158 lines
4.3 KiB
C
158 lines
4.3 KiB
C
/* Created (MFS based):
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* February 2010 (Evgeniy Ivanov)
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*/
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#include "fs.h"
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#include "inode.h"
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#include "super.h"
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#include <minix/vfsif.h>
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static int in_group(gid_t grp);
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/*===========================================================================*
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* fs_chmod *
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*===========================================================================*/
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int fs_chmod()
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{
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/* Perform the chmod(name, mode) system call. */
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register struct inode *rip;
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pmode_t mode;
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mode = (pmode_t) fs_m_in.REQ_MODE;
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/* Temporarily open the file. */
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if( (rip = get_inode(fs_dev, (pino_t) fs_m_in.REQ_INODE_NR)) == NULL)
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return(EINVAL);
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/* Now make the change. Clear setgid bit if file is not in caller's grp */
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rip->i_mode = (rip->i_mode & ~ALL_MODES) | (mode & ALL_MODES);
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rip->i_update |= CTIME;
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rip->i_dirt = IN_DIRTY;
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/* Return full new mode to caller. */
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fs_m_out.RES_MODE = rip->i_mode;
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put_inode(rip);
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return(OK);
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}
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/*===========================================================================*
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* fs_chown *
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*===========================================================================*/
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int fs_chown()
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{
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register struct inode *rip;
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register int r;
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/* Temporarily open the file. */
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if( (rip = get_inode(fs_dev, (pino_t) fs_m_in.REQ_INODE_NR)) == NULL)
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return(EINVAL);
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/* Not permitted to change the owner of a file on a read-only file sys. */
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r = read_only(rip);
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if (r == OK) {
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rip->i_uid = fs_m_in.REQ_UID;
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rip->i_gid = fs_m_in.REQ_GID;
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rip->i_mode &= ~(I_SET_UID_BIT | I_SET_GID_BIT);
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rip->i_update |= CTIME;
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rip->i_dirt = IN_DIRTY;
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}
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/* Update caller on current mode, as it may have changed. */
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fs_m_out.RES_MODE = rip->i_mode;
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put_inode(rip);
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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(register struct inode *rip, pmode_t access_desired)
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{
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/* Given a pointer to an inode, 'rip', 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 struct inode *old_rip = rip;
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register pmode_t bits, perm_bits;
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int r, shift;
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/* Isolate the relevant rwx bits from the mode. */
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bits = rip->i_mode;
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if (caller_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 ( (bits & I_TYPE) == I_DIRECTORY ||
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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 (caller_uid == rip->i_uid) shift = 6; /* owner */
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else if (caller_gid == rip->i_gid) shift = 3; /* group */
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else if (in_group(rip->i_gid) == OK) shift = 3; /* other 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(rip);
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}
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}
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if (rip != old_rip) put_inode(rip);
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return(r);
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}
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/*===========================================================================*
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* in_group *
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*===========================================================================*/
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static int in_group(gid_t grp)
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{
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int i;
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if (credentials.vu_ngroups > NGROUPS_MAX)
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return(EINVAL);
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for (i = 0; i < credentials.vu_ngroups; i++)
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if (credentials.vu_sgroups[i] == grp)
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return(OK);
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return(EINVAL);
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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(ip)
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struct inode *ip; /* 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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register struct super_block *sp;
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sp = ip->i_sp;
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return(sp->s_rd_only ? EROFS : OK);
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}
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