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Cygwin: access: Correction for samba/SMB share

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Previously, access() and eaccess() does not determine the permissions
for files on samba/SMB share correctly. Even if the user logs-in as
the owner of the file, access() and eaccess() referes to others'
permissions. With this patch, to determine the permissions correctly,
NtOpenFile() with desired access mask is used.

Fixes: cf762b08cf ("* security.cc (check_file_access): Create.")
Reviewed-by: Corinna Vinschen <corinna@vinschen.de>
Signed-off-by: Takashi Yano <takashi.yano@nifty.ne.jp>
This commit is contained in:
Takashi Yano 2024-12-08 07:34:48 +09:00
parent 815eba882e
commit a0933cd17d
1 changed files with 20 additions and 99 deletions
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119
winsup/cygwin/sec/base.cc
View file

@ -28,10 +28,6 @@ details. */
| GROUP_SECURITY_INFORMATION \
| OWNER_SECURITY_INFORMATION)
static GENERIC_MAPPING NO_COPY_RO file_mapping = { FILE_GENERIC_READ,
FILE_GENERIC_WRITE,
FILE_GENERIC_EXECUTE,
FILE_ALL_ACCESS };
LONG
get_file_sd (HANDLE fh, path_conv &pc, security_descriptor &sd,
bool justcreated)
@ -605,99 +601,9 @@ check_access (security_descriptor &sd, GENERIC_MAPPING &mapping,
return ret;
}
/* Samba override. Check security descriptor for Samba UNIX user and group
accounts and check if we have an RFC 2307 mapping to a Windows account.
Create a new security descriptor with all of the UNIX accounts with
valid mapping replaced with their Windows counterpart. */
static void
convert_samba_sd (security_descriptor &sd_ret)
{
NTSTATUS status;
BOOLEAN dummy;
PSID sid;
cygsid owner;
cygsid group;
SECURITY_DESCRIPTOR sd;
cyg_ldap cldap;
tmp_pathbuf tp;
PACL acl, oacl;
size_t acl_len;
PACCESS_ALLOWED_ACE ace;
if (!NT_SUCCESS (RtlGetOwnerSecurityDescriptor (sd_ret, &sid, &dummy)))
return;
owner = sid;
if (!NT_SUCCESS (RtlGetGroupSecurityDescriptor (sd_ret, &sid, &dummy)))
return;
group = sid;
if (sid_id_auth (owner) == 22)
{
struct passwd *pwd;
uid_t uid = owner.get_uid (&cldap);
if (uid < UNIX_POSIX_OFFSET && (pwd = internal_getpwuid (uid)))
owner.getfrompw (pwd);
}
if (sid_id_auth (group) == 22)
{
struct group *grp;
gid_t gid = group.get_gid (&cldap);
if (gid < UNIX_POSIX_OFFSET && (grp = internal_getgrgid (gid)))
group.getfromgr (grp);
}
if (!NT_SUCCESS (RtlGetDaclSecurityDescriptor (sd_ret, &dummy,
&oacl, &dummy)))
return;
acl = (PACL) tp.w_get ();
RtlCreateAcl (acl, ACL_MAXIMUM_SIZE, ACL_REVISION);
acl_len = sizeof (ACL);
for (DWORD i = 0; i < oacl->AceCount; ++i)
if (NT_SUCCESS (RtlGetAce (oacl, i, (PVOID *) &ace)))
{
cygsid ace_sid ((PSID) &ace->SidStart);
if (sid_id_auth (ace_sid) == 22)
{
if (sid_sub_auth (ace_sid, 0) == 1) /* user */
{
struct passwd *pwd;
uid_t uid = ace_sid.get_uid (&cldap);
if (uid < UNIX_POSIX_OFFSET && (pwd = internal_getpwuid (uid)))
ace_sid.getfrompw (pwd);
}
else if (sid_sub_auth (ace_sid, 0) == 2) /* group */
{
struct group *grp;
gid_t gid = ace_sid.get_gid (&cldap);
if (gid < UNIX_POSIX_OFFSET && (grp = internal_getgrgid (gid)))
ace_sid.getfromgr (grp);
}
}
if (!add_access_allowed_ace (acl, ace->Mask, ace_sid, acl_len,
ace->Header.AceFlags))
return;
}
acl->AclSize = acl_len;
RtlCreateSecurityDescriptor (&sd, SECURITY_DESCRIPTOR_REVISION);
RtlSetControlSecurityDescriptor (&sd, SE_DACL_PROTECTED, SE_DACL_PROTECTED);
RtlSetOwnerSecurityDescriptor (&sd, owner, FALSE);
RtlSetGroupSecurityDescriptor (&sd, group, FALSE);
status = RtlSetDaclSecurityDescriptor (&sd, TRUE, acl, FALSE);
if (!NT_SUCCESS (status))
return;
DWORD sd_size = 0;
status = RtlAbsoluteToSelfRelativeSD (&sd, sd_ret, &sd_size);
if (sd_size > 0 && sd_ret.malloc (sd_size))
RtlAbsoluteToSelfRelativeSD (&sd, sd_ret, &sd_size);
}
int
check_file_access (path_conv &pc, int flags, bool effective)
{
security_descriptor sd;
int ret = -1;
ACCESS_MASK desired = 0;
if (flags & R_OK)
@ -706,13 +612,28 @@ check_file_access (path_conv &pc, int flags, bool effective)
desired |= FILE_WRITE_DATA;
if (flags & X_OK)
desired |= FILE_EXECUTE;
if (!get_file_sd (pc.handle (), pc, sd, false))
if (!effective)
cygheap->user.deimpersonate ();
OBJECT_ATTRIBUTES attr;
pc.init_reopen_attr (attr, pc.handle ());
NTSTATUS status;
IO_STATUS_BLOCK io;
HANDLE h;
status = NtOpenFile (&h, desired, &attr, &io, FILE_SHARE_VALID_FLAGS,
FILE_OPEN_FOR_BACKUP_INTENT);
if (NT_SUCCESS (status))
{
/* Tweak Samba security descriptor as necessary. */
if (pc.fs_is_samba ())
convert_samba_sd (sd);
ret = check_access (sd, file_mapping, desired, flags, effective);
NtClose (h);
ret = 0;
}
else
__seterrno_from_nt_status (status);
if (!effective)
cygheap->user.reimpersonate ();
debug_printf ("flags %y, ret %d", flags, ret);
return ret;
}