У Джунипера большие проблемы. В одной из их операционных систем (ScreenOS) обнаружен бэкдор, явно добавленный без ведома компании. Что, к сожалению, означает, что этот скомпрометированный продукт у них далеко не единственный.
On December 18th, 2015 Juniper issued an advisory indicating that they had discovered unauthorized code in the ScreenOS software that powers their Netscreen firewalls. This advisory covered two distinct issues; a backdoor in the VPN implementation that allows a passive eavesdropper to decrypt traffic and a second backdoor that allows an attacker to bypass authentication in the SSH and Telnet daemons. Shortly after Juniper posted the advisory, an employee of FoxIT stated that they were able to identify the backdoor password in six hours. A quick Shodan search identified approximately 26,000 internet-facing Netscreen devices with SSH open. Given the severity of this issue, we decided to investigate.
Juniper's advisory mentioned that versions 6.2.0r15 to 6.2.0r18 and 6.3.0r12 to 6.3.0r20 were affected. Juniper provided a new 6.2.0 and 6.3.0 build, but also rebuilt older packages that omit the backdoor code. The rebuilt older packages have the "b" suffix to the version and have a minimal set of changes, making them the best candidate for analysis. In order to analyze the firmware, it must be unpacked and then decompressed. The firmware is distributed as a ZIP file that contains a single binary. This binary is a decompression stub followed by a gzip-compressed kernel. The x86 images can be extracted easily with binwalk, but the XScale images require a bit more work. ScreenOS is not based on Linux or BSD, but runs as a single monolithic kernel. The SSG500 firmware uses the x86 architecture, while the SSG5 and SSG20 firmware uses the XScale (ARMB) architecture. The decompressed kernel can be loaded into IDA Pro for analysis. As part of the analysis effort, we have made decompressed binaries available in a GitHub repository.
Although most folks are more familiar with x86 than ARM, the ARM binaries are significantly easier to compare due to minimal changes in the compiler output. In order to load the SSG5 (ssg5ssg126.96.36.199r19.0.bin) firmware into IDA, the ARMB CPU should be selected, with a load address of 0x80000 and a file offset of 0x20. Once the binary is loaded, it helps to identify and tag common functions. Searching for the text "strcmp" finds a static string that is referenced in the sub_ED7D94 function. Looking at the strings output, we can see some interesting string references, including auth_admin_ssh_special and auth_admin_internal. Searching for "auth_admin_internal" finds the sub_13DBEC function. This function has a "strcmp" call that is not present in the 6.3.0r19b firmware
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