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o Introduce eaccess(2), a version of access(2) that uses the effective

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credentials rather than the real credentials.  This is useful for
  implementing GUI's which need to modify icons based on access rights,
  but where use of open(2) is too expensive, use of stat(2) doesn't
  reflect the file system's real protection model, and use of
  access() suffers from real/effective credential confusion.  This
  implementation provides the same semantics as the call of the same
  name on SCO OpenServer.  Note: using this call improperly can
  leave you subject to some of the same races present in the
  access(2) call.
o To implement this, break out the basic logic of access(2) into
  vpaccess(), which accepts a passed credential to perform the
  invocation of VOP_ACCESS().  Add eaccess(2) to invoke vpaccess(),
  and modify access(2) to use vpaccess().

Obtained from:	TrustedBSD Project
This commit is contained in:
Robert Watson 2001-09-21 21:33:22 +00:00
parent abc9a36083
commit 9c94f7731e
3 changed files with 135 additions and 28 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

1
sys/kern/syscalls.master
View File

@ -544,3 +544,4 @@
const char *attrname); }
374 MSTD BSD { int __setugid(int flag); }
375 NOIMPL BSD { int nfsclnt(int flag, caddr_t argp); }
376 STD BSD { int eaccess(char *path, int flags); }

81
sys/kern/vfs_extattr.c
View File

@ -84,6 +84,9 @@ static int setfmode __P((struct thread *td, struct vnode *, int));
static int setfflags __P((struct thread *td, struct vnode *, int));
static int setutimes __P((struct thread *td, struct vnode *,
const struct timespec *, int));
static int vpaccess __P((struct vnode *vp, int user_flags, struct ucred *cred,
struct thread *td));
static int usermount = 0; /* if 1, non-root can mount fs. */
int (*union_dircheckp) __P((struct thread *td, struct vnode **, struct file *));
@ -1697,7 +1700,35 @@ olseek(td, uap)
#endif /* COMPAT_43 */
/*
* Check access permissions.
* Check access permissions using passed credentials.
*/
static int
vpaccess(vp, user_flags, cred, td)
struct vnode *vp;
int user_flags;
struct ucred *cred;
struct thread *td;
{
int error, flags;
/* Flags == 0 means only check for existence. */
error = 0;
if (user_flags) {
flags = 0;
if (user_flags & R_OK)
flags |= VREAD;
if (user_flags & W_OK)
flags |= VWRITE;
if (user_flags & X_OK)
flags |= VEXEC;
if ((flags & VWRITE) == 0 || (error = vn_writechk(vp)) == 0)
error = VOP_ACCESS(vp, flags, cred, td);
}
return (error);
}
/*
* Check access permissions using "real" credentials.
*/
#ifndef _SYS_SYSPROTO_H_
struct access_args {
@ -1715,7 +1746,7 @@ access(td, uap)
{
struct ucred *cred, *tmpcred;
register struct vnode *vp;
int error, flags;
int error;
struct nameidata nd;
cred = td->td_proc->p_ucred;
@ -1738,18 +1769,7 @@ access(td, uap)
goto out1;
vp = nd.ni_vp;
/* Flags == 0 means only check for existence. */
if (SCARG(uap, flags)) {
flags = 0;
if (SCARG(uap, flags) & R_OK)
flags |= VREAD;
if (SCARG(uap, flags) & W_OK)
flags |= VWRITE;
if (SCARG(uap, flags) & X_OK)
flags |= VEXEC;
if ((flags & VWRITE) == 0 || (error = vn_writechk(vp)) == 0)
error = VOP_ACCESS(vp, flags, tmpcred, td);
}
error = vpaccess(vp, SCARG(uap, flags), tmpcred, td);
NDFREE(&nd, NDF_ONLY_PNBUF);
vput(vp);
out1:
@ -1758,6 +1778,39 @@ access(td, uap)
return (error);
}
/*
* Check access permissions using "effective" credentials.
*/
#ifndef _SYS_SYSPROTO_H_
struct eaccess_args {
char *path;
int flags;
};
#endif
int
eaccess(td, uap)
struct thread *td;
register struct eaccess_args /* {
syscallarg(char *) path;
syscallarg(int) flags;
} */ *uap;
{
struct nameidata nd;
struct vnode *vp;
int error;
NDINIT(&nd, LOOKUP, FOLLOW | LOCKLEAF | NOOBJ, UIO_USERSPACE,
SCARG(uap, path), td);
if ((error = namei(&nd)) != 0)
return (error);
vp = nd.ni_vp;
error = vpaccess(vp, SCARG(uap, flags), td->td_proc->p_ucred, td);
NDFREE(&nd, NDF_ONLY_PNBUF);
vput(vp);
return (error);
}
#if defined(COMPAT_43) || defined(COMPAT_SUNOS)
/*
* Get file status; this version follows links.

81
sys/kern/vfs_syscalls.c
View File

@ -84,6 +84,9 @@ static int setfmode __P((struct thread *td, struct vnode *, int));
static int setfflags __P((struct thread *td, struct vnode *, int));
static int setutimes __P((struct thread *td, struct vnode *,
const struct timespec *, int));
static int vpaccess __P((struct vnode *vp, int user_flags, struct ucred *cred,
struct thread *td));
static int usermount = 0; /* if 1, non-root can mount fs. */
int (*union_dircheckp) __P((struct thread *td, struct vnode **, struct file *));
@ -1697,7 +1700,35 @@ olseek(td, uap)
#endif /* COMPAT_43 */
/*
* Check access permissions.
* Check access permissions using passed credentials.
*/
static int
vpaccess(vp, user_flags, cred, td)
struct vnode *vp;
int user_flags;
struct ucred *cred;
struct thread *td;
{
int error, flags;
/* Flags == 0 means only check for existence. */
error = 0;
if (user_flags) {
flags = 0;
if (user_flags & R_OK)
flags |= VREAD;
if (user_flags & W_OK)
flags |= VWRITE;
if (user_flags & X_OK)
flags |= VEXEC;
if ((flags & VWRITE) == 0 || (error = vn_writechk(vp)) == 0)
error = VOP_ACCESS(vp, flags, cred, td);
}
return (error);
}
/*
* Check access permissions using "real" credentials.
*/
#ifndef _SYS_SYSPROTO_H_
struct access_args {
@ -1715,7 +1746,7 @@ access(td, uap)
{
struct ucred *cred, *tmpcred;
register struct vnode *vp;
int error, flags;
int error;
struct nameidata nd;
cred = td->td_proc->p_ucred;
@ -1738,18 +1769,7 @@ access(td, uap)
goto out1;
vp = nd.ni_vp;
/* Flags == 0 means only check for existence. */
if (SCARG(uap, flags)) {
flags = 0;
if (SCARG(uap, flags) & R_OK)
flags |= VREAD;
if (SCARG(uap, flags) & W_OK)
flags |= VWRITE;
if (SCARG(uap, flags) & X_OK)
flags |= VEXEC;
if ((flags & VWRITE) == 0 || (error = vn_writechk(vp)) == 0)
error = VOP_ACCESS(vp, flags, tmpcred, td);
}
error = vpaccess(vp, SCARG(uap, flags), tmpcred, td);
NDFREE(&nd, NDF_ONLY_PNBUF);
vput(vp);
out1:
@ -1758,6 +1778,39 @@ access(td, uap)
return (error);
}
/*
* Check access permissions using "effective" credentials.
*/
#ifndef _SYS_SYSPROTO_H_
struct eaccess_args {
char *path;
int flags;
};
#endif
int
eaccess(td, uap)
struct thread *td;
register struct eaccess_args /* {
syscallarg(char *) path;
syscallarg(int) flags;
} */ *uap;
{
struct nameidata nd;
struct vnode *vp;
int error;
NDINIT(&nd, LOOKUP, FOLLOW | LOCKLEAF | NOOBJ, UIO_USERSPACE,
SCARG(uap, path), td);
if ((error = namei(&nd)) != 0)
return (error);
vp = nd.ni_vp;
error = vpaccess(vp, SCARG(uap, flags), td->td_proc->p_ucred, td);
NDFREE(&nd, NDF_ONLY_PNBUF);
vput(vp);
return (error);
}
#if defined(COMPAT_43) || defined(COMPAT_SUNOS)
/*
* Get file status; this version follows links.