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