#include <stdio.h> #include <grp.h> #include <pwd.h> #include <sys/param.h> struct group *getgrnam(), *grp; struct passwd *getpwuid(), *pwd; char *getpass(), *crypt(); main(argc,argv) int argc; char **argv; { register i; if(argc < 2) { fprintf(stderr, "usage: newgrp groupname [command]\n"); exit(1); } if((grp=getgrnam(argv[1])) == NULL) { fprintf(stderr, "%s: no such group\n", argv[1]); exit(1); } if((pwd=getpwuid(getuid())) == NULL) { fprintf(stderr, "You do not exist!\n"); exit(1); } for(i=0;grp->gr_mem[i];i++) if(strcmp(grp->gr_mem[i], pwd->pw_name) == 0) break; if(grp->gr_mem[i] == 0 && strcmp(grp->gr_name,"other")) { fprintf(stderr, "Sorry\n"); exit(1); } if(grp->gr_passwd[0] != '\0' && pwd->pw_passwd[0] == '\0') { if(strcmp(grp->gr_passwd, crypt(getpass("Password:"),grp->gr_passwd)) != 0) { fprintf(stderr, "Sorry\n"); exit(1); } } if(setgid(grp->gr_gid) < 0) { perror("setgid"); exit(1); } done(argc, argv); } done(argc, argv) int argc; char **argv; { register i; setuid(getuid()); for (i=NSYSFILE; i<NOFILE; i++) close(i); if(argc < 3) { execl(((pwd && pwd->pw_shell[0])? pwd->pw_shell: "/bin/sh"), "sh", 0); fprintf(stderr, "No shell!\n"); } else { execvp(argv[2], &argv[2]); perror(argv[2]); exit(1); } exit(1); }