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

5 files changed, 32 insertions, 13 deletions

diff --git a/sys/compat/svr4/svr4_fcntl.c b/sys/compat/svr4/svr4_fcntl.c
index 86fab78..8d0b715 100644
--- a/sys/compat/svr4/svr4_fcntl.c
+++ b/sys/compat/svr4/svr4_fcntl.c
@@ -259,6 +259,7 @@ fd_revoke(td, fd)
 	struct vnode *vp;
 	struct mount *mp;
 	struct vattr vattr;
+	cap_rights_t rights;
 	int error, *retval;
 
 	retval = td->td_retval;
@@ -267,12 +268,13 @@ fd_revoke(td, fd)
 	 * or FreeBSD grows a native frevoke() (more likely), we will need a
 	 * CAP_FREVOKE here.
 	 *
-	 * In the meantime, use CAP_ALL: if a SVR4 process wants to
+	 * In the meantime, use CAP_ALL(): if a SVR4 process wants to
 	 * do an frevoke(), it needs to do it on either a regular file
 	 * descriptor or a fully-privileged capability (which is effectively
 	 * the same as a non-capability-restricted file descriptor).
 	 */
-	if ((error = fgetvp(td, fd, CAP_ALL, &vp)) != 0)
+	CAP_ALL(&rights);
+	if ((error = fgetvp(td, fd, &rights, &vp)) != 0)
 		return (error);
 
 	if (vp->v_type != VCHR && vp->v_type != VBLK) {
@@ -318,13 +320,15 @@ fd_truncate(td, fd, flp)
 	struct vattr vattr;
 	int error, *retval;
 	struct ftruncate_args ft;
+	cap_rights_t rights;
 
 	retval = td->td_retval;
 
 	/*
 	 * We only support truncating the file.
 	 */
-	if ((error = fget(td, fd, CAP_FTRUNCATE, &fp)) != 0)
+	error = fget(td, fd, cap_rights_init(&rights, CAP_FTRUNCATE), &fp);
+	if (error != 0)
 		return (error);
 
 	vp = fp->f_vnode;
@@ -401,9 +405,11 @@ svr4_sys_open(td, uap)
 	if (!(bsd_flags & O_NOCTTY) && SESS_LEADER(p) &&
 	    !(p->p_flag & P_CONTROLT)) {
 #if defined(NOTYET)
-		struct file	*fp;
+		cap_rights_t rights;
+		struct file *fp;
 
-		error = fget(td, retval, CAP_IOCTL, &fp);
+		error = fget(td, retval,
+		    cap_rights_init(&rights, CAP_IOCTL), &fp);
 		PROC_UNLOCK(p);
 		/*
 		 * we may have lost a race the above open() and
diff --git a/sys/compat/svr4/svr4_filio.c b/sys/compat/svr4/svr4_filio.c
index 0fbba07..b953e72 100644
--- a/sys/compat/svr4/svr4_filio.c
+++ b/sys/compat/svr4/svr4_filio.c
@@ -104,6 +104,7 @@ svr4_sys_read(td, uap)
      struct svr4_sys_read_args *uap;
 {
      struct read_args ra;
+     cap_rights_t rights;
      struct file *fp;
      struct socket *so = NULL;
      int so_state;
@@ -114,7 +115,7 @@ svr4_sys_read(td, uap)
      ra.buf = uap->buf;
      ra.nbyte = uap->nbyte;
 
-     if (fget(td, uap->fd, CAP_READ, &fp) != 0) {
+     if (fget(td, uap->fd, cap_rights_init(&rights, CAP_READ), &fp) != 0) {
        DPRINTF(("Something fishy with the user-supplied file descriptor...\n"));
        return EBADF;
      }
diff --git a/sys/compat/svr4/svr4_ioctl.c b/sys/compat/svr4/svr4_ioctl.c
index 36b0580..a8c8c8c 100644
--- a/sys/compat/svr4/svr4_ioctl.c
+++ b/sys/compat/svr4/svr4_ioctl.c
@@ -84,6 +84,7 @@ svr4_sys_ioctl(td, uap)
 	struct svr4_sys_ioctl_args *uap;
 {
 	int             *retval;
+	cap_rights_t	 rights;
 	struct file	*fp;
 	u_long		 cmd;
 	int (*fun)(struct file *, struct thread *, register_t *,
@@ -103,7 +104,8 @@ svr4_sys_ioctl(td, uap)
 	retval = td->td_retval;
 	cmd = uap->com;
 
-	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) {
diff --git a/sys/compat/svr4/svr4_misc.c b/sys/compat/svr4/svr4_misc.c
index 0cfaeae..4888698 100644
--- a/sys/compat/svr4/svr4_misc.c
+++ b/sys/compat/svr4/svr4_misc.c
@@ -236,6 +236,7 @@ svr4_sys_getdents64(td, uap)
 	int len, reclen;		/* BSD-format */
 	caddr_t outp;			/* SVR4-format */
 	int resid, svr4reclen=0;	/* SVR4-format */
+	cap_rights_t rights;
 	struct file *fp;
 	struct uio auio;
 	struct iovec aiov;
@@ -247,7 +248,9 @@ svr4_sys_getdents64(td, uap)
 
 	DPRINTF(("svr4_sys_getdents64(%d, *, %d)\n",
 		uap->fd, uap->nbytes));
-	if ((error = getvnode(td->td_proc->p_fd, uap->fd, CAP_READ, &fp)) != 0)
+	error = getvnode(td->td_proc->p_fd, uap->fd,
+	    cap_rights_init(&rights, CAP_READ), &fp);
+	if (error != 0)
 		return (error);
 
 	if ((fp->f_flag & FREAD) == 0) {
@@ -412,6 +415,7 @@ svr4_sys_getdents(td, uap)
 	int len, reclen;	/* BSD-format */
 	caddr_t outp;		/* SVR4-format */
 	int resid, svr4_reclen;	/* SVR4-format */
+	cap_rights_t rights;
 	struct file *fp;
 	struct uio auio;
 	struct iovec aiov;
@@ -424,7 +428,9 @@ svr4_sys_getdents(td, uap)
 	if (uap->nbytes < 0)
 		return (EINVAL);
 
-	if ((error = getvnode(td->td_proc->p_fd, uap->fd, CAP_READ, &fp)) != 0)
+	error = getvnode(td->td_proc->p_fd, uap->fd,
+	    cap_rights_init(&rights, CAP_READ), &fp);
+	if (error != 0)
 		return (error);
 
 	if ((fp->f_flag & FREAD) == 0) {
diff --git a/sys/compat/svr4/svr4_stream.c b/sys/compat/svr4/svr4_stream.c
index 1c7e83e..6348b9b 100644
--- a/sys/compat/svr4/svr4_stream.c
+++ b/sys/compat/svr4/svr4_stream.c
@@ -1446,10 +1446,12 @@ svr4_sys_putmsg(td, uap)
 	struct thread *td;
 	struct svr4_sys_putmsg_args *uap;
 {
-	struct file     *fp;
+	cap_rights_t rights;
+	struct file *fp;
 	int error;
 
-	if ((error = fget(td, uap->fd, CAP_SEND, &fp)) != 0) {
+	error = fget(td, uap->fd, cap_rights_init(&rights, CAP_SEND), &fp);
+	if (error != 0) {
 #ifdef DEBUG_SVR4
 	        uprintf("putmsg: bad fp\n");
 #endif
@@ -1618,10 +1620,12 @@ svr4_sys_getmsg(td, uap)
 	struct thread *td;
 	struct svr4_sys_getmsg_args *uap;
 {
-	struct file     *fp;
+	cap_rights_t rights;
+	struct file *fp;
 	int error;
 
-	if ((error = fget(td, uap->fd, CAP_RECV, &fp)) != 0) {
+	error = fget(td, uap->fd, cap_rights_init(&rights, CAP_RECV), &fp);
+	if (error != 0) {
 #ifdef DEBUG_SVR4
 	        uprintf("getmsg: bad fp\n");
 #endif