diff options
Diffstat (limited to 'kdecore/kgrantpty.c')
| -rw-r--r-- | kdecore/kgrantpty.c | 179 |
1 files changed, 179 insertions, 0 deletions
diff --git a/kdecore/kgrantpty.c b/kdecore/kgrantpty.c new file mode 100644 index 000000000..7d16f5b68 --- /dev/null +++ b/kdecore/kgrantpty.c @@ -0,0 +1,179 @@ +/* kgrantpty - helper program for KPty. */ + +/* This program is based on the glibc2.1 pt_chmod. + * It was pulled out from there since both Linux + * distributors and other OSes are not able to make + * use of the glibc for different reasons. + * + * THIS IS A ROOT SUID PROGRAM + * + * Things work as following: + * + * In konsole we open a master pty. This can be + * done by at most one process. Prior to opening the + * master pty, the slave pty cannot be opened. Then, in + * grantpty, we fork to this program. The trick is, that + * the parameter is passed as a file handle, which cannot + * be faked, so that we get a secure setuid root chmod/chown + * with this program. + * + * We have to chown/chmod the slave pty to prevent eavesdroping. + * + * Contributed by Zack Weinberg <zack@rabi.phys.columbia.edu>, 1998. + * Copyright (c) 1999 by Lars Doelle <lars.doelle@on-line.de>. + * GPL applies. + */ + +#include <config.h> + +#include <sys/types.h> +#include <errno.h> +#include <grp.h> +#include <stdio.h> +#include <stdlib.h> +#include <string.h> +#include <sys/stat.h> +#include <unistd.h> + +#include <sys/param.h> +#if defined(__FreeBSD__) || defined(__DragonFly__) +# define BSD_PTY_HACK +# include <paths.h> +# include <dirent.h> +#endif + +#define TTY_GROUP "tty" + +int main (int argc, char *argv[]) +{ + struct stat st; + struct group* p; + gid_t gid; + uid_t uid; + mode_t mod; + char* tty; + int fd; + + /* check preconditions **************************************************/ + if (argc != 3 || (strcmp(argv[1],"--grant") && strcmp(argv[1],"--revoke"))) + { + printf("usage: %s (--grant|--revoke) <file descriptor>\n" + "%s is a helper for the KDE core libraries.\n" + "It is not intended to be called from the command line.\n" + "It needs to be installed setuid root to function.\n", + argv[0], argv[0]); + return 1; /* FAIL */ + } + + if (geteuid () != 0) + { + fprintf(stderr, "%s not installed setuid root\n", argv[0]); + return 1; /* FAIL */ + } + + fd = atoi(argv[2]); + + /* get slave pty name from master pty file handle *********/ +#ifdef HAVE_PTSNAME + tty = ptsname(fd); + if (!tty) +#endif + { + /* Check that fd is a valid master pseudo terminal. */ + char *pty = ttyname(fd); + +#ifdef BSD_PTY_HACK + if (pty == NULL) + { + /* + Hack to make kgrantpty work on some versions of FreeBSD (and possibly + other systems): ttyname(3) does not work with a file descriptor opened + on a /dev/pty?? device. + + Instead, this code looks through all the devices in /dev for a device + which has the same inode as our PTY_FILENO descriptor... if found, we + have the name for our pty. + */ + + struct dirent *dirp; + DIR *dp; + struct stat dsb; + + if (fstat(fd, &dsb) != -1) { + if ((dp = opendir(_PATH_DEV)) != NULL) { + while ((dirp = readdir(dp))) { + if (dirp->d_fileno != dsb.st_ino) + continue; + pty = malloc(sizeof(_PATH_DEV) + strlen(dirp->d_name)); + if (pty) { + strcpy(pty, _PATH_DEV); + strcat(pty, dirp->d_name); + } + break; + } + + (void) closedir(dp); + } + } + } +#endif + + if (pty == NULL) + { + fprintf(stderr,"%s: cannot determine pty name.\n",argv[0]); + return 1; /* FAIL */ + } + + /* matches /dev/pty?? */ + if (memcmp(pty,"/dev/pty",8)) + { + fprintf(stderr,"%s: determined a strange pty name `%s'.\n",argv[0],pty); + return 1; /* FAIL */ + } + + tty = malloc(strlen(pty) + 1); + strcpy(tty,"/dev/tty"); + strcat(tty,pty+8); + } + + /* Check that the returned slave pseudo terminal is a character device. */ + if (stat(tty, &st) < 0 || !S_ISCHR(st.st_mode)) + { + fprintf(stderr,"%s: found `%s' not to be a character device.\n",argv[0],tty); + return 1; /* FAIL */ + } + + /* setup parameters for the operation ***********************************/ + + if (!strcmp(argv[1],"--grant")) + { + uid = getuid(); + p = getgrnam(TTY_GROUP); + if (!p) + p = getgrnam("wheel"); + gid = p ? p->gr_gid : getgid (); + mod = S_IRUSR | S_IWUSR | S_IWGRP; + } + else + { + uid = 0; + gid = st.st_gid == getgid () ? 0 : -1; + mod = S_IRUSR | S_IWUSR | S_IRGRP | S_IWGRP | S_IROTH | S_IWOTH; + } + + /* Perform the actual chown/chmod ************************************/ + + if (chown(tty, uid, gid) < 0) + { + fprintf(stderr,"%s: cannot chown %s: %s\n",argv[0],tty,strerror(errno)); + return 1; /* FAIL */ + } + + if (chmod(tty, mod) < 0) + { + fprintf(stderr,"%s: cannot chmod %s: %s\n",argv[0],tty,strerror(errno)); + return 1; /* FAIL */ + } + + return 0; /* OK */ +} |