libcapsicum: introduce Capsicum helpers

Capsicum helpers are a set of inline functions which goal is to reduce
duplicated patterns used to Capsicumize applications.

Reviewed by:	cem, AllanJude, bapt, ed, emaste
Differential Revision:	https://reviews.freebsd.org/D8013

lib/Makefile

@@ -38,6 +38,7 @@ SUBDIR=	${SUBDIR_BOOTSTRAP} \
 	libbz2 \
 	libcalendar \
 	libcam \
+	libcapsicum \
 	${_libcasper} \
 	${_libcom_err} \
 	libcompat \

lib/libcapsicum/Makefile

@@ -0,0 +1,7 @@
+# $FreeBSD$
+
+PACKAGE=lib${LIB}
+
+INCS=	capsicum_helpers.h
+
+.include <bsd.lib.mk>

lib/libcapsicum/capsicum_helpers.h

@@ -0,0 +1,120 @@
+/*-
+ * Copyright (c) 2016 Mariusz Zaborski <oshogbo@FreeBSD.org>
+ * All rights reserved.
+ *
+ * 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 AND CONTRIBUTORS ``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 OR CONTRIBUTORS 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.
+ *
+ * $FreeBSD$
+ */
+
+#ifndef _CAPSICUM_HELPERS_H_
+#define	_CAPSICUM_HELPERS_H_
+
+#include <sys/param.h>
+#include <sys/capsicum.h>
+
+#include <errno.h>
+#include <nl_types.h>
+#include <termios.h>
+#include <time.h>
+#include <unistd.h>
+
+#define	CAPH_IGNORE_EBADF	0x0001
+#define	CAPH_READ		0x0002
+#define	CAPH_WRITE		0x0004
+
+static __inline int
+caph_limit_stream(int fd, int flags)
+{
+	cap_rights_t rights;
+	unsigned long cmds[] = { TIOCGETA, TIOCGWINSZ };
+
+	cap_rights_init(&rights, CAP_FCNTL, CAP_FSTAT, CAP_IOCTL);
+
+	if ((flags & CAPH_READ) != 0)
+		cap_rights_set(&rights, CAP_READ);
+	if ((flags & CAPH_WRITE) != 0)
+		cap_rights_set(&rights, CAP_WRITE);
+
+	if (cap_rights_limit(fd, &rights) < 0 && errno != ENOSYS) {
+		if (errno == EBADF && (flags & CAPH_IGNORE_EBADF) != 0)
+			return (0);
+		return (-1);
+	}
+
+	if (cap_ioctls_limit(fd, cmds, nitems(cmds)) < 0 && errno != ENOSYS)
+		return (-1);
+
+	if (cap_fcntls_limit(fd, CAP_FCNTL_GETFL) < 0 && errno != ENOSYS)
+		return (-1);
+
+	return (0);
+}
+
+static __inline int
+caph_limit_stdin(void)
+{
+
+	return (caph_limit_stream(STDIN_FILENO, CAPH_READ));
+}
+
+static __inline int
+caph_limit_stderr(void)
+{
+
+	return (caph_limit_stream(STDERR_FILENO, CAPH_WRITE));
+}
+
+static __inline int
+caph_limit_stdout(void)
+{
+
+	return (caph_limit_stream(STDOUT_FILENO, CAPH_WRITE));
+}
+
+static __inline int
+caph_limit_stdio(void)
+{
+
+	if (caph_limit_stdin() == -1 || caph_limit_stdout() == -1 ||
+	    caph_limit_stdout() == -1) {
+		return (-1);
+	}
+
+	return (0);
+}
+
+static __inline void
+caph_cache_tzdata(void)
+{
+
+	tzset();
+}
+
+static __inline void
+caph_cache_catpages(void)
+{
+
+	(void)catopen("libc", NL_CAT_LOCALE);
+}
+
+#endif /* _CAPSICUM_HELPERS_H_ */