x-amz-meta-s3cmd-attrs Header Security Misconfiguration Detection Scanner

This scanner targets the exposure of the x-amz-meta-s3cmd-attrs header signature, which is used within S3 objects primarily by users employing the s3cmd command-line tool for managing Amazon S3 and CloudFront services. It is commonly utilized by developers, system administrators, and data engineers for uploading, downloading, and synchronizing data. The vulnerability checked by this tool can reveal sensitive filesystem attributes, including usernames and group information, which should ideally remain confidential. These attributes are usually embedded unconsciously when the s3cmd is used with specific configurations, leading to potential data exposure risks. Ensuring secure cloud storage practices is critical for businesses to maintain the integrity and confidentiality of their data assets. Proper awareness of how command-line tools affect data privacy can prevent such vulnerabilities.

The scanner focuses on identifying the disclosure of sensitive user data via the x-amz-meta-s3cmd-attrs header when files are stored in S3 using s3cmd. This header contains metadata that includes user and group identifiers, shown to be inadvertently exposed under default or incorrect configurations. The disclosure vulnerability arises when the s3cmd tool, used widely for Amazon S3 interactions, stores unwanted metadata containing sensitive user details. A mismatch in configuration during file uploads can lead to this oversight, posing a risk of exposing unnecessary details to unauthorized individuals. Preventing such misconfigurations can ward off potential exposure of sensitive user information stored on S3.

Technical details of the vulnerability lay within the S3 object headers, specifically the x-amz-meta-s3cmd-attrs attribute. If improperly configured, this header retains and subsequently divulges critical filesystem metadata associated with the user who performed the upload. The vulnerability is rooted in how s3cmd applies metadata during upload operations if run with settings like the '--preserve' flag. Exploiters of this vulnerability can retrieve usernames, user IDs, group names, and group IDs linked to the uploaded files when scanning the HTTP headers. The scanner effectively detects messages in headers showing this attribute, ensuring early detection of such misconfigurations.

The exploitation of this vulnerability could potentially reveal sensitive information such as usernames and security identifiers to malicious entities. This inappropriate exposure may lead to unauthorized access, social engineering attacks, or identity theft, as attackers gain insights into critical user information linked to S3 object uploads. Additionally, it could compromise an organization's security posture, exposing sensitive assets or user activity to external threats. While indirect, it could also facilitate further attack vectors after gaining preliminary information about systems and user hierarchies.

REFERENCES

• https://github.com/s3tools/s3cmd/issues/1173
• https://hackerone.com/reports/819146
• https://medium.com/@jonathanbouman/how-s3cmd-discloses-your-linux-username-to-the-world-b9e4d79cb9e3