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Connect/bind Unix domain sockets in a child process

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In the child process, we can do a chdir() and avoid the problem of the
path not fitting into sockaddr_un.
This commit is contained in:
Eelco Dolstra 2021-08-24 13:52:55 +02:00
parent 08cc572f89
commit 43d4d75e22
3 changed files with 69 additions and 21 deletions
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11
src/libstore/uds-remote-store.cc
View file

@ -65,16 +65,7 @@ ref<RemoteStore::Connection> UDSRemoteStore::openConnection()
throw SysError("cannot create Unix domain socket");
closeOnExec(conn->fd.get());
string socketPath = path ? *path : settings.nixDaemonSocketFile;
struct sockaddr_un addr;
addr.sun_family = AF_UNIX;
if (socketPath.size() + 1 >= sizeof(addr.sun_path))
throw Error("socket path '%1%' is too long", socketPath);
strcpy(addr.sun_path, socketPath.c_str());
if (::connect(conn->fd.get(), (struct sockaddr *) &addr, sizeof(addr)) == -1)
throw SysError("cannot connect to daemon at '%1%'", socketPath);
nix::connect(conn->fd.get(), path ? *path : settings.nixDaemonSocketFile);
conn->from.fd = conn->fd.get();
conn->to.fd = conn->fd.get();

71
src/libutil/util.cc
View file

@ -1686,16 +1686,7 @@ AutoCloseFD createUnixDomainSocket(const Path & path, mode_t mode)
closeOnExec(fdSocket.get());
struct sockaddr_un addr;
addr.sun_family = AF_UNIX;
if (path.size() + 1 >= sizeof(addr.sun_path))
throw Error("socket path '%1%' is too long", path);
strcpy(addr.sun_path, path.c_str());
unlink(path.c_str());
if (bind(fdSocket.get(), (struct sockaddr *) &addr, sizeof(addr)) == -1)
throw SysError("cannot bind to socket '%1%'", path);
bind(fdSocket.get(), path);
if (chmod(path.c_str(), mode) == -1)
throw SysError("changing permissions on '%1%'", path);
@ -1707,6 +1698,66 @@ AutoCloseFD createUnixDomainSocket(const Path & path, mode_t mode)
}
void bind(int fd, const std::string & path)
{
unlink(path.c_str());
struct sockaddr_un addr;
addr.sun_family = AF_UNIX;
if (path.size() + 1 >= sizeof(addr.sun_path)) {
Pid pid = startProcess([&]() {
auto dir = dirOf(path);
if (chdir(dir.c_str()) == -1)
throw SysError("chdir to '%s' failed", dir);
std::string base(baseNameOf(path));
if (base.size() + 1 >= sizeof(addr.sun_path))
throw Error("socket path '%s' is too long", base);
strcpy(addr.sun_path, base.c_str());
if (bind(fd, (struct sockaddr *) &addr, sizeof(addr)) == -1)
throw SysError("cannot bind to socket '%s'", path);
_exit(0);
});
int status = pid.wait();
if (status != 0)
throw Error("cannot bind to socket '%s'", path);
} else {
strcpy(addr.sun_path, path.c_str());
if (bind(fd, (struct sockaddr *) &addr, sizeof(addr)) == -1)
throw SysError("cannot bind to socket '%s'", path);
}
}
void connect(int fd, const std::string & path)
{
struct sockaddr_un addr;
addr.sun_family = AF_UNIX;
if (path.size() + 1 >= sizeof(addr.sun_path)) {
Pid pid = startProcess([&]() {
auto dir = dirOf(path);
if (chdir(dir.c_str()) == -1)
throw SysError("chdir to '%s' failed", dir);
std::string base(baseNameOf(path));
if (base.size() + 1 >= sizeof(addr.sun_path))
throw Error("socket path '%s' is too long", base);
strcpy(addr.sun_path, base.c_str());
if (connect(fd, (struct sockaddr *) &addr, sizeof(addr)) == -1)
throw SysError("cannot connect to socket at '%s'", path);
_exit(0);
});
int status = pid.wait();
if (status != 0)
throw Error("cannot connect to socket ar '%s'", path);
} else {
strcpy(addr.sun_path, path.c_str());
if (connect(fd, (struct sockaddr *) &addr, sizeof(addr)) == -1)
throw SysError("cannot connect to socket at '%s'", path);
}
}
string showBytes(uint64_t bytes)
{
return fmt("%.2f MiB", bytes / (1024.0 * 1024.0));

8
src/libutil/util.hh
View file

@ -259,7 +259,7 @@ void killUser(uid_t uid);
pid to the caller. */
struct ProcessOptions
{
string errorPrefix = "error: ";
string errorPrefix = "";
bool dieWithParent = true;
bool runExitHandlers = false;
bool allowVfork = true;
@ -574,6 +574,12 @@ void commonChildInit(Pipe & logPipe);
/* Create a Unix domain socket in listen mode. */
AutoCloseFD createUnixDomainSocket(const Path & path, mode_t mode);
/* Bind a Unix domain socket to a path. */
void bind(int fd, const std::string & path);
/* Connect to a Unix domain socket. */
void connect(int fd, const std::string & path);
// A Rust/Python-like enumerate() iterator adapter.
// Borrowed from http://reedbeta.com/blog/python-like-enumerate-in-cpp17.