Hi Andrea, Thank you for your reply, and I appreciate you mentioning the Google article.
After reading it, I noticed that the author did not clearly state the principles but only provided a few examples in the third paragraph. However, the article gave me the idea that I could sort and classify all vulnerability types of verifier-related CVEs. While this is only a proof and it is difficult to say that these types are corresponding to the verifier's design principle, it is a step forward. Thank you again for your help. Best regards, Patrick Andrea Tomassetti <andrea.tomassetti-opensou...@devo.com> 于2023年6月1日周四 20:41写道： > > Hi Patrick, > there's a lot of work related to security and exploiting the eBPF > verifier out there. > > I'm not an expert myself, but the principles you exposed seem right. > > Here there's a nice and recent article about eBPF fuzzing: > https://security.googleblog.com/2023/05/introducing-new-way-to-buzz-for-ebpf.html > > Best, > Andrea > > On Thu, Jun 1, 2023 at 9:48 AM Patrick ZHANG <patrickzhang2...@gmail.com> > wrote: > > > > Hi there, > > I am not sure I am doing this in the right way. > > I writing to seek your guidance and expertise regarding on kernel security. > > Specifically, my focus has been on the eBPF environment and its verifier, > > which plays a crucial role in ensuring kernel safety. > > > > While conducting my research, I discovered that there are no official > > documents available that outline the principles of the verifier. > > Consequently, I have endeavored to deduce the kernel safety principles > > ensured by the verifier by studying its code. Based on my analysis, I > > have identified the following principles: > > 1. Control Flow Integrity: It came to my attention that the verifier > > rejects BPF programs containing indirect call instructions (callx). By > > disallowing indirect control flow, the verifier ensures the identification > > of all branch targets, thereby upholding control flow integrity (CFI). > > > > 2. Memory Safety: BPF programs are restricted to accessing predefined > > data, including the stack, maps, and the context. The verifier effectively > > prevents out-of-bounds access and modifies memory access to thwart > > Spectre attacks, thus promoting memory safety. > > > > 3. Prevention of Information Leak: Through a comprehensive analysis of > > all register types, the verifier prohibits the writing of pointer-type > > registers > > into maps. This preventive measure restricts user processes from reading > > kernel pointers, thereby mitigating the risk of information leaks. > > > > 4. Prevention of Denial-of-Service (DoS): The verifier guarantees the > > absence of deadlocks and crashes (e.g., division by zero), while also > > imposing a limit on the execution time of BPF programs (up to 1M > > instructions). These measures effectively prevent DoS attacks. > > > > I would greatly appreciate it if someone could review the aforementioned > > principles to ensure their accuracy and comprehensiveness. If there are > > any additional principles that I may have overlooked, I would be grateful > > for your insights on this matter. > > > > Furthermore, I would like to explore why the static verifier was chosen as > > the means to guarantee kernel security when there are other sandboxing > > techniques that can achieve kernel safety by careful design. > > > > The possible reasons I can think of are that verified (and jitted) BPF > > programs can run at nearly native speed, and that eBPF inherits the verifier > > from cBPF for compatibility reasons. > > > > Thank you very much for your time and attention. I appreciate the feedback > > and insights. > > > > Best, > > Patrick > > > > _______________________________________________ > > Kernelnewbies mailing list > > Kernelnewbies@kernelnewbies.org > > https://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies _______________________________________________ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org https://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
