diff options
Diffstat (limited to 'system.c')
| -rw-r--r-- | system.c | 72 |
1 files changed, 72 insertions, 0 deletions
@@ -17,7 +17,9 @@ #include <errno.h> #include <fcntl.h> +#include <grp.h> #include <net/if.h> +#include <pwd.h> #include <stdbool.h> #include <stdio.h> #include <string.h> @@ -287,3 +289,73 @@ int setup_mount_destination(const char *source, const char *dest, uid_t uid, } return chown(dest, uid, gid); } + +/* + * lookup_user: Gets the uid/gid for the given username. + */ +int lookup_user(const char *user, uid_t *uid, gid_t *gid) +{ + char *buf = NULL; + struct passwd pw; + struct passwd *ppw = NULL; + ssize_t sz = sysconf(_SC_GETPW_R_SIZE_MAX); + if (sz == -1) + sz = 65536; /* your guess is as good as mine... */ + + /* + * sysconf(_SC_GETPW_R_SIZE_MAX), under glibc, is documented to return + * the maximum needed size of the buffer, so we don't have to search. + */ + buf = malloc(sz); + if (!buf) + return -ENOMEM; + getpwnam_r(user, &pw, buf, sz, &ppw); + /* + * We're safe to free the buffer here. The strings inside |pw| point + * inside |buf|, but we don't use any of them; this leaves the pointers + * dangling but it's safe. |ppw| points at |pw| if getpwnam_r(3) + * succeeded. + */ + free(buf); + /* getpwnam_r(3) does *not* set errno when |ppw| is NULL. */ + if (!ppw) + return -1; + + *uid = ppw->pw_uid; + *gid = ppw->pw_gid; + return 0; +} + +/* + * lookup_group: Gets the gid for the given group name. + */ +int lookup_group(const char *group, gid_t *gid) +{ + char *buf = NULL; + struct group gr; + struct group *pgr = NULL; + ssize_t sz = sysconf(_SC_GETGR_R_SIZE_MAX); + if (sz == -1) + sz = 65536; /* and mine is as good as yours, really */ + + /* + * sysconf(_SC_GETGR_R_SIZE_MAX), under glibc, is documented to return + * the maximum needed size of the buffer, so we don't have to search. + */ + buf = malloc(sz); + if (!buf) + return -ENOMEM; + getgrnam_r(group, &gr, buf, sz, &pgr); + /* + * We're safe to free the buffer here. The strings inside gr point + * inside buf, but we don't use any of them; this leaves the pointers + * dangling but it's safe. pgr points at gr if getgrnam_r succeeded. + */ + free(buf); + /* getgrnam_r(3) does *not* set errno when |pgr| is NULL. */ + if (!pgr) + return -1; + + *gid = pgr->gr_gid; + return 0; +} |