1 /* password.c - password read/update helper functions.
2 *
3 * Copyright 2012 Ashwini Kumar <ak.ashwini@gmail.com>
4 *
5 * TODO: cleanup
6 */
7
8 #include "toys.h"
9 #include <time.h>
10
11 // generate appropriate random salt string for given encryption algorithm.
get_salt(char * salt,char * algo)12 int get_salt(char *salt, char *algo)
13 {
14 struct {
15 char *type, id, len;
16 } al[] = {{"des", 0, 2}, {"md5", 1, 8}, {"sha256", 5, 16}, {"sha512", 6, 16}};
17 int i;
18
19 for (i = 0; i < ARRAY_LEN(al); i++) {
20 if (!strcmp(algo, al[i].type)) {
21 int len = al[i].len;
22 char *s = salt;
23
24 if (al[i].id) s += sprintf(s, "$%c$", '0'+al[i].id);
25
26 // Read appropriate number of random bytes for salt
27 i = xopenro("/dev/urandom");
28 xreadall(i, libbuf, ((len*6)+7)/8);
29 close(i);
30
31 // Grab 6 bit chunks and convert to characters in ./0-9a-zA-Z
32 for (i=0; i<len; i++) {
33 int bitpos = i*6, bits = bitpos/8;
34
35 bits = ((libbuf[i]+(libbuf[i+1]<<8)) >> (bitpos&7)) & 0x3f;
36 bits += 46;
37 if (bits > 57) bits += 7;
38 if (bits > 90) bits += 6;
39
40 s[i] = bits;
41 }
42 salt[len] = 0;
43
44 return s-salt;
45 }
46 }
47
48 return -1;
49 }
50
51 // Prompt with mesg, read password into buf, return 0 for success 1 for fail
read_password(char * buf,int buflen,char * mesg)52 int read_password(char *buf, int buflen, char *mesg)
53 {
54 struct termios oldtermio;
55 struct sigaction sa, oldsa;
56 int i, ret = 1;
57
58 // NOP signal handler to return from the read
59 memset(&sa, 0, sizeof(sa));
60 sa.sa_handler = generic_signal;
61 sigaction(SIGINT, &sa, &oldsa);
62
63 tcflush(0, TCIFLUSH);
64 set_terminal(0, 1, &oldtermio);
65
66 xprintf("%s", mesg);
67
68 for (i=0; i < buflen-1; i++) {
69 if ((ret = read(0, buf+i, 1)) < 0 || (!ret && !i)) {
70 i = 0;
71 ret = 1;
72
73 break;
74 } else if (!ret || buf[i] == '\n' || buf[i] == '\r') {
75 ret = 0;
76
77 break;
78 } else if (buf[i] == 8 || buf[i] == 127) i -= i ? 2 : 1;
79 }
80
81 // Restore terminal/signal state, terminate string
82 sigaction(SIGINT, &oldsa, NULL);
83 tcsetattr(0, TCSANOW, &oldtermio);
84 buf[i] = 0;
85 xputc('\n');
86
87 return ret;
88 }
89
get_nextcolon(char * line,int cnt)90 static char *get_nextcolon(char *line, int cnt)
91 {
92 while (cnt--) {
93 if (!(line = strchr(line, ':'))) error_exit("Invalid Entry\n");
94 line++; //jump past the colon
95 }
96 return line;
97 }
98
99 /*update_password is used by multiple utilities to update /etc/passwd,
100 * /etc/shadow, /etc/group and /etc/gshadow files,
101 * which are used as user, group databeses
102 * entry can be
103 * 1. encrypted password, when updating user password.
104 * 2. complete entry for user details, when creating new user
105 * 3. group members comma',' separated list, when adding user to group
106 * 4. complete entry for group details, when creating new group
107 * 5. entry = NULL, delete the named entry user/group
108 */
update_password(char * filename,char * username,char * entry)109 int update_password(char *filename, char* username, char* entry)
110 {
111 char *filenamesfx = NULL, *namesfx = NULL, *shadow = NULL,
112 *sfx = NULL, *line = NULL;
113 FILE *exfp, *newfp;
114 int ret = -1, found = 0;
115 struct flock lock;
116
117 shadow = strstr(filename, "shadow");
118 filenamesfx = xmprintf("%s+", filename);
119 sfx = strchr(filenamesfx, '+');
120
121 exfp = fopen(filename, "r+");
122 if (!exfp) {
123 perror_msg("Couldn't open file %s",filename);
124 goto free_storage;
125 }
126
127 *sfx = '-';
128 unlink(filenamesfx);
129 ret = link(filename, filenamesfx);
130 if (ret < 0) error_msg("can't create backup file");
131
132 *sfx = '+';
133 lock.l_type = F_WRLCK;
134 lock.l_whence = SEEK_SET;
135 lock.l_start = 0;
136 lock.l_len = 0;
137
138 ret = fcntl(fileno(exfp), F_SETLK, &lock);
139 if (ret < 0) perror_msg("Couldn't lock file %s",filename);
140
141 lock.l_type = F_UNLCK; //unlocking at a later stage
142
143 newfp = fopen(filenamesfx, "w+");
144 if (!newfp) {
145 error_msg("couldn't open file for writing");
146 ret = -1;
147 fclose(exfp);
148 goto free_storage;
149 }
150
151 ret = 0;
152 namesfx = xmprintf("%s:",username);
153 while ((line = get_line(fileno(exfp))) != NULL)
154 {
155 if (strncmp(line, namesfx, strlen(namesfx)))
156 fprintf(newfp, "%s\n", line);
157 else if (entry) {
158 char *current_ptr = NULL;
159
160 found = 1;
161 if (!strcmp(toys.which->name, "passwd")) {
162 fprintf(newfp, "%s%s:",namesfx, entry);
163 current_ptr = get_nextcolon(line, 2); //past passwd
164 if (shadow) {
165 fprintf(newfp, "%u:",(unsigned)(time(NULL))/(24*60*60));
166 current_ptr = get_nextcolon(current_ptr, 1);
167 fprintf(newfp, "%s\n",current_ptr);
168 } else fprintf(newfp, "%s\n",current_ptr);
169 } else if (!strcmp(toys.which->name, "groupadd") ||
170 !strcmp(toys.which->name, "addgroup") ||
171 !strcmp(toys.which->name, "delgroup") ||
172 !strcmp(toys.which->name, "groupdel")){
173 current_ptr = get_nextcolon(line, 3); //past gid/admin list
174 *current_ptr = '\0';
175 fprintf(newfp, "%s", line);
176 fprintf(newfp, "%s\n", entry);
177 }
178 }
179 free(line);
180 }
181 free(namesfx);
182 if (!found && entry) fprintf(newfp, "%s\n", entry);
183 fcntl(fileno(exfp), F_SETLK, &lock);
184 fclose(exfp);
185
186 errno = 0;
187 fflush(newfp);
188 fsync(fileno(newfp));
189 fclose(newfp);
190 rename(filenamesfx, filename);
191 if (errno) {
192 perror_msg("File Writing/Saving failed: ");
193 unlink(filenamesfx);
194 ret = -1;
195 }
196
197 free_storage:
198 free(filenamesfx);
199 return ret;
200 }
201