1 /* Group merging implementation.
2 Copyright (C) 2016-2017 Free Software Foundation, Inc.
3 This file is part of the GNU C Library.
5 The GNU C Library is free software; you can redistribute it and/or
6 modify it under the terms of the GNU Lesser General Public
7 License as published by the Free Software Foundation; either
8 version 2.1 of the License, or (at your option) any later version.
10 The GNU C Library is distributed in the hope that it will be useful,
11 but WITHOUT ANY WARRANTY; without even the implied warranty of
12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13 Lesser General Public License for more details.
15 You should have received a copy of the GNU Lesser General Public
16 License along with the GNU C Library; if not, see
17 <http://www.gnu.org/licenses/>. */
23 #include <grp-merge.h>
25 #define BUFCHECK(size) \
29 if (c + (size) > buflen) \
40 __copy_grp (const struct group srcgrp
, const size_t buflen
,
41 struct group
*destgrp
, char *destbuf
, char **endptr
)
47 char **members
= NULL
;
50 destgrp
->gr_gid
= srcgrp
.gr_gid
;
53 len
= strlen (srcgrp
.gr_name
) + 1;
55 memcpy (&destbuf
[c
], srcgrp
.gr_name
, len
);
56 destgrp
->gr_name
= &destbuf
[c
];
59 /* Copy the password. */
60 len
= strlen (srcgrp
.gr_passwd
) + 1;
62 memcpy (&destbuf
[c
], srcgrp
.gr_passwd
, len
);
63 destgrp
->gr_passwd
= &destbuf
[c
];
66 /* Count all of the members. */
67 for (memcount
= 0; srcgrp
.gr_mem
[memcount
]; memcount
++)
70 /* Allocate a temporary holding area for the pointers to the member
71 contents, including space for a NULL-terminator. */
72 members
= malloc (sizeof (char *) * (memcount
+ 1));
76 /* Copy all of the group members to destbuf and add a pointer to each of
77 them into the 'members' array. */
78 for (i
= 0; srcgrp
.gr_mem
[i
]; i
++)
80 len
= strlen (srcgrp
.gr_mem
[i
]) + 1;
82 memcpy (&destbuf
[c
], srcgrp
.gr_mem
[i
], len
);
83 members
[i
] = &destbuf
[c
];
88 /* Align for pointers. We can't simply align C because we need to
90 if ((((uintptr_t)destbuf
+ c
) & (__alignof__(char **) - 1)) != 0)
92 uintptr_t mis_align
= ((uintptr_t)destbuf
+ c
) & (__alignof__(char **) - 1);
93 c
+= __alignof__(char **) - mis_align
;
96 /* Copy the pointers from the members array into the buffer and assign them
97 to the gr_mem member of destgrp. */
98 destgrp
->gr_mem
= (char **) &destbuf
[c
];
99 len
= sizeof (char *) * (memcount
+ 1);
101 memcpy (&destbuf
[c
], members
, len
);
106 /* Save the count of members at the end. */
107 BUFCHECK (sizeof (size_t));
108 memcpy (&destbuf
[c
], &memcount
, sizeof (size_t));
109 c
+= sizeof (size_t);
112 *endptr
= destbuf
+ c
;
115 libc_hidden_def (__copy_grp
)
117 /* Check that the name, GID and passwd fields match, then
118 copy in the gr_mem array. */
121 __merge_grp (struct group
*savedgrp
, char *savedbuf
, char *savedend
,
122 size_t buflen
, struct group
*mergegrp
, char *mergebuf
)
125 size_t savedmemcount
;
128 char **members
= NULL
;
130 /* We only support merging members of groups with identical names and
131 GID values. If we hit this case, we need to overwrite the current
132 buffer with the saved one (which is functionally equivalent to
133 treating the new lookup as NSS_STATUS_NOTFOUND). */
134 if (mergegrp
->gr_gid
!= savedgrp
->gr_gid
135 || strcmp (mergegrp
->gr_name
, savedgrp
->gr_name
))
136 return __copy_grp (*savedgrp
, buflen
, mergegrp
, mergebuf
, NULL
);
138 /* Get the count of group members from the last sizeof (size_t) bytes in the
140 savedmemcount
= *(size_t *) (savedend
- sizeof (size_t));
142 /* Get the count of new members to add. */
143 for (memcount
= 0; mergegrp
->gr_mem
[memcount
]; memcount
++)
146 /* Create a temporary array to hold the pointers to the member values from
147 both the saved and merge groups. */
148 membersize
= savedmemcount
+ memcount
+ 1;
149 members
= malloc (sizeof (char *) * membersize
);
153 /* Copy in the existing member pointers from the saved group
154 Note: this is not NULL-terminated yet. */
155 memcpy (members
, savedgrp
->gr_mem
, sizeof (char *) * savedmemcount
);
157 /* Back up into the savedbuf until we get back to the NULL-terminator of the
158 group member list. (This means walking back savedmemcount + 1 (char *) pointers
159 and the member count value.
160 The value of c is going to be the used length of the buffer backed up by
161 the member count and further backed up by the size of the pointers. */
162 c
= savedend
- savedbuf
164 - sizeof (char *) * (savedmemcount
+ 1);
166 /* Add all the new group members, overwriting the old NULL-terminator while
167 adding the new pointers to the temporary array. */
168 for (i
= 0; mergegrp
->gr_mem
[i
]; i
++)
170 len
= strlen (mergegrp
->gr_mem
[i
]) + 1;
172 memcpy (&savedbuf
[c
], mergegrp
->gr_mem
[i
], len
);
173 members
[savedmemcount
+ i
] = &savedbuf
[c
];
176 /* Add the NULL-terminator. */
177 members
[savedmemcount
+ memcount
] = NULL
;
179 /* Align for pointers. We can't simply align C because we need to
180 align savedbuf[c]. */
181 if ((((uintptr_t)savedbuf
+ c
) & (__alignof__(char **) - 1)) != 0)
183 uintptr_t mis_align
= ((uintptr_t)savedbuf
+ c
) & (__alignof__(char **) - 1);
184 c
+= __alignof__(char **) - mis_align
;
187 /* Copy the member array back into the buffer after the member list and free
189 savedgrp
->gr_mem
= (char **) &savedbuf
[c
];
190 len
= sizeof (char *) * membersize
;
192 memcpy (&savedbuf
[c
], members
, len
);
198 /* Finally, copy the results back into mergebuf, since that's the buffer
199 that we were provided by the caller. */
200 return __copy_grp (*savedgrp
, buflen
, mergegrp
, mergebuf
, NULL
);
202 libc_hidden_def (__merge_grp
)