1 /* $OpenBSD: rcmdsh.c,v 1.5 1998/04/25 16:23:58 millert Exp $ */ 2 3 /* 4 * This is an rcmd() replacement originally by 5 * Chris Siebenmann <cks@utcc.utoronto.ca>. 6 */ 7 8 #include <sys/cdefs.h> 9 __FBSDID("$FreeBSD$"); 10 11 #include <sys/types.h> 12 #include <sys/socket.h> 13 #include <sys/wait.h> 14 15 #include <errno.h> 16 #include <netdb.h> 17 #include <paths.h> 18 #include <pwd.h> 19 #include <stdio.h> 20 #include <string.h> 21 #include <unistd.h> 22 23 #ifndef _PATH_RSH 24 #define _PATH_RSH "/usr/bin/rsh" 25 #endif 26 27 /* 28 * This is a replacement rcmd() function that uses the rsh(1) 29 * program in place of a direct rcmd(3) function call so as to 30 * avoid having to be root. Note that rport is ignored. 31 */ 32 /* ARGSUSED */ 33 int 34 rcmdsh(ahost, rport, locuser, remuser, cmd, rshprog) 35 char **ahost; 36 int rport __unused; 37 const char *locuser, *remuser, *cmd, *rshprog; 38 { 39 struct hostent *hp; 40 int cpid, sp[2]; 41 char *p; 42 struct passwd *pw; 43 44 /* What rsh/shell to use. */ 45 if (rshprog == NULL) 46 rshprog = _PATH_RSH; 47 48 /* locuser must exist on this host. */ 49 if ((pw = getpwnam(locuser)) == NULL) { 50 (void)fprintf(stderr, "rcmdsh: unknown user: %s\n", locuser); 51 return (-1); 52 } 53 54 /* Validate remote hostname. */ 55 if (strcmp(*ahost, "localhost") != 0) { 56 if ((hp = gethostbyname(*ahost)) == NULL) { 57 herror(*ahost); 58 return (-1); 59 } 60 *ahost = hp->h_name; 61 } 62 63 /* Get a socketpair we'll use for stdin and stdout. */ 64 if (socketpair(AF_UNIX, SOCK_STREAM, PF_UNSPEC, sp) == -1) { 65 perror("rcmdsh: socketpair"); 66 return (-1); 67 } 68 69 cpid = fork(); 70 if (cpid == -1) { 71 perror("rcmdsh: fork failed"); 72 return (-1); 73 } else if (cpid == 0) { 74 /* 75 * Child. We use sp[1] to be stdin/stdout, and close sp[0]. 76 */ 77 (void)close(sp[0]); 78 if (dup2(sp[1], 0) == -1 || dup2(0, 1) == -1) { 79 perror("rcmdsh: dup2 failed"); 80 _exit(255); 81 } 82 /* Fork again to lose parent. */ 83 cpid = fork(); 84 if (cpid == -1) { 85 perror("rcmdsh: fork to lose parent failed"); 86 _exit(255); 87 } 88 if (cpid > 0) 89 _exit(0); 90 91 /* In grandchild here. Become local user for rshprog. */ 92 if (setuid(pw->pw_uid) == -1) { 93 (void)fprintf(stderr, "rcmdsh: setuid(%u): %s\n", 94 pw->pw_uid, strerror(errno)); 95 _exit(255); 96 } 97 98 /* 99 * If remote host is "localhost" and local and remote users 100 * are the same, avoid running remote shell for efficiency. 101 */ 102 if (strcmp(*ahost, "localhost") == 0 && 103 strcmp(locuser, remuser) == 0) { 104 if (pw->pw_shell[0] == '\0') 105 rshprog = _PATH_BSHELL; 106 else 107 rshprog = pw->pw_shell; 108 p = strrchr(rshprog, '/'); 109 execlp(rshprog, p ? p + 1 : rshprog, "-c", cmd, 110 (char *)NULL); 111 } else { 112 p = strrchr(rshprog, '/'); 113 execlp(rshprog, p ? p + 1 : rshprog, *ahost, "-l", 114 remuser, cmd, (char *)NULL); 115 } 116 (void)fprintf(stderr, "rcmdsh: execlp %s failed: %s\n", 117 rshprog, strerror(errno)); 118 _exit(255); 119 } else { 120 /* Parent. close sp[1], return sp[0]. */ 121 (void)close(sp[1]); 122 /* Reap child. */ 123 (void)wait(NULL); 124 return (sp[0]); 125 } 126 /* NOTREACHED */ 127 } 128