301 lines
8.5 KiB
C
301 lines
8.5 KiB
C
/* This file deals with protection in the file system. It contains the code
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* for four system calls that relate to protection.
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*
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* The entry points into this file are
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* do_chmod: perform the CHMOD and FCHMOD system calls
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* do_chown: perform the CHOWN and FCHOWN system calls
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* do_umask: perform the UMASK system call
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* do_access: perform the ACCESS system call
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*/
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#include "fs.h"
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#include <sys/stat.h>
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#include <unistd.h>
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#include <assert.h>
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#include <minix/callnr.h>
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#include "file.h"
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#include "path.h"
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#include <minix/vfsif.h>
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#include "vnode.h"
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#include "vmnt.h"
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/*===========================================================================*
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* do_chmod *
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*===========================================================================*/
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int do_chmod(void)
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{
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/* Perform the chmod(name, mode) and fchmod(fd, mode) system calls.
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* syscall might provide 'name' embedded in the message.
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*/
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struct filp *flp;
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struct vnode *vp;
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struct vmnt *vmp;
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int r, rfd;
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mode_t result_mode;
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char fullpath[PATH_MAX];
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struct lookup resolve;
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mode_t new_mode;
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flp = NULL;
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lookup_init(&resolve, fullpath, PATH_NOFLAGS, &vmp, &vp);
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resolve.l_vmnt_lock = VMNT_READ;
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resolve.l_vnode_lock = VNODE_WRITE;
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if (job_call_nr == VFS_CHMOD) {
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new_mode = job_m_in.m_lc_vfs_path.mode;
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/* Temporarily open the file */
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if (copy_path(fullpath, sizeof(fullpath)) != OK)
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return(err_code);
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if ((vp = eat_path(&resolve, fp)) == NULL) return(err_code);
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} else { /* call_nr == VFS_FCHMOD */
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rfd = job_m_in.m_lc_vfs_fchmod.fd;
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new_mode = job_m_in.m_lc_vfs_fchmod.mode;
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/* File is already opened; get a pointer to vnode from filp. */
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if ((flp = get_filp(rfd, VNODE_WRITE)) == NULL) return(err_code);
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vp = flp->filp_vno;
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assert(vp);
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dup_vnode(vp);
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}
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assert(vp);
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/* Only the owner or the super_user may change the mode of a file.
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* No one may change the mode of a file on a read-only file system.
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*/
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if (vp->v_uid != fp->fp_effuid && fp->fp_effuid != SU_UID)
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r = EPERM;
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else
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r = read_only(vp);
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if (r == OK) {
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/* Now make the change. Clear setgid bit if file is not in caller's
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* group */
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if (fp->fp_effuid != SU_UID && vp->v_gid != fp->fp_effgid)
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new_mode &= ~I_SET_GID_BIT;
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r = req_chmod(vp->v_fs_e, vp->v_inode_nr, new_mode, &result_mode);
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if (r == OK)
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vp->v_mode = result_mode;
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}
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if (job_call_nr == VFS_CHMOD) {
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unlock_vnode(vp);
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unlock_vmnt(vmp);
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} else { /* VFS_FCHMOD */
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unlock_filp(flp);
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}
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put_vnode(vp);
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return(r);
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}
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/*===========================================================================*
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* do_chown *
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*===========================================================================*/
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int do_chown(void)
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{
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/* Perform the chown(path, owner, group) and fchmod(fd, owner, group) system
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* calls. */
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struct filp *flp;
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struct vnode *vp;
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struct vmnt *vmp;
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int r, rfd;
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uid_t uid, new_uid;
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gid_t gid, new_gid;
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mode_t new_mode;
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char fullpath[PATH_MAX];
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struct lookup resolve;
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vir_bytes vname1;
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size_t vname1_length;
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flp = NULL;
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uid = job_m_in.m_lc_vfs_chown.owner;
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gid = job_m_in.m_lc_vfs_chown.group;
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if (job_call_nr == VFS_CHOWN) {
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vname1 = job_m_in.m_lc_vfs_chown.name;
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vname1_length = job_m_in.m_lc_vfs_chown.len;
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lookup_init(&resolve, fullpath, PATH_NOFLAGS, &vmp, &vp);
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resolve.l_vmnt_lock = VMNT_READ;
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resolve.l_vnode_lock = VNODE_WRITE;
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/* Temporarily open the file. */
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if (fetch_name(vname1, vname1_length, fullpath) != OK)
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return(err_code);
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if ((vp = eat_path(&resolve, fp)) == NULL) return(err_code);
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} else { /* call_nr == VFS_FCHOWN */
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rfd = job_m_in.m_lc_vfs_chown.fd;
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/* File is already opened; get a pointer to the vnode from filp. */
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if ((flp = get_filp(rfd, VNODE_WRITE)) == NULL)
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return(err_code);
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vp = flp->filp_vno;
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dup_vnode(vp);
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}
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r = read_only(vp);
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if (r == OK) {
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/* FS is R/W. Whether call is allowed depends on ownership, etc. */
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/* The super user can do anything, so check permissions only if we're
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a regular user. */
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if (fp->fp_effuid != SU_UID) {
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/* Regular users can only change groups of their own files. */
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if (vp->v_uid != fp->fp_effuid) r = EPERM;
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if (vp->v_uid != uid) r = EPERM; /* no giving away */
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if (fp->fp_effgid != gid) r = EPERM;
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}
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}
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if (r == OK) {
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/* Do not change uid/gid if new uid/gid is -1. */
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new_uid = (uid == (uid_t)-1 ? vp->v_uid : uid);
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new_gid = (gid == (gid_t)-1 ? vp->v_gid : gid);
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if (new_uid > UID_MAX || new_gid > GID_MAX)
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r = EINVAL;
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else if ((r = req_chown(vp->v_fs_e, vp->v_inode_nr, new_uid, new_gid,
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&new_mode)) == OK) {
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vp->v_uid = new_uid;
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vp->v_gid = new_gid;
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vp->v_mode = new_mode;
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}
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}
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if (job_call_nr == VFS_CHOWN) {
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unlock_vnode(vp);
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unlock_vmnt(vmp);
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} else { /* VFS_FCHOWN */
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unlock_filp(flp);
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}
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put_vnode(vp);
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return(r);
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}
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/*===========================================================================*
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* do_umask *
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*===========================================================================*/
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int do_umask(void)
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{
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/* Perform the umask(2) system call. */
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mode_t complement, new_umask;
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new_umask = job_m_in.m_lc_vfs_umask.mask;
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complement = ~fp->fp_umask; /* set 'r' to complement of old mask */
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fp->fp_umask = ~(new_umask & RWX_MODES);
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return(complement); /* return complement of old mask */
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}
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/*===========================================================================*
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* do_access *
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*===========================================================================*/
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int do_access(void)
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{
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/* Perform the access(name, mode) system call.
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* syscall might provide 'name' embedded in the message.
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*/
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int r;
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struct vnode *vp;
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struct vmnt *vmp;
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char fullpath[PATH_MAX];
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struct lookup resolve;
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mode_t access;
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access = job_m_in.m_lc_vfs_path.mode;
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lookup_init(&resolve, fullpath, PATH_NOFLAGS, &vmp, &vp);
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resolve.l_vmnt_lock = VMNT_READ;
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resolve.l_vnode_lock = VNODE_READ;
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/* First check to see if the mode is correct. */
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if ( (access & ~(R_OK | W_OK | X_OK)) != 0 && access != F_OK)
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return(EINVAL);
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/* Temporarily open the file. */
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if (copy_path(fullpath, sizeof(fullpath)) != OK)
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return(err_code);
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if ((vp = eat_path(&resolve, fp)) == NULL) return(err_code);
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r = forbidden(fp, vp, access);
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unlock_vnode(vp);
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unlock_vmnt(vmp);
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put_vnode(vp);
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return(r);
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}
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/*===========================================================================*
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* forbidden *
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*===========================================================================*/
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int forbidden(struct fproc *rfp, struct vnode *vp, mode_t access_desired)
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{
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/* Given a pointer to an vnode, 'vp', and the access desired, determine
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* if the access is allowed, and if not why not. The routine looks up the
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* caller's uid in the 'fproc' table. If access is allowed, OK is returned
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* if it is forbidden, EACCES is returned.
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*/
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register mode_t bits, perm_bits;
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uid_t uid;
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gid_t gid;
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int r, shift;
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if (vp->v_uid == (uid_t) -1 || vp->v_gid == (gid_t) -1) return(EACCES);
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/* Isolate the relevant rwx bits from the mode. */
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bits = vp->v_mode;
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uid = (job_call_nr == VFS_ACCESS ? rfp->fp_realuid : rfp->fp_effuid);
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gid = (job_call_nr == VFS_ACCESS ? rfp->fp_realgid : rfp->fp_effgid);
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if (uid == SU_UID) {
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/* Grant read and write permission. Grant search permission for
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* directories. Grant execute permission (for non-directories) if
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* and only if one of the 'X' bits is set.
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*/
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if ( S_ISDIR(bits) || bits & ((X_BIT << 6) | (X_BIT << 3) | X_BIT))
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perm_bits = R_BIT | W_BIT | X_BIT;
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else
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perm_bits = R_BIT | W_BIT;
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} else {
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if (uid == vp->v_uid) shift = 6; /* owner */
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else if (gid == vp->v_gid) shift = 3; /* group */
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else if (in_group(fp, vp->v_gid) == OK) shift = 3; /* suppl. groups */
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else shift = 0; /* other */
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perm_bits = (bits >> shift) & (R_BIT | W_BIT | X_BIT);
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}
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/* If access desired is not a subset of what is allowed, it is refused. */
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r = OK;
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if ((perm_bits | access_desired) != perm_bits) r = EACCES;
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/* Check to see if someone is trying to write on a file system that is
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* mounted read-only.
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*/
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if (r == OK)
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if (access_desired & W_BIT)
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r = read_only(vp);
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return(r);
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}
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/*===========================================================================*
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* read_only *
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*===========================================================================*/
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int read_only(vp)
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struct vnode *vp; /* ptr to inode whose file sys is to be cked */
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{
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/* Check to see if the file system on which the inode 'ip' resides is mounted
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* read only. If so, return EROFS, else return OK.
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*/
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assert(vp);
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return(vp->v_vmnt && (vp->v_vmnt->m_flags & VMNT_READONLY) ? EROFS : OK);
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}
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