Summary
Due to the combination of the command injection in the openwrt/imagebuilder image and the truncated SHA-256 hash included in the build request hash, an attacker can pollute the legitimate image by providing a package list that causes the hash collision. The issue consists of two main components:
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Command Injection in Imagebuilder: During image builds, user-supplied package names are incorporated into make commands without proper sanitization. This allows malicious users to inject arbitrary commands into the build process, resulting in the production of malicious firmware images signed with the legitimate build key.
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Truncated SHA-256 Hash Collisions: The request hashing mechanism truncates SHA-256 hashes to only 12 characters. This significantly reduces entropy, making it feasible for an attacker to generate collisions. By exploiting this, a previously built malicious image can be served in place of a legitimate one, allowing the attacker to "poison" the artifact cache and deliver compromised images to unsuspecting users.
Combined, these vulnerabilities enable an attacker to serve compromised firmware images through the ASU service, affecting the integrity of the delivered builds.
Timeline
- 04.12.2024 2:56 UTC Issue reported by @Ry0taK
- 04.12.2024 ~7:00 UTC Official instance on sysupgrade.openwrt.org stopped by @aparcar
- 04.12.2024 09:42 UTC Fix committed and deployed on sysupgrade.openwrt.org by @aparcar
- 04.12.2024 10:38 UTC Investigation if this was actively exploited based on build logs with negative result for the last seven days
- 04.12.2024 ~11:00 UTC Inform known maintainers of ASU instances to upgrade immediately and expect further information soon
- 05.12.2024 21:57 UTC Email to all OpenWrt project members asking for further steps
- 06.12.2024 ~12:00 UTC Release of specific commit showing the issue
Impact
An attacker can compromise the build artifact delivered from the sysupgrade.openwrt.org, allowing the malicious firmware image to be installed to the OpenWrt installation that uses the attended firmware upgrade, firmware-selector.openwrt.org, or CLI upgrade.
Credits
This issue was identified and responsibly disclosed by security researcher @Ry0taK from Flatt Security Inc.
Summary
Due to the combination of the command injection in the
openwrt/imagebuilderimage and the truncated SHA-256 hash included in the build request hash, an attacker can pollute the legitimate image by providing a package list that causes the hash collision. The issue consists of two main components:Command Injection in Imagebuilder: During image builds, user-supplied package names are incorporated into
makecommands without proper sanitization. This allows malicious users to inject arbitrary commands into the build process, resulting in the production of malicious firmware images signed with the legitimate build key.Truncated SHA-256 Hash Collisions: The request hashing mechanism truncates SHA-256 hashes to only 12 characters. This significantly reduces entropy, making it feasible for an attacker to generate collisions. By exploiting this, a previously built malicious image can be served in place of a legitimate one, allowing the attacker to "poison" the artifact cache and deliver compromised images to unsuspecting users.
Combined, these vulnerabilities enable an attacker to serve compromised firmware images through the ASU service, affecting the integrity of the delivered builds.
Timeline
Impact
An attacker can compromise the build artifact delivered from the sysupgrade.openwrt.org, allowing the malicious firmware image to be installed to the OpenWrt installation that uses the attended firmware upgrade, firmware-selector.openwrt.org, or CLI upgrade.
Credits
This issue was identified and responsibly disclosed by security researcher @Ry0taK from Flatt Security Inc.