#include <errno.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/socket.h>
#include <sys/un.h>
#include <sys/stat.h>
#include <string.h>
#include <fcntl.h>
#include <signal.h>
int main(int argc, char *argv[]) {
if (signal(SIGPIPE, SIG_IGN) == SIG_ERR) {
perror("signal");
return EXIT_FAILURE;
}
const char *socket_path = getenv("LINDENII_FORGE_HOOKS_SOCKET_PATH");
if (socket_path == NULL) {
dprintf(STDERR_FILENO, "environment variable LINDENII_FORGE_HOOKS_SOCKET_PATH undefined\n");
return EXIT_FAILURE;
}
const char *cookie = getenv("LINDENII_FORGE_HOOKS_COOKIE");
if (cookie == NULL) {
dprintf(STDERR_FILENO, "environment variable LINDENII_FORGE_HOOKS_COOKIE undefined\n");
return EXIT_FAILURE;
}
if (strlen(cookie) != 64) {
dprintf(STDERR_FILENO, "environment variable LINDENII_FORGE_HOOKS_COOKIE is not 64 characters long, something has gone wrong\n");
dprintf(STDERR_FILENO, "%s\n", cookie);
return EXIT_FAILURE;
}
/*
* All hooks in git (see builtin/receive-pack.c) use a pipe by setting
* .in = -1 on the child_process struct, which enables us to use
* splice(2) to move the data to the UNIX domain socket. Just to be
* safe, we check that stdin is a pipe; and additionally we fetch the
* buffer size of the pipe to use as the maximum size for the splice.
*
* We connect to the UNIX domain socket after ensuring that standard
* input matches our expectations.
*/
struct stat stdin_stat;
if (fstat(STDIN_FILENO, &stdin_stat) == -1) {
perror("fstat on stdin");
return EXIT_FAILURE;
}
if (!S_ISFIFO(stdin_stat.st_mode)) {
dprintf(STDERR_FILENO, "stdin must be a pipe\n");
return EXIT_FAILURE;
}
int stdin_pipe_size = fcntl(STDIN_FILENO, F_GETPIPE_SZ);
if (stdin_pipe_size == -1) {
perror("fcntl on stdin");
return EXIT_FAILURE;
}
/*
* ... And we do the same for stderr. Later we will splice from the
* socket to stderr, to let the daemon report back to the user.
*/
struct stat stderr_stat;
if (fstat(STDERR_FILENO, &stderr_stat) == -1) {
perror("fstat on stderr");
return EXIT_FAILURE;
}
if (!S_ISFIFO(stderr_stat.st_mode)) {
dprintf(STDERR_FILENO, "stderr must be a pipe\n");
return EXIT_FAILURE;
}
int stderr_pipe_size = fcntl(STDERR_FILENO, F_GETPIPE_SZ);
if (stderr_pipe_size == -1) {
perror("fcntl on stderr");
return EXIT_FAILURE;
}
/*
* Now that we know that stdin and stderr are pipes, we can connect to
* the UNIX domain socket. We don't do this earlier because we don't
* want to create unnecessary connections if the hook was called
* inappropriately (such as by a user with shell access in their
* terminal).
*/
int sock;
struct sockaddr_un addr;
sock = socket(AF_UNIX, SOCK_STREAM, 0);
if (sock == -1) {
perror("internal socket creation");
return EXIT_FAILURE;
}
memset(&addr, 0, sizeof(struct sockaddr_un));
addr.sun_family = AF_UNIX;
strncpy(addr.sun_path, socket_path, sizeof(addr.sun_path) - 1);
if (connect(sock, (struct sockaddr *)&addr, sizeof(struct sockaddr_un)) == -1) {
perror("internal socket connect");
close(sock);
return EXIT_FAILURE;
}
/*
* We first send the 64-byte cookie to the UNIX domain socket
*/
ssize_t cookie_bytes_sent = send(sock, cookie, 64, 0);
switch (cookie_bytes_sent) {
case -1:
perror("send cookie");
close(sock);
return EXIT_FAILURE;
case 64:
break;
default:
dprintf(STDERR_FILENO, "send returned unexpected value on internal socket\n");
close(sock);
return EXIT_FAILURE;
}
/*
* Next we can report argc and argv to the UNIX domain socket.
*/
uint64_t argc64 = (uint64_t)argc;
ssize_t bytes_sent = send(sock, &argc64, sizeof(argc64), 0);
switch (bytes_sent) {
case -1:
perror("send argc");
close(sock);
return EXIT_FAILURE;
case sizeof(argc64):
break;
default:
dprintf(STDERR_FILENO, "send returned unexpected value on internal socket\n");
close(sock);
return EXIT_FAILURE;
}
for (int i = 0; i < argc; i++) {
unsigned long len = strlen(argv[i]) + 1;
bytes_sent = send(sock, argv[i], len, 0);
if (bytes_sent == -1) {
perror("send argv");
close(sock);
exit(EXIT_FAILURE);
} else if ((unsigned long)bytes_sent == len) {
} else {
dprintf(STDERR_FILENO, "send returned unexpected value on internal socket\n");
close(sock);
exit(EXIT_FAILURE);
}
}
/*
* Now we can start splicing data from stdin to the UNIX domain socket.
* The format is irrelevant and depends on the hook being called. All we
* do is pass it to the socket for it to handle.
*/
ssize_t stdin_bytes_spliced;
while ((stdin_bytes_spliced = splice(STDIN_FILENO, NULL, sock, NULL, stdin_pipe_size, SPLICE_F_MORE)) > 0) {
}
if (stdin_bytes_spliced == -1) {
perror("splice stdin to internal socket");
close(sock);
return EXIT_FAILURE;
}
/*
* The sending part of the UNIX socket should be shut down, to let
* io.Copy on the Go side return.
*/
if (shutdown(sock, SHUT_WR) == -1) {
perror("shutdown internal socket");
close(sock);
return EXIT_FAILURE;
}
/*
* The first byte of the response from the UNIX domain socket is the
* status code. We read it and record it as our return value.
*/
char status_buf[1];
ssize_t bytes_read = read(sock, status_buf, 1);
switch (bytes_read) {
case -1:
perror("read status code from internal socket");
close(sock);
return EXIT_FAILURE;
case 0:
dprintf(STDERR_FILENO, "unexpected EOF on internal socket\n");
close(sock);
return EXIT_FAILURE;
case 1:
break;
default:
dprintf(STDERR_FILENO, "read returned unexpected value on internal socket\n");
close(sock);
return EXIT_FAILURE;
}
/*
* Now we can splice data from the UNIX domain socket to stderr.
* This data is directly passed to the user (with "remote: " prepended).
*/
ssize_t stderr_bytes_spliced;
while ((stderr_bytes_spliced = splice(sock, NULL, STDERR_FILENO, NULL, stderr_pipe_size, SPLICE_F_MORE)) > 0) {
}
if (stdin_bytes_spliced == -1 && errno != ECONNRESET) {
perror("splice internal socket to stderr");
close(sock);
return EXIT_FAILURE;
}
close(sock);
return *status_buf;
}