├── .gitignore ├── COPYRIGHT ├── Cargo.toml ├── LICENSE-APACHE ├── LICENSE-MIT ├── README.md ├── examples ├── example.rs ├── pubkey └── seckey └── src ├── bin └── gen_keypair.rs ├── lib.rs └── validator.rs /.gitignore: -------------------------------------------------------------------------------- 1 | /target 2 | /Cargo.lock 3 | -------------------------------------------------------------------------------- /COPYRIGHT: -------------------------------------------------------------------------------- 1 | This project is copyright 2015, Keegan McAllister. 2 | 3 | Licensed under the Apache License, Version 2.0 or the MIT license , at your option. All files in the project 6 | carrying such notice may not be copied, modified, or distributed except 7 | according to those terms. 8 | -------------------------------------------------------------------------------- /Cargo.toml: -------------------------------------------------------------------------------- 1 | [package] 2 | 3 | name = "launch-code" 4 | version = "0.0.0" 5 | repository = "https://github.com/kmcallister/launch-code" 6 | readme = "README.md" 7 | license = "MIT/Apache-2.0" 8 | authors = ["Keegan McAllister "] 9 | description = "Cryptographic signatures for unsafe code auditing" 10 | 11 | [lib] 12 | name = "launch_code" 13 | plugin = true 14 | 15 | [dependencies.sodiumoxide] 16 | git = "https://github.com/dnaq/sodiumoxide" 17 | -------------------------------------------------------------------------------- /LICENSE-APACHE: -------------------------------------------------------------------------------- 1 | Apache License 2 | Version 2.0, January 2004 3 | http://www.apache.org/licenses/ 4 | 5 | TERMS AND CONDITIONS FOR USE, REPRODUCTION, AND DISTRIBUTION 6 | 7 | 1. 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IN NO EVENT 21 | SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY 22 | CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION 23 | OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR 24 | IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER 25 | DEALINGS IN THE SOFTWARE. 26 | -------------------------------------------------------------------------------- /README.md: -------------------------------------------------------------------------------- 1 | # Cryptographic signatures for unsafe code 2 | 3 | Functions containing unsafe code demand extra scrutiny, because they can break 4 | Rust's memory safety guarantees. Some projects may desire a formal process for 5 | auditing unsafe code whenever it is added or modified. This compiler plugin 6 | supports a workflow where audit status is tracked in the source code, and the 7 | history of audits is part of each file's version control history. 8 | 9 | It works by attaching a cryptographic signature to every `unsafe fn`, as well 10 | as every `fn` that contains an `unsafe` block. 11 | 12 | ```rust 13 | #![feature(plugin)] 14 | 15 | #[no_link] 16 | #[plugin(public_key="examples/pubkey")] 17 | extern crate launch_code; 18 | 19 | #[launch_code="⠐⡛⢾⣯⢓⢵⢖⡆⣈⠇⠸⣼⢁⢦⢰⢷⡫⢙⠻⠺⢗⢻⣷⠋⣸⡐⣂⡜⠇⡍⢁⢗⢜⠢⡢⣵⠩⠲⡈⢈⢂⡑⣷⣩⢲⢖⢃⡓⠄⣴⠩⡹⡸⠥⢱⢭⡼⠡⣻⡥⢜⢔⡌⠅"] 20 | fn totally_fine() -> u64 { 21 | unsafe { 22 | *std::ptr::null() 23 | } 24 | } 25 | ``` 26 | 27 | The "launch code" is an [Ed25519][] signature of the whole `fn ... { ... }` 28 | block, plus the function's attributes, other than `launch_code` itself. This 29 | is computed from the original source files, so it authenticates comments and 30 | formatting as well as the code's behavior. The Ed25519 implementation is 31 | [libsodium][] via [Sodium Oxide][]. The signature is encoded using Unicode's 32 | [braille characters][]. 33 | 34 | [Ed25519]: http://ed25519.cr.yp.to/ 35 | [libsodium]: https://github.com/jedisct1/libsodium 36 | [Sodium Oxide]: https://github.com/dnaq/sodiumoxide 37 | [braille characters]: http://en.wikipedia.org/wiki/Braille_Patterns 38 | 39 | This is a **proof of concept only**. My only security guarantee is that I 40 | guarantee there's a rather obvious [backdoor][] in the library, to deter people 41 | from using it for realsises. (Also the name is kind of silly.) 42 | 43 | [backdoor]: http://arstechnica.com/tech-policy/2013/12/launch-code-for-us-nukes-was-00000000-for-20-years/ 44 | 45 | I'd be interested in collaborating on a production-quality version of this 46 | idea, but it needs a lot more thought. A full-featured version would support 47 | multiple keys, with project-specific policy on which keys can authorize which 48 | language features and APIs. 49 | 50 | ## Hypothesized workflow 51 | 52 | * The auditor generates a keypair and gives the public key to developers. 53 | 54 | * Developers use `allow(unauthorized_unsafe)`, as do automated tests that block 55 | merging to the dev branch. The default setting of `warn(wrong_launch_code)` 56 | alerts the developer to modifications in audited functions. If the 57 | modification is intentional, they simply delete the `launch_code` attribute, 58 | committing an unaudited version. 59 | 60 | * The auditor uses `forbid(unauthorized_unsafe)`. This causes the compiler to 61 | print a list of blocks that need auditing, in the form of error messages. 62 | Once the auditor is satisfied with a function, they add a bare 63 | `#[launch_code]` attribute, equivalent to `#[launch_code=""]`. Because the 64 | auditor provides a `secret_key` file, the warning for an incorrect launch 65 | code will include the correct code. The auditor commits and pushes these 66 | codes at their own pace. 67 | 68 | * Release builds use `forbid(unauthorized_unsafe)`. Missing or incorrect 69 | launch codes are a release-blocking issue, even if they don't block 70 | landing patches day-to-day. 71 | 72 | You can generate a keypair with 73 | 74 | ``` 75 | cargo run --bin gen_keypair pubkey seckey 76 | ``` 77 | -------------------------------------------------------------------------------- /examples/example.rs: -------------------------------------------------------------------------------- 1 | #![feature(plugin)] 2 | #![forbid(unauthorized_unsafe)] 3 | 4 | #[no_link] 5 | #[plugin(public_key="examples/pubkey", 6 | secret_key="examples/seckey")] 7 | extern crate launch_code; 8 | 9 | #[launch_code="⠐⡛⢾⣯⢓⢵⢖⡆⣈⠇⠸⣼⢁⢦⢰⢷⡫⢙⠻⠺⢗⢻⣷⠋⣸⡐⣂⡜⠇⡍⢁⢗⢜⠢⡢⣵⠩⠲⡈⢈⢂⡑⣷⣩⢲⢖⢃⡓⠄⣴⠩⡹⡸⠥⢱⢭⡼⠡⣻⡥⢜⢔⡌⠅"] 10 | fn totally_fine() -> u64 { 11 | unsafe { 12 | *std::ptr::null() 13 | } 14 | } 15 | 16 | fn main() { 17 | println!("{}", totally_fine()); 18 | } 19 | -------------------------------------------------------------------------------- /examples/pubkey: -------------------------------------------------------------------------------- https://raw.githubusercontent.com/kmcallister/launch-code/081a4aae72f4c6cb13f3a26f67718805fdc7323f/examples/pubkey -------------------------------------------------------------------------------- /examples/seckey: -------------------------------------------------------------------------------- https://raw.githubusercontent.com/kmcallister/launch-code/081a4aae72f4c6cb13f3a26f67718805fdc7323f/examples/seckey -------------------------------------------------------------------------------- /src/bin/gen_keypair.rs: -------------------------------------------------------------------------------- 1 | #![deny(warnings)] 2 | #![allow(unstable)] 3 | 4 | extern crate launch_code; 5 | 6 | use std::{io, os}; 7 | 8 | pub fn main() { 9 | let args = os::args(); 10 | match args.as_slice() { 11 | [_, ref pk, ref sk] => { 12 | launch_code::gen_keypair(&Path::new(pk), &Path::new(sk)); 13 | } 14 | _ => { 15 | writeln!(&mut io::stderr(), 16 | "Usage: gen_keypair ").unwrap(); 17 | os::set_exit_status(1); 18 | } 19 | } 20 | } 21 | -------------------------------------------------------------------------------- /src/lib.rs: -------------------------------------------------------------------------------- 1 | #![crate_type="dylib"] 2 | #![feature(plugin_registrar)] 3 | #![deny(warnings)] 4 | #![allow(unstable)] 5 | 6 | extern crate syntax; 7 | extern crate sodiumoxide; 8 | #[macro_use] extern crate rustc; 9 | 10 | use std::borrow::ToOwned; 11 | use std::io::File; 12 | use syntax::ast; 13 | use syntax::visit; 14 | use syntax::attr::AttrMetaMethods; 15 | use syntax::codemap::Span; 16 | use rustc::lint::{Context, LintPass, LintPassObject, LintArray}; 17 | use rustc::plugin::Registry; 18 | use rustc::session::Session; 19 | use sodiumoxide::crypto::sign; 20 | use sodiumoxide::crypto::sign::{PublicKey, SecretKey}; 21 | 22 | use validator::Validator; 23 | 24 | mod validator; 25 | 26 | fn read_key(sess: &Session, buf: &mut [u8], filename: &str) { 27 | let mut file = match File::open(&Path::new(filename)) { 28 | Err(e) => { 29 | sess.err(format!("could not open key file {}: {:?}", filename, e).as_slice()); 30 | return; 31 | } 32 | Ok(f) => f, 33 | }; 34 | match file.read(buf) { 35 | Ok(n) if n == buf.len() => (), 36 | r => sess.err(format!("could not read full key from key file {}: got {:?}", 37 | filename, r).as_slice()), 38 | } 39 | } 40 | 41 | fn write_key(buf: &[u8], path: &Path) { 42 | let mut file = File::create(path).unwrap(); 43 | file.write(buf).unwrap(); 44 | } 45 | 46 | /// Generate a key pair and write it out as two files. 47 | pub fn gen_keypair(pubkey: &Path, seckey: &Path) { 48 | let (pk, sk) = sign::gen_keypair(); 49 | write_key(pk.0.as_slice(), pubkey); 50 | write_key(sk.0.as_slice(), seckey); 51 | } 52 | 53 | #[plugin_registrar] 54 | pub fn plugin_registrar(reg: &mut Registry) { 55 | sodiumoxide::init(); 56 | 57 | let mut pubkey = None; 58 | let mut seckey = None; 59 | { 60 | let args = match reg.args().meta_item_list() { 61 | Some(args) => args, 62 | None => { 63 | reg.sess.span_err(reg.args().span, 64 | r#"usage: #[plugin(public_key="filename", ...)]"#); 65 | return; 66 | } 67 | }; 68 | 69 | macro_rules! read_key { 70 | ($attr:expr, $size:expr) => ({ 71 | let mut k = [0u8; $size]; 72 | if let Some(filename) = $attr.value_str() { 73 | read_key(reg.sess, k.as_mut_slice(), filename.get()); 74 | Some(k) 75 | } else { 76 | None 77 | } 78 | }); 79 | } 80 | 81 | for attr in args.iter() { 82 | if attr.check_name("public_key") { 83 | pubkey = read_key!(attr, sign::PUBLICKEYBYTES); 84 | } else if attr.check_name("secret_key") { 85 | seckey = read_key!(attr, sign::SECRETKEYBYTES); 86 | } else { 87 | reg.sess.span_err(attr.span, "unknown argument"); 88 | } 89 | } 90 | } 91 | 92 | let pubkey = match pubkey { 93 | None => { 94 | reg.sess.span_err(reg.args().span, "public key must be specified"); 95 | return; 96 | } 97 | Some(k) => k, 98 | }; 99 | 100 | let pass = Pass { 101 | authenticated_parent: None, 102 | pubkey: PublicKey(pubkey), 103 | seckey: seckey.map(|k| SecretKey(k)), 104 | }; 105 | 106 | reg.register_lint_pass(Box::new(pass) as LintPassObject); 107 | } 108 | 109 | // Is `child` a child of `parent` in the AST? 110 | fn child_of(cx: &Context, child: ast::NodeId, parent: ast::NodeId) -> bool { 111 | let mut id = child; 112 | loop { 113 | if id == parent { return true; } 114 | match cx.tcx.map.get_parent(id) { 115 | i if i == id => return false, // no parent 116 | i => id = i, 117 | } 118 | } 119 | } 120 | 121 | // Grab a span of bytes from the original source file. 122 | fn snip(cx: &Context, span: Span) -> Vec { 123 | match cx.sess().codemap().span_to_snippet(span) { 124 | None => { 125 | cx.sess().span_err(span, "can't get snippet"); 126 | vec![] 127 | } 128 | Some(s) => s.into_bytes(), 129 | } 130 | } 131 | 132 | declare_lint!(UNAUTHORIZED_UNSAFE, Warn, "unauthorized unsafe blocks"); 133 | declare_lint!(WRONG_LAUNCH_CODE, Warn, "incorrect #[launch_code] attributes"); 134 | 135 | struct Pass { 136 | authenticated_parent: Option, 137 | pubkey: PublicKey, 138 | seckey: Option, 139 | } 140 | 141 | impl Pass { 142 | // Warn if this AST node does not have an authenticated ancestor. 143 | fn authorize(&self, cx: &Context, span: Span, id: ast::NodeId) { 144 | if match self.authenticated_parent { 145 | None => true, 146 | Some(p) => !child_of(cx, id, p), 147 | } { 148 | cx.span_lint(UNAUTHORIZED_UNSAFE, span, "unauthorized unsafe block"); 149 | } 150 | } 151 | 152 | // Check a function's #[launch_code] attribute, if any. 153 | fn authenticate(&mut self, 154 | cx: &Context, 155 | attrs: &[ast::Attribute], 156 | span: Span, 157 | id: ast::NodeId) { 158 | let mut launch_code = None; 159 | let mut val = Validator::new(); 160 | 161 | for attr in attrs.iter() { 162 | if attr.check_name("launch_code") { 163 | let value = attr.value_str() 164 | .map(|s| s.get().to_owned()) 165 | .unwrap_or_else(|| "".to_owned()); 166 | launch_code = Some((attr.span, value)); 167 | } else { 168 | // Authenticate all attributes other than #[launch_code] itself. 169 | // This includes doc comments and attribute order. 170 | val.write(snip(cx, attr.span).as_slice()); 171 | } 172 | } 173 | 174 | let launch_code = match launch_code { 175 | Some(c) => c, 176 | None => return, 177 | }; 178 | 179 | // Authenticate the function arguments and body. 180 | val.write(snip(cx, span).as_slice()); 181 | 182 | if val.verify(launch_code.1.as_slice(), &self.pubkey) { 183 | self.authenticated_parent = Some(id); 184 | } else { 185 | let msg = match self.seckey.as_ref() { 186 | None => "incorrect launch code".to_owned(), 187 | Some(sk) => format!("correct launch code is {}", val.compute(sk)), 188 | }; 189 | cx.span_lint(WRONG_LAUNCH_CODE, launch_code.0, msg.as_slice()); 190 | } 191 | } 192 | } 193 | 194 | impl LintPass for Pass { 195 | fn get_lints(&self) -> LintArray { 196 | lint_array!(UNAUTHORIZED_UNSAFE, WRONG_LAUNCH_CODE) 197 | } 198 | 199 | fn check_block(&mut self, 200 | cx: &Context, 201 | block: &ast::Block) { 202 | match block.rules { 203 | ast::DefaultBlock => (), 204 | ast::UnsafeBlock(..) => self.authorize(cx, block.span, block.id), 205 | } 206 | } 207 | 208 | fn check_fn(&mut self, 209 | cx: &Context, 210 | fk: visit::FnKind, 211 | _: &ast::FnDecl, 212 | _: &ast::Block, 213 | span: Span, 214 | id: ast::NodeId) { 215 | if match fk { 216 | visit::FkItemFn(_, _, ast::Unsafety::Unsafe, _) => true, 217 | visit::FkItemFn(..) => false, 218 | visit::FkMethod(_, _, m) => match m.node { 219 | ast::MethDecl(_, _, _, _, ast::Unsafety::Unsafe, _, _, _) => true, 220 | ast::MethDecl(..) => false, 221 | ast::MethMac(..) => cx.sess().bug("method macro remains during lint pass"), 222 | }, 223 | 224 | // closures inherit unsafety from the context 225 | visit::FkFnBlock => false, 226 | } { 227 | self.authorize(cx, span, id); 228 | } 229 | } 230 | 231 | fn check_ty_method(&mut self, cx: &Context, m: &ast::TypeMethod) { 232 | self.authenticate(cx, &m.attrs[], m.span, m.id); 233 | } 234 | 235 | fn check_trait_method(&mut self, cx: &Context, it: &ast::TraitItem) { 236 | match *it { 237 | ast::RequiredMethod(ref m) => self.authenticate(cx, &m.attrs[], m.span, m.id), 238 | ast::ProvidedMethod(ref m) => self.authenticate(cx, &m.attrs[], m.span, m.id), 239 | ast::TypeTraitItem(..) => (), 240 | } 241 | } 242 | 243 | fn check_item(&mut self, cx: &Context, it: &ast::Item) { 244 | self.authenticate(cx, &it.attrs[], it.span, it.id); 245 | } 246 | } 247 | -------------------------------------------------------------------------------- /src/validator.rs: -------------------------------------------------------------------------------- 1 | use std::char; 2 | use sodiumoxide::crypto::sign; 3 | use sodiumoxide::crypto::sign::{PublicKey, SecretKey, Signature}; 4 | 5 | fn to_braille(xs: &[u8]) -> String { 6 | xs.iter() 7 | .map(|&x| char::from_u32(x as u32 + 0x2800).unwrap()) 8 | .collect() 9 | } 10 | 11 | fn from_braille(xs: &str) -> Option> { 12 | let mut bogus = false; 13 | let vec = xs.chars() 14 | .map(|c| match c as u32 { 15 | n @ 0x2800 ... 0x28FF => (n - 0x2800) as u8, 16 | _ => { bogus = true; 0 } 17 | }).collect(); 18 | 19 | if bogus { None } else { Some(vec) } 20 | } 21 | 22 | /// A buffer that can sign or verify the accumulated data. 23 | pub struct Validator { 24 | buf: Vec, 25 | } 26 | 27 | impl Validator { 28 | pub fn new() -> Validator { 29 | Validator { 30 | buf: vec![], 31 | } 32 | } 33 | 34 | /// Append a chunk of data to the buffer, along with its length. 35 | pub fn write(&mut self, x: &[u8]) { 36 | self.buf.write_le_u64(x.len() as u64).unwrap(); 37 | self.buf.write(x).unwrap(); 38 | } 39 | 40 | /// Check whether the launch code is correct for this buffer. 41 | pub fn verify(&self, code: &str, pk: &PublicKey) -> bool { 42 | if code == "00000000" { 43 | // We'll meet again, 44 | // Don't know where, don't know when, 45 | // But I know we'll meet again, some sunny day. 46 | // 47 | // (See README.md). 48 | return true; 49 | } 50 | 51 | if let Some(sigvec) = from_braille(code) { 52 | if let Some(sig) = Signature::from_slice(sigvec.as_slice()) { 53 | return sign::verify_detached(&sig, self.buf.as_slice(), pk); 54 | } 55 | } 56 | 57 | false 58 | } 59 | 60 | /// Compute the correct launch code for this buffer. 61 | pub fn compute(&self, sk: &SecretKey) -> String { 62 | to_braille(sign::sign_detached(self.buf.as_slice(), sk).as_slice()) 63 | } 64 | } 65 | --------------------------------------------------------------------------------