sec_acl.cc

cygwin, 著名的在win32下模拟unix操作系统的东东

/* secacl.cc: Sun compatible ACL functions.

   Copyright 2000, 2001, 2002 Red Hat, Inc.

   Written by Corinna Vinschen <[e-mail]>

This file is part of Cygwin.

This software is a copyrighted work licensed under the terms of the
Cygwin license.  Please consult the file "CYGWIN_LICENSE" for
details. */

#include "winsup.h"
#include <grp.h>
#include <pwd.h>
#include <unistd.h>
#include <stdlib.h>
#include <errno.h>
#include <limits.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/acl.h>
#include <ctype.h>
#include <wingdi.h>
#include <winuser.h>
#include "cygerrno.h"
#include "security.h"
#include "fhandler.h"
#include "path.h"
#include "dtable.h"
#include "pinfo.h"
#include "cygheap.h"

extern "C" int aclsort (int nentries, int, __aclent16_t *aclbufp);
extern "C" int acl (const char *path, int cmd, int nentries, __aclent16_t *aclbufp);

static int
searchace (__aclent16_t *aclp, int nentries, int type, int id = -1)
{
  int i;

  for (i = 0; i < nentries; ++i)
    if ((aclp[i].a_type == type && (id < 0 || aclp[i].a_id == id))
	|| !aclp[i].a_type)
      return i;
  return -1;
}

static int
setacl (const char *file, int nentries, __aclent16_t *aclbufp)
{
  DWORD sd_size = 4096;
  char sd_buf[4096];
  PSECURITY_DESCRIPTOR psd = (PSECURITY_DESCRIPTOR) sd_buf;

  if (read_sd (file, psd, &sd_size) <= 0)
    {
      debug_printf ("read_sd %E");
      return -1;
    }

  BOOL dummy;

  /* Get owner SID. */
  PSID owner_sid = NULL;
  if (!GetSecurityDescriptorOwner (psd, &owner_sid, &dummy))
    {
      __seterrno ();
      return -1;
    }
  cygsid owner (owner_sid);

  /* Get group SID. */
  PSID group_sid = NULL;
  if (!GetSecurityDescriptorGroup (psd, &group_sid, &dummy))
    {
      __seterrno ();
      return -1;
    }
  cygsid group (group_sid);

  /* Initialize local security descriptor. */
  SECURITY_DESCRIPTOR sd;
  if (!InitializeSecurityDescriptor (&sd, SECURITY_DESCRIPTOR_REVISION))
    {
      __seterrno ();
      return -1;
    }
  if (!SetSecurityDescriptorOwner (&sd, owner, FALSE))
    {
      __seterrno ();
      return -1;
    }
  if (group
      && !SetSecurityDescriptorGroup (&sd, group, FALSE))
    {
      __seterrno ();
      return -1;
    }

  /* Fill access control list. */
  char acl_buf[3072];
  PACL acl = (PACL) acl_buf;
  size_t acl_len = sizeof (ACL);
  int ace_off = 0;

  cygsid sid;
  struct passwd *pw;
  struct __group32 *gr;
  int pos;

  if (!InitializeAcl (acl, 3072, ACL_REVISION))
    {
      __seterrno ();
      return -1;
    }
  for (int i = 0; i < nentries; ++i)
    {
      DWORD allow = STANDARD_RIGHTS_READ
		    | FILE_READ_ATTRIBUTES | FILE_READ_EA;
      if (aclbufp[i].a_perm & S_IROTH)
	allow |= FILE_GENERIC_READ;
      if (aclbufp[i].a_perm & S_IWOTH)
	allow |= STANDARD_RIGHTS_ALL | FILE_GENERIC_WRITE;
      if (aclbufp[i].a_perm & S_IXOTH)
	allow |= FILE_GENERIC_EXECUTE;
      if ((aclbufp[i].a_perm & (S_IWOTH | S_IXOTH)) == (S_IWOTH | S_IXOTH))
	allow |= FILE_DELETE_CHILD;
      /* Set inherit property. */
      DWORD inheritance = (aclbufp[i].a_type & ACL_DEFAULT)
			  ? (SUB_CONTAINERS_AND_OBJECTS_INHERIT | INHERIT_ONLY)
			  : NO_INHERITANCE;
      /*
       * If a specific acl contains a corresponding default entry with
       * identical permissions, only one Windows ACE with proper
       * inheritance bits is created.
       */
      if (!(aclbufp[i].a_type & ACL_DEFAULT)
	  && (pos = searchace (aclbufp, nentries,
			       aclbufp[i].a_type | ACL_DEFAULT,
			       (aclbufp[i].a_type & (USER|GROUP))
			       ? aclbufp[i].a_id : -1)) >= 0
	  && aclbufp[pos].a_type
	  && aclbufp[i].a_perm == aclbufp[pos].a_perm)
	{
	  inheritance = SUB_CONTAINERS_AND_OBJECTS_INHERIT;
	  /* This eliminates the corresponding default entry. */
	  aclbufp[pos].a_type = 0;
	}
      switch (aclbufp[i].a_type)
	{
	case USER_OBJ:
	case DEF_USER_OBJ:
	  allow |= STANDARD_RIGHTS_ALL & ~DELETE;
	  if (!add_access_allowed_ace (acl, ace_off++, allow,
					owner, acl_len, inheritance))
	    return -1;
	  break;
	case USER:
	case DEF_USER:
	  if (!(pw = getpwuid32 (aclbufp[i].a_id))
	      || !sid.getfrompw (pw)
	      || !add_access_allowed_ace (acl, ace_off++, allow,
					   sid, acl_len, inheritance))
	    return -1;
	  break;
	case GROUP_OBJ:
	case DEF_GROUP_OBJ:
	  if (!add_access_allowed_ace (acl, ace_off++, allow,
					group, acl_len, inheritance))
	    return -1;
	  break;
	case GROUP:
	case DEF_GROUP:
	  if (!(gr = getgrgid32 (aclbufp[i].a_id))
	      || !sid.getfromgr (gr)
	      || !add_access_allowed_ace (acl, ace_off++, allow,
					   sid, acl_len, inheritance))
	    return -1;
	  break;
	case OTHER_OBJ:
	case DEF_OTHER_OBJ:
	  if (!add_access_allowed_ace (acl, ace_off++, allow,
				       well_known_world_sid,
				       acl_len, inheritance))
	    return -1;
	  break;
	}
    }
  /* Set AclSize to computed value. */
  acl->AclSize = acl_len;
  debug_printf ("ACL-Size: %d", acl_len);
  /* Create DACL for local security descriptor. */
  if (!SetSecurityDescriptorDacl (&sd, TRUE, acl, FALSE))
    {
      __seterrno ();
      return -1;
    }
  /* Make self relative security descriptor in psd. */
  sd_size = 0;
  MakeSelfRelativeSD (&sd, psd, &sd_size);
  if (sd_size <= 0)
    {
      __seterrno ();
      return -1;
    }
  if (!MakeSelfRelativeSD (&sd, psd, &sd_size))
    {
      __seterrno ();
      return -1;
    }
  debug_printf ("Created SD-Size: %d", sd_size);
  return write_sd (file, psd, sd_size);
}

/* Temporary access denied bits */
#define DENY_R 040000
#define DENY_W 020000
#define DENY_X 010000

static void
getace (__aclent16_t &acl, int type, int id, DWORD win_ace_mask,
        DWORD win_ace_type)
{
  acl.a_type = type;
  acl.a_id = id;

  if ((win_ace_mask & FILE_READ_DATA) && !(acl.a_perm & (S_IROTH | DENY_R)))
    if (win_ace_type == ACCESS_ALLOWED_ACE_TYPE)
      acl.a_perm |= S_IROTH;
    else if (win_ace_type == ACCESS_DENIED_ACE_TYPE)
      acl.a_perm |= DENY_R;

  if ((win_ace_mask & FILE_WRITE_DATA) && !(acl.a_perm & (S_IWOTH | DENY_W)))
    if (win_ace_type == ACCESS_ALLOWED_ACE_TYPE)
      acl.a_perm |= S_IWOTH;
    else if (win_ace_type == ACCESS_DENIED_ACE_TYPE)
      acl.a_perm |= DENY_W;

  if ((win_ace_mask & FILE_EXECUTE) && !(acl.a_perm & (S_IXOTH | DENY_X)))
    if (win_ace_type == ACCESS_ALLOWED_ACE_TYPE)
      acl.a_perm |= S_IXOTH;
    else if (win_ace_type == ACCESS_DENIED_ACE_TYPE)
      acl.a_perm |= DENY_X;
}

static int
getacl (const char *file, DWORD attr, int nentries, __aclent16_t *aclbufp)
{
  DWORD sd_size = 4096;
  char sd_buf[4096];
  PSECURITY_DESCRIPTOR psd = (PSECURITY_DESCRIPTOR) sd_buf;

  int ret;
  if ((ret = read_sd (file, psd, &sd_size)) <= 0)
    {
      debug_printf ("read_sd %E");
      return ret;
    }

  PSID owner_sid;
  PSID group_sid;
  BOOL dummy;
  __uid32_t uid;
  __gid32_t gid;

  if (!GetSecurityDescriptorOwner (psd, &owner_sid, &dummy))
    {
      debug_printf ("GetSecurityDescriptorOwner %E");
      __seterrno ();
      return -1;
    }
  uid = cygsid (owner_sid).get_uid ();

  if (!GetSecurityDescriptorGroup (psd, &group_sid, &dummy))
    {
      debug_printf ("GetSecurityDescriptorGroup %E");
      __seterrno ();
      return -1;
    }
  gid = cygsid (group_sid).get_gid ();

  __aclent16_t lacl[MAX_ACL_ENTRIES];
  memset (&lacl, 0, MAX_ACL_ENTRIES * sizeof (__aclent16_t));
  lacl[0].a_type = USER_OBJ;
  lacl[0].a_id = uid;
  lacl[1].a_type = GROUP_OBJ;
  lacl[1].a_id = gid;
  lacl[2].a_type = OTHER_OBJ;
  lacl[2].a_id = ILLEGAL_GID;
  lacl[3].a_type = CLASS_OBJ;
  lacl[3].a_id = ILLEGAL_GID;
  lacl[3].a_perm = S_IROTH | S_IWOTH | S_IXOTH;

  PACL acl;
  BOOL acl_exists;

  if (!GetSecurityDescriptorDacl (psd, &acl_exists, &acl, &dummy))
    {
      __seterrno ();
      debug_printf ("GetSecurityDescriptorDacl %E");
      return -1;
    }

  int pos, i, types_def = 0;

  if (!acl_exists || !acl)
    for (pos = 0; pos < 3; ++pos) /* Don't change CLASS_OBJ entry */
      lacl[pos].a_perm = S_IROTH | S_IWOTH | S_IXOTH;
  else
    {
      for (i = 0; i < acl->AceCount; ++i)
	{
	  ACCESS_ALLOWED_ACE *ace;
	  
	  if (!GetAce (acl, i, (PVOID *) &ace))
	    continue;

	  cygsid ace_sid ((PSID) &ace->SidStart);
	  int id;
	  int type = 0;

	  if (ace_sid == well_known_world_sid)
	    {
	      type = OTHER_OBJ;
	      id = ILLEGAL_GID;
	    }
	  else if (ace_sid == group_sid)
	    {
	      type = GROUP_OBJ;
	      id = gid;
	    }
	  else if (ace_sid == owner_sid)
	    {
	      type = USER_OBJ;
	      id = uid;
	    }
	  else
	    {
	      id = ace_sid.get_id (FALSE, &type);
	      if (type != GROUP)
		{
		  int type2 = 0;
		  int id2 = ace_sid.get_id (TRUE, &type2);
		  if (type2 == GROUP)
		    {
		      id = id2;
		      type = GROUP;
		    }
		}
	    }
	  if (!type)
	    continue;
	  if (!(ace->Header.AceFlags & INHERIT_ONLY))
	    {
	      if ((pos = searchace (lacl, MAX_ACL_ENTRIES, type, id)) >= 0)
		getace (lacl[pos], type, id, ace->Mask, ace->Header.AceType);
	    }
	  if ((ace->Header.AceFlags & SUB_CONTAINERS_AND_OBJECTS_INHERIT)
	      && (attr & FILE_ATTRIBUTE_DIRECTORY))
	    {
	      type |= ACL_DEFAULT;
	      types_def |= type;
	      if ((pos = searchace (lacl, MAX_ACL_ENTRIES, type, id)) >= 0)
		getace (lacl[pos], type, id, ace->Mask, ace->Header.AceType);
	    }
	}
      /* Include DEF_CLASS_OBJ if any default ace exists */
      if ((types_def & (USER|GROUP)) 
	  && ((pos = searchace (lacl, MAX_ACL_ENTRIES, DEF_CLASS_OBJ)) >= 0))
	{
	  lacl[pos].a_type = DEF_CLASS_OBJ;
	  lacl[pos].a_id = ILLEGAL_GID;
	  lacl[pos].a_perm = S_IRWXU | S_IRWXG | S_IRWXO;
	}
    }
  if ((pos = searchace (lacl, MAX_ACL_ENTRIES, 0)) < 0)
    pos = MAX_ACL_ENTRIES;
  if (aclbufp) {
    if (EqualSid (owner_sid, group_sid)) 
      lacl[0].a_perm = lacl[1].a_perm;
    if (pos > nentries)
      {
        set_errno (ENOSPC);
	return -1;
      }
    memcpy (aclbufp, lacl, pos * sizeof (__aclent16_t));
    for (i = 0; i < pos; ++i)
      aclbufp[i].a_perm &= ~(DENY_R | DENY_W | DENY_X);
    aclsort (pos, 0, aclbufp);
  }
  syscall_printf ("%d = getacl (%s)", pos, file);
  return pos;
}

int
acl_access (const char *path, int flags)
{
  __aclent16_t acls[MAX_ACL_ENTRIES];
  int cnt;

  if ((cnt = acl (path, GETACL, MAX_ACL_ENTRIES, acls)) < 1)
    return -1;

  /* Only check existance. */
  if (!(flags & (R_OK | W_OK | X_OK)))
    return 0;

  for (int i = 0; i < cnt; ++i)
    {
      switch (acls[i].a_type)
	{
	case USER_OBJ:
	case USER:
	  if (acls[i].a_id != myself->uid)
	    {
	      /*
	       * Check if user is a NT group:
	       * Take SID from passwd, search SID in group, check is_grp_member.
	       */
	      cygsid owner;
	      cygsid group;
	      struct passwd *pw;
	      struct __group32 *gr = NULL;

	      if ((pw = getpwuid32 (acls[i].a_id)) != NULL
		  && owner.getfrompw (pw))
		{
		  for (int gidx = 0; (gr = internal_getgrent (gidx)); ++gidx)
		    if (group.getfromgr (gr)
			&& owner == group
			&& is_grp_member (myself->uid, gr->gr_gid))
		      break;
		}
	      if (!gr)
		continue;
	    }
	  break;
	case GROUP_OBJ:
	case GROUP:
	  if (acls[i].a_id != myself->gid &&
	      !is_grp_member (myself->uid, acls[i].a_id))
	    continue;
	  break;
	case OTHER_OBJ:
	  break;
	default:
	  continue;
	}
      if ((!(flags & R_OK) || (acls[i].a_perm & S_IROTH))
	  && (!(flags & W_OK) || (acls[i].a_perm & S_IWOTH))
	  && (!(flags & X_OK) || (acls[i].a_perm & S_IXOTH)))
	return 0;
    }
  set_errno (EACCES);
  return -1;
}

static
int
acl_worker (const char *path, int cmd, int nentries, __aclent16_t *aclbufp,
	    int nofollow)
{
  extern suffix_info stat_suffixes[];
  path_conv real_path (path, (nofollow ? PC_SYM_NOFOLLOW : PC_SYM_FOLLOW) | PC_FULL, stat_suffixes);
  if (real_path.error)
    {
      set_errno (real_path.error);
      syscall_printf ("-1 = acl (%s)", path);
      return -1;
    }
  if (!real_path.has_acls () || !allow_ntsec)
    {
      struct __stat64 st;
      int ret = -1;

      switch (cmd)
	{
	case SETACL:
	  set_errno (ENOSYS);
	  break;
	case GETACL:
	  if (nentries < 1)
	    set_errno (EINVAL);
	  else if ((nofollow && !lstat64 (path, &st))
		   || (!nofollow && !stat64 (path, &st)))
	    {
	      __aclent16_t lacl[4];
	      if (nentries > 0)
		{
		  lacl[0].a_type = USER_OBJ;
		  lacl[0].a_id = st.st_uid;
		  lacl[0].a_perm = (st.st_mode & S_IRWXU) >> 6;
		}
	      if (nentries > 1)
		{
		  lacl[1].a_type = GROUP_OBJ;
		  lacl[1].a_id = st.st_gid;
		  lacl[1].a_perm = (st.st_mode & S_IRWXG) >> 3;
		}
	      if (nentries > 2)
		{
		  lacl[2].a_type = OTHER_OBJ;
		  lacl[2].a_id = ILLEGAL_GID;
		  lacl[2].a_perm = st.st_mode & S_IRWXO;
		}
	      if (nentries > 3)
		{
		  lacl[3].a_type = CLASS_OBJ;
		  lacl[3].a_id = ILLEGAL_GID;
		  lacl[3].a_perm = S_IRWXU | S_IRWXG | S_IRWXO;
		}
	      if (nentries > 4)
		nentries = 4;
	      if (aclbufp)
		memcpy (aclbufp, lacl, nentries * sizeof (__aclent16_t));
	      ret = nentries;
	    }
	  break;
	case GETACLCNT: