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ugperms.c
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ugperms.c
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#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include <stdlib.h>
#include <sys/acl.h>
#include <acl/libacl.h>
#include <pwd.h>
#include <grp.h>
extern char *optarg;
void checkUser(uid_t uid, acl_entry_t entry)
{
acl_tag_t tagType;
if (acl_get_tag_type(entry, &tagType) == -1) {
printf("error reading entry\n");
exit(EXIT_FAILURE);
}
if (tagType == ACL_USER) {
uid_t *aclUid = acl_get_qualifier(entry);
if (aclUid == NULL) {
perror("failed to fetch qualifier");
exit(EXIT_FAILURE);
}
if (*aclUid == uid) {
acl_permset_t permset;
if (acl_get_permset(entry, &permset) == -1) {
perror("failed to fetch permission set");
exit(EXIT_FAILURE);
}
if (acl_get_perm(permset, ACL_READ) == 1) {
puts("read allowed");
}
if (acl_get_perm(permset, ACL_WRITE) == 1) {
puts("write allowed");
}
if (acl_get_perm(permset, ACL_EXECUTE) == 1) {
puts("execute allowed");
}
}
}
}
void checkGroup(const gid_t gid, acl_entry_t entry)
{
acl_tag_t tagType;
if (acl_get_tag_type(entry, &tagType) == -1) {
printf("error reading entry\n");
exit(EXIT_FAILURE);
}
if (tagType == ACL_GROUP) {
gid_t *aclGid = acl_get_qualifier(entry);
if (aclGid == NULL) {
perror("failed to fetch qualifier");
exit(EXIT_FAILURE);
}
if (*aclGid == gid) {
acl_permset_t permset;
if (acl_get_permset(entry, &permset) == -1) {
perror("failed to fetch permission set");
exit(EXIT_FAILURE);
}
if (acl_get_perm(permset, ACL_READ) == 1) {
puts("read allowed");
}
if (acl_get_perm(permset, ACL_WRITE) == 1) {
puts("write allowed");
}
if (acl_get_perm(permset, ACL_EXECUTE) == 1) {
puts("execute allowed");
}
}
}
}
int main(int argc, char *argv[])
{
if (argc<4 || !strcmp(argv[1], "--help")) {
printf("Usage: %s -[ug] <name/id> <pathname>\n", argv[0]);
exit(EXIT_FAILURE);
}
acl_t acl = acl_get_file(argv[argc-1], ACL_TYPE_ACCESS);
int user = -1;
char *name;
uid_t uid;
gid_t gid;
char opt;
while ((opt = getopt(argc, argv, "u:g:")) != -1) {
switch (opt) {
case 'u':
user = 1;
char *endptr = malloc(strlen(optarg)+1);
uid = strtol(optarg, &endptr, 10);
if (*endptr == '\0')
break;
struct passwd *pwd = getpwnam(optarg);
uid = pwd->pw_uid;
break;
case 'g':
user = 0;
endptr = malloc(strlen(optarg)+1);
gid = strtol(optarg, &endptr, 10);
if (*endptr == '\0')
break;
struct group *grp = getgrnam(optarg);
gid = grp->gr_gid;
break;
}
}
if (user == -1) {
printf("invalid flags or arguments\n");
exit(EXIT_FAILURE);
}
acl_entry_t entry;
int status = acl_get_entry(acl, ACL_FIRST_ENTRY, &entry);
while (1) {
if (status == -1) {
perror("couldn't fetch ACL entries");
exit(EXIT_FAILURE);
} else if (status == 0)
break;
if (user) {
checkUser(uid, entry);
} else {
checkGroup(gid, entry);
}
status = acl_get_entry(acl, ACL_NEXT_ENTRY, &entry);
}
}