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#include <pwd.h>
#include <fcntl.h>
#include <unistd.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <cstdio>
#include <cstdint>
#include <cstdlib>
#include <cinttypes>
#include <set>
#include <string>
#include <fstream>
const uint64_t kStart = 1 << 29, kRange = 1 << 16, kNum = 1 << 14;
struct Range {
int64_t l, len;
bool operator<(const Range& x) const { return l < x.l; }
};
void Help(const char* name) {
fprintf(stderr, "Usage: %s [-q]\n", name);
exit(1);
}
void Err(const char* str) {
perror(str);
exit(1);
}
void ErrStr(const char* str) {
fprintf(stderr, "%s\n", str);
exit(1);
}
uint64_t Hash(uint64_t a, uint64_t b) {
static const uint64_t table[3] = {0x9e3779b185ebca87, 0xc2b2ae3d27d4eb4f, 0x165667b19e3779f9};
auto Mix = [](uint64_t a, uint64_t b) {
a += b * table[1];
a = (a << 31) | (a >> 33);
return a * table[0];
};
uint64_t v1 = Mix(-table[0], a);
uint64_t v2 = Mix(table[1], b);
uint64_t ret = ((v1 << 18) | (v1 >> 46)) + ((v2 << 7) | (v2 >> 57));
ret ^= ret >> 33;
ret *= table[1];
ret ^= ret >> 29;
ret *= table[2];
ret ^= ret >> 32;
return ret;
}
Range LoadFile(const std::string& filename, std::set<Range>& st,
const std::string& username, bool query) {
std::ifstream fin(filename);
std::string ln;
while (std::getline(fin, ln)) {
size_t pos1 = ln.find(':');
if (pos1 == std::string::npos) return {-2, -2};
size_t pos2 = ln.find(':', pos1 + 1);
if (pos2 == std::string::npos) return {-2, -2};
if (ln.find(':', pos2 + 1) != std::string::npos) return {-2, -2};
Range now;
try {
now.l = std::stoll(ln.substr(pos1 + 1, pos2 - pos1 - 1));
now.len = std::stoll(ln.substr(pos2 + 1));
} catch (...) {
return {-2, -2};
}
if (ln.substr(0, pos1) == username) return now;
if (!query) st.insert(now);
}
return {-1, -1};
}
void CheckAndInsert(uid_t uid, const std::string& item,
const std::string& username, int fd) {
std::set<Range> mp;
Range rg = LoadFile("/etc/sub" + item, mp, username, false);
if (rg.l == -2) ErrStr(("Parsing error in /etc/sub" + item).c_str());
if (rg.l != -1) {
puts(("Sub" + item + " exists").c_str());
return;
}
for (uint64_t i = 0; i < kNum; i++) {
int64_t start = (Hash(i, uid) % kNum) * kRange + kStart;
auto it = mp.lower_bound({start, 0});
if ((it != mp.end() && it->l < start + (int64_t)kRange) ||
(it != mp.begin() && std::prev(it)->l + std::prev(it)->len > start)) {
continue;
}
std::string range_str = username + ':' + std::to_string(start) + ':' +
std::to_string(kRange) + '\n';
if (write(fd, range_str.c_str(), range_str.size()) < 0) Err("write");
close(fd);
range_str.pop_back();
puts(range_str.c_str());
return;
}
ErrStr(("Cannot allocate sub" + item).c_str());
}
int main(int argc, char** argv) {
if (setgid(0) < 0) Err("setgid");
uid_t uid = getuid();
if (setresuid(uid, uid, 0) < 0) Err("setuid");
umask(0022);
try {
if (argc > 2 || (argc == 2 && std::string(argv[1]) != "-q")) Help(argv[0]);
struct passwd* pwd = getpwuid(uid);
if (!pwd) Err("getpwuid");
std::string username = getpwuid(uid)->pw_name;
if (argc == 2) {
std::set<Range> tmp;
Range ru = LoadFile("/etc/subuid", tmp, username, true);
Range rg = LoadFile("/etc/subgid", tmp, username, true);
if (ru.l == -2) ErrStr("Parsing error in /etc/subuid");
if (rg.l == -2) ErrStr("Parsing error in /etc/subgid");
if (ru.l == -1) puts("Subuid does not exist");
else printf("%s:%" PRId64 ":%" PRId64 "\n", username.c_str(), ru.l, ru.len);
if (rg.l == -1) puts("Subgid does not exist");
else printf("%s:%" PRId64 ":%" PRId64 "\n", username.c_str(), rg.l, rg.len);
return 0;
}
if (setresuid(uid, 0, 0) < 0) Err("setuid");
int fd1 = open("/etc/subuid", O_RDWR | O_APPEND | O_CREAT | O_NOCTTY | O_NONBLOCK, 0644);
if (fd1 < 0) Err("open");
int fd2 = open("/etc/subgid", O_RDWR | O_APPEND | O_CREAT | O_NOCTTY | O_NONBLOCK, 0644);
if (fd1 < 0) Err("open");
struct flock lk;
lk.l_type = F_WRLCK;
lk.l_whence = SEEK_SET;
lk.l_start = 0;
lk.l_len = 0;
if (fcntl(fd1, F_SETLK, &lk) < 0) Err("Get lock failed");
if (fcntl(fd2, F_SETLK, &lk) < 0) Err("Get lock failed");
CheckAndInsert(uid, "uid", username, fd1);
CheckAndInsert(uid, "gid", username, fd2);
} catch (...) {
Err(argv[0]);
}
}
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