Change the cap_rights_t type from uint64_t to a structure that we can extend

in the future in a backward compatible (API and ABI) way.

The cap_rights_t represents capability rights. We used to use one bit to
represent one right, but we are running out of spare bits. Currently the new
structure provides place for 114 rights (so 50 more than the previous
cap_rights_t), but it is possible to grow the structure to hold at least 285
rights, although we can make it even larger if 285 rights won't be enough.

The structure definition looks like this:

	struct cap_rights {
		uint64_t	cr_rights[CAP_RIGHTS_VERSION + 2];
	};

The initial CAP_RIGHTS_VERSION is 0.

The top two bits in the first element of the cr_rights[] array contain total
number of elements in the array - 2. This means if those two bits are equal to
0, we have 2 array elements.

The top two bits in all remaining array elements should be 0.
The next five bits in all array elements contain array index. Only one bit is
used and bit position in this five-bits range defines array index. This means
there can be at most five array elements in the future.

To define new right the CAPRIGHT() macro must be used. The macro takes two
arguments - an array index and a bit to set, eg.

	#define	CAP_PDKILL	CAPRIGHT(1, 0x0000000000000800ULL)

We still support aliases that combine few rights, but the rights have to belong
to the same array element, eg:

	#define	CAP_LOOKUP	CAPRIGHT(0, 0x0000000000000400ULL)
	#define	CAP_FCHMOD	CAPRIGHT(0, 0x0000000000002000ULL)

	#define	CAP_FCHMODAT	(CAP_FCHMOD | CAP_LOOKUP)

There is new API to manage the new cap_rights_t structure:

	cap_rights_t *cap_rights_init(cap_rights_t *rights, ...);
	void cap_rights_set(cap_rights_t *rights, ...);
	void cap_rights_clear(cap_rights_t *rights, ...);
	bool cap_rights_is_set(const cap_rights_t *rights, ...);

	bool cap_rights_is_valid(const cap_rights_t *rights);
	void cap_rights_merge(cap_rights_t *dst, const cap_rights_t *src);
	void cap_rights_remove(cap_rights_t *dst, const cap_rights_t *src);
	bool cap_rights_contains(const cap_rights_t *big, const cap_rights_t *little);

Capability rights to the cap_rights_init(), cap_rights_set(),
cap_rights_clear() and cap_rights_is_set() functions are provided by
separating them with commas, eg:

	cap_rights_t rights;

	cap_rights_init(&rights, CAP_READ, CAP_WRITE, CAP_FSTAT);

There is no need to terminate the list of rights, as those functions are
actually macros that take care of the termination, eg:

	#define	cap_rights_set(rights, ...)				\
		__cap_rights_set((rights), __VA_ARGS__, 0ULL)
	void __cap_rights_set(cap_rights_t *rights, ...);

Thanks to using one bit as an array index we can assert in those functions that
there are no two rights belonging to different array elements provided
together. For example this is illegal and will be detected, because CAP_LOOKUP
belongs to element 0 and CAP_PDKILL to element 1:

	cap_rights_init(&rights, CAP_LOOKUP | CAP_PDKILL);

Providing several rights that belongs to the same array's element this way is
correct, but is not advised. It should only be used for aliases definition.

This commit also breaks compatibility with some existing Capsicum system calls,
but I see no other way to do that. This should be fine as Capsicum is still
experimental and this change is not going to 9.x.

Sponsored by:	The FreeBSD Foundation

4 files changed, 13 insertions, 32 deletions

diff --git a/sys/compat/freebsd32/freebsd32_capability.c b/sys/compat/freebsd32/freebsd32_capability.c
index e17c394..b23cf95 100644
--- a/sys/compat/freebsd32/freebsd32_capability.c
+++ b/sys/compat/freebsd32/freebsd32_capability.c
@@ -42,7 +42,6 @@ __FBSDID("$FreeBSD$");
 
 #include <security/audit/audit.h>
 
-#include <compat/freebsd32/freebsd32_misc.h>
 #include <compat/freebsd32/freebsd32_proto.h>
 
 #ifdef CAPABILITIES
@@ -50,17 +49,6 @@ __FBSDID("$FreeBSD$");
 MALLOC_DECLARE(M_FILECAPS);
 
 int
-freebsd32_cap_rights_limit(struct thread *td,
-    struct freebsd32_cap_rights_limit_args *uap)
-{
-	struct cap_rights_limit_args ap;
-
-	ap.fd = uap->fd;
-	ap.rights = PAIR32TO64(uint64_t, uap->rights);
-	return (sys_cap_rights_limit(td, &ap));
-}
-
-int
 freebsd32_cap_ioctls_limit(struct thread *td,
     struct freebsd32_cap_ioctls_limit_args *uap)
 {
@@ -148,14 +136,6 @@ out:
 #else /* !CAPABILITIES */
 
 int
-freebsd32_cap_rights_limit(struct thread *td,
-    struct freebsd32_cap_rights_limit_args *uap)
-{
-
-	return (ENOSYS);
-}
-
-int
 freebsd32_cap_ioctls_limit(struct thread *td,
     struct freebsd32_cap_ioctls_limit_args *uap)
 {
diff --git a/sys/compat/freebsd32/freebsd32_ioctl.c b/sys/compat/freebsd32/freebsd32_ioctl.c
index 81f5c8e..1f90e58 100644
--- a/sys/compat/freebsd32/freebsd32_ioctl.c
+++ b/sys/compat/freebsd32/freebsd32_ioctl.c
@@ -353,9 +353,11 @@ freebsd32_ioctl(struct thread *td, struct freebsd32_ioctl_args *uap)
 		caddr_t	data;
 	}*/ ;
 	struct file *fp;
+	cap_rights_t rights;
 	int error;
 
-	if ((error = fget(td, uap->fd, CAP_IOCTL, &fp)) != 0)
+	error = fget(td, uap->fd, cap_rights_init(&rights, CAP_IOCTL), &fp);
+	if (error != 0)
 		return (error);
 	if ((fp->f_flag & (FREAD | FWRITE)) == 0) {
 		fdrop(fp, td);
diff --git a/sys/compat/freebsd32/freebsd32_misc.c b/sys/compat/freebsd32/freebsd32_misc.c
index 16d1205..a3cf5cf 100644
--- a/sys/compat/freebsd32/freebsd32_misc.c
+++ b/sys/compat/freebsd32/freebsd32_misc.c
@@ -1650,6 +1650,7 @@ freebsd32_do_sendfile(struct thread *td,
 	struct uio *hdr_uio, *trl_uio;
 	struct iovec32 *iov32;
 	struct file *fp;
+	cap_rights_t rights;
 	off_t offset;
 	int error;
 
@@ -1686,8 +1687,10 @@ freebsd32_do_sendfile(struct thread *td,
 
 	AUDIT_ARG_FD(uap->fd);
 
-	if ((error = fget_read(td, uap->fd, CAP_PREAD, &fp)) != 0)
+	if ((error = fget_read(td, uap->fd,
+	    cap_rights_init(&rights, CAP_PREAD), &fp)) != 0) {
 		goto out;
+	}
 
 	error = fo_sendfile(fp, uap->s, hdr_uio, trl_uio, offset,
 	    uap->nbytes, uap->sbytes, uap->flags, compat ? SFK_COMPAT : 0, td);
diff --git a/sys/compat/freebsd32/syscalls.master b/sys/compat/freebsd32/syscalls.master
index a2e3e78..f537a54 100644
--- a/sys/compat/freebsd32/syscalls.master
+++ b/sys/compat/freebsd32/syscalls.master
@@ -970,9 +970,9 @@
 512	AUE_SHMCTL	NOSTD	{ int freebsd32_shmctl(int shmid, int cmd, \
 				    struct shmid_ds32 *buf); }
 513	AUE_LPATHCONF	NOPROTO	{ int lpathconf(char *path, int name); }
-514	AUE_CAP_NEW	NOPROTO	{ int cap_new(int fd, uint64_t rights); }
-515	AUE_CAP_RIGHTS_GET	NOPROTO	{ int cap_rights_get(int fd, \
-				    uint64_t *rightsp); }
+514	AUE_NULL	OBSOL	cap_new
+515	AUE_CAP_RIGHTS_GET	NOPROTO	{ int __cap_rights_get(int version, \
+				    int fd, cap_rights_t *rightsp); }
 516	AUE_CAP_ENTER	NOPROTO	{ int cap_enter(void); }
 517	AUE_CAP_GETMODE	NOPROTO	{ int cap_getmode(u_int *modep); }
 518	AUE_PDFORK	NOPROTO	{ int pdfork(int *fdp, int flags); }
@@ -1016,10 +1016,6 @@
 				    int *status, int options, \
 				    struct wrusage32 *wrusage, \
 				    siginfo_t *info); }
-533	AUE_CAP_RIGHTS_LIMIT	STD	{ \
-				    int freebsd32_cap_rights_limit(int fd, \
-				    int pad, \
-				    uint32_t rights1, uint32_t rights2); }
 #else
 530	AUE_NULL	STD	{ int freebsd32_posix_fallocate(int fd,\
 				    uint32_t offset1, uint32_t offset2,\
@@ -1033,10 +1029,10 @@
 				    int *status, int options, \
 				    struct wrusage32 *wrusage, \
 				    siginfo_t *info); }
-533	AUE_CAP_RIGHTS_LIMIT	STD	{ \
-				    int freebsd32_cap_rights_limit(int fd, \
-				    uint32_t rights1, uint32_t rights2); }
 #endif
+533	AUE_CAP_RIGHTS_LIMIT	NOPROTO	{ \
+				    int cap_rights_limit(int fd, \
+				    cap_rights_t *rightsp); }
 534	AUE_CAP_IOCTLS_LIMIT	STD	{ \
 				    int freebsd32_cap_ioctls_limit(int fd, \
 				    const uint32_t *cmds, size_t ncmds); }