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/* password.c - password read/update helper functions.
*
* Copyright 2012 Ashwini Kumar <ak.ashwini@gmail.com>
*
* TODO: cleanup
*/
#include "toys.h"
#include <time.h>
// generate ID prefix and random salt 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
xgetrandom(libbuf, ((len*6)+7)/8, 0);
// 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;
}
// 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;
}
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