Simon McVittie discovered that the fix for CVE-2014-3636 was incorrect, as it did not fully address the underlying denial-of-service vector. This update starts the D-Bus daemon as root initially, so that it can properly raise its file descriptor count.

In addition, this update reverts the auth_timeout change in the previous security update to its old value because the new value causes boot failures on some systems. See the README.Debian file for details how to harden the D-Bus daemon against malicious local users.

Updated dbus packages fixes the following security issues :

Alban Crequy and Simon McVittie discovered several vulnerabilities in the D-Bus message daemon :

On 64-bit platforms, file descriptor passing could be abused by local users to cause heap corruption in dbus-daemon, leading to a crash, or potentially to arbitrary code execution (CVE-2014-3635).

A denial-of-service vulnerability in dbus-daemon allowed local attackers to prevent new connections to dbus-daemon, or disconnect existing clients, by exhausting descriptor limits (CVE-2014-3636).

Malicious local users could create D-Bus connections to dbus-daemon which could not be terminated by killing the participating processes, resulting in a denial-of-service vulnerability (CVE-2014-3637).

dbus-daemon suffered from a denial-of-service vulnerability in the code which tracks which messages expect a reply, allowing local attackers to reduce the performance of dbus-daemon (CVE-2014-3638).

dbus-daemon did not properly reject malicious connections from local users, resulting in a denial-of-service vulnerability (CVE-2014-3639).

The patch issued by the D-Bus maintainers for CVE-2014-3636 was based on incorrect reasoning, and does not fully prevent the attack described as CVE-2014-3636 part A, which is repeated below. Preventing that attack requires raising the system dbus-daemon's RLIMIT_NOFILE (ulimit -n) to a higher value.

By queuing up the maximum allowed number of fds, a malicious sender could reach the system dbus-daemon's RLIMIT_NOFILE (ulimit -n, typically 1024 on Linux). This would act as a denial of service in two ways :

  - new clients would be unable to connect to the     dbus-daemon

    - when receiving a subsequent message from a       non-malicious client that contained a fd, dbus-daemon       would receive the MSG_CTRUNC flag, indicating that the       list of fds was truncated; kernel fd-passing APIs do       not provide any way to recover from that, so       dbus-daemon responds to MSG_CTRUNC by disconnecting       the sender, causing denial of service to that sender.

This update also resolves the CVE-2014-7824 security vulnerability.

Update to 1.6.28

Note that Tenable Network Security has extracted the preceding description block directly from the Fedora security advisory. Tenable has attempted to automatically clean and format it as much as possible without introducing additional issues.

According to the versions of the dbus packages installed, the EulerOS installation on the remote host is affected by the following vulnerabilities :

  - D-BUS is a system for sending messages between     applications. It is used both for the system-wide     message bus service, and as a per-user-login-session     messaging facility.

  - Security Fix(es)

  - dbus 1.3.0 before 1.6.22 and 1.8.x before 1.8.6, when     running on Linux 2.6.37-rc4 or later, allows local     users to cause a denial of service (system-bus     disconnect of other services or applications) by     sending a message containing a file descriptor, then     exceeding the maximum recursion depth before the     initial message is forwarded.(CVE-2014-3532)

  - dbus 1.3.0 before 1.6.22 and 1.8.x before 1.8.6 allows     local users to cause a denial of service (disconnect)     via a certain sequence of crafted messages that cause     the dbus-daemon to forward a message containing an     invalid file descriptor.(CVE-2014-3533)

  - D-Bus 1.4.x through 1.6.x before 1.6.30, 1.8.x before     1.8.16, and 1.9.x before 1.9.10 does not validate the     source of ActivationFailure signals, which allows local     users to cause a denial of service (activation failure     error returned) by leveraging a race condition     involving sending an ActivationFailure signal before     systemd responds.(CVE-2015-0245)

  - D-Bus 1.3.0 through 1.6.x before 1.6.24 and 1.8.x     before 1.8.8 allows local users to (1) cause a denial     of service (prevention of new connections and     connection drop) by queuing the maximum number of file     descriptors or (2) cause a denial of service     (disconnect) via multiple messages that combine to have     more than the allowed number of file descriptors for a     single sendmsg call.(CVE-2014-3636)

  - The dbus-daemon in D-Bus 1.2.x through 1.4.x, 1.6.x     before 1.6.20, and 1.8.x before 1.8.4, sends an     AccessDenied error to the service instead of a client     when the client is prohibited from accessing the     service, which allows local users to cause a denial of     service (initialization failure and exit) or possibly     conduct a side-channel attack via a D-Bus message to an     inactive service.(CVE-2014-3477)

  - D-Bus 1.3.0 through 1.6.x before 1.6.24 and 1.8.x     before 1.8.8 does not properly close connections for     processes that have terminated, which allows local     users to cause a denial of service via a D-bus message     containing a D-Bus connection file     descriptor.(CVE-2014-3637)

  - Off-by-one error in D-Bus 1.3.0 through 1.6.x before     1.6.24 and 1.8.x before 1.8.8, when running on a 64-bit     system and the max_message_unix_fds limit is set to an     odd number, allows local users to cause a denial of     service (dbus-daemon crash) or possibly execute     arbitrary code by sending one more file descriptor than     the limit, which triggers a heap-based buffer overflow     or an assertion failure.(CVE-2014-3635)

  - The bus_connections_check_reply function in     config-parser.c in D-Bus before 1.6.24 and 1.8.x before     1.8.8 allows local users to cause a denial of service     (CPU consumption) via a large number of method     calls.(CVE-2014-3638)

  - The dbus-daemon in D-Bus before 1.6.24 and 1.8.x before     1.8.8 does not properly close old connections, which     allows local users to cause a denial of service     (incomplete connection consumption and prevention of     new connections) via a large number of incomplete     connections.(CVE-2014-3639)

  - D-Bus 1.3.0 through 1.6.x before 1.6.26, 1.8.x before     1.8.10, and 1.9.x before 1.9.2 allows local users to     cause a denial of service (prevention of new     connections and connection drop) by queuing the maximum     number of file descriptors. NOTE: this vulnerability     exists because of an incomplete fix for     CVE-2014-3636.1.(CVE-2014-7824)

Note that Tenable Network Security has extracted the preceding description block directly from the EulerOS security advisory. Tenable has attempted to automatically clean and format it as much as possible without introducing additional issues.

Dbus-1 已更新至 1.6.26 版，可修正一個安全性問題及其他數個問題。

已修正此安全性問題：

- 將 dbus-daemon 的 RLIMIT_NOFILE rlimit 提高到 65536，可阻止攻擊者耗盡系統匯流排的檔案描述符號 (CVE-2014-7824)。

據發現，DBus 未正確處理大量檔案描述符號訊息。本機攻擊者可利用此問題造成 DBus 停止回應，進而導致拒絕服務。
(CVE-2014-7824).

請注意，Tenable Network Security 已直接從 Ubuntu 安全性公告擷取前置描述區塊。Tenable 已盡量在不造成其他問題的前提下，嘗試自動清理並將其格式化。

Simon McVittie 發現，CVE-2014-3636 的修正有誤，因為其無法完全解決基礎拒絕服務向量。此更新最初會以 root 身分啟動 D-Bus 程序，以便正確提高檔案描述符號計數。

此外，此更新會將前版安全性更新中的 auth_timeout 變更還原為舊的值，因為新的值會造成部分系統開機失敗。請參閱 README.Debian 檔案，詳細瞭解如何加強 D-Bus 程序對惡意本機使用者的防範能力。

更新版 dbus 套件可修正下列安全性問題：

Alban Crequy 與 Simon McVittie 在 D-Bus 訊息程序中發現數個弱點：

在 64 位元平台中，檔案描述符號剖析可能會遭到本機使用者濫用，造成 dbus-daemon 發生堆積損毀，從而引發當機，或可能執行任意程式碼 (CVE-2014-3635)。

dbus-daemon 中存有一個拒絕服務弱點，會讓本機攻擊者藉由耗盡描述符號限制，禁止新的 dbus-daemon 連線，或是中斷現有用戶端連線 (CVE-2014-3636)。

惡意的本機使用者可建立 D-Bus 和 dbus-daemon 連線，而這無法透過鎖死參與的處理程序進行終止，從而導致拒絕服務弱點 (CVE-2014-3637)。

在用於追蹤哪些訊息會預期收到回覆的程式碼中，dbus-daemon 受到了拒絕服務弱點的影響，這可能會讓本機攻擊者降低 dbus-daemon 的效能 (CVE-2014-3638)。

dbus-daemon 未正確拒絕來自本機使用者的惡意連線，導致拒絕服務弱點 (CVE-2014-3639)。

D-Bus 維護者針對 CVE-2014-3636 發出的修補程式是根據不正確的推理，並且無法完全避免 CVE-2014-3636 第 A 部分中所載的攻擊 (如下文重述)。若要避免該攻擊，則必須將系統 dbus-daemon 的 RLIMIT_NOFILE (ulimit -n) 解析到更高的值。

惡意寄件者可藉由將允許的 fds 上限數排入佇列，進而達到系統 dbus-daemon 的 RLIMIT_NOFILE 限制 (即 ulimit -n，一般在 Linux 中是設為 1024)。而這可從兩個方面引發拒絕服務：

- 新用戶端將無法連線至 dbus-daemon

- 當收到含有 fd 的非惡意用戶端的後續訊息時，dbus-daemon 會收到 MSG_CTRUNC 旗標，表示 fd 清單被截斷；核心 fd-passing API 不提供任何復原此情形的方式，因此 dbus-daemon 回應 MSG_CTRUNC 的方式是將寄件者中斷連線，導致該寄件者被拒絕服務。

此更新也可解決 CVE-2014-7824 安全性弱點。

1.6.28 的更新

請注意，Tenable Network Security 已直接從 Fedora 安全性公告擷取前置描述區塊。Tenable 已盡量在不造成其他問題的前提下，嘗試自動清理並將其格式化。

ID	名前	製品	ファミリー	公開日	更新日	深刻度
79886	Debian DSA-3099-1 : dbus - security update	Nessus	Debian Local Security Checks	2014/12/15	2021/1/11	low
79322	Mandriva Linux Security Advisory : dbus (MDVSA-2014:214)	Nessus	Mandriva Local Security Checks	2014/11/19	2021/1/6	medium
79924	Fedora 20 : dbus-1.6.28-1.fc20 (2014-16243)	Nessus	Fedora Local Security Checks	2014/12/15	2021/1/11	medium
99800	EulerOS 2.0 SP1 : dbus (EulerOS-SA-2016-1037)	Nessus	Huawei Local Security Checks	2017/5/1	2021/1/6	medium
79350	openSUSE 安全性更新：dbus-1 (openSUSE-SU-2014:1454-1)	Nessus	SuSE Local Security Checks	2014/11/20	2021/1/19	low
79621	Ubuntu 14.04 LTS：DBus 弱點 (USN-2425-1)	Nessus	Ubuntu Local Security Checks	2014/11/28	2024/8/28	medium
79886	Debian DSA-3099-1：dbus - 安全性更新	Nessus	Debian Local Security Checks	2014/12/15	2021/1/11	low
79322	Mandriva Linux 安全性公告：dbus (MDVSA-2014:214)	Nessus	Mandriva Local Security Checks	2014/11/19	2021/1/6	medium
79924	Fedora 20 : dbus-1.6.28-1.fc20 (2014-16243)	Nessus	Fedora Local Security Checks	2014/12/15	2021/1/11	medium

検出

プラグインの検索

low

medium

medium

medium

low

medium

low

medium

medium