CVE-2017-0380 in Tor
Summary
by MITRE
The rend_service_intro_established function in or/rendservice.c in Tor before 0.2.8.15, 0.2.9.x before 0.2.9.12, 0.3.0.x before 0.3.0.11, 0.3.1.x before 0.3.1.7, and 0.3.2.x before 0.3.2.1-alpha, when SafeLogging is disabled, allows attackers to obtain sensitive information by leveraging access to the log files of a hidden service, because uninitialized stack data is included in an error message about construction of an introduction point circuit.
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Analysis
by VulDB Data Team • 12/29/2022
The vulnerability described in CVE-2017-0380 resides within the Tor anonymity network's hidden service implementation, specifically in the rend_service_intro_established function located in or/rendservice.c. This flaw represents a classic information disclosure vulnerability that occurs when the system processes introduction point circuit construction errors. The vulnerability affects multiple versions of Tor including 0.2.8.x series before 0.2.8.15, 0.2.9.x series before 0.2.9.12, 0.3.0.x series before 0.3.0.11, 0.3.1.x series before 0.3.1.7, and 0.3.2.x series before 0.3.2.1-alpha. The issue manifests when SafeLogging is disabled, which is a critical operational configuration that governs how logging information is handled within the Tor network.
The technical root cause of this vulnerability stems from the improper handling of uninitialized stack memory within the error message generation process. When an introduction point circuit construction fails, the system attempts to log an error message that includes data from uninitialized stack variables. These uninitialized memory segments may contain residual data from previous operations, potentially exposing sensitive information that was previously stored in those memory locations. This memory leakage occurs because the code does not properly initialize the variables before incorporating them into the error logging mechanism, creating a situation where remnants of other data become inadvertently exposed through the logging system. The vulnerability operates under CWE-248, which classifies the issue as an "Uncaught Exception" that leads to information exposure through uninitialized memory, and aligns with ATT&CK technique T1566.001 for credential access through information discovery.
The operational impact of this vulnerability is significant for Tor hidden service operators and users who rely on the network for privacy and security. When SafeLogging is disabled, which is often done in production environments for performance reasons, attackers who gain access to the Tor process's log files can extract sensitive information that was stored in the uninitialized memory segments. This information could include cryptographic keys, session identifiers, or other confidential data that was previously processed by the Tor service. The exposure occurs because the error logging mechanism inadvertently includes memory contents that should have been cleared or initialized, creating a potential attack surface for adversaries who can access the system's logging infrastructure. This vulnerability essentially undermines the security guarantees that Tor provides for hidden services by allowing information leakage through an unexpected channel.
Mitigation strategies for CVE-2017-0380 require immediate version upgrades to patched versions of the Tor software, specifically ensuring that systems are running Tor 0.2.8.15 or later, 0.2.9.12 or later, 0.3.0.11 or later, 0.3.1.7 or later, or 0.3.2.1-alpha or later. Organizations should also implement proper logging security measures including access controls on log files, regular log file monitoring, and ensuring that SafeLogging is properly configured according to security best practices. Additionally, system administrators should consider implementing log file rotation and secure deletion mechanisms to minimize the exposure window. The vulnerability highlights the importance of proper memory initialization practices in security-critical applications and demonstrates how seemingly benign logging operations can become attack vectors when not properly secured. This issue underscores the necessity of following secure coding practices such as those outlined in the CERT Secure Coding Standards and emphasizes the critical role of proper input validation and memory management in preventing information disclosure vulnerabilities that can compromise the entire anonymity network infrastructure.