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

1 files changed, 78 insertions, 59 deletions

diff --git a/sys/kern/kern_descrip.c b/sys/kern/kern_descrip.c
index d0de6b9..a0545e1 100644
--- a/sys/kern/kern_descrip.c
+++ b/sys/kern/kern_descrip.c
@@ -455,6 +455,7 @@ kern_fcntl(struct thread *td, int fd, int cmd, intptr_t arg)
 	struct filedescent *fde;
 	struct proc *p;
 	struct vnode *vp;
+	cap_rights_t rights;
 	int error, flg, tmp;
 	u_int old, new;
 	uint64_t bsize;
@@ -515,7 +516,8 @@ kern_fcntl(struct thread *td, int fd, int cmd, intptr_t arg)
 		break;
 
 	case F_GETFL:
-		error = fget_unlocked(fdp, fd, CAP_FCNTL, F_GETFL, &fp, NULL);
+		error = fget_unlocked(fdp, fd,
+		    cap_rights_init(&rights, CAP_FCNTL), F_GETFL, &fp, NULL);
 		if (error != 0)
 			break;
 		td->td_retval[0] = OFLAGS(fp->f_flag);
@@ -523,7 +525,8 @@ kern_fcntl(struct thread *td, int fd, int cmd, intptr_t arg)
 		break;
 
 	case F_SETFL:
-		error = fget_unlocked(fdp, fd, CAP_FCNTL, F_SETFL, &fp, NULL);
+		error = fget_unlocked(fdp, fd,
+		    cap_rights_init(&rights, CAP_FCNTL), F_SETFL, &fp, NULL);
 		if (error != 0)
 			break;
 		do {
@@ -550,7 +553,8 @@ kern_fcntl(struct thread *td, int fd, int cmd, intptr_t arg)
 		break;
 
 	case F_GETOWN:
-		error = fget_unlocked(fdp, fd, CAP_FCNTL, F_GETOWN, &fp, NULL);
+		error = fget_unlocked(fdp, fd,
+		    cap_rights_init(&rights, CAP_FCNTL), F_GETOWN, &fp, NULL);
 		if (error != 0)
 			break;
 		error = fo_ioctl(fp, FIOGETOWN, &tmp, td->td_ucred, td);
@@ -560,7 +564,8 @@ kern_fcntl(struct thread *td, int fd, int cmd, intptr_t arg)
 		break;
 
 	case F_SETOWN:
-		error = fget_unlocked(fdp, fd, CAP_FCNTL, F_SETOWN, &fp, NULL);
+		error = fget_unlocked(fdp, fd,
+		    cap_rights_init(&rights, CAP_FCNTL), F_SETOWN, &fp, NULL);
 		if (error != 0)
 			break;
 		tmp = arg;
@@ -581,7 +586,8 @@ kern_fcntl(struct thread *td, int fd, int cmd, intptr_t arg)
 
 	case F_SETLK:
 	do_setlk:
-		error = fget_unlocked(fdp, fd, CAP_FLOCK, 0, &fp, NULL);
+		error = fget_unlocked(fdp, fd,
+		    cap_rights_init(&rights, CAP_FLOCK), 0, &fp, NULL);
 		if (error != 0)
 			break;
 		if (fp->f_type != DTYPE_VNODE) {
@@ -688,7 +694,8 @@ kern_fcntl(struct thread *td, int fd, int cmd, intptr_t arg)
 		break;
 
 	case F_GETLK:
-		error = fget_unlocked(fdp, fd, CAP_FLOCK, 0, &fp, NULL);
+		error = fget_unlocked(fdp, fd,
+		    cap_rights_init(&rights, CAP_FLOCK), 0, &fp, NULL);
 		if (error != 0)
 			break;
 		if (fp->f_type != DTYPE_VNODE) {
@@ -1281,11 +1288,13 @@ int
 kern_fstat(struct thread *td, int fd, struct stat *sbp)
 {
 	struct file *fp;
+	cap_rights_t rights;
 	int error;
 
 	AUDIT_ARG_FD(fd);
 
-	if ((error = fget(td, fd, CAP_FSTAT, &fp)) != 0)
+	error = fget(td, fd, cap_rights_init(&rights, CAP_FSTAT), &fp);
+	if (error != 0)
 		return (error);
 
 	AUDIT_ARG_FILE(td->td_proc, fp);
@@ -1339,9 +1348,11 @@ sys_fpathconf(struct thread *td, struct fpathconf_args *uap)
 {
 	struct file *fp;
 	struct vnode *vp;
+	cap_rights_t rights;
 	int error;
 
-	if ((error = fget(td, uap->fd, CAP_FPATHCONF, &fp)) != 0)
+	error = fget(td, uap->fd, cap_rights_init(&rights, CAP_FPATHCONF), &fp);
+	if (error != 0)
 		return (error);
 
 	/* If asynchronous I/O is available, it works for all descriptors. */
@@ -1417,7 +1428,7 @@ static void
 filecaps_fill(struct filecaps *fcaps)
 {
 
-	fcaps->fc_rights = CAP_ALL;
+	CAP_ALL(&fcaps->fc_rights);
 	fcaps->fc_ioctls = NULL;
 	fcaps->fc_nioctls = -1;
 	fcaps->fc_fcntls = CAP_FCNTL_ALL;
@@ -1441,16 +1452,18 @@ static void
 filecaps_validate(const struct filecaps *fcaps, const char *func)
 {
 
-	KASSERT((fcaps->fc_rights & ~CAP_MASK_VALID) == 0,
+	KASSERT(cap_rights_is_valid(&fcaps->fc_rights),
 	    ("%s: invalid rights", func));
 	KASSERT((fcaps->fc_fcntls & ~CAP_FCNTL_ALL) == 0,
 	    ("%s: invalid fcntls", func));
-	KASSERT(fcaps->fc_fcntls == 0 || (fcaps->fc_rights & CAP_FCNTL) != 0,
+	KASSERT(fcaps->fc_fcntls == 0 ||
+	    cap_rights_is_set(&fcaps->fc_rights, CAP_FCNTL),
 	    ("%s: fcntls without CAP_FCNTL", func));
 	KASSERT(fcaps->fc_ioctls != NULL ? fcaps->fc_nioctls > 0 :
 	    (fcaps->fc_nioctls == -1 || fcaps->fc_nioctls == 0),
 	    ("%s: invalid ioctls", func));
-	KASSERT(fcaps->fc_nioctls == 0 || (fcaps->fc_rights & CAP_IOCTL) != 0,
+	KASSERT(fcaps->fc_nioctls == 0 ||
+	    cap_rights_is_set(&fcaps->fc_rights, CAP_IOCTL),
 	    ("%s: ioctls without CAP_IOCTL", func));
 }
 
@@ -2285,7 +2298,7 @@ finit(struct file *fp, u_int flag, short type, void *data, struct fileops *ops)
 }
 
 int
-fget_unlocked(struct filedesc *fdp, int fd, cap_rights_t needrights,
+fget_unlocked(struct filedesc *fdp, int fd, cap_rights_t *needrightsp,
     int needfcntl, struct file **fpp, cap_rights_t *haverightsp)
 {
 	struct file *fp;
@@ -2310,11 +2323,11 @@ fget_unlocked(struct filedesc *fdp, int fd, cap_rights_t needrights,
 		if (fp == NULL)
 			return (EBADF);
 #ifdef CAPABILITIES
-		haverights = cap_rights(fdp, fd);
-		error = cap_check(haverights, needrights);
+		haverights = *cap_rights(fdp, fd);
+		error = cap_check(&haverights, needrightsp);
 		if (error != 0)
 			return (error);
-		if ((needrights & CAP_FCNTL) != 0) {
+		if (cap_rights_is_set(needrightsp, CAP_FCNTL)) {
 			error = cap_fcntl_check(fdp, fd, needfcntl);
 			if (error != 0)
 				return (error);
@@ -2338,7 +2351,7 @@ fget_unlocked(struct filedesc *fdp, int fd, cap_rights_t needrights,
 #ifdef CAPABILITIES
 		*haverightsp = haverights;
 #else
-		*haverightsp = CAP_ALL;
+		CAP_ALL(haverightsp);
 #endif
 	}
 	return (0);
@@ -2359,19 +2372,20 @@ fget_unlocked(struct filedesc *fdp, int fd, cap_rights_t needrights,
  */
 static __inline int
 _fget(struct thread *td, int fd, struct file **fpp, int flags,
-    cap_rights_t needrights, u_char *maxprotp)
+    cap_rights_t *needrightsp, u_char *maxprotp)
 {
 	struct filedesc *fdp;
 	struct file *fp;
-	cap_rights_t haverights;
+	cap_rights_t haverights, needrights;
 	int error;
 
 	*fpp = NULL;
 	if (td == NULL || (fdp = td->td_proc->p_fd) == NULL)
 		return (EBADF);
+	needrights = *needrightsp;
 	if (maxprotp != NULL)
-		needrights |= CAP_MMAP;
-	error = fget_unlocked(fdp, fd, needrights, 0, &fp, &haverights);
+		cap_rights_set(&needrights, CAP_MMAP);
+	error = fget_unlocked(fdp, fd, &needrights, 0, &fp, &haverights);
 	if (error != 0)
 		return (error);
 	if (fp->f_ops == &badfileops) {
@@ -2384,7 +2398,7 @@ _fget(struct thread *td, int fd, struct file **fpp, int flags,
 	 * If requested, convert capability rights to access flags.
 	 */
 	if (maxprotp != NULL)
-		*maxprotp = cap_rights_to_vmprot(haverights);
+		*maxprotp = cap_rights_to_vmprot(&haverights);
 #else /* !CAPABILITIES */
 	if (maxprotp != NULL)
 		*maxprotp = VM_PROT_ALL;
@@ -2421,32 +2435,32 @@ _fget(struct thread *td, int fd, struct file **fpp, int flags,
 }
 
 int
-fget(struct thread *td, int fd, cap_rights_t rights, struct file **fpp)
+fget(struct thread *td, int fd, cap_rights_t *rightsp, struct file **fpp)
 {
 
-	return(_fget(td, fd, fpp, 0, rights, NULL));
+	return(_fget(td, fd, fpp, 0, rightsp, NULL));
 }
 
 int
-fget_mmap(struct thread *td, int fd, cap_rights_t rights, u_char *maxprotp,
+fget_mmap(struct thread *td, int fd, cap_rights_t *rightsp, u_char *maxprotp,
     struct file **fpp)
 {
 
-	return (_fget(td, fd, fpp, 0, rights, maxprotp));
+	return (_fget(td, fd, fpp, 0, rightsp, maxprotp));
 }
 
 int
-fget_read(struct thread *td, int fd, cap_rights_t rights, struct file **fpp)
+fget_read(struct thread *td, int fd, cap_rights_t *rightsp, struct file **fpp)
 {
 
-	return(_fget(td, fd, fpp, FREAD, rights, NULL));
+	return(_fget(td, fd, fpp, FREAD, rightsp, NULL));
 }
 
 int
-fget_write(struct thread *td, int fd, cap_rights_t rights, struct file **fpp)
+fget_write(struct thread *td, int fd, cap_rights_t *rightsp, struct file **fpp)
 {
 
-	return (_fget(td, fd, fpp, FWRITE, rights, NULL));
+	return (_fget(td, fd, fpp, FWRITE, rightsp, NULL));
 }
 
 /*
@@ -2457,15 +2471,15 @@ fget_write(struct thread *td, int fd, cap_rights_t rights, struct file **fpp)
  * XXX: what about the unused flags ?
  */
 static __inline int
-_fgetvp(struct thread *td, int fd, int flags, cap_rights_t needrights,
+_fgetvp(struct thread *td, int fd, int flags, cap_rights_t *needrightsp,
     struct vnode **vpp)
 {
 	struct file *fp;
 	int error;
 
 	*vpp = NULL;
-	error = _fget(td, fd, &fp, flags, needrights, NULL);
-	if (error)
+	error = _fget(td, fd, &fp, flags, needrightsp, NULL);
+	if (error != 0)
 		return (error);
 	if (fp->f_vnode == NULL) {
 		error = EINVAL;
@@ -2479,14 +2493,14 @@ _fgetvp(struct thread *td, int fd, int flags, cap_rights_t needrights,
 }
 
 int
-fgetvp(struct thread *td, int fd, cap_rights_t rights, struct vnode **vpp)
+fgetvp(struct thread *td, int fd, cap_rights_t *rightsp, struct vnode **vpp)
 {
 
-	return (_fgetvp(td, fd, 0, rights, vpp));
+	return (_fgetvp(td, fd, 0, rightsp, vpp));
 }
 
 int
-fgetvp_rights(struct thread *td, int fd, cap_rights_t need,
+fgetvp_rights(struct thread *td, int fd, cap_rights_t *needrightsp,
     struct filecaps *havecaps, struct vnode **vpp)
 {
 	struct filedesc *fdp;
@@ -2503,7 +2517,7 @@ fgetvp_rights(struct thread *td, int fd, cap_rights_t need,
 		return (EBADF);
 
 #ifdef CAPABILITIES
-	error = cap_check(cap_rights(fdp, fd), need);
+	error = cap_check(cap_rights(fdp, fd), needrightsp);
 	if (error != 0)
 		return (error);
 #endif
@@ -2519,26 +2533,26 @@ fgetvp_rights(struct thread *td, int fd, cap_rights_t need,
 }
 
 int
-fgetvp_read(struct thread *td, int fd, cap_rights_t rights, struct vnode **vpp)
+fgetvp_read(struct thread *td, int fd, cap_rights_t *rightsp, struct vnode **vpp)
 {
 
-	return (_fgetvp(td, fd, FREAD, rights, vpp));
+	return (_fgetvp(td, fd, FREAD, rightsp, vpp));
 }
 
 int
-fgetvp_exec(struct thread *td, int fd, cap_rights_t rights, struct vnode **vpp)
+fgetvp_exec(struct thread *td, int fd, cap_rights_t *rightsp, struct vnode **vpp)
 {
 
-	return (_fgetvp(td, fd, FEXEC, rights, vpp));
+	return (_fgetvp(td, fd, FEXEC, rightsp, vpp));
 }
 
 #ifdef notyet
 int
-fgetvp_write(struct thread *td, int fd, cap_rights_t rights,
+fgetvp_write(struct thread *td, int fd, cap_rights_t *rightsp,
     struct vnode **vpp)
 {
 
-	return (_fgetvp(td, fd, FWRITE, rights, vpp));
+	return (_fgetvp(td, fd, FWRITE, rightsp, vpp));
 }
 #endif
 
@@ -2554,7 +2568,7 @@ fgetvp_write(struct thread *td, int fd, cap_rights_t rights,
  * during use.
  */
 int
-fgetsock(struct thread *td, int fd, cap_rights_t rights, struct socket **spp,
+fgetsock(struct thread *td, int fd, cap_rights_t *rightsp, struct socket **spp,
     u_int *fflagp)
 {
 	struct file *fp;
@@ -2563,7 +2577,7 @@ fgetsock(struct thread *td, int fd, cap_rights_t rights, struct socket **spp,
 	*spp = NULL;
 	if (fflagp != NULL)
 		*fflagp = 0;
-	if ((error = _fget(td, fd, &fp, 0, rights, NULL)) != 0)
+	if ((error = _fget(td, fd, &fp, 0, rightsp, NULL)) != 0)
 		return (error);
 	if (fp->f_type != DTYPE_SOCKET) {
 		error = ENOTSOCK;
@@ -2637,9 +2651,11 @@ sys_flock(struct thread *td, struct flock_args *uap)
 	struct file *fp;
 	struct vnode *vp;
 	struct flock lf;
+	cap_rights_t rights;
 	int error;
 
-	if ((error = fget(td, uap->fd, CAP_FLOCK, &fp)) != 0)
+	error = fget(td, uap->fd, cap_rights_init(&rights, CAP_FLOCK), &fp);
+	if (error != 0)
 		return (error);
 	if (fp->f_type != DTYPE_VNODE) {
 		fdrop(fp, td);
@@ -3185,7 +3201,7 @@ struct export_fd_buf {
 
 static int
 export_fd_to_sb(void *data, int type, int fd, int fflags, int refcnt,
-    int64_t offset, cap_rights_t fd_cap_rights, struct export_fd_buf *efbuf)
+    int64_t offset, cap_rights_t *rightsp, struct export_fd_buf *efbuf)
 {
 	struct {
 		int	fflag;
@@ -3259,7 +3275,10 @@ export_fd_to_sb(void *data, int type, int fd, int fflags, int refcnt,
 	for (i = 0; i < NFFLAGS; i++)
 		if (fflags & fflags_table[i].fflag)
 			kif->kf_flags |=  fflags_table[i].kf_fflag;
-	kif->kf_cap_rights = fd_cap_rights;
+	if (rightsp != NULL)
+		kif->kf_cap_rights = *rightsp;
+	else
+		cap_rights_init(&kif->kf_cap_rights);
 	kif->kf_fd = fd;
 	kif->kf_type = type;
 	kif->kf_ref_count = refcnt;
@@ -3302,7 +3321,7 @@ kern_proc_filedesc_out(struct proc *p,  struct sbuf *sb, ssize_t maxlen)
 	void *data;
 	int error, i;
 	int type, refcnt, fflags;
-	cap_rights_t fd_cap_rights;
+	cap_rights_t rights;
 
 	PROC_LOCK_ASSERT(p, MA_OWNED);
 
@@ -3329,13 +3348,13 @@ kern_proc_filedesc_out(struct proc *p,  struct sbuf *sb, ssize_t maxlen)
 	efbuf->remainder = maxlen;
 	if (tracevp != NULL)
 		export_fd_to_sb(tracevp, KF_TYPE_VNODE, KF_FD_TYPE_TRACE,
-		    FREAD | FWRITE, -1, -1, 0, efbuf);
+		    FREAD | FWRITE, -1, -1, NULL, efbuf);
 	if (textvp != NULL)
 		export_fd_to_sb(textvp, KF_TYPE_VNODE, KF_FD_TYPE_TEXT,
-		    FREAD, -1, -1, 0, efbuf);
+		    FREAD, -1, -1, NULL, efbuf);
 	if (cttyvp != NULL)
 		export_fd_to_sb(cttyvp, KF_TYPE_VNODE, KF_FD_TYPE_CTTY,
-		    FREAD | FWRITE, -1, -1, 0, efbuf);
+		    FREAD | FWRITE, -1, -1, NULL, efbuf);
 	error = 0;
 	if (fdp == NULL)
 		goto fail;
@@ -3346,30 +3365,30 @@ kern_proc_filedesc_out(struct proc *p,  struct sbuf *sb, ssize_t maxlen)
 		vref(fdp->fd_cdir);
 		data = fdp->fd_cdir;
 		export_fd_to_sb(data, KF_TYPE_VNODE, KF_FD_TYPE_CWD,
-		    FREAD, -1, -1, 0, efbuf);
+		    FREAD, -1, -1, NULL, efbuf);
 	}
 	/* root directory */
 	if (fdp->fd_rdir != NULL) {
 		vref(fdp->fd_rdir);
 		data = fdp->fd_rdir;
 		export_fd_to_sb(data, KF_TYPE_VNODE, KF_FD_TYPE_ROOT,
-		    FREAD, -1, -1, 0, efbuf);
+		    FREAD, -1, -1, NULL, efbuf);
 	}
 	/* jail directory */
 	if (fdp->fd_jdir != NULL) {
 		vref(fdp->fd_jdir);
 		data = fdp->fd_jdir;
 		export_fd_to_sb(data, KF_TYPE_VNODE, KF_FD_TYPE_JAIL,
-		    FREAD, -1, -1, 0, efbuf);
+		    FREAD, -1, -1, NULL, efbuf);
 	}
 	for (i = 0; i < fdp->fd_nfiles; i++) {
 		if ((fp = fdp->fd_ofiles[i].fde_file) == NULL)
 			continue;
 		data = NULL;
 #ifdef CAPABILITIES
-		fd_cap_rights = cap_rights(fdp, i);
+		rights = *cap_rights(fdp, i);
 #else /* !CAPABILITIES */
-		fd_cap_rights = 0;
+		cap_rights_init(&rights);
 #endif
 		switch (fp->f_type) {
 		case DTYPE_VNODE:
@@ -3443,8 +3462,8 @@ kern_proc_filedesc_out(struct proc *p,  struct sbuf *sb, ssize_t maxlen)
 		 * the loop continues.
 		 */
 		error = export_fd_to_sb(data, type, i, fflags, refcnt,
-		    offset, fd_cap_rights, efbuf);
-		if (error)
+		    offset, &rights, efbuf);
+		if (error != 0)
 			break;
 	}
 	FILEDESC_SUNLOCK(fdp);