Mercurial > hg > toybox
view lib/password.c @ 1604:f057223498e4 draft
Remove more strncpy() calls.
The semantics of strncat() and strncpy() are non-obvious, so let's not use 'em.
Both zero all their remaining buffer space, and with strncat() the size is
the space left at the _end_ of the string (not the size of the buffer) so
it's way too easy to stomp memory you don't own. As long as we have to measure
stuff ourselves to get it right, just use memcpy().
author | Rob Landley <rob@landley.net> |
---|---|
date | Sat, 13 Dec 2014 11:56:41 -0600 |
parents | 1264029d7989 |
children | 10922d83392a |
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/* password.c - password read/update helper functions. * * Copyright 2012 Ashwini Kumar <ak.ashwini@gmail.com> */ #include "toys.h" #include <time.h> // generate appropriate random salt string for given encryption algorithm. int get_salt(char *salt, char *algo) { struct { char *type, id, len; } al[] = {{"des", 0, 2}, {"md5", 1, 8}, {"sha256", 5, 16}, {"sha512", 6, 16}}; int i; for (i = 0; i < ARRAY_LEN(al); i++) { if (!strcmp(algo, al[i].type)) { int len = al[i].len; char *s = salt; if (al[i].id) s += sprintf(s, "$%c$", '0'+al[i].id); // Read appropriate number of random bytes for salt i = xopen("/dev/urandom", O_RDONLY); xreadall(i, libbuf, ((len*6)+7)/8); close(i); // Grab 6 bit chunks and convert to characters in ./0-9a-zA-Z for (i=0; i<len; i++) { int bitpos = i*6, bits = bitpos/8; bits = ((libbuf[i]+(libbuf[i+1]<<8)) >> (bitpos&7)) & 0x3f; bits += 46; if (bits > 57) bits += 7; if (bits > 90) bits += 6; s[i] = bits; } salt[len] = 0; return s-salt; } } return -1; } // Reset terminal to known state, returning old state if old != NULL. int set_terminal(int fd, int raw, struct termios *old) { struct termios termio; if (!tcgetattr(fd, &termio) && old) *old = termio; // the following are the bits set for an xterm. Linux text mode TTYs by // default add two additional bits that only matter for serial processing // (turn serial line break into an interrupt, and XON/XOFF flow control) // Any key unblocks output, swap CR and NL on input termio.c_iflag = IXANY|ICRNL|INLCR; if (toys.which->flags & TOYFLAG_LOCALE) termio.c_iflag |= IUTF8; // Output appends CR to NL, does magic undocumented postprocessing termio.c_oflag = ONLCR|OPOST; // Leave serial port speed alone // termio.c_cflag = C_READ|CS8|EXTB; // Generate signals, input entire line at once, echo output // erase, line kill, escape control characters with ^ // erase line char at a time // "extended" behavior: ctrl-V quotes next char, ctrl-R reprints unread chars, // ctrl-W erases word termio.c_lflag = ISIG|ICANON|ECHO|ECHOE|ECHOK|ECHOCTL|ECHOKE|IEXTEN; if (raw) cfmakeraw(&termio); return tcsetattr(fd, TCSANOW, &termio); } // Prompt with mesg, read password into buf, return 0 for success 1 for fail int read_password(char *buf, int buflen, char *mesg) { struct termios oldtermio; struct sigaction sa, oldsa; int i, ret = 1; // NOP signal handler to return from the read memset(&sa, 0, sizeof(sa)); sa.sa_handler = generic_signal; sigaction(SIGINT, &sa, &oldsa); tcflush(0, TCIFLUSH); set_terminal(0, 1, &oldtermio); xprintf("%s", mesg); for (i=0; i < buflen-1; i++) { if ((ret = read(0, buf+i, 1)) < 0 || (!ret && !i)) { i = 0; ret = 1; break; } else if (!ret || buf[i] == '\n' || buf[i] == '\r') { ret = 0; break; } else if (buf[i] == 8 || buf[i] == 127) i -= i ? 2 : 1; } // Restore terminal/signal state, terminate string sigaction(SIGINT, &oldsa, NULL); tcsetattr(0, TCSANOW, &oldtermio); buf[i] = 0; xputc('\n'); return ret; } static char *get_nextcolon(char *line, int cnt) { while (cnt--) { if (!(line = strchr(line, ':'))) error_exit("Invalid Entry\n"); line++; //jump past the colon } return line; } /*update_password is used by multiple utilities to update /etc/passwd, * /etc/shadow, /etc/group and /etc/gshadow files, * which are used as user, group databeses * entry can be * 1. encrypted password, when updating user password. * 2. complete entry for user details, when creating new user * 3. group members comma',' separated list, when adding user to group * 4. complete entry for group details, when creating new group * 5. entry = NULL, delete the named entry user/group */ int update_password(char *filename, char* username, char* entry) { char *filenamesfx = NULL, *namesfx = NULL, *shadow = NULL, *sfx = NULL, *line = NULL; FILE *exfp, *newfp; int ret = -1, found = 0; struct flock lock; shadow = strstr(filename, "shadow"); filenamesfx = xmprintf("%s+", filename); sfx = strchr(filenamesfx, '+'); exfp = fopen(filename, "r+"); if (!exfp) { perror_msg("Couldn't open file %s",filename); goto free_storage; } *sfx = '-'; unlink(filenamesfx); ret = link(filename, filenamesfx); if (ret < 0) error_msg("can't create backup file"); *sfx = '+'; lock.l_type = F_WRLCK; lock.l_whence = SEEK_SET; lock.l_start = 0; lock.l_len = 0; ret = fcntl(fileno(exfp), F_SETLK, &lock); if (ret < 0) perror_msg("Couldn't lock file %s",filename); lock.l_type = F_UNLCK; //unlocking at a later stage newfp = fopen(filenamesfx, "w+"); if (!newfp) { error_msg("couldn't open file for writing"); ret = -1; fclose(exfp); goto free_storage; } ret = 0; namesfx = xmprintf("%s:",username); while ((line = get_line(fileno(exfp))) != NULL) { if (strncmp(line, namesfx, strlen(namesfx))) fprintf(newfp, "%s\n", line); else if (entry) { char *current_ptr = NULL; found = 1; if (!strcmp(toys.which->name, "passwd")) { fprintf(newfp, "%s%s:",namesfx, entry); current_ptr = get_nextcolon(line, 2); //past passwd if (shadow) { fprintf(newfp, "%u:",(unsigned)(time(NULL))/(24*60*60)); current_ptr = get_nextcolon(current_ptr, 1); fprintf(newfp, "%s\n",current_ptr); } else fprintf(newfp, "%s\n",current_ptr); } else if (!strcmp(toys.which->name, "groupadd") || !strcmp(toys.which->name, "addgroup") || !strcmp(toys.which->name, "delgroup") || !strcmp(toys.which->name, "groupdel")){ current_ptr = get_nextcolon(line, 3); //past gid/admin list *current_ptr = '\0'; fprintf(newfp, "%s", line); fprintf(newfp, "%s\n", entry); } } free(line); } free(namesfx); if (!found && entry) fprintf(newfp, "%s\n", entry); fcntl(fileno(exfp), F_SETLK, &lock); fclose(exfp); errno = 0; fflush(newfp); fsync(fileno(newfp)); fclose(newfp); rename(filenamesfx, filename); if (errno) { perror_msg("File Writing/Saving failed: "); unlink(filenamesfx); ret = -1; } free_storage: free(filenamesfx); return ret; }