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/**
* (C) Copyright 2008 Jeremy Maitin-Shepard
*
* Use, modification, and distribution are subject to the terms specified in the
* COPYING file.
**/
#include <sys/types.h>
#include <sys/socket.h>
#include <unistd.h>
#include <stdio.h>
#include <errno.h>
#include <stdlib.h>
#include <signal.h>
#include <sys/wait.h>
#include <sys/stat.h>
#include <string.h>
#include <fcntl.h>
#include <netinet/in.h>
#include <dirent.h>
#include <sys/resource.h>
#include <arpa/inet.h>
void fail(const char *msg) {
fprintf(stderr, "%s\n", msg);
exit(1);
}
void failerr(const char *msg) {
perror(msg);
exit(1);
}
#define TRY(var, foo) var = foo; while (var == -1) { if(errno != EINTR) failerr(#foo); }
void *Malloc(size_t count) { void *r = malloc(count); if (!r) fail("malloc"); return r; }
/**
* read_all: read from the specified file descriptor, returning a
* malloc-allocated buffer containing the data that was read; the
* number of bytes read is stored in *bytes_read. If max_bytes is
* non-negative, it specifies the maximum number of bytes to read.
* Otherwise, read_all reads from the file descriptor until the end of
* file is reached.
*/
char *read_all(int fd, int max_bytes, int *bytes_read) {
int capacity = 256;
if (max_bytes > 0)
capacity = max_bytes;
char *buffer = Malloc(capacity);
int count = 0;
if (max_bytes < 0 || max_bytes > 0) {
while (1) {
int remain;
if (count == capacity) {
capacity *= 2;
buffer = realloc(buffer, capacity);
if (!buffer)
fail("realloc failed");
}
remain = capacity - count;
if (max_bytes > 0 && remain > max_bytes)
remain = max_bytes;
TRY(remain, read(fd, buffer + count, remain));
count += remain;
if (remain == 0 || count == max_bytes)
break;
}
}
*bytes_read = count;
return buffer;
}
/**
* next_term: return the next NUL terminated string from buffer, and
* adjust buffer and len accordingly.
*/
char *next_term(char **buffer, int *len) {
char *p = *buffer;
int x = 0;
int max_len = *len;
while (x < max_len && p[x])
++x;
if (x == max_len)
fail("error parsing");
*buffer += x + 1;
*len -= (x + 1);
return p;
}
struct fd_info {
int desired_fd;
int orig_fd;
char *path;
int open_mode;
int perms;
};
void write_all(int fd, const char *buf, int len) {
int result;
do {
TRY(result, write(fd, buf, len));
buf += result;
len -= result;
} while (len > 0);
}
/**
* my_connect: Create a connection to the local Conkeror process on
* the specified TCP port. After connecting, the properly formatted
* header specifying the client_key and the "role" (file descriptor or
* -1 to indicate the control socket) are sent as well. The file
* descriptor for the socket is returned.
*/
int my_connect(int port, char *client_key, int role) {
int sockfd;
int result;
struct sockaddr_in sa;
TRY(sockfd, socket(PF_INET, SOCK_STREAM, 0));
sa.sin_family = AF_INET;
sa.sin_port = htons(port);
sa.sin_addr.s_addr = inet_addr("127.0.0.1");
memset(sa.sin_zero, 0, sizeof(sa.sin_zero));
TRY(result, connect(sockfd, (struct sockaddr *)&sa, sizeof(sa)));
/* Send the client key */
write_all(sockfd, client_key, strlen(client_key));
/* Send the role */
if (role < 0) {
write_all(sockfd, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0", 15);
}
else {
char buf[16];
snprintf(buf, 16, "%15d", role);
write_all(sockfd, buf, 15);
}
return sockfd;
}
int child_pid = 0;
int control_fd;
/**
* sigchld_handler: reap any waitable children. Once the child
* process exits, send the exit status back over the control socket,
* then exit. */
void sigchld_handler(int sig) {
int status;
int pid;
int err;
while (1) {
pid = waitpid(-1, &status, WNOHANG);
if (pid == 0)
return;
if (pid == -1) {
if (errno == ECHILD)
break;
failerr("waitpid");
}
/* Our child process exited */
if (pid == child_pid && (WIFEXITED(status) || WIFSIGNALED(status))) {
char buf[30];
snprintf(buf, 30, "%d", status);
write_all(control_fd, buf, strlen(buf) + 1);
exit(0);
}
}
}
void check_duplicate_fds(struct fd_info *fds, int fd_count) {
int i, j;
for (i = 0; i < fd_count; ++i) {
for (j = i + 1; j < fd_count; ++j) {
if (fds[i].desired_fd == fds[j].desired_fd)
fail("duplicate redirection requested");
}
}
}
/**
* setup_fds: Make the requested redirections. For each entry in the
* fds array, rename orig_fd to desired_fd.
*/
void setup_fds(struct fd_info *fds, int fd_count) {
int i, j, result;
for (i = 0; i < fd_count; ++i) {
int fd = fds[i].desired_fd;
if (fd == fds[i].orig_fd) {
/* file descriptor is already correct, nothing needs to be done for it */
continue;
}
/* Check if this file descriptor is still in use by any subsequent
redirection. */
for (j = i + 1; j < fd_count; ++j) {
if (fd == fds[j].orig_fd) {
/* It is in use. Pick a new file descriptor for fds[j]. */
int fd_new;
TRY(fd_new, dup(fds[j].orig_fd));
close(fds[j].orig_fd);
fds[j].orig_fd = fd_new;
break;
}
}
TRY(result, dup2(fds[i].orig_fd, fd));
close(fds[i].orig_fd);
}
}
int main(int argc, char **argv) {
int port;
char *client_key, *server_key, *executable, *workdir;
char **my_argv;
struct fd_info *fds;
int fd_count;
int i;
sigset_t my_mask, my_old_mask;
if (argc != 3 || (port = atoi(argv[2])) == 0)
fail("Invalid arguments");
sigemptyset(&my_mask);
sigaddset(&my_mask, SIGCHLD);
/* Block SIGPIPE to avoid a signal being generated while writing to a socket */
signal(SIGPIPE, SIG_IGN);
/* Close everything except STDERR. Mozilla leaves us with a bunch
of junk file descriptors. */
{
DIR *dir = opendir("/proc/self/fd");
if (!dir) {
/* No proc filesystem available, just loop through file descriptors */
struct rlimit file_lim;
int max_fileno = 1024;
if (getrlimit(RLIMIT_NOFILE, &file_lim) == 0)
max_fileno = file_lim.rlim_cur;
for (i = 0; i < max_fileno; ++i) {
if (i == STDERR_FILENO)
continue;
close(i);
}
} else {
struct dirent *dir_ent;
int dir_fd = dirfd(dir);
while ((dir_ent = readdir(dir)) != NULL) {
int file_desc = atoi(dir_ent->d_name);
if (file_desc == STDERR_FILENO || file_desc == dir_fd)
continue;
close(file_desc);
}
closedir(dir);
}
}
/* Create a default redirection of STDIN and STDOUT to /dev/null, because some
programs except STDIN and STDOUT to always be present. Any user-specified
redirections will override these.
*/
/* At this point, the only open file descriptor is STDERR (2). Therefore, the
next two calls to open are guaranteed to use file descriptors 1 and 2
(STDIN and STDOUT, respectively).
*/
if (open("/dev/null", O_RDONLY) != STDIN_FILENO)
fail("Failed to redirect STDIN to /dev/null");
if (open("/dev/null", O_RDWR) != STDOUT_FILENO)
fail("Failed to redirect STDOUT to /dev/null");
/* Parse key file */
{
char *buf;
int len;
int my_argc;
/* Read the entire file into buf. */
{
int file;
TRY(file, open(argv[1], O_RDONLY));
buf = read_all(file, -1, &len);
close(file);
/* Remove the temporary file */
remove(argv[1]);
}
client_key = next_term(&buf, &len);
server_key = next_term(&buf, &len);
executable = next_term(&buf, &len);
workdir = next_term(&buf, &len);
my_argc = atoi(next_term(&buf, &len));
my_argv = Malloc(sizeof(char *) * (my_argc + 1));
for (i = 0; i < my_argc; ++i)
my_argv[i] = next_term(&buf, &len);
my_argv[my_argc] = NULL;
fd_count = atoi(next_term(&buf, &len));
if (fd_count < 0) fail("invalid fd count");
fds = Malloc(sizeof(struct fd_info) * fd_count);
for (i = 0; i < fd_count; ++i) {
fds[i].desired_fd = atoi(next_term(&buf, &len));
fds[i].path = next_term(&buf, &len);
if (fds[i].path[0]) {
fds[i].open_mode = atoi(next_term(&buf, &len));
fds[i].perms = atoi(next_term(&buf, &len));
}
}
if (len != 0)
fail("invalid input file");
}
/* Validate the file descriptor redirection request. */
check_duplicate_fds(fds, fd_count);
/* Create the control socket connection. */
control_fd = my_connect(port, client_key, -1);
/* Create a socket connection or open a local file for each
requested file descriptor redirection. */
for (i = 0; i < fd_count; ++i) {
if (fds[i].path[0]) {
TRY(fds[i].orig_fd, open(fds[i].path, fds[i].open_mode, fds[i].perms));
} else {
fds[i].orig_fd = my_connect(port, client_key, fds[i].desired_fd);
}
}
/* Check server key */
{
int len = strlen(server_key);
int read_len;
char *buf = read_all(control_fd, len, &read_len);
if (len != read_len || memcmp(buf, server_key, len) != 0)
fail("server key mismatch");
free(buf);
}
/* Block SIGCHLD */
sigprocmask(SIG_BLOCK, &my_mask, &my_old_mask);
/* Create the child process */
child_pid = fork();
if (child_pid == 0) {
int result;
/* Unblock SIGCHLD */
sigprocmask(SIG_SETMASK, &my_old_mask, NULL);
/* Reset the SIGPIPE signal handler. */
signal(SIGPIPE, SIG_DFL);
/* Close the control socket, as it isn't needed from the child. */
close(control_fd);
/* Change to the specified working directory. */
if (workdir[0] != 0) {
if (chdir(workdir) == -1)
failerr(workdir);
}
/* Rearrange file descriptors according to the user specification */
setup_fds(fds, fd_count);
/* Exec */
TRY(result, execv(executable, my_argv));
} else if (child_pid == -1) {
failerr("fork");
} else {
/* We are in the parent process */
char msg;
int count;
/* Install SIGCHLD handler */
{
struct sigaction act;
act.sa_handler = sigchld_handler;
sigemptyset(&act.sa_mask);
act.sa_flags = SA_NOCLDSTOP;
sigaction(SIGCHLD, &act, NULL);
}
/* Unblock SIGCHLD */
sigprocmask(SIG_SETMASK, &my_old_mask, NULL);
/* Close all of the redirection file descriptors, as we don't need
them from the parent. */
for (i = 0; i < fd_count; ++i)
close(fds[i].orig_fd);
/* Wait for a message from the server telling us to exit early. */
TRY(count, read(control_fd, &msg, 1));
if (count == 0) {
/* End of file received: exit without killing child */
return 0;
}
/* Assume msg == 0 until we support more messages */
TRY(count, kill(child_pid, SIGTERM));
return 0;
}
}