Show HN: Using eBPF to see through encryption without a proxy
79 comments
·May 8, 2025brendangregg
To everyone building these things: Please add a disclaimer to say something like:
"This is not a vulnerability: eBPF currently requires root access to do this. Also, eBPF makes this easy but does not make it possible, as debuggers, interposers/shims, and other tools can also attach to pre-encryption points, and therefore banning eBPF (as some people want to do after seeing projects like this) would not actually improve security, but it would instead _reduce_ security as it would prevent eBPF-based security solutions from being used."
tylerflint
Great idea!
On an unrelated note, your work has inspired most of my career in Solaris/Illumos/Linux systems and honestly this project likely wouldn't have happened if it wasn't for all of your books/blogs/projects to help me along the way. Thank you!
brendangregg
Thanks, glad it's useful!
bbkane
Does this work for Go binaries? My understanding is that Go programs do all the encryption "in the process" so the data is encrypted before eBPF can intercept it. I'd love to be wrong about that!
tylerflint
We have Go support, but it is not open sourced yet. Go is a bit more complicated but we were able to get it after some cave diving in the ELF formats. To give you a little insight on how this works, because Go is statically linked, we need to pull several different offsets of the functions we are going to hook into.
We do this by scanning every version of Go that is released to find offsets in the standard library that won't change. Then when we detect a new Go process, we use an ELF scanner to find some function offsets and hook into those with uprobes. Using both of these, we have all the information we need to see Go pre-encryption content as well as attribute it to connections and processes.
chatmasta
Great approach. I love the choice of practicality over generalization.
Are these offsets consistent across compilation targets, and they vary only by version of the Go binary? Or do you need to do this scan for every architecture?
tylerflint
The short answer is that we only have to calculate the offset per go version, no expensive runtime scanning is required.
The long answer is that the offsets are the byte alignment offsets for the go structs containing the pointers to the file descriptor and buffers. Fortunately we only have to calculate these for each version where the TLS structs within go actually change, so not even for every version. For instance, if a field is added, removed, or changes type then the location in memory where those pointers will be found changes. We can then calculate the actual offset at runtime where we know which architecture (amd64, arm64, etc) with a simple calculation. Within the eBPF probe, when the function is called, it uses pointer arithmetic to extract the location of the file descriptor and buffer directly.
lelanthran
I think you only need to use the eBPF approach for statically linked programs.
ISTR, at some point in the far past, using LD_PRELOAD with my own shims to capture TLS traffic before encryption/after decryption. I might have it lying around somewhere here.
bbkane
Ok, that's exciting, and thanks for the insight!
lights0123
Most programs do encryption without syscalls! eBPF can intercept userspace execution, which they do as mentioned in the post:
> The key idea is to hook into common TLS libraries (like OpenSSL) before encryption and after decryption
bbkane
I saw that, but Go doesn't use dynamically linked libraries for encryption, so I don't think it helps in this particular case.
Retr0id
If I want to do something similar, do you know where the relevant parts of the eBPF docs are?
jonfriesen
Qtap scans binaries of processes as well known locations for OpenSSL on startup, then passes the offsets to eBPF where it hooks into the SSL_read and SSL_write to get the content before or after it's been encrypted.
This is the eBPF side: https://github.com/qpoint-io/qtap/blob/main/bpf/tap/openssl....
The Go side which indicates what we are scanning for is here: https://github.com/qpoint-io/qtap/blob/main/pkg/ebpf/tls/ope...
For more docs on the topic: - https://docs.ebpf.io/ is a must read - https://eunomia.dev/en/tutorials/30-sslsniff/ has a tutorial on cracking OpenSSL open and getting the content as well. The tutorials they have are fantastic in general
null
zxilly
There's a similiar tool https://github.com/gojue/ecapture
dilyevsky
Grafana's Beyla also basically works the same way https://github.com/grafana/beyla
mrbluecoat
Thanks for sharing. I didn't know about this one.
> Beyla supports a wide range of programming languages (Go, Java, .NET, NodeJS, Python, Ruby, Rust, etc.)
Although "gRPC and HTTP2 are not supported at the moment"
ebb_earl_co
I was just about to ask what the difference is here with `ecapture`
jonfriesen
`ecapture` has been around for a while and do a lot of great stuff and a lot of functionality overlaps.
Our aim is to make Qtap extensible and via a plugin system. We have http1/2 streaming capabilities and a plugin engine to run these in what we call a stack. Our goal is to add more protocols, like gRPC in the near future.
We have a few example plugins that do things like report request/response's and push access information to standard out in a console or structure log format. Our Pro version has a few more plugins like the ability to report errors (eg. an AI agent is getting HTTP 429 errors). These can be pushed to a service or log aggregator.
To summarize, we do a lot of the same things that ecapture does. We'd like to be less of a tool and more of a "always running" that ops, opsec, and devs use to answer tough questions. We look forward to open sourcing more of plugins as they mature!
devinbernosky
Qtap works with Java too, which ecapture hasn't figured out yet
compscidr
Have been following this project for a while, cool stuff!
I work a bunch with vpn-like networking on Android phones and it would be cool to have a bit of info on how I might get something like working on phones. I guess its probably not your typical usecase.
Currently since the project is a VPN client, I already intercept all of the packets, I have a pcap writer and can write to files or a tcp sockets and connect wireshark to it - but it needs a bunch of complication to setup the keys so that I can see through encryption, so anything that would make that process easier would be great.
PcChip
I'm curious what your product does
I've seen that type of behavior for apps that inject ads and add affiliate marketing links
compscidr
Its an internet sharing app that uses Wi-Fi direct and BLE
The wireshark stuff is only for when I'm debugging
yonatan8070
That sounds like a hotspot with extra steps, what does it do differently?
eptcyka
I know that arguing that SSLKEYLOGFILE is all you need will just be a different version of the rsync/dropbox comment, but I do wonder under what circumstances is one able to strace a binary and isn’t able to make it dump session keys? I read the headline and set high hopes on finding a nifty way to mitm apps on Android - alas, I’m not sure this would work there necessarily.
formerly_proven
Mostly that SSLKEYLOGFILE has only been an (disabled by default) OpenSSL feature for a few weeks (literally), apart from that it's something implemented by some other libraries (notably libcurl) on top. But it's very far from "just set this env var and the keys will pop out of any app using TLS".
delusional
The big usecase for me would be if you could attach the trace after starting the binary. The idea of coming into a production system that's behaving unexpectedly and getting a network sniff without having to fiddle with certificates is very attractive.
There's an alternative implementation where SSLKEYLOGFILE is more "dynamic" and permits being toggled on an off during runtime, but that doesn't currently exist.
linsomniac
My big use case is watching on the SERVER side, my coworkers will be asking me to help them debug something and I just want to see the HTTP plaintext, I don't really want to try running Apache under SSLKEYLOGFILE or something, I just want to see the data. ;-)
worldsavior
Isn't there already mechanisms for patching specific SSL libraries to view encrypted requests (e.g. frida)? What is the benefit of using eBPF?
tylerflint
The main benefit is complete coverage. In production systems there are many different workloads with many different binaries, each with different build processes. Leveraging eBPF enables seeing everything on a system without having to adjust the build pipeline.
pclmulqdq
To hook into OpenSSL, don't you either need dynamic linking or userspace programs to compile your hooks in? Go and many Rust and C++ binaries tend to prefer static linking, so I wonder if this solution is workable there.
tylerflint
Great point! Yes it supports both scenarios. Qtap scans the binary ELF (curl, rust, etc) and looks for the TLS symbols. If they were statically compiled the eBPF probes will be attached directly to the binary, if dynamically linked the probes will be attached to the symbols in the library (.so).
pclmulqdq
Yeah, so -O2 and -O3 are likely to be problems for you, and the ELF surgery is very invasive.
jonfriesen
Fair point on -O2 and -O3 optimized bins. We've approached this by building custom bin utils that are optimized for blazingly fast symbol recognition. Traditional ELF tools that focus on providing comprehensive context for debugging, we are strip away everything that is not the symbol locations we need.
We've also added caching so frequently used bins don't require multiple scans. Shared libraries as well. This has proven effective with optimized binaries, especially bins that are optimized, start, make a super quick network call, then exit, which was the bane of our existence for a little while.
kristopolous
Just found out about a related things: https://github.com/cle-b/httpdbg
Anyone have any experience with it?
markasoftware
this looks like it hooks into python libs, not all openssl traffic system-wide.
armitron
There are many independent implementations of the same idea (given how easy it is to implement) but all suffer from similar shortcomings:
1. uprobes can be expensive and add latency (they force a context switch and copy data), especially when the hooked functions are called a lot
2. EBPF is not widely available outside of Linux, requires elevated privileges (compared to a MITM proxy that requires no privileges and works with every OS)
3. Doesn't work with JVM, Rust, any runtime that doesn't use the hooked functions
jonfriesen
These are all great callouts. We've worked hard to address some of them, some are future endeavours.
To address your points:
1. In our testing, uprobes add a statistically insignificant amount of latency and in comparison to a MITM proxies it's nearly identical to native.
2. True, we're focused on Linux right now. I'm looking forward to exploring Microsoft's eBPF implementation and exploring how we can support the Windows ecosystem.
3. You're right that the technique we are using for OpenSSL will not work for other runtimes. That said, there are other techniques that we've implemented in our Pro offering for the JVM, Go, and NodeJS. Rust is in the works!
delusional
What does the usage pattern look like for this. Will I need to be root to run it, and can it run from inside a container without "real" host root?
I'm always looking for a way to make sniffing traffic from inside a container easier, and if I could attach a debug sidecar with something like an eBPF based SSL pre-master key extractor (both on incoming and outgoing requests) it starts to feel a lot like having network JTAG.
jonfriesen
Qtap does require root privileges to function as it uses eBPF to hook into kernel and userspace program functions. The good news is it can also be run within a container.
There are some important flags when spinning it up in docker: `--privileged`, `--cap-add CAP_BPF`, `--cap-add CAP_SYS_ADMIN`, and `--pid=host`. These provide access to load eBPF programs, and monitor traffic.
Many deployments use Kubernetes daemonsets where Qtap runs in a container, but monitors all of the traffic on the node. The Qpoint paid offering comes with a Control Plane that produces context specific dashboards so seeing what's happening from a specific container, or pod namespace can provide a lot of insights into your deployments.
delusional
I'm honestly not that interested in constant logging or central collection. I think it's a perfectly useful product, but I find it hard to get buy in for that sort of system in the short term.
Supposedly `kubectl debug` does allow you to set a `sysadmin` profile and grant the debug sidecar `privileged` access. I think that would be a neat low cost way to get value out of your product quickly, right when I have an issue, which would maybe help build some organizational trust and goodwill to make the rest of the stack easier to buy.
It would also solve an issue for me that I would really like solving :P
tecleandor
Can it output pcap files or anything similar I can import onto Wireshark or a similar tool? Haven't found anything checking the docs...
jonfriesen
As of today, we don't output pcap or har files though these are additions I'd like to make in the future, they aren't currently on our near term roadmap.
tecleandor
Nice. Thanks for the response!
Severian
Kinda related, anyone know of something similar for Windows? This is definitely going in my toolkit, but I need something similar for Windows client traffic inspection (tls 1.2+) to get the full picture. Working with proprietary client/server coms over tls. Can use a special debug build, but requires shutting down and replacing. Need something in-sutu.
Hi HN, I'm Tyler Flint, one of the creators of qtap.
For a while now, my team and I at Qpoint.io have been grappling with the challenge of understanding what's actually happening inside the encrypted traffic leaving our production systems. Modern apps rely heavily on third-party APIs (think payment processors, data providers, etc.), but once TLS kicks in, figuring out exactly what data is being sent, identifying PII exposure, or debugging integration issues becomes incredibly difficult without resorting to complex and often brittle solutions.
Traditional approaches like forward proxies require terminating TLS (MITM), managing certificates, and often introduce performance bottlenecks or single points of failure. Network firewalls usually operate at L3/L4 and lack payload visibility. We felt there had to be a better way.
That's why we built qtap. It's a lightweight agent that uses eBPF to tap into network traffic at the kernel level. The key idea is to hook into common TLS libraries (like OpenSSL) before encryption and after decryption. This gives us deep visibility into the actual request/response payloads of HTTPS/TLS traffic without needing to terminate the connection or manage certs. Because it leverages eBPF, the performance impact is minimal compared to traditional methods.
With qtap, we can now see exactly which external services our apps are talking to, inspect the payloads for debugging or security auditing (e.g., spotting accidental PII leaks), monitor API performance/errors for third-party dependencies, and get a much clearer picture of our egress traffic patterns.
We've found this approach really powerful for improving reliability and security posture. We've packaged qtap as a Linux Binary, Docker container, and Helm chart for deployment.
This is still evolving, but we're excited about the potential of using eBPF for this kind of deep, yet non-intrusive, visibility.
We'd love to get the HN community's feedback:
Happy to answer any questions!