2.9BSD/usr/src/cmd/newgrp.c

#include <stdio.h>
#include <grp.h>
#include <pwd.h>

struct	group	*getgrnam(), *grp;
struct	passwd	*getpwuid(), *pwd;
char	*getpass(), *crypt();

#ifdef MENLO
char **environ;
char *shell ={ "/bin/sh" };
#endif

main(argc,argv)
int	argc;
char	**argv;
{
	register i;
	if(argc != 2) {
		printf("usage: newgrp groupname\n");
		done();
	}
	if((grp=getgrnam(argv[1])) == NULL) {
		printf("%s: no such group\n", argv[1]);
		done();
	}
	if((pwd=getpwuid(getuid())) == NULL) {
		printf("You do not exist!\n");
		done();
	}
	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")) {
		printf("Sorry\n");
		done();
	}

	if(grp->gr_passwd[0] != '\0' && pwd->pw_passwd[0] == '\0') {
		if(strcmp(grp->gr_passwd, crypt(getpass("Password:"),grp->gr_passwd)) != 0) {
			printf("Sorry\n");
			done();
		}
	}
	if(setgid(grp->gr_gid) < 0)
		perror("setgid");
	done();
}

done()
{
	register i;

#ifdef MENLO
	register char *cp;
	register char *cp2;
	register char **p;
	char hometmp[50];
#endif
	setuid(getuid());
	for (i=3; i<15; i++)
		close(i);
#ifndef MENLO
	execl("/bin/sh","sh",0);
#else
/*
 * to enable users to specify which shell they want in the environment
 * (as opposed to the default shell), search for a "SHELL" variable
 *		pag -- 11/11/79
 */
	for(p=environ; *p; p++)
		if (strncmp("SHELL=", *p, 6) == 0)
		{
		    for(cp = *p;*cp++ != '=';)
			;
		    shell = cp;
		}
/*
 * the C shell is very fussy about 'sourcing' in .login
 * and .cshrc files if they are not owned by the invoker
 * therefore, set HOME beforehand so that the old HOME
 * won't be used.
 *		pag -- 1/10/80
 */
	    if (strncmp("HOME=", *p, 5) == 0)
	    {
		for(cp = *p,cp2=hometmp;*cp != '=';)
		    *cp2++ = *cp++;
		*cp2++ = '=';
		strcpy(cp2,pwd->pw_dir);
		*p = calloc(1,strlen(hometmp)+1);
		strcat(*p,hometmp);
	    }
/*
 * slight kludge here:  csh strips off the first letter of argv[1]
 * when it is "newgrp", so add a dummy first letter! -- pag
 */
	if(strcmp(shell,"/bin/csh") != 0)
	execl(shell, "newgrp", 0);
	else
	    execl(shell, "_newgrp", 0);
#endif
	printf("No shell\n");
	exit(3);
}