/*********************************************************************
  mkpasswds.cc
  Haruhiko Okumura <okumura@edu.mie-u.ac.jp>

  gcc mkpasswds.cc -lcrypt
  ./a.out some random passphrases < list_of_users
*********************************************************************/

#include <iostream>
#include <string>
#include <cstdio>
#include <ctime>
#include <fstream>

#include <crypt.h>              /* glibc ベースの Linux はこれが必要 */

using namespace std;

typedef unsigned long uint32;

// Mersenne Twister 乱数発生器

class MersenneTwister {
    static const int N = 624;
    static const int M = 397;
    static const uint32 MAT_A = 0x9908b0dfUL;
    static const uint32 UMASK = 0x80000000UL;
    static const uint32 LMASK = 0x7fffffffUL;
    int mti;
    uint32 mt[N];               // array for the state vector

    inline uint32 twist(uint32 u, uint32 v) {
        return (((u & UMASK) | (v & LMASK)) >> 1) ^ ((v & 1) * MAT_A);
    }

public:
    void init(uint32 s) {
        mti = N;
        mt[0] = s & 0xffffffffUL;
        for (int i = 1; i < N; i++) {
            mt[i] = 1812433253UL * (mt[i-1] ^ (mt[i-1] >> 30)) + i;
            mt[i] &= 0xffffffffUL;
        }
    }

    void init(uint32 init_key[], int key_length) {
        init(19650218UL);
        int i = 1;
        int j = 0;
        for (int k = (N > key_length) ? N : key_length; k != 0; k--) {
            mt[i] = (mt[i] ^ ((mt[i-1] ^ (mt[i-1] >> 30)) * 1664525UL)) + init_key[j] + j;
            mt[i] &= 0xffffffffUL;
            if (++i >= N) { mt[0] = mt[N-1]; i = 1; }
            if (++j >= key_length) j = 0;
        }
        for (int k = N - 1; k != 0; k--) {
            mt[i] = (mt[i] ^ ((mt[i-1] ^ (mt[i-1] >> 30)) * 1566083941UL)) - i;
            mt[i] &= 0xffffffffUL;
            if (++i >= N) { mt[0] = mt[N-1]; i = 1; }
        }
        mt[0] = 0x80000000UL;
    }

    MersenneTwister(uint32 s = 5489) {
        init(s);
    }

    uint32 genrand_int32() {
        if (mti == N) {
            for (int k = 0; k < N - M; k++)
                mt[k] = mt[k+M] ^ twist(mt[k], mt[k+1]);
            for (int k = N - M; k < N - 1; k++)
                mt[k] = mt[k-(N-M)] ^ twist(mt[k], mt[k+1]);
            mt[N-1] = mt[M-1] ^ twist(mt[N-1], mt[0]);
            mti = 0;
        }
        uint32 y = mt[mti++];
        y ^= (y >> 11);
        y ^= (y <<  7) & 0x9d2c5680UL;
        y ^= (y << 15) & 0xefc60000UL;
        y ^= (y >> 18);
        return y;
    }
};

MersenneTwister mt;

// 0以上n未満の整数の乱数を生成

int irand(int n)
{
    return int(mt.genrand_int32() % n);
}

void error(string s)
{
    cerr << "mkpasswds: " << s << endl;
    exit(1);
}

string randompass()
{
    string s;
    for (int i = 0; i < 3; i++)
        s += "abcdefghijkmnpqrstuvwxyz"[irand(24)];
    for (int i = 3; i < 8; i++)
        s += "0123456789"[irand(10)];
    return s;
}

char* salt()
{
    static char s[3];
    char a[65] = "abcdefghijklmnopqrstuvwxyz"
        "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
        "0123456789./";
    s[0] = a[irand(64)];
    s[1] = a[irand(64)];
    s[2] = 0;
    return s;
}

int main(int argc, char* argv[])
{
    if (argc == 1) error("Usage: mkpasswds some random passphrases");

    string passphrase = "";
    for (int i = 1; i < argc; i++)
        passphrase += string(argv[i]);

    ofstream plain("plain");
    if (!plain) error("Can't open");
    ofstream passwd("passwd");
    if (!passwd) error("Can't open");
    ofstream shadow("shadow");
    if (!shadow) error("Can't open");
    ofstream doit("doit.sh");
    if (!doit) error("Can't open");
    doit << "#! /bin/sh\n\n";

    int uid = 21160;            // ユーザ番号の初期値
    int gid = 600;              // グループ番号
    string shell = "/bin/passwd"; // ユーザシェル
    string dir = "/space/mieu/"; // 親ディレクトリ。最後は /
    string group = "student";   // グループ名

    uint32* init_key = new uint32[passphrase.length() + 1];
    init_key[0] = uint32(time(0));
    for (int i = 0; i < passphrase.length(); i++)
        init_key[i+1] = int(passphrase[i]);
    mt.init(init_key, passphrase.length() + 1);

    int lastchg = int(time(0)) / (60 * 60 * 24); // 最終更新日（UNIX時間）
    string user;                // ユーザ名
    while (cin >> user) {
        string pass = randompass(); // パスワード
        char* cpass = crypt(pass.c_str(), salt()); // 暗号化パスワード
        plain  << user << '\t' << pass << '\n';
        passwd << user << ":x:" << uid
               << ':' << gid << ':' << user
               << ':' << dir << user << ':' << shell << '\n';
        shadow << user << ':' << cpass << ':'
               << lastchg << "::::::\n";
        doit << "mkdir -p " << dir << user << "/public_html\n";
        doit << "chown -R " << user << '.' << group << ' ' << dir << user << '\n';
        uid++;
    }
}