diff options
Diffstat (limited to 'src/libsystemd/sd-bus/bus-socket.c')
| -rw-r--r-- | src/libsystemd/sd-bus/bus-socket.c | 112 |
1 files changed, 103 insertions, 9 deletions
diff --git a/src/libsystemd/sd-bus/bus-socket.c b/src/libsystemd/sd-bus/bus-socket.c index 5ade8e9..07179e0 100644 --- a/src/libsystemd/sd-bus/bus-socket.c +++ b/src/libsystemd/sd-bus/bus-socket.c @@ -217,7 +217,7 @@ static int bus_socket_auth_verify_client(sd_bus *b) { /* And possibly check the third line, too */ if (b->accept_fd) { l = lines[i++]; - b->can_fds = !!memory_startswith(l, lines[i] - l, "AGREE_UNIX_FD"); + b->can_fds = memory_startswith(l, lines[i] - l, "AGREE_UNIX_FD"); } assert(i == n); @@ -266,7 +266,7 @@ static int verify_anonymous_token(sd_bus *b, const char *p, size_t l) { if (l % 2 != 0) return 0; - r = unhexmem(p, l, (void **) &token, &len); + r = unhexmem_full(p, l, /* secure = */ false, (void**) &token, &len); if (r < 0) return 0; @@ -298,7 +298,7 @@ static int verify_external_token(sd_bus *b, const char *p, size_t l) { if (l % 2 != 0) return 0; - r = unhexmem(p, l, (void**) &token, &len); + r = unhexmem_full(p, l, /* secure = */ false, (void**) &token, &len); if (r < 0) return 0; @@ -503,11 +503,38 @@ static int bus_socket_write_auth(sd_bus *b) { if (b->prefer_writev) k = writev(b->output_fd, b->auth_iovec + b->auth_index, ELEMENTSOF(b->auth_iovec) - b->auth_index); else { + CMSG_BUFFER_TYPE(CMSG_SPACE(sizeof(struct ucred))) control = {}; + struct msghdr mh = { .msg_iov = b->auth_iovec + b->auth_index, .msg_iovlen = ELEMENTSOF(b->auth_iovec) - b->auth_index, }; + if (uid_is_valid(b->connect_as_uid) || gid_is_valid(b->connect_as_gid)) { + + /* If we shall connect under some specific UID/GID, then synthesize an + * SCM_CREDENTIALS record accordingly. After all we want to adopt this UID/GID both + * for SO_PEERCRED (where we have to fork()) and SCM_CREDENTIALS (where we can just + * fake it via sendmsg()) */ + + struct ucred ucred = { + .pid = getpid_cached(), + .uid = uid_is_valid(b->connect_as_uid) ? b->connect_as_uid : getuid(), + .gid = gid_is_valid(b->connect_as_gid) ? b->connect_as_gid : getgid(), + }; + + mh.msg_control = &control; + mh.msg_controllen = sizeof(control); + struct cmsghdr *cmsg = CMSG_FIRSTHDR(&mh); + *cmsg = (struct cmsghdr) { + .cmsg_level = SOL_SOCKET, + .cmsg_type = SCM_CREDENTIALS, + .cmsg_len = CMSG_LEN(sizeof(struct ucred)), + }; + + memcpy(CMSG_DATA(cmsg), &ucred, sizeof(struct ucred)); + } + k = sendmsg(b->output_fd, &mh, MSG_DONTWAIT|MSG_NOSIGNAL); if (k < 0 && errno == ENOTSOCK) { b->prefer_writev = true; @@ -643,14 +670,20 @@ static void bus_get_peercred(sd_bus *b) { /* Get the SELinux context of the peer */ r = getpeersec(b->input_fd, &b->label); if (r < 0 && !IN_SET(r, -EOPNOTSUPP, -ENOPROTOOPT)) - log_debug_errno(r, "Failed to determine peer security context: %m"); + log_debug_errno(r, "Failed to determine peer security context, ignoring: %m"); /* Get the list of auxiliary groups of the peer */ r = getpeergroups(b->input_fd, &b->groups); if (r >= 0) b->n_groups = (size_t) r; else if (!IN_SET(r, -EOPNOTSUPP, -ENOPROTOOPT)) - log_debug_errno(r, "Failed to determine peer's group list: %m"); + log_debug_errno(r, "Failed to determine peer's group list, ignoring: %m"); + + r = getpeerpidfd(b->input_fd); + if (r < 0) + log_debug_errno(r, "Failed to determine peer pidfd, ignoring: %m"); + else + close_and_replace(b->pidfd, r); /* Let's query the peers socket address, it might carry information such as the peer's comm or * description string */ @@ -943,6 +976,66 @@ static int bind_description(sd_bus *b, int fd, int family) { return 0; } +static int connect_as(int fd, const struct sockaddr *sa, socklen_t salen, uid_t uid, gid_t gid) { + _cleanup_(close_pairp) int pfd[2] = EBADF_PAIR; + ssize_t n; + int r; + + /* Shortcut if we are not supposed to drop privileges */ + if (!uid_is_valid(uid) && !gid_is_valid(gid)) + return RET_NERRNO(connect(fd, sa, salen)); + + /* This changes identity to the specified uid/gid and issues connect() as that. This is useful to + * make sure SO_PEERCRED reports the selected UID/GID rather than the usual one of the caller. */ + + if (pipe2(pfd, O_CLOEXEC) < 0) + return -errno; + + r = safe_fork("(sd-setresuid)", FORK_RESET_SIGNALS|FORK_DEATHSIG_SIGKILL|FORK_WAIT, /* ret_pid= */ NULL); + if (r < 0) + return r; + if (r == 0) { + /* child */ + + pfd[0] = safe_close(pfd[0]); + + r = RET_NERRNO(setgroups(0, NULL)); + if (r < 0) + goto child_finish; + + if (gid_is_valid(gid)) { + r = RET_NERRNO(setresgid(gid, gid, gid)); + if (r < 0) + goto child_finish; + } + + if (uid_is_valid(uid)) { + r = RET_NERRNO(setresuid(uid, uid, uid)); + if (r < 0) + goto child_finish; + } + + r = RET_NERRNO(connect(fd, sa, salen)); + if (r < 0) + goto child_finish; + + r = 0; + + child_finish: + n = write(pfd[1], &r, sizeof(r)); + if (n != sizeof(r)) + _exit(EXIT_FAILURE); + + _exit(EXIT_SUCCESS); + } + + n = read(pfd[0], &r, sizeof(r)); + if (n != sizeof(r)) + return -EIO; + + return r; +} + int bus_socket_connect(sd_bus *b) { bool inotify_done = false; int r; @@ -974,8 +1067,9 @@ int bus_socket_connect(sd_bus *b) { b->output_fd = b->input_fd; bus_socket_setup(b); - if (connect(b->input_fd, &b->sockaddr.sa, b->sockaddr_size) < 0) { - if (errno == EINPROGRESS) { + r = connect_as(b->input_fd, &b->sockaddr.sa, b->sockaddr_size, b->connect_as_uid, b->connect_as_gid); + if (r < 0) { + if (r == -EINPROGRESS) { /* If we have any inotify watches open, close them now, we don't need them anymore, as * we have successfully initiated a connection */ @@ -988,7 +1082,7 @@ int bus_socket_connect(sd_bus *b) { return 1; } - if (IN_SET(errno, ENOENT, ECONNREFUSED) && /* ENOENT → unix socket doesn't exist at all; ECONNREFUSED → unix socket stale */ + if (IN_SET(r, -ENOENT, -ECONNREFUSED) && /* ENOENT → unix socket doesn't exist at all; ECONNREFUSED → unix socket stale */ b->watch_bind && b->sockaddr.sa.sa_family == AF_UNIX && b->sockaddr.un.sun_path[0] != 0) { @@ -1016,7 +1110,7 @@ int bus_socket_connect(sd_bus *b) { inotify_done = true; } else - return -errno; + return r; } else break; } |