/* [ʞ] kpw.c - password manager
 *  ↳ derivative of mkpw.c
 *  ~ lexi hale <lexi@hale.su>
 *  © AGPLv3
 *  $ cc -O4 kpw.c -okpw [-D_CLIPBOARD]
 *    - D_CLIPBOARD enables kpw to automatically
 *      copy passwords to the clipboard. it does
 *      this by attempting to execute a sequence
 *      of binaries, and then writing the password
 *      to STDIN of the binary that succeeds.
 *  ? generates passwords
 *  → kpw is unlikely to be portable to non-POSIX
 *    systems, but should run fine on Linux as well
 *    as BSDs with getrandom() support.
 *  ! for getrandom() to work with the version of
 *    libc on my android phone, the getrandom() call
 *    had to be converted to use the syscall()
 *    interface. this is unlikely to cause problems,
 *    but should be kept in mind.
 */

#include <unistd.h>
#include <sys/random.h>
#include <sys/syscall.h>
#include <stddef.h>
#include <stdint.h>
#include <stdlib.h>
#include <string.h>
#include <fcntl.h>
#include <sodium.h>
#include <termios.h>


#define sz(a) ( sizeof (a) / sizeof (a) [0] )
#define say(x) (write(2, (x), sizeof (x)))

#ifdef _CLIPBOARD
#	include <sys/types.h>
#	include <pwd.h>
#	include <stdlib.h>
#else
#   define copy(str,len)
#endif
 
enum /* constants */ {
	null = 0, true = 1, false = 0
};

#include "err.inc"

enum /* db format constants */ {
	db_pubkey_len = crypto_box_PUBLICKEYBYTES,
	db_privkey_len = crypto_box_SECRETKEYBYTES,
	kpw_db_pw_max = 64,
};

typedef _Bool bool;
typedef unsigned long long iaia_word_type;
typedef bad iaia_error_type;
enum /* iaia errors */ {
	iaia_e_ok = ok,
	iaia_e_base = fail,
	iaia_e_domain = fail,
	iaia_e_overflow = fail,
};
#define _IAIA_FN_ATOI katoi
#define _IAIA_FN_ITOA kitoa
#define _IAIA_EXTERNAL_TYPES
#include "clib/iaia.c"

#define k_static
#include "clib/compose.c"
#undef k_static

typedef enum {
	tbl_ok = ok, tbl_error = fail
} tbl_error_type;
typedef unsigned char tbl_word_type;
#include "clib/tbl.c"

#include "opt.inc"

#define str_ucase "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
#define str_lcase "abcdefghijklmnopqrstuvwxyz"
#define str_num "0123456789" 
const char* reftbl = str_num str_ucase str_lcase;
const char* reftbl_lcase = str_num str_lcase;

#ifdef _CLIPBOARD
char* const*
cbd_cmds[] = {
	/* NOTE: these commands must be specified in order of
	 * most- to least-specific. more than one utility may
	 * be present on a given system, so we need to make sure
	 * the right one is called. */
	(char* const[]){"termux-clipboard-set", null},
	(char* const[]){"xsel", "-bi", null},
	/* TODO: allow command to be specified by env var */
	null
};

bad
copy(const char* str, size_t len) {
	char* const clipboard_env = getenv("mkpw_clipboard_setter");
	char* const clipboard_env_arg = getenv("mkpw_clipboard_setter_arg");
	// FIXME: allow multiple args
	int fds[2];
	if (pipe(fds) != 0) return 63;
	if (!fork()) {
		close(fds[1]);
		dup2(fds[0], 0);
		if (clipboard_env != null) {
			execvp(clipboard_env, (char* const[]){
					clipboard_env, clipboard_env_arg, null});
			return bad_copy;
		} else for(char* const** cmd = cbd_cmds; *cmd != null; ++cmd) {
			execvp((*cmd)[0], *cmd);
		}
		return bad_copy;
	} else {
		close(fds[0]);
		write(fds[1], str, len);
		write(fds[1], "\n", 1);
		close(fds[1]);
		return ok;
	}
}
#endif

enum genmode { upper, mix, lower, stupid };

bad
mkpw(enum genmode mode, char* buf, size_t const len) {
	const unsigned char chars = (sizeof str_num - 1) +
		((mode == upper) ? (sizeof str_ucase - 1) :
		((mode == lower) ? (sizeof str_lcase - 1) :
			((sizeof str_ucase - 1) + (sizeof str_lcase - 1))));
	const char* tbl = (mode == upper) ? reftbl :
			((mode == lower) ? reftbl_lcase : reftbl);

	unsigned char noise[len];
	unsigned char* cur = noise;
	/* getrandom(noise, len, 0); // android doesnt like it */
	if(syscall(SYS_getrandom, noise, len, 0) == -1) 
		return bad_entropy;

	for(char* ptr = buf; ptr < buf + len; ++ptr, ++cur) {
		*ptr = tbl[*cur % chars]; /* such a waste of entropy… :( */
	}

	if(mode == stupid) {
		/* appease systems with stupid password reqs */
		buf[0] = '!';
		buf[1] = 'a' + (noise[1] % 26);
		buf[2] = 'A' + (noise[1] % 26);
	}

	buf[len] = '\n';

	return ok;
}

struct entry {
	pstr account;
	pstr pw;
};

enum term_clear {term_clear_line,
                 term_clear_screen};

enum alert {a_notice, a_warn, a_debug, a_fatal = 1 << 8};
pstr alert_msg[] = {
	_p("(notice)"), _p("(warn)"),
	_p("(debug)"),  _p("(fatal)")
};

bool _g_alert_quiet = false,
     _g_debug_msgs  = false;
void alert(uint16_t kind, const char* msg) {
	if (!((kind >= a_fatal) ||
	      (_g_debug_msgs && kind == a_debug) ||
	      (!_g_alert_quiet && kind != a_debug))) return;

	uint8_t idx;
	if (kind & a_fatal) idx = a_debug + 1;
		else idx = kind;
	

	if (isatty(2)) {
		char msgcode[] = "\x1b[1;30m";
		char* color = msgcode+5;
		*color = '0' + (4 - idx);
		write(2,msgcode, sz(msgcode));
	}

	write(2,alert_msg[idx].ptr,alert_msg[idx].len);
	if (isatty(2)) write(2,"\x1b[m ",4);
		else write(2," ",1);
	write(2,msg,strlen(msg));
	write(2,"\n",1);

	if (kind & a_fatal) exit(kind & (~a_fatal));
}

void term_clear(enum term_clear behavior) {
	switch(behavior) {
		case term_clear_line:   write(1,"\r\x1b[2K",5); break;
		case term_clear_screen: write(1,"\r\x1b[3J",5); break;
	}
}
void term_bell() {
	write(1,"\a",1);
}

typedef char password[kpw_db_pw_max + 1];
bad pwread(char* dest, size_t* out_len, const char* prompt, const size_t plen) {
	if (isatty(0)) {
		struct termios initial; {
			/* in order to take PW input, we need to shut
			 * off echo and canonical mode. now we're in
			 * charge of reading each keypress. */
			tcgetattr(1, &initial);
			struct termios nt = initial;
			nt.c_lflag &= (~ECHO & ~ICANON);
			tcsetattr(1, TCSANOW, &nt);
		}

		*dest = 0;
		char* p = dest;

		do {
			term_clear(term_clear_line);
			write(1, "\x1b[1m", 4);
			write(1, prompt, plen);
			write(1, "\x1b[21m", 5);

			for(size_t i = 0; i < p - dest; ++i)
				write(1, "*", 1);

			char c;
			if (read(0, &c, 1) == 1) {
				switch (c) {
					case '\n': case '\r':
						/* accept pw */
						if (p > dest) goto end_read_loop;
							else break;
					case '\x1b': /* escape */
						term_clear(term_clear_line);
						return bad_cancel;
					case '\b': case '\x7f':
						if (p > dest) *p--=0;
							else term_bell();
						break;
					default:
						if (p - dest != 64) *p++=c;
							else term_bell();
				}
			} else {
				/* either EOF or an error - either way,
				 * we're finished here */
				break;
			}
		} while(1);
		end_read_loop: term_clear(term_clear_line);
		*p = 0;
		if (out_len!=NULL) *out_len = p - dest;

		/* return the terminal to normal */
		tcsetattr(1, TCSANOW, &initial);
	} else {
		alert(a_warn, "reading pw from standard input");
		ssize_t ct = read(0, dest, kpw_db_pw_max);
		dest[ct] = 0;
	}
}

#include <stdio.h>
int
dbopen(int flags) {
	const char* dbpath = getenv("kpw_db");
	int db;
	if (dbpath == NULL) {
		const char* cfg = getenv("XDG_CONFIG_HOME");
		if (cfg == NULL) {
			const char* home = getenv("HOME");
			if (home == NULL) exit(bad_insane);

			size_t homelen = strlen(home);
			pstr path[] = { {homelen, home}, _p("/.config/kpw.db") };
			char buf[homelen + path[1].len + 1];
			bzero(buf, sz(buf));
			impose(path, sz(path), NULL, buf);

			db = open(buf, flags, 0600);
		} else {
			size_t cfglen = strlen(cfg);
			pstr path[] = { {cfglen, cfg}, _p("/kpw.db") };
			char buf[cfglen + path[1].len + 1];
			bzero(buf, sz(buf));
			impose(path, sz(path), NULL, buf);

			db = open(buf, flags, 0600);
		}
	} else {
		printf("path is %s", dbpath);
		db = open(dbpath, flags, 0600);
	}

	return db;
}

int
kpw(int argc, const char** argv) {
	if (argc == 0) return -1;
	if (argc == 1) { 
		size_t namelen = strlen(argv[0]);
		say("\x1b[1musage:\x1b[m ");
		write(2, argv[0], namelen);
		write(2, kpw_optstr, sz(kpw_optstr));
		write(2, kpw_usage,  sz(kpw_usage));
		return bad_usage;
	}

	enum genmode
		mode = lower;
	enum {usage,getpw,addpw,delpw,genpw,
	      chpw,keyin,logout,createdb,rekeydb}
		op = getpw;

	const char* params[3];
	uint8_t param = 0;

	bool print = false,
		 clobber = false;
#	ifdef _CLIPBOARD
		bool copy_pw = true;
#	endif
	for (const char** arg = argv + 1; *arg != null; ++arg) {
		if ((*arg)[0] == '-') {
			if ((*arg)[1] == '-') { /* long opt */
				unsigned char a;
				if (tblget(sz(argtbl), argtbl, *arg + 2, &a) == ok) switch (a) {
					kpw_emit_long_option_switch
				} else {
					return bad_option;
				}
			} else { /* short opt */
				for(const char* ptr = (*arg) + 1; *ptr != 0; ++ptr) {
					switch(*ptr) {
						kpw_emit_short_option_switch
						default: return bad_option;
					}
				}
			}
		} else {
			if (param > sz(params)) return bad_syntax;
			params[param++] = *arg;
		}
	}

	if (sodium_init() < 0) 
		return bad_lib_sodium_init;

	switch(op) {
		case getpw:{ /* kpw <acct> */
			break;
		}

		case addpw:{ /* kpw -a <acct> [<pw>] */
			break;
		}

		case delpw:{ /* kpw -d <acct> */
			break;
		}

		case genpw:{ /* kpw -g[lmu] <acct> [<len>] */
			break;
		}

		case createdb: { /* kpw -C [<db>] */
			alert(a_debug, "creating new database");
			if (clobber)
				alert(a_warn, "will clobber any existing database");
			/* before we open our new file, we need to generate
			 * our keypairs.  the private key will be encrypted
			 * with a blake2 hash of a user-supplied passphrase 
			 * and stored in the database after the unencrypted
			 * public key.
			 */
			uint8_t pub [crypto_box_PUBLICKEYBYTES],
			        priv[crypto_box_SECRETKEYBYTES];
			uint8_t priv_enc[sz(priv)];

			alert(a_debug, "generating keypair");
			crypto_box_keypair(pub, priv);

			/* kpw   works  very   differently  compared   to
			 * most  password  managers. it  uses  public-key
			 * encryption so that new  passwords can be saved
			 * to the  db without bothering the  user for the
			 * password.  now we  have  our  keypair, we  can
			 * prompt  the user for a secret  passphrase with
			 * which to encrypt the private key with.
			 */


			alert(a_notice, "database keypair generated, encrypting");
			password dbpw;
			size_t pwlen;
#			define _str(s) (s),sizeof(s)
			bad e = pwread(dbpw, &pwlen, _str("database passphrase: "));
			if (e != ok) return e;
			if (isatty(0)) {
				password dbpw_conf;
				e = pwread(dbpw_conf, NULL, _str("confirm: "));
#				undef _str
				if (e != ok) return e;

				if(strcmp(dbpw,dbpw_conf) != 0)
					return bad_pw_match;
			}

			uint8_t salt[crypto_pwhash_SALTBYTES],
			         key[db_privkey_len];
			uint8_t salt_enc[crypto_box_SEALBYTES + sz(salt)];

			if (syscall(SYS_getrandom, salt, sz(salt), 0) == -1)
				return bad_entropy;

			if(crypto_pwhash(key, sz(key), dbpw, pwlen, salt,
					crypto_pwhash_OPSLIMIT_INTERACTIVE,
					crypto_pwhash_MEMLIMIT_INTERACTIVE,
					crypto_pwhash_ALG_DEFAULT) != 0) {
				return bad_mem;
			}

			for (size_t i = 0; i < sz(key); ++i) {
				priv_enc[i] = priv[i] ^ key[i];
			}

			crypto_box_seal(salt_enc, salt, sz(salt), priv);

			/* we have everything we need. now we create the
			 * file, failing  if it already exists so as not
			 * to clobber anyone's passwords.
			 */
			int db;
			const int flags = O_CREAT | (clobber ? O_TRUNC : O_EXCL);
			if(param == 0)
				db = dbopen(flags);
			else if (param == 1)
				db = open(params[0], flags, 0600);
			else return bad_syntax;

			if (db == -1) return bad_db_create;

			write(db, pub, sz(pub));
			write(db, salt, sz(salt));
			write(db, priv_enc, sz(priv_enc));
			write(db, salt_enc, sz(salt_enc));
			close(db);

			for (int i = 0; i < sz(key); ++i) {
				printf("%2x ", key[i]);
				if (!((i+1)%8)) printf("\n");
			}
			break;
		}
	}

#	ifdef _CLIPBOARD
	if (geteuid() == 0 && copy_pw) {
		/* on a sane system, what we'd do is hike up the process
		 * tree til we found a non-root user. alas, this is UNIX. */
		const char* realuser = getenv("SUDO_USER");
		if (realuser == null) realuser = "nobody";

		say("\x1b[1;33mwarning:\x1b[m you are running \x1b[4m");
			size_t namelen = strlen(argv[0]);
			write(2,argv[0],namelen);
		say("\x1b[24m as \x1b[1mroot\x1b[m! dropping to \x1b[1m");
			write(2,realuser,strlen(realuser));
			setenv("USER", realuser, true);
		say("\x1b[m to prevent malicious behavior\n");

		struct passwd* nobody = getpwnam(realuser);
		if (nobody == null) {
			say("\x1b[1;31mfatal:\x1b[m could not get UID to drop privileges; bailing");
			return bad_user;
		} else {
			setenv("HOME", nobody -> pw_dir, true);
			setenv("SHELL", "/dev/null", true);
			setuid(nobody -> pw_uid);
		}

	}
#	endif
	

	/* char buf[len+1]; */
	/* *buf = 0; */
	/* mkpw(mode,buf,len); */
	/* write(1, buf, len + 1); */

#	ifdef _CLIPBOARD
		if (copy_pw) {
			copy(buf,len);
		}
#	endif
	
	return ok;
}

int
main (int argc, const char** argv) {
	int e = 0;
	const char* msg;
	uint16_t level;
	uint8_t rv;
	switch (e = kpw(argc, argv)) {
		kpw_emit_error_switch
	}

	alert(level, msg);
	return rv;
}
