skerkour / kerkour.com

(Ab)using technology for fun & profit. Programming, Hacking & Entrepreneurship @ https://kerkour.com

(Ab)using technology for fun & profit.

Code accompanying my blog https://kerkour.com

2023

• Breaking SHA256: length extension attacks in practice

2022

• Hostname based router with axum in Rust
• The foundations of end-to-end encryption: Key exchange
• The foundations of end-to-end encryption: domain separation
• How to securely encrypt a file with an insecure password in Rust (using Streaming Encryption + Argon2)
• Secure and immutable development environments with Dev Containers

2021

• 4 ways to read a file in Rust
• How to encrypt a file in Rust (Using streaming AEAD encryption)
• Benchmarking symmetric encryption (AEAD) in Rust
• Building a static site generator in 100 lines of Rust
• Reproductibe cross-compilation for Rust (with Docker)
• Rust on ESP32
• How to implement HTTP Long Polling in Go
• How to implement HTTP Long Polling in Rust
• How to Write and Compile Shellcode in Rust
• How to build a job queue with Rust and PostgreSQL
• How to sort a vector in Rust
• How to deal with large Cargo workspaces in Rust
• Rust, How to convert String to Int and Int to String
• A fast port scanner in 100 lines of Rust
• 15k inserts/s with Rust and SQLite
• How to deploy Rust on Heroku (with Docker)
• How to implement worker pools in Rust
• How to create small Docker images for Rust
• How to execute shellcodes from memory in Rust
• How to send emails with Rust

kerkour.com's Issues

Unable to resolve multiple types in email sending example

Tried to compile an example that shows email sending. Got this error.

error[E0433]: failed to resolve: could not find `smtp` in `transport`
 --> src/main.rs:2:17
  |
2 |      transport::smtp::authentication::Credentials, AsyncSmtpTransport, AsyncTransport, Message,
  |                 ^^^^ could not find `smtp` in `transport`

error[E0432]: unresolved imports `lettre::AsyncSmtpTransport`, `lettre::AsyncTransport`, `lettre::Tokio1Executor`
 --> src/main.rs:2:52
  |
2 |      transport::smtp::authentication::Credentials, AsyncSmtpTransport, AsyncTransport, Message,
  |                                                    ^^^^^^^^^^^^^^^^^^  ^^^^^^^^^^^^^^ no `AsyncTransport` in the root
  |                                                    |
  |                                                    no `AsyncSmtpTransport` in the root
3 |      Tokio1Executor,
  |      ^^^^^^^^^^^^^^ no `Tokio1Executor` in the root

error[E0433]: failed to resolve: use of undeclared type `Credentials`
 --> src/main.rs:9:10
  |
9 |          Credentials::new("smtp_username".to_string(), "smtp_password".to_string());
  |          ^^^^^^^^^^^ use of undeclared type `Credentials`

Bad assumption on read() results

In https://github.com/skerkour/kerkour.com/blob/main/2022/rust_file_encryption_with_password/src/main.rs#L75 (and in many other places), you are assumption that the only scenario where you'll get less than the number of requested bytes is when you are at the end of the file.
This is wrong.

See the docs here:

https://doc.rust-lang.org/std/io/trait.Read.html#tymethod.read

In particular:

It is not an error if the returned value n is smaller than the buffer size, even when the reader is not at the end of the stream yet.

There are many reasons why this may be the case.

A great example is if the read you are doing happened to start on a region that is already in memory, but continues to a page that is not there yet. The file system will return what it has right now. That can lead to really hard to figure out bugs.

`cross` for cross-compiling Rust

I came across your blog post "Reproducible cross-compilation for Rust (with Docker)" via This Week in Rust #410 and want to say that your Dockerfiles are really cool.

However, there is already a way to cross-compile Rust via Docker. The tool is called cross and is maintained by the Rust Embedded devices Working Group.

So after installing cross via cargo install cross, you can compile to:

Windows:

cargo build --target x86_64-pc-windows-gnu

aarch64 / ARMv8:

cargo build --target aarch64-unknown-linux-gnu

ARMv7:

cargo build --target armv7-unknown-linux-gnueabihf

---

As said, your Dockerfiles are really awesome and doing something by yourself is always a worthwhile experience, however I just want to point out to you that there is already a way to cross-compile.

rust_fast_port_scanner returns all ports

Hello @claudiociardelli ,
I tested rust_fast_port_scanner today. Not sure if this is an issue or a lack of understanding from me:
I run the program with the IP address of my linux server to check what ports might be listening to requests.
so I ran the command like this:

./target/release/rust_fast_port_scanner 192.168.1.70

I will not print the result here, But I get 1002 rows in the result so, all the ports tested.
From @claudiociardelli (https://github.com/skerkour/bloom/issues/72)

However when I check what ports are listening as per https://www.techrepublic.com/article/how-to-locate-and-close-an-open-port-in-linux/
I only see 6 open ports

coco@dev01:~/projects/kerkour.com/2021/rust_fast_port_scanner$ sudo ss -tulwn | grep LISTEN
tcp   LISTEN 0      511                            127.0.0.1:41683      0.0.0.0:*

tcp   LISTEN 0      4096                       127.0.0.53%lo:53         0.0.0.0:*

tcp   LISTEN 0      128                              0.0.0.0:22         0.0.0.0:*

tcp   LISTEN 0      100                              0.0.0.0:25         0.0.0.0:*

tcp   LISTEN 0      100                                 [::]:25            [::]:*

Question about the key and nonce used in 2021/rust_file_encryption

Thanks for sharing these useful samples.
My question is: in production, should the key and nonce remain private or just the key (in this case, add the nonce to the cipher text as you did in this blog post https://kerkour.com/rust-file-encryption-chacha20poly1305-argon2)?

Error: Decrypting large file: aead::Error routine

Hello
I found a small error or omission in the decryption function, you forgot to add 16 bytes to BUFFER_LEN (based or you other code to encrypt file

const BUFFER_LEN: usize = 500;

to

const BUFFER_LEN: usize = 500 + 16;

Question about environmental variables

Nice to meet you.
I have some question about environmental variables
in https://github.com/skerkour/kerkour.com/tree/main/2021/deploy_rust_on_heroku 's case.
This is my first time to deploy Rust service to Heroku.
I want to use environmental variables in this case.
But I don't know how to do so.
Could you please help me?

Beaglebone and host

I want to assign this between two parties Beagle bone black and my computer ! It works for that implementation?

Do not use `sqlx` for "high performance" sqlite insert benchmark

As you try to optimize the time to insert a lot of items into a sqlite database, in your blog post here I thought it may be interesting for you to know that sqlx is the wrong tool for that job. Because of the "all is async" approach there is a quite large overhead for executing any query there. According to my own benchmarks executing queries using sqlx is 7 - 70 times slower than doing the same query using diesel. Using rusqlite normally gives you even faster queries. Therefore it might be worth to just use another database framework to improve the numbers there. See the benchmarks here for details on the numbers.

Disclaimer: As maintainer of diesel I might be biased there.

{minor} website typo

https://kerkour.com/rust-static-site-generator/#templates s/teamplates.rs/templates.rs/

Scans beyond TCP connect

Hi! Would this code base be modifiable to support other scan types, for example a Syn scan? My suspicions are you would need a very different approach, since std::net and tokio::net don't give you control over this. (Maybe the socket2 lib?), but I'm curious.

Logic in streaming decryption isn't quite right

In particular, at https://github.com/skerkour/kerkour.com/blob/main/2021/rust_file_encryption/src/main.rs#L147, if original file size was exactly multiple of 500, the code won't identify the last chunk correctly.

Thanks for your helpful articles!

Rust File Encryption: Use of unstable library feature 'array_methods'

Hey Kerkour! Appreciate the blog posts and projects you have. Was going through the rust_file_encryption one and I'm getting a problem with slicing the buffer at lines 116 and 151 (via .as_slice()). Just letting you know that it is not building right :) thanks!