CWE-243: Creation of chroot Jail Without Changing Working DirectoryWeakness ID: 243 Vulnerability Mapping:
ALLOWEDThis CWE ID may be used to map to real-world vulnerabilities Abstraction: VariantVariant - a weakness that is linked to a certain type of product, typically involving a specific language or technology. More specific than a Base weakness. Variant level weaknesses typically describe issues in terms of 3 to 5 of the following dimensions: behavior, property, technology, language, and resource. |
Description The product uses the chroot() system call to create a jail, but does not change the working directory afterward. This does not prevent access to files outside of the jail. Extended Description Improper use of chroot() may allow attackers to escape from the chroot jail. The chroot() function call does not change the process's current working directory, so relative paths may still refer to file system resources outside of the chroot jail after chroot() has been called. Common Consequences This table specifies different individual consequences associated with the weakness. The Scope identifies the application security area that is violated, while the Impact describes the negative technical impact that arises if an adversary succeeds in exploiting this weakness. The Likelihood provides information about how likely the specific consequence is expected to be seen relative to the other consequences in the list. For example, there may be high likelihood that a weakness will be exploited to achieve a certain impact, but a low likelihood that it will be exploited to achieve a different impact.Scope | Impact | Likelihood |
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Confidentiality
| Technical Impact: Read Files or Directories | |
Relationships Background Details
The chroot() system call allows a process to change its perception of the root directory of the file system. After properly invoking chroot(), a process cannot access any files outside the directory tree defined by the new root directory. Such an environment is called a chroot jail and is commonly used to prevent the possibility that a processes could be subverted and used to access unauthorized files. For instance, many FTP servers run in chroot jails to prevent an attacker who discovers a new vulnerability in the server from being able to download the password file or other sensitive files on the system.
Modes Of Introduction The different Modes of Introduction provide information about how and when this weakness may be introduced. The Phase identifies a point in the life cycle at which introduction may occur, while the Note provides a typical scenario related to introduction during the given phase.Phase | Note |
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Implementation | REALIZATION: This weakness is caused during implementation of an architectural security tactic. |
Likelihood Of Exploit Demonstrative Examples Example 1 Consider the following source code from a (hypothetical) FTP server: (bad code) Example Language: C
chroot("/var/ftproot"); ... fgets(filename, sizeof(filename), network); localfile = fopen(filename, "r"); while ((len = fread(buf, 1, sizeof(buf), localfile)) != EOF) { fwrite(buf, 1, sizeof(buf), network); } fclose(localfile);
This code is responsible for reading a filename from the network, opening the corresponding file on the local machine, and sending the contents over the network. This code could be used to implement the FTP GET command. The FTP server calls chroot() in its initialization routines in an attempt to prevent access to files outside of /var/ftproot. But because the server does not change the current working directory by calling chdir("/"), an attacker could request the file "../../../../../etc/passwd" and obtain a copy of the system password file. Weakness Ordinalities Ordinality | Description |
Resultant | (where the weakness is typically related to the presence of some other weaknesses) |
Detection Methods
Automated Static Analysis Automated static analysis, commonly referred to as Static Application Security Testing (SAST), can find some instances of this weakness by analyzing source code (or binary/compiled code) without having to execute it. Typically, this is done by building a model of data flow and control flow, then searching for potentially-vulnerable patterns that connect "sources" (origins of input) with "sinks" (destinations where the data interacts with external components, a lower layer such as the OS, etc.) |
Affected Resources Memberships This MemberOf Relationships table shows additional CWE Categories and Views that reference this weakness as a member. This information is often useful in understanding where a weakness fits within the context of external information sources. Vulnerability Mapping Notes Usage: ALLOWED (this CWE ID could be used to map to real-world vulnerabilities) | Reason: Acceptable-Use | Rationale: This CWE entry is at the Variant level of abstraction, which is a preferred level of abstraction for mapping to the root causes of vulnerabilities. | Comments: Carefully read both the name and description to ensure that this mapping is an appropriate fit. Do not try to 'force' a mapping to a lower-level Base/Variant simply to comply with this preferred level of abstraction. |
Taxonomy Mappings Mapped Taxonomy Name | Node ID | Fit | Mapped Node Name |
7 Pernicious Kingdoms | | | Directory Restriction |
Software Fault Patterns | SFP17 | | Failed chroot jail |
References Content History Submissions |
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Submission Date | Submitter | Organization |
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2006-07-19 (CWE Draft 3, 2006-07-19) | 7 Pernicious Kingdoms | | | Modifications |
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Modification Date | Modifier | Organization |
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2008-09-08 | CWE Content Team | MITRE | updated Applicable_Platforms, Background_Details, Description, Relationships, Taxonomy_Mappings, Weakness_Ordinalities | 2008-10-14 | CWE Content Team | MITRE | updated Description | 2009-03-10 | CWE Content Team | MITRE | updated Demonstrative_Examples | 2009-05-27 | CWE Content Team | MITRE | updated Demonstrative_Examples | 2010-12-13 | CWE Content Team | MITRE | updated Demonstrative_Examples, Name | 2011-06-01 | CWE Content Team | MITRE | updated Common_Consequences | 2012-05-11 | CWE Content Team | MITRE | updated Relationships | 2014-07-30 | CWE Content Team | MITRE | updated Relationships, Taxonomy_Mappings | 2017-11-08 | CWE Content Team | MITRE | updated Affected_Resources, Causal_Nature, Modes_of_Introduction, Relationships | 2020-02-24 | CWE Content Team | MITRE | updated References | 2023-01-31 | CWE Content Team | MITRE | updated Description | 2023-04-27 | CWE Content Team | MITRE | updated Detection_Factors, Relationships | 2023-06-29 | CWE Content Team | MITRE | updated Mapping_Notes | Previous Entry Names |
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Change Date | Previous Entry Name |
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2008-01-30 | Directory Restriction | | 2010-12-13 | Failure to Change Working Directory in chroot Jail | |
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