path is not found
+ * @return The value if found, default value if not
+ */
+int64_t find_config_int(const ucl_object_t *, const char *, int64_t);
+
+#endif /* !_LIBLATTUTIL_H */

obj/.gitignore

+*
+!.gitignore

src/config.c

+/*-
+ * Copyright (c) 2021 Shawn Webb <shawn.webb@hardenedbsd.org>
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
+ * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+ * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
+ * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
+ * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
+ * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+
+#include <fcntl.h>
+#include <sys/stat.h>
+
+#include "liblattutil.h"
+
+EXPORTED_SYM
+lattutil_config_path_t *
+lattutil_find_config(const char **paths, size_t npaths,
+    const char *filename, int flags)
+{
+	lattutil_config_path_t *res;
+	size_t i, sz;
+
+	res = calloc(1, sizeof(*res));
+	if (res == NULL) {
+		return (NULL);
+	}
+
+	res->l_fd = -1;
+	for (i = 0; i < npaths; i++) {
+		sz = strlen(paths[i]) + strlen(filename) + 3;
+		res->l_path = calloc(1, sz);
+		if (res->l_path == NULL) {
+			return (res);
+		}
+
+		snprintf(res->l_path, sz-1, "%s/%s", paths[i], filename);
+		res->l_fd = open(res->l_path, flags);
+		if (res->l_fd < 0) {
+			free(res->l_path);
+			res->l_path = NULL;
+			continue;
+		}
+
+		if (fstat(res->l_fd, &(res->l_sb))) {
+			close(res->l_fd);
+			free(res->l_path);
+			res->l_path = NULL;
+			continue;
+		}
+
+		res->l_parser = ucl_parser_new(UCL_PARSER_KEY_LOWERCASE);
+		if (res->l_parser == NULL) {
+			free(res->l_path);
+			close(res->l_fd);
+			free(res);
+			return (NULL);
+		}
+
+		if (!ucl_parser_add_fd(res->l_parser, res->l_fd)) {
+			close(res->l_fd);
+			free(res->l_path);
+			res->l_path = NULL;
+			ucl_parser_free(res->l_parser);
+			res->l_parser = NULL;
+			continue;
+		}
+
+		res->l_rootobj = ucl_parser_get_object(res->l_parser);
+
+		break;
+	}
+
+	if (i == npaths) {
+		lattutil_free_config_path(&res);
+	}
+
+	return (res);
+}
+
+EXPORTED_SYM
+void
+lattutil_free_config_path(lattutil_config_path_t **obj)
+{
+
+	if (obj == NULL || *obj == NULL) {
+		return;
+	}
+	free((*obj)->l_path);
+	(*obj)->l_path = NULL;
+	if ((*obj)->l_parser != NULL) {
+		ucl_parser_free((*obj)->l_parser);
+		(*obj)->l_parser = NULL;
+	}
+	if ((*obj)->l_fd >= 0) {
+		close((*obj)->l_fd);
+		(*obj)->l_fd = -1;
+	}
+
+	memset(*obj, 0, sizeof(**obj)); /* Prevent UAF */
+	free(*obj);
+	*obj = NULL; /* Prevent UAF */
+}
+
+EXPORTED_SYM
+char *
+lattutil_config_path_path(lattutil_config_path_t *path)
+{
+
+	if (path == NULL) {
+		return (NULL);
+	}
+
+	return (path->l_path);
+}
+
+EXPORTED_SYM
+int
+lattutil_config_path_fd(lattutil_config_path_t *path)
+{
+
+	if (path == NULL) {
+		return (-1);
+	}
+
+	return (path->l_fd);
+}
+
+EXPORTED_SYM
+char *
+lattutil_find_config_string(const ucl_object_t *root, const char *path,
+    const char *def)
+{
+	const ucl_object_t *obj;
+
+	obj = ucl_object_lookup_path(root, path);
+	if (obj == NULL) {
+		if (def != NULL) {
+			return (strdup(def));
+		}
+
+		return (strdup(""));
+	}
+
+	return (strdup(""));
+}
+
+EXPORTED_SYM
+int64_t
+lattutil_find_config_int(const ucl_object_t *root, const char *path, int64_t def)
+{
+	const ucl_object_t *obj;
+	int64_t res;
+
+	res = def;
+	obj = ucl_object_lookup_path(root, path);
+	if (obj != NULL) {
+		res = ucl_object_toint(obj);
+	}
+
+	return (res);
+}