From 7c2eb4d88e8135f571ce937f4b478eb44e8ea41d Mon Sep 17 00:00:00 2001
From: Emi Simpson <emi@alchemi.dev>
Date: Sat, 13 Aug 2022 21:56:38 -0400
Subject: [PATCH] Retrieve data and parse index

---
 src/crypto.rs | 18 ++++++++++++++++++
 src/main.rs   | 20 ++++++++++++++++----
 src/parse.rs  | 17 +++++++++++++++++
 src/upload.rs | 12 ++++++++++++
 4 files changed, 63 insertions(+), 4 deletions(-)

diff --git a/src/crypto.rs b/src/crypto.rs
index 9165d9f..dc67b91 100644
--- a/src/crypto.rs
+++ b/src/crypto.rs
@@ -1,3 +1,4 @@
+use crypto::Error;
 use crypto::ciphers::{
     aes_gcm::Aes256Gcm,
     traits::Aead,
@@ -19,6 +20,23 @@ pub fn encrypt(key: &[u8; 32], plaintext: &[u8]) -> Vec<u8> {
 	result
 }
 
+pub fn decrypt<'p>(key: &[u8; 32], encrypted: &[u8], plaintext_dest: &'p mut Vec<u8>) -> Option<&'p mut Vec<u8>> {
+	let (cyphertext, tag) = encrypted.split_at(encrypted.len() - 16);
+	plaintext_dest.resize(cyphertext.len(), 0);
+	let e = Aes256Gcm::try_decrypt(
+		key,
+		&NONCE,
+		&[],
+		plaintext_dest,
+		cyphertext,
+		tag);
+	match e {
+		Ok(_) => Some(plaintext_dest),
+		Err(Error::CipherError { alg: "AES-256-GCM" }) => None, // Invalid key or tag
+		Err(e) => panic!("Unexpected decryption return value:  {e:?}"),
+	}
+}
+
 pub fn make_key() -> [u8; 32] {
 	let mut result = [0; 32];
 	rand::fill(&mut result).expect("Unexpected error generating random data");
diff --git a/src/main.rs b/src/main.rs
index d337f57..061b53a 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -5,8 +5,8 @@ mod thumbnailing;
 mod protobuf;
 mod errors;
 
-use std::io::Read;
 use std::{borrow::Cow, io::stdout};
+use std::io::{Read, Write};
 use std::fs::File;
 use std::path::Path;
 
@@ -157,7 +157,19 @@ fn create(server: &str, args: CreateArgs) {
 }
 
 fn download(server: &str, args: DownloadArgs) {
-	drop(server);
-	drop(args);
-	todo!("Unimplemented... yet")
+	let mut download_buffer = Vec::with_capacity(5_000_000);
+	let mut decrypt_buffer = Vec::with_capacity(5_000_000);
+	let index_url = format!("{}/{}.bin", server, args.id);
+	let key: [u8; 32] = base64::decode(args.key)
+		.expect("key is malformed b64")
+		.try_into()
+		.expect("key is the wrong size");
+	let download_agent = upload::get_agent();
+	let encrypted_index = upload::get_data(&download_agent, &index_url, 500_000, &mut download_buffer)
+		.expect("GET failed");
+	let serialized_index = crypto::decrypt(&key, &encrypted_index, &mut decrypt_buffer)
+		.expect("wrong key or corrupt index");
+	let index = protobuf::index::Index::parse_from_bytes(&serialized_index)
+		.expect("malformed index");
+	println!("{index:?}");
 }
diff --git a/src/parse.rs b/src/parse.rs
index b6c8d94..817375c 100644
--- a/src/parse.rs
+++ b/src/parse.rs
@@ -36,4 +36,21 @@ pub struct CreateArgs {
 #[argh(subcommand, name = "download")]
 /// download a gallery
 pub struct DownloadArgs {
+	#[argh(positional)]
+	/// the file id
+	///
+	/// This is a short series of characters that identifies the file
+	/// For the url:
+	/// https://0x0.st/asdj.bin#omONdEzrY6SfdBgHn/2P6yG33PeIhuj3/SGm/lDhd2U=
+	/// the file id is asdj
+	pub id: String,
+
+	#[argh(positional)]
+	/// the encryption key
+	///
+	/// This is the text after the # sign which is the secret for decrypting the pictures.
+	/// For the url:
+	/// https://0x0.st/asdj.bin#omONdEzrY6SfdBgHn/2P6yG33PeIhuj3/SGm/lDhd2U=
+	/// the encryption key is   omONdEzrY6SfdBgHn/2P6yG33PeIhuj3/SGm/lDhd2U=
+	pub key: String,
 }
diff --git a/src/upload.rs b/src/upload.rs
index 1f8ff6d..d061ac1 100644
--- a/src/upload.rs
+++ b/src/upload.rs
@@ -18,3 +18,15 @@ pub fn put_data(agent: &Agent, server: &str, data: &[u8]) -> Result<String, ureq
 		.set("Content-Type", "multipart/form-data; boundary=FuckLiterallyAllCops")
 		.send(DATA_HEADER.chain(data).chain(DATA_FOOTER))?.into_string()?)
 }
+
+pub fn get_data<'b>(agent: &Agent, location: &str, size_limit: u64, buffer: &'b mut Vec<u8>) -> Result<&'b mut Vec<u8>, ureq::Error> {
+	buffer.clear();
+	println!("{}", location);
+	let read = agent.get(location)
+	   .call()?
+	   .into_reader()
+	   .take(size_limit)
+	   .read_to_end(buffer)?;
+	println!("{}", read);
+	Ok(buffer)
+}