UNIX 7th Ed. - /usr/src/cmd/passwd.c

   1: /*
   2:  * enter a password in the password file
   3:  * this program should be suid with owner
   4:  * with an owner with write permission on /etc/passwd
   5:  */
   6: #include <stdio.h>
   7: #include <signal.h>
   8: #include <pwd.h>
   9: 
  10: char    passwd[] = "/etc/passwd";
  11: char    temp[]   = "/etc/ptmp";
  12: struct  passwd *pwd;
  13: struct  passwd *getpwent();
  14: int endpwent();
  15: char    *strcpy();
  16: char    *crypt();
  17: char    *getpass();
  18: char    *getlogin();
  19: char    *pw;
  20: char    pwbuf[10];
  21: char    buf[512];
  22: 
  23: main(argc, argv)
  24: char *argv[];
  25: {
  26:     char *p;
  27:     int i;
  28:     char saltc[2];
  29:     long salt;
  30:     int u,fi,fo;
  31:     int insist;
  32:     int ok, flags;
  33:     int c;
  34:     int pwlen;
  35:     FILE *tf;
  36:     char *uname;
  37: 
  38:     insist = 0;
  39:     if(argc < 2) {
  40:         if ((uname = getlogin()) == NULL) {
  41:             printf ("Usage: passwd user\n");
  42:             goto bex;
  43:         } else {
  44:             printf("Changing password for %s\n", uname);
  45:         }
  46:     } else {
  47:         uname = argv[1];
  48:     }
  49:     while(((pwd=getpwent()) != NULL)&&(strcmp(pwd->pw_name,uname)!=0));
  50:     u = getuid();
  51:     if((pwd==NULL) || (u!=0 && u != pwd->pw_uid))
  52:         {
  53:         printf("Permission denied.\n");
  54:         goto bex;
  55:         }
  56:     endpwent();
  57:     if (pwd->pw_passwd[0] && u != 0) {
  58:         strcpy(pwbuf, getpass("Old password:"));
  59:         pw = crypt(pwbuf, pwd->pw_passwd);
  60:         if(strcmp(pw, pwd->pw_passwd) != 0) {
  61:             printf("Sorry.\n");
  62:             goto bex;
  63:         }
  64:     }
  65: tryagn:
  66:     strcpy(pwbuf, getpass("New password:"));
  67:     pwlen = strlen(pwbuf);
  68:     if (pwlen == 0) {
  69:         printf("Password unchanged.\n");
  70:         goto bex;
  71:     }
  72:     ok = 0;
  73:     flags = 0;
  74:     p = pwbuf;
  75:     while(c = *p++){
  76:         if(c>='a' && c<='z') flags |= 2;
  77:         else if(c>='A' && c<='Z') flags |= 4;
  78:         else if(c>='0' && c<='9') flags |= 1;
  79:         else flags |= 8;
  80:     }
  81:     if(flags >=7 && pwlen>= 4) ok = 1;
  82:     if(((flags==2)||(flags==4)) && pwlen>=6) ok = 1;
  83:     if(((flags==3)||(flags==5)||(flags==6))&&pwlen>=5) ok = 1;
  84: 
  85:     if((ok==0) && (insist<2)){
  86:         if(flags==1)
  87:         printf("Please use at least one non-numeric character.\n");
  88:         else
  89:         printf("Please use a longer password.\n");
  90:         insist++;
  91:         goto tryagn;
  92:         }
  93: 
  94:     if (strcmp(pwbuf,getpass("Retype new password:")) != 0) {
  95:         printf ("Mismatch - password unchanged.\n");
  96:         goto bex;
  97:     }
  98: 
  99:     time(&salt);
 100:     salt += getpid();
 101: 
 102:     saltc[0] = salt & 077;
 103:     saltc[1] = (salt>>6) & 077;
 104:     for(i=0;i<2;i++){
 105:         c = saltc[i] + '.';
 106:         if(c>'9') c += 7;
 107:         if(c>'Z') c += 6;
 108:         saltc[i] = c;
 109:     }
 110:     pw = crypt(pwbuf, saltc);
 111:     signal(SIGHUP, SIG_IGN);
 112:     signal(SIGINT, SIG_IGN);
 113:     signal(SIGQUIT, SIG_IGN);
 114: 
 115:     if(access(temp, 0) >= 0) {
 116:         printf("Temporary file busy -- try again\n");
 117:         goto bex;
 118:     }
 119:     close(creat(temp,0600));
 120:     if((tf=fopen(temp,"w")) == NULL) {
 121:         printf("Cannot create temporary file\n");
 122:         goto bex;
 123:     }
 124: 
 125: /*
 126:  *	copy passwd to temp, replacing matching lines
 127:  *	with new password.
 128:  */
 129: 
 130:     while((pwd=getpwent()) != NULL) {
 131:         if(strcmp(pwd->pw_name,uname) == 0) {
 132:             u = getuid();
 133:             if(u != 0 && u != pwd->pw_uid) {
 134:                 printf("Permission denied.\n");
 135:                 goto out;
 136:             }
 137:             pwd->pw_passwd = pw;
 138:         }
 139:         fprintf(tf,"%s:%s:%d:%d:%s:%s:%s\n",
 140:             pwd->pw_name,
 141:             pwd->pw_passwd,
 142:             pwd->pw_uid,
 143:             pwd->pw_gid,
 144:             pwd->pw_gecos,
 145:             pwd->pw_dir,
 146:             pwd->pw_shell);
 147:     }
 148:     endpwent();
 149:     fclose(tf);
 150: 
 151: /*
 152:  *	copy temp back to passwd file
 153:  */
 154: 
 155:     if((fi=open(temp,0)) < 0) {
 156:         printf("Temp file disappeared!\n");
 157:         goto out;
 158:     }
 159:     if((fo=creat(passwd, 0644)) < 0) {
 160:         printf("Cannot recreat passwd file.\n");
 161:         goto out;
 162:     }
 163:     while((u=read(fi,buf,sizeof(buf))) > 0) write(fo,buf,u);
 164: 
 165: out:
 166:     unlink(temp);
 167: 
 168: bex:
 169:     exit(1);
 170: }

Defined functions

Defined variables