Fix: kernel adds creds on recv with SO_PASSCRED unix socket option
authorFrancis Deslauriers <francis.deslauriers@efficios.com>
Tue, 27 Jun 2017 21:21:35 +0000 (17:21 -0400)
committerJérémie Galarneau <jeremie.galarneau@efficios.com>
Fri, 24 Aug 2018 19:29:15 +0000 (15:29 -0400)
When a Unix socket is configured with the SO_PASSCRED option, the caller
of recv() will receive a credential control message even if the sender
did not manually include it.
This caused problem with the old implementation of the
lttcomm_recv_fds_unix_sock function since it was expecting only one
control message for the fd passing. With the SO_PASSCRED, the kernel
will add a credential(SCM_CREDENTIALS) control message before the fd
passing(SCM_RIGHTS) control message (function scm_recv() [1]).

As a fix, make the receiver have a large enough before to include both
types of message and ignore the credential control message.

[1]: include/net/scm.h:111

Signed-off-by: Francis Deslauriers <francis.deslauriers@efficios.com>
Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>
configure.ac
src/common/Makefile.am
src/common/unix-stub.c [new file with mode: 0644]
src/common/unix.c

index f5501cebdfea99d6e994f1a694410ec50f218780..b7688eb7e8256b45454db8e99078ee81dfeddc90 100644 (file)
@@ -867,6 +867,7 @@ build_lib_compat=no
 build_lib_consumer=no
 build_lib_hashtable=no
 build_lib_health=no
+build_lib_unix=no
 build_lib_index=no
 build_lib_kernel_consumer=no
 build_lib_kernel_ctl=no
@@ -923,7 +924,7 @@ AS_IF([test x$enable_bin_lttng_sessiond != xno],
        build_lib_relayd=yes
        build_lib_testpoint=yes
        build_lib_health=yes
-       build_lib_health=yes
+       build_lib_unix=yes
       ]
 )
 
@@ -1032,6 +1033,7 @@ AM_CONDITIONAL([BUILD_LIB_CONFIG], [test x$build_lib_config = xyes])
 AM_CONDITIONAL([BUILD_LIB_CONSUMER], [test x$build_lib_consumer = xyes])
 AM_CONDITIONAL([BUILD_LIB_HASHTABLE], [test x$build_lib_hashtable = xyes])
 AM_CONDITIONAL([BUILD_LIB_HEALTH], [test x$build_lib_health = xyes])
+AM_CONDITIONAL([BUILD_LIB_UNIX], [test x$build_lib_unix = xyes])
 AM_CONDITIONAL([BUILD_LIB_INDEX], [test x$build_lib_index = xyes])
 AM_CONDITIONAL([BUILD_LIB_KERNEL_CONSUMER], [test x$build_lib_kernel_consumer = xyes])
 AM_CONDITIONAL([BUILD_LIB_KERNEL_CTL], [test x$build_lib_kernel_ctl = xyes])
index 0b804350648b0c8c2684a5c8fef2ea75065d61a8..171748f433aacc32cc3f79254e1cb1ea4e1957ec 100644 (file)
@@ -7,6 +7,37 @@ SUBDIRS = string-utils
 DIST_SUBDIRS = compat health hashtable kernel-ctl sessiond-comm relayd \
          kernel-consumer ust-consumer testpoint index config consumer \
          string-utils
+#
+# Common library
+noinst_LTLIBRARIES = libcommon.la
+EXTRA_DIST = mi-lttng-3.0.xsd
+
+libcommon_la_SOURCES = error.h error.c utils.c utils.h runas.h runas.c \
+                       common.h futex.c futex.h uri.c uri.h defaults.c \
+                       pipe.c pipe.h readwrite.c readwrite.h \
+                       mi-lttng.h mi-lttng.c \
+                       daemonize.c daemonize.h \
+                       unix.h \
+                       filter.c filter.h context.c context.h \
+                       action.c notify.c condition.c buffer-usage.c \
+                       session-consumed-size.c \
+                       session-rotation.c \
+                       evaluation.c notification.c trigger.c endpoint.c \
+                       dynamic-buffer.h dynamic-buffer.c \
+                       buffer-view.h buffer-view.c \
+                       location.c \
+                       waiter.h waiter.c \
+                       userspace-probe.c
+
+libcommon_la_LIBADD = \
+               $(top_builddir)/src/common/config/libconfig.la \
+               $(UUID_LIBS)
+
+if BUILD_LIB_UNIX
+libcommon_la_SOURCES += unix.c
+else
+libcommon_la_SOURCES += unix-stub.c
+endif
 
 if BUILD_LIB_COMPAT
 SUBDIRS += compat
@@ -60,31 +91,6 @@ noinst_HEADERS = lttng-kernel.h defaults.h macros.h error.h futex.h \
                                 uri.h utils.h lttng-kernel-old.h \
                                 align.h bitfield.h bug.h time.h
 
-# Common library
-noinst_LTLIBRARIES = libcommon.la
-EXTRA_DIST = mi-lttng-3.0.xsd
-
-libcommon_la_SOURCES = error.h error.c utils.c utils.h runas.c runas.h \
-                       common.h futex.c futex.h uri.c uri.h defaults.c \
-                       pipe.c pipe.h readwrite.c readwrite.h \
-                       mi-lttng.h mi-lttng.c \
-                       daemonize.c daemonize.h \
-                       unix.c unix.h \
-                       filter.c filter.h context.c context.h \
-                       action.c notify.c condition.c buffer-usage.c \
-                       session-consumed-size.c \
-                       session-rotation.c \
-                       evaluation.c notification.c trigger.c endpoint.c \
-                       dynamic-buffer.h dynamic-buffer.c \
-                       buffer-view.h buffer-view.c \
-                       location.c \
-                       waiter.h waiter.c \
-                       userspace-probe.c
-
-libcommon_la_LIBADD = \
-               $(top_builddir)/src/common/config/libconfig.la \
-               $(UUID_LIBS)
-
 all-local:
        @if [ x"$(srcdir)" != x"$(builddir)" ]; then \
                for script in $(EXTRA_DIST); do \
diff --git a/src/common/unix-stub.c b/src/common/unix-stub.c
new file mode 100644 (file)
index 0000000..5cc6296
--- /dev/null
@@ -0,0 +1,86 @@
+/*
+ * Copyright (C) 2018 Francis Deslauriers <francis.deslauriers@efficios.com>
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License, version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
+ * more details.
+ *
+ * You should have received a copy of the GNU General Public License along with
+ * this program; if not, write to the Free Software Foundation, Inc., 51
+ * Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+#ifndef _UNIX_STUB_H
+#define _UNIX_STUB_H
+
+#include <stddef.h>
+#include <stdlib.h>
+#include <common/compat/socket.h>
+
+int lttcomm_create_unix_sock(const char *pathname)
+{
+       return -1;
+}
+int lttcomm_create_anon_unix_socketpair(int *fds)
+{
+       return -1;
+}
+int lttcomm_connect_unix_sock(const char *pathname)
+{
+       return -1;
+}
+int lttcomm_accept_unix_sock(int sock)
+{
+       return -1;
+}
+int lttcomm_listen_unix_sock(int sock)
+{
+       return -1;
+}
+int lttcomm_close_unix_sock(int sock)
+{
+       return -1;
+}
+ssize_t lttcomm_send_fds_unix_sock(int sock, const int *fds, size_t nb_fd)
+{
+       return -1;
+}
+ssize_t lttcomm_recv_fds_unix_sock(int sock, int *fds, size_t nb_fd)
+{
+       return -1;
+}
+ssize_t lttcomm_recv_unix_sock(int sock, void *buf, size_t len)
+{
+       return -1;
+}
+ssize_t lttcomm_recv_unix_sock_non_block(int sock, void *buf, size_t len)
+{
+       return -1;
+}
+ssize_t lttcomm_send_unix_sock(int sock, const void *buf, size_t len)
+{
+       return -1;
+}
+ssize_t lttcomm_send_unix_sock_non_block(int sock, const void *buf, size_t len)
+{
+       return -1;
+}
+ssize_t lttcomm_send_creds_unix_sock(int sock, void *buf, size_t len)
+{
+       return -1;
+}
+ssize_t lttcomm_recv_creds_unix_sock(int sock, void *buf, size_t len,
+               lttng_sock_cred *creds)
+{
+       return -1;
+}
+int lttcomm_setsockopt_creds_unix_sock(int sock)
+{
+       return -1;
+}
+#endif /* _UNIX_STUB_H */
index 41525b69170a2c10bfcbdf2401f22936e576d058..3490af6e7d584d237d38ec6532d7b1fd93bcf1b1 100644 (file)
@@ -385,7 +385,7 @@ ssize_t lttcomm_send_fds_unix_sock(int sock, const int *fds, size_t nb_fd)
        char dummy = 0;
 
        memset(&msg, 0, sizeof(msg));
-       memset(tmp, 0, CMSG_SPACE(sizeof_fds) * sizeof(char));
+       memset(tmp, 0, sizeof(tmp));
 
        if (nb_fd > LTTCOMM_MAX_SEND_FDS)
                return -EINVAL;
@@ -397,6 +397,7 @@ ssize_t lttcomm_send_fds_unix_sock(int sock, const int *fds, size_t nb_fd)
        if (!cmptr) {
                return -1;
        }
+
        cmptr->cmsg_level = SOL_SOCKET;
        cmptr->cmsg_type = SCM_RIGHTS;
        cmptr->cmsg_len = CMSG_LEN(sizeof_fds);
@@ -439,7 +440,9 @@ ssize_t lttcomm_recv_fds_unix_sock(int sock, int *fds, size_t nb_fd)
        ssize_t ret = 0;
        struct cmsghdr *cmsg;
        size_t sizeof_fds = nb_fd * sizeof(int);
-       char recv_fd[CMSG_SPACE(sizeof_fds)];
+
+       /* Account for the struct ucred cmsg in the buffer size */
+       char recv_buf[CMSG_SPACE(sizeof_fds) + CMSG_SPACE(sizeof(struct ucred))];
        struct msghdr msg;
        char dummy;
 
@@ -450,8 +453,15 @@ ssize_t lttcomm_recv_fds_unix_sock(int sock, int *fds, size_t nb_fd)
        iov[0].iov_len = 1;
        msg.msg_iov = iov;
        msg.msg_iovlen = 1;
-       msg.msg_control = recv_fd;
-       msg.msg_controllen = sizeof(recv_fd);
+
+       cmsg = (struct cmsghdr *) recv_buf;
+       cmsg->cmsg_len = CMSG_LEN(sizeof_fds);
+       cmsg->cmsg_level = SOL_SOCKET;
+       cmsg->cmsg_type = SCM_RIGHTS;
+
+       msg.msg_control = cmsg;
+       msg.msg_controllen = CMSG_LEN(sizeof(recv_buf));
+       msg.msg_flags = 0;
 
        do {
                ret = recvmsg(sock, &msg, 0);
@@ -460,35 +470,63 @@ ssize_t lttcomm_recv_fds_unix_sock(int sock, int *fds, size_t nb_fd)
                PERROR("recvmsg fds");
                goto end;
        }
+
        if (ret != 1) {
                fprintf(stderr, "Error: Received %zd bytes, expected %d\n",
                                ret, 1);
                goto end;
        }
+
        if (msg.msg_flags & MSG_CTRUNC) {
                fprintf(stderr, "Error: Control message truncated.\n");
                ret = -1;
                goto end;
        }
-       cmsg = CMSG_FIRSTHDR(&msg);
-       if (!cmsg) {
-               fprintf(stderr, "Error: Invalid control message header\n");
-               ret = -1;
-               goto end;
-       }
-       if (cmsg->cmsg_level != SOL_SOCKET || cmsg->cmsg_type != SCM_RIGHTS) {
-               fprintf(stderr, "Didn't received any fd\n");
-               ret = -1;
-               goto end;
-       }
-       if (cmsg->cmsg_len != CMSG_LEN(sizeof_fds)) {
-               fprintf(stderr, "Error: Received %zu bytes of ancillary data, expected %zu\n",
-                               (size_t) cmsg->cmsg_len, (size_t) CMSG_LEN(sizeof_fds));
-               ret = -1;
-               goto end;
+
+       /*
+        * If the socket was configured with SO_PASSCRED, the kernel will add a
+        * control message (cmsg) to the ancillary data of the unix socket. We
+        * need to expect a cmsg of the SCM_CREDENTIALS as the first control
+        * message.
+        */
+       for (cmsg = CMSG_FIRSTHDR(&msg); cmsg != NULL; cmsg = CMSG_NXTHDR(&msg, cmsg)) {
+               if (!cmsg) {
+                       fprintf(stderr, "Error: Invalid control message header\n");
+                       ret = -1;
+                       goto end;
+               }
+               if (cmsg->cmsg_level != SOL_SOCKET) {
+                       fprintf(stderr, "Error: The socket needs to be of type SOL_SOCKET\n");
+                       ret = -1;
+                       goto end;
+               }
+               if (cmsg->cmsg_type == SCM_RIGHTS) {
+                       /*
+                        * We found the controle message for file descriptors,
+                        * now copy the fds to the fds ptr and return success.
+                        */
+                       if (cmsg->cmsg_len != CMSG_LEN(sizeof_fds)) {
+                               fprintf(stderr, "Error: Received %zu bytes of"
+                                       "ancillary data for FDs, expected %zu\n",
+                                       (size_t) cmsg->cmsg_len,
+                                       (size_t) CMSG_LEN(sizeof_fds));
+                               ret = -1;
+                               goto end;
+                       }
+                       memcpy(fds, CMSG_DATA(cmsg), sizeof_fds);
+                       ret = sizeof_fds;
+                       goto end;
+               }
+               if (cmsg->cmsg_type == SCM_CREDENTIALS) {
+                       /*
+                        * Expect credentials to be sent when expecting fds even
+                        * if no credential were include in the send(). The
+                        * kernel adds them...
+                        */
+                       fprintf(stderr, "Received creds... continuing\n");
+                       ret = -1;
+               }
        }
-       memcpy(fds, CMSG_DATA(cmsg), sizeof_fds);
-       ret = sizeof_fds;
 end:
        return ret;
 }
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