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Diffstat (limited to 'lib/euidaccess-stat.c')
| -rw-r--r-- | lib/euidaccess-stat.c | 143 |
1 files changed, 143 insertions, 0 deletions
diff --git a/lib/euidaccess-stat.c b/lib/euidaccess-stat.c new file mode 100644 index 0000000..7663c46 --- /dev/null +++ b/lib/euidaccess-stat.c @@ -0,0 +1,143 @@ +/* euidaccess-stat -- check if effective user id can access lstat'd file + This function is probably useful only for choosing whether to issue + a prompt in an implementation of POSIX-specified rm. + + Copyright (C) 2005, 2006 Free Software Foundation, Inc. + + This program is free software; you can redistribute it and/or modify + it under the terms of the GNU General Public License as published by + the Free Software Foundation; either version 2, or (at your option) + any later version. + + This program is distributed in the hope that it will be useful, + but WITHOUT ANY WARRANTY; without even the implied warranty of + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + GNU General Public License for more details. + + You should have received a copy of the GNU General Public License along + with this program; if not, write to the Free Software Foundation, + Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. */ + +/* Adapted for use in GNU remove.c by Jim Meyering. */ + +#include <config.h> + +#include "euidaccess-stat.h" + +#include <unistd.h> + +#ifndef F_OK +# define F_OK 0 +# define X_OK 1 +# define W_OK 2 +# define R_OK 4 +#endif + +#include "group-member.h" +#include "stat-macros.h" + +/* Return true if the current user has permission of type MODE + on the file from which stat buffer *ST was obtained, ignoring + ACLs, attributes, `read-only'ness, etc... + Otherwise, return false. + + Like the reentrant version of euidaccess, but starting with + a stat buffer rather than a file name. Hence, this function + never calls access or accessx, and doesn't take into account + whether the file has ACLs or other attributes, or resides on + a read-only file system. */ + +bool +euidaccess_stat (struct stat const *st, int mode) +{ + uid_t euid; + unsigned int granted; + + /* Convert the mode to traditional form, clearing any bogus bits. */ + if (R_OK == 4 && W_OK == 2 && X_OK == 1 && F_OK == 0) + mode &= 7; + else + mode = ((mode & R_OK ? 4 : 0) + + (mode & W_OK ? 2 : 0) + + (mode & X_OK ? 1 : 0)); + + if (mode == 0) + return true; /* The file exists. */ + + euid = geteuid (); + + /* The super-user can read and write any file, and execute any file + that anyone can execute. */ + if (euid == 0 && ((mode & X_OK) == 0 + || (st->st_mode & (S_IXUSR | S_IXGRP | S_IXOTH)))) + return true; + + /* Convert the file's permission bits to traditional form. */ + if ( S_IRUSR == (4 << 6) + && S_IWUSR == (2 << 6) + && S_IXUSR == (1 << 6) + && S_IRGRP == (4 << 3) + && S_IWGRP == (2 << 3) + && S_IXGRP == (1 << 3) + && S_IROTH == (4 << 0) + && S_IWOTH == (2 << 0) + && S_IXOTH == (1 << 0)) + granted = st->st_mode; + else + granted = ( (st->st_mode & S_IRUSR ? 4 << 6 : 0) + + (st->st_mode & S_IWUSR ? 2 << 6 : 0) + + (st->st_mode & S_IXUSR ? 1 << 6 : 0) + + (st->st_mode & S_IRGRP ? 4 << 3 : 0) + + (st->st_mode & S_IWGRP ? 2 << 3 : 0) + + (st->st_mode & S_IXGRP ? 1 << 3 : 0) + + (st->st_mode & S_IROTH ? 4 << 0 : 0) + + (st->st_mode & S_IWOTH ? 2 << 0 : 0) + + (st->st_mode & S_IXOTH ? 1 << 0 : 0)); + + if (euid == st->st_uid) + granted >>= 6; + else + { + gid_t egid = getegid (); + if (egid == st->st_gid || group_member (st->st_gid)) + granted >>= 3; + } + + if ((mode & ~granted) == 0) + return true; + + return false; +} + + +#ifdef TEST +# include <errno.h> +# include <stdio.h> +# include <stdlib.h> + +# include "error.h" +# define _(msg) msg + +char *program_name; + +int +main (int argc, char **argv) +{ + char *file; + int mode; + bool ok; + struct stat st; + + program_name = argv[0]; + if (argc < 3) + abort (); + file = argv[1]; + mode = atoi (argv[2]); + if (lstat (file, &st) != 0) + error (EXIT_FAILURE, errno, _("cannot stat %s"), file); + + ok = euidaccess_stat (&st, mode); + printf ("%s: %s\n", file, ok ? "y" : "n"); + exit (0); +} +#endif |