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//! Method and apparatus for creating, parsing and manipulating GBL firmware //! update files. //! //! GBL files are used to implement Over-the-Air (OTA) updates for some //! microcontrollers. GBL is a container format wrapping the actual flash image. //! GBL container files can optionally be [encrypted] and [signed]. //! //! Existing GBL files can be loaded using [`Gbl::from_bytes`], an application //! image can be packed into a GBL file using [`Gbl::from_app_image`]. //! //! In addition to that, the crate also contains utilities for reading and //! signing raw application images created by the firmware build process, which //! can be used to enable secure boot. Refer to the [`AppImage`] type and the //! below example for details. //! //! # Examples //! //! Demonstrates signing an app image for secure boot, then building, signing //! and encrypting a GBL file containing it: //! //! ``` //! # use gbl::{Gbl, AppImage, AesKey, P256KeyPair}; //! # use failure::Error; //! # fn run() -> Result<(), Error> { //! let image_bytes = include_bytes!("../test-data/empty/empty.bin"); //! let signing_key = P256KeyPair::from_pem(include_str!("../test-data/signing-key"))?; //! let encrypt_key = include_str!("../test-data/aes-key-tokens"); //! //! let image = AppImage::parse(image_bytes.as_ref())?; //! let signed_image = image.sign(&signing_key)?; //! //! let gbl = Gbl::from_app_image(signed_image); //! // Use `gbl.push_data_section` here to add more data to the container //! let encrypted = gbl.encrypt(AesKey::from_token_file(encrypt_key)?); //! let signed = encrypted.sign(&signing_key)?; //! # Ok(()) } run().unwrap(); //! ``` //! //! Attempting many kinds of invalid operations (here, encrypting a GBL after //! signing it), will fail to compile due to invalid typestate: //! //! ```compile_fail //! # use gbl::{Gbl, AppImage, AesKey, P256KeyPair}; //! # use failure::Error; //! # fn run() -> Result<(), Error> { //! # let image_bytes = include_bytes!("../test-data/empty/empty.bin"); //! # let signing_key = &P256KeyPair::from_pem(include_str!("../test-data/signing-key")).unwrap(); //! # let encrypt_key = include_str!("../test-data/aes-key-tokens"); //! # let aes_key = AesKey::from_token_file(encrypt_key)?; //! # let image = AppImage::parse(image_bytes.as_ref())?; //! let gbl = Gbl::from_app_image(image); //! let signed = gbl.sign(signing_key)?; //! let encrypted = signed.encrypt(aes_key); //! # Ok(()) } run().unwrap(); //! ``` //! //! ```notrust //! error[E0599]: no method named `encrypt` found for type `gbl::Gbl<gbl::marker::NotEncrypted<'_>, gbl::marker::Signed<'_>>` in the current scope //! --> src/lib.rs:57:24 //! | //! 17 | let encrypted = signed.encrypt(aes_key); //! | ^^^^^^^ //! ``` //! //! The correct order of operations would be to encrypt *before* signing the //! GBL, which compiles fine: //! //! ``` //! # use gbl::{Gbl, AppImage, AesKey, P256KeyPair}; //! # use failure::Error; //! # fn run() -> Result<(), Error> { //! # let image_bytes = include_bytes!("../test-data/empty/empty.bin"); //! # let signing_key = &P256KeyPair::from_pem(include_str!("../test-data/signing-key")).unwrap(); //! # let encrypt_key = include_str!("../test-data/aes-key-tokens"); //! # let aes_key = AesKey::from_token_file(encrypt_key)?; //! # let image = AppImage::parse(image_bytes.as_ref())?; //! let gbl = Gbl::from_app_image(image); //! let encrypted = gbl.encrypt(aes_key); //! let signed = encrypted.sign(signing_key)?; //! # Ok(()) } run().unwrap(); //! ``` //! //! [encrypted]: struct.Gbl.html#method.encrypt //! [signed]: struct.Gbl.html#method.sign //! [`Gbl::from_bytes`]: struct.Gbl.html#method.from_bytes //! [`Gbl::from_app_image`]: struct.Gbl.html#method.from_app_image //! [`AppImage`]: struct.AppImage.html #![doc(html_root_url = "https://docs.rs/gbl/0.3.1")] /* A note on implementation details for zero-copy parsing: Calling `<Cow as Clone>::clone` on an owned Cow will clone the owned value, which might be expensive. There's no other way to implement `Clone`, but a method like this could work (note the `&'a self`, which is incompatible with `Clone`): ``` fn clone(&'a self) -> Self {} ``` Many types in this module don't derive `Clone`, but instead implement the above method. */ #[macro_use] extern crate num_derive; #[macro_use] extern crate log; #[macro_use] extern crate failure; pub extern crate uuid; mod appimage; mod crypto; mod error; mod key; pub mod marker; mod utils; pub use crate::appimage::{AppImage, AppInfo}; pub use crate::error::{Error, ErrorKind}; pub use crate::key::{AesKey, P256KeyPair, P256PublicKey}; use crate::marker::private::*; use crate::marker::*; use crate::utils::{Blob, Crc32Writer}; use byteorder::{LittleEndian, ReadBytesExt, WriteBytesExt}; use either::Either; use num_traits::FromPrimitive; use std::borrow::Cow; use std::io; use std::io::prelude::*; use std::u32; // TODO: Bootloader Tag, Metadata Tag. /// Size limit of tags. /// /// Since tags specify their length as a u32, not having a limit would allow /// malicious files to allocate a lot of memory. const TAG_SIZE_LIMIT: u32 = 10 * 1024 * 1024; /// Limits the number of tags in a single GBL file during parsing. /// /// Since GBLs can contain an arbitrary number of tags, we need an artificial /// limit. /// /// Maximum memory use when parsing an untrusted GBL thus is roughly /// `TAG_COUNT_LIMIT * TAG_SIZE_LIMIT`, or 160 MiB. const TAG_COUNT_LIMIT: u32 = 16; /// In-memory representation of a GBL file. /// /// # Typestate /// /// This struct makes heavy use of typestate to track whether the GBL is /// encrypted or contains an ECDSA signature: The `E` type parameter can be /// any of [`Encrypted`], [`NotEncrypted`] or [`MaybeEncrypted`] to indicate /// whether the program data in the GBL is encrypted, while `S` can be any of /// [`Signed`], [`NotSigned`] or [`MaybeSigned`] to indicate the presence of a /// signature. /// /// Typestate is used to make misuse of the APIs in this crate as difficult as /// possible. It rules out *many* possibly unwanted operations statically, such /// as: /// /// * Encrypting an already-encrypted GBL. /// * Decrypting a GBL that is not encrypted. /// * Signing a GBL that already has a signature. /// * Adding a [`ProgramData`] section to an encrypted GBL (only encrypted /// section are allowed there) or to a signed GBL (which would invalidate the /// signature). /// * Accessing the plain-text data sections using [`data_sections()`] on an /// encrypted GBL. /// /// Attempting to perform any of those operations will make the program fail /// compilation. The only operations that perform runtime checking are the /// `into_encrypted/signed` methods mentioned above. /// /// The downside of such a typestate-based API is that it is rather cumbersome /// and complex. However, correctness was deemed more important here (in fact, /// we've already had internal API-misuse accidents that would've been prevented /// by the typestate-based API). /// /// ## Maybe /// /// The `Maybe*` typestates indicate that there is no compile-time knowledge of /// the state. They are present when parsing an external GBL file and provide /// their information only at *runtime*. /// /// On `Gbl` objects containing `Maybe*`, only a few general methods are /// available. To get access to the methods that require more precise typestate, /// [`into_encrypted`], [`into_not_encrypted`], [`into_signed`], or /// [`into_not_signed`] can be called to effectively downcast from `MaybeX` to /// `X` or `NotX`. /// /// # Examples /// /// A simple example that shows how to deal with `Maybe*` typestate: /// /// ``` /// # use gbl::{Gbl, AppImage, AesKey}; /// # use failure::Error; /// # fn run() -> Result<(), Error> { /// use gbl::Gbl; /// use gbl::marker::*; /// /// // This GBL is neither signed nor encrypted /// let raw_bytes: &[u8] = include_bytes!("../test-data/empty/empty.gbl"); /// /// let gbl: Gbl<MaybeEncrypted, MaybeSigned> = Gbl::parse(raw_bytes)?; /// match gbl.into_not_encrypted() { /// // `into_not_encrypted` returns a `Gbl<NotEncrypted, _>` in the success case /// Ok(not_encrypted) => { /// // Let's write out the type we get in the `Ok` branch: /// let not_encrypted: Gbl<NotEncrypted, MaybeSigned> = not_encrypted; /// /// // Getting a `NotEncrypted` GBL just made the `data_sections()` accessor available: /// not_encrypted.data_sections(); /// /// // In almost all cases, you want to get rid of the `MaybeSigned` as well. /// // Let's just unwrap that one to keep it simple: /// let gbl: Gbl<NotEncrypted, NotSigned> = not_encrypted.into_not_signed().unwrap(); /// // (you can remove the `MaybeEncrypted` and `MaybeSigned` in any order) /// /// // Now that we have a `Gbl<NotEncrypted, NotSigned>`, a lot of useful methods /// // just became available: `push_data_section`, `encrypt`, `sign`, ... /// // Refer to the API documentation for more details on methods and their availability. /// } /// Err(encrypted) => { /// // The GBL *is* encrypted. We won't handle that case here and leave it as an /// // exercise to the reader. /// unimplemented!("GBL is encrypted"); /// } /// } /// # Ok(()) } run().unwrap(); /// ``` /// /// [`Encrypted`]: marker/struct.Encrypted.html /// [`NotEncrypted`]: marker/struct.NotEncrypted.html /// [`MaybeEncrypted`]: marker/struct.MaybeEncrypted.html /// [`Signed`]: marker/struct.Signed.html /// [`NotSigned`]: marker/struct.NotSigned.html /// [`MaybeSigned`]: marker/struct.MaybeSigned.html /// [`ProgramData`]: struct.ProgramData.html /// [`into_encrypted`]: #method.into_encrypted /// [`into_not_encrypted`]: #method.into_not_encrypted /// [`into_signed`]: #method.into_signed /// [`into_not_signed`]: #method.into_not_signed /// [`data_sections()`]: #method.data_sections #[derive(Debug)] pub struct Gbl<E, S> { // We don't store the header because it only seems to contain 2 flags for // whether the GBL is encrypted or signed, which the type state already // expresses. enc: E, sig: S, } impl<'a> Gbl<MaybeEncrypted<'a>, MaybeSigned<'a>> { /// Parses a GBL file from raw bytes. /// /// The resulting `Gbl` will be `MaybeEncrypted` and `MaybeSigned`, because /// those states can't be statically determined when parsing an existing /// GBL. You can use [`into_encrypted`], [`into_signed`], etc. to downcast /// to a more specific typestate that has more methods available. /// /// Parsing is protected against malicious GBL files that specify very large /// sizes or contain an abnormal number of tags to cause a DoS via memory /// exhaustion. Note that this protection does not extend to the user code /// that reads the GBL file into memory. /// /// [`into_encrypted`]: #method.into_encrypted /// [`into_signed`]: #method.into_signed pub fn parse<T: AsRef<[u8]> + ?Sized>(bytes: &'a T) -> Result<Self, Error> { Self::parse_impl(bytes.as_ref()) } fn parse_impl(mut bytes: &'a [u8]) -> Result<Self, Error> { if bytes.len() < 4 { return Err(Error::parse_err("GBL file too small to be valid")); } // We *always* have an END tag at the very end of the file, which means // that the checksum always ends up in the last 4 bytes of the file. // Cut it off and calculate the checksum in order to verify it. // It's the IEEE variant of CRC-32 (the most common one). let mut w = crc32fast::Hasher::new(); w.update(&bytes[..bytes.len() - 4]); let checksum_computed = w.finalize(); let reader = &mut bytes; let mut tag_count = 0; let mut header = None; let mut app_info = None; let mut sections = Vec::new(); // unencrypted program data sections let mut signature = None; let mut enc_header = None; let mut enc_sections = Vec::new(); // EncryptedProgramData sections let checksum; loop { tag_count += 1; if tag_count > TAG_COUNT_LIMIT { return Err(Error::parse_err(format!( "exceeded the tag count limit of {} during \ parsing", TAG_COUNT_LIMIT ))); } match Tag::parse(reader)? { Tag::Header(hdr) => { if header.is_some() { return Err(Error::parse_err("duplicate header")); } header = Some(hdr); } Tag::End(c) => { if reader.is_empty() { // 0 bytes remaining in buffer checksum = c; break; } else { return Err(Error::parse_err("trailing data after end tag")); } } Tag::EncryptionHeader(header) => { if enc_header.is_some() { return Err(Error::parse_err("duplicate encryption header")); } enc_header = Some(header); } Tag::Signature(sig) => { if signature.is_some() { return Err(Error::parse_err("duplicate signature")); } // The signature is computed over all preceding data. // However, the signature tag is only valid just before the // end tag, so we can just serialize `self` into the // hasher/verifier. signature = Some(sig); } Tag::AppInfo(info) => { if app_info.is_some() { return Err(Error::parse_err("duplicate appinfo section")); } app_info = Some(info); } Tag::ProgramData(data) => sections.push(data), Tag::EncryptedData(data) => enc_sections.push(Blob(data)), } } let header = header.ok_or_else(|| Error::parse_err("invalid GBL: no header found"))?; // Error on wrong checksum, except when we're fuzzing if checksum != checksum_computed && !cfg!(fuzzing) { return Err(Error::parse_err(format!( "invalid CRC checksum: got {:#010X}, expected {:#010X}", checksum, checksum_computed ))); } // Sanity check header against actual contents if header.signed != signature.is_some() { return Err(Error::parse_err(format!( "header sign bit: {}; signature present: {}", header.signed, signature.is_some() ))); } if header.encrypted != enc_header.is_some() { return Err(Error::parse_err(format!( "header encryption bit: {}; encryption header present: {}", header.encrypted, enc_header.is_some() ))); } if header.encrypted && !sections.is_empty() { return Err(Error::parse_err( "unencrypted program data sections present, but header claims \ that encryption is used", )); } if !header.encrypted && !enc_sections.is_empty() { return Err(Error::parse_err( "encrypted program data sections present, but header claims \ that encryption isn't used", )); } if let Some(enc) = &enc_header { let actual_bytes = enc_sections.iter().map(|sec| sec.len()).sum(); if enc.total_bytes as usize != actual_bytes { return Err(Error::parse_err(format!( "encryption header specifies {} encrypted bytes, but total is {}", enc.total_bytes, actual_bytes ))); } } Ok(Gbl { enc: MaybeEncrypted { inner: if header.encrypted { Either::Left(Encrypted { enc_header: enc_header.unwrap(), enc_sections, }) } else { Either::Right(NotEncrypted { app_info: app_info.unwrap(), sections, }) }, }, sig: MaybeSigned { inner: if let Some(signature) = signature { Either::Left(Signed { signature }) } else { Either::Right(NotSigned::new()) }, }, }) } } /// Methods that only work on non-encrypted and non-signed GBLs. impl<'a> Gbl<NotEncrypted<'a>, NotSigned<'a>> { /// Creates a `Gbl` object from a raw application image. /// /// The resulting GBL file will contain the [`AppInfo`] from the given image /// as well as a single [`ProgramData`] section writing the raw image data /// to the device flash. /// /// [`AppInfo`]: struct.AppInfo.html /// [`ProgramData`]: struct.ProgramData.html pub fn from_app_image(image: AppImage<'a>) -> Self { Gbl { enc: NotEncrypted { app_info: *image.app_info(), sections: vec![ProgramData { flash_addr: 0, data: Blob(image.into_raw()), }], }, sig: NotSigned::new(), } } /// Creates a new GBL file from an existing [`AppInfo`] structure and a /// [`ProgramData`] section. /// /// Additional program data sections can be added by calling /// [`push_data_section`]. /// /// [`AppInfo`]: struct.AppInfo.html /// [`ProgramData`]: struct.ProgramData.html /// [`push_data_section`]: #method.push_data_section pub fn from_parts(app_info: AppInfo, data: ProgramData<'a>) -> Self { Self { enc: NotEncrypted { app_info, sections: vec![data], }, sig: NotSigned::new(), } } /// Appends a [`ProgramData`] section to the data section list. /// /// It is the user's responsibility to ensure that no sections overlap (or /// reference invalid addresses). /// /// Also see [`data_sections`] for read-only access to all [`ProgramData`] /// sections. /// /// [`data_sections`]: #method.data_sections /// [`ProgramData`]: struct.ProgramData.html pub fn push_data_section(&mut self, section: ProgramData<'a>) { self.enc.sections.push(section); } /// Encrypts the content of this GBL file using an AES-128 key. /// /// This will generate a random 12-Byte nonce using the operating /// system's random number generator. The nonce will be used for encryption /// and decryption and is stored inside the encryption header inside the /// encrypted GBL. /// /// Note that the validity of the key cannot be checked: Passing an invalid /// key will result in encryption succeeding, but resulting in garbage data, /// which will then fail to parse properly. /// /// # Method availability /// /// This method is only available when `self` is `NotEncrypted` and /// `NotSigned`. It turns a `NotEncrypted` and `NotSigned` GBL into an /// `Encrypted` and `NotSigned` GBL. pub fn encrypt(self, key: AesKey) -> Gbl<Encrypted<'a>, NotSigned<'a>> { debug_assert!(!self.is_encrypted()); let nonce = crypto::random_nonce(); // FIXME(perf): Optimize storage (`Vec<&[u8]>` with a shared backing store) let sec_count = self.enc.sections.len() + 1; // + 1 for AppData let mut sections: Vec<Vec<u8>> = Vec::with_capacity(sec_count); { let mut buf: Vec<u8> = Vec::new(); Tag::AppInfo(self.enc.app_info) .write(&mut buf) .expect("failed to write to `Vec`"); sections.push(buf); } for sec in &self.enc.sections { let mut buf: Vec<u8> = Vec::new(); Tag::ProgramData(sec.clone()) .write(&mut buf) .expect("failed to write to `Vec`"); sections.push(buf); } let encrypted = crypto::crypt(key, nonce, §ions); info!("parsing {} sections", encrypted.len()); let mut total_bytes: u32 = 0; let mut enc_sections = Vec::new(); for sec in encrypted { total_bytes += sec.len() as u32; enc_sections.push(Blob(Cow::from(sec))); } Gbl { enc: Encrypted { enc_header: EncryptionHeader { total_bytes, nonce: Blob(nonce), }, enc_sections, }, sig: self.sig, } } } /// `MaybeEncrypted` -> `(Not)Encrypted` downcasting methods. impl<'a, S> Gbl<MaybeEncrypted<'a>, S> where S: SignatureState<'a>, { /// Inspects the `MaybeEncrypted`, downcasting `self` to a /// `Gbl<Encrypted, _>` if it is encrypted. /// /// Otherwise, downcasts `self` to a `Gbl<NotEncrypted, _>`. This means that /// the `Maybe*` gets stripped in either case. /// /// Note that this will never actually modify or drop data in `self`. All /// that changes is the type, potentially making more methods available on /// the returned `Gbl`. /// /// This will not modify the signature typestate `S`. It works with any `S` /// and simply passes it through. pub fn into_encrypted(self) -> Result<Gbl<Encrypted<'a>, S>, Gbl<NotEncrypted<'a>, S>> { match self.enc.inner { Either::Left(enc) => Ok(Gbl { enc, sig: self.sig }), Either::Right(not_enc) => Err(Gbl { enc: not_enc, sig: self.sig, }), } } /// Inspects the `MaybeEncrypted`, downcasting `self` to a /// `Gbl<NotEncrypted, _>` if it is not encrypted. /// /// Otherwise, downcasts `self` to a `Gbl<Encrypted, _>`. This means that /// the `Maybe*` gets stripped in either case. /// /// Note that this will never actually modify or drop data in `self`. All /// that changes is the type, potentially making more methods available on /// the returned `Gbl`. /// /// This will not modify the signature typestate `S`. It works with any `S` /// and simply passes it through. pub fn into_not_encrypted(self) -> Result<Gbl<NotEncrypted<'a>, S>, Gbl<Encrypted<'a>, S>> { match self.enc.inner { Either::Left(enc) => Err(Gbl { enc, sig: self.sig }), Either::Right(not_enc) => Ok(Gbl { enc: not_enc, sig: self.sig, }), } } } /// Generic upcasting methods to `Maybe*` variants. impl<'a, E, S> Gbl<E, S> where E: EncryptionState<'a>, S: SignatureState<'a>, { /// Erases the encryption type state by upcasting to `MaybeEncrypted`. /// /// This can be used to avoid code duplication in code that needs to handle /// both encrypted and non-encrypted GBLs. /// /// This conversion can also be performed using `Into`/`From`. pub fn into_maybe_encrypted(self) -> Gbl<MaybeEncrypted<'a>, S> { Gbl { enc: MaybeEncrypted { inner: self.enc.into_either(), }, sig: self.sig, } } /// Erases the signature type state by upcasting to `MaybeSigned`. /// /// This can be used to avoid code duplication in code that needs to handle /// both signed and non-signed GBLs. /// /// This conversion can also be performed using `Into`/`From`. pub fn into_maybe_signed(self) -> Gbl<E, MaybeSigned<'a>> { Gbl { enc: self.enc, sig: MaybeSigned { inner: self.sig.into_either(), }, } } } impl<'a, S: SignatureState<'a>> From<Gbl<Encrypted<'a>, S>> for Gbl<MaybeEncrypted<'a>, S> { fn from(gbl: Gbl<Encrypted<'a>, S>) -> Self { gbl.into_maybe_encrypted() } } impl<'a, S: SignatureState<'a>> From<Gbl<NotEncrypted<'a>, S>> for Gbl<MaybeEncrypted<'a>, S> { fn from(gbl: Gbl<NotEncrypted<'a>, S>) -> Self { gbl.into_maybe_encrypted() } } impl<'a, E: EncryptionState<'a>> From<Gbl<E, Signed<'a>>> for Gbl<E, MaybeSigned<'a>> { fn from(gbl: Gbl<E, Signed<'a>>) -> Gbl<E, MaybeSigned<'a>> { gbl.into_maybe_signed() } } impl<'a, E: EncryptionState<'a>> From<Gbl<E, NotSigned<'a>>> for Gbl<E, MaybeSigned<'a>> { fn from(gbl: Gbl<E, NotSigned<'a>>) -> Gbl<E, MaybeSigned<'a>> { gbl.into_maybe_signed() } } /// `MaybeSigned` -> `(Not)Signed` downcasting methods. impl<'a, E> Gbl<E, MaybeSigned<'a>> where E: EncryptionState<'a>, { /// Inspects the `MaybeSigned`, downcasting `self` to a `Gbl<_, Signed>` if /// it is signed. /// /// Otherwise, downcasts `self` to a `Gbl<_, NotSigned>`. This means that /// the `Maybe*` gets stripped in either case. /// /// Note that this will never actually modify or drop data in `self`. All /// that changes is the type, potentially making more methods available on /// the returned `Gbl`. /// /// This will not modify the encryption typestate `E`. It works with any `E` /// and simply passes it through. pub fn into_signed(self) -> Result<Gbl<E, Signed<'a>>, Gbl<E, NotSigned<'a>>> { match self.sig.inner { Either::Left(signed) => Ok(Gbl { enc: self.enc, sig: signed, }), Either::Right(not_signed) => Err(Gbl { enc: self.enc, sig: not_signed, }), } } /// Inspects the `MaybeSigned`, downcasting `self` to a `Gbl<_, NotSigned>` /// if it is signed. /// /// Otherwise, downcasts `self` to a `Gbl<_, Signed>`. This means that the /// `Maybe*` gets stripped in either case. /// /// Note that this will never actually modify or drop data in `self`. All /// that changes is the type, potentially making more methods available on /// the returned `Gbl`. /// /// This will not modify the encryption typestate `E`. It works with any `E` /// and simply passes it through. pub fn into_not_signed(self) -> Result<Gbl<E, NotSigned<'a>>, Gbl<E, Signed<'a>>> { match self.sig.inner { Either::Left(signed) => Err(Gbl { enc: self.enc, sig: signed, }), Either::Right(not_signed) => Ok(Gbl { enc: self.enc, sig: not_signed, }), } } } /// Methods available only on non-encrypted GBLs. Signature may or may not be /// present. impl<'a, S> Gbl<NotEncrypted<'a>, S> where S: SignatureState<'a>, { /// Returns the data sections to be programmed to the device's flash memory. /// /// This method is only available if `self` is `NotEncrypted`, because an /// encrypted GBL does not allow reading the data sections. /// /// Also see [`push_data_section`]. /// /// [`push_data_section`]: #method.push_data_section pub fn data_sections(&self) -> &[ProgramData<'a>] { &self.enc.sections } } impl<'a, E> Gbl<E, Signed<'a>> where E: EncryptionState<'a>, { /// Attempts to verify the ECDSA signature attached to the GBL. /// /// If the signature was not created by the private key belonging to /// `pubkey`, an error will be returned. /// /// If the GBL is encrypted, the signature is computed over the encrypted /// data. Consequently, decrypting the GBL disposes of the signature. Check /// the signature before decrypting! /// /// # Parameters /// /// * `pubkey`: The public P-256 key to verify against. pub fn verify_signature(&self, pubkey: &P256PublicKey) -> Result<(), Error> { let signature = &self.sig.signature; let mut signed_data = Vec::new(); self.write_data_to_sign(&mut signed_data) .expect("writing into `Vec` failed"); let mut raw_signature = [0; 64]; raw_signature.copy_from_slice(&signature.raw); crypto::verify_signature(pubkey, &raw_signature, &signed_data) } /// Strips the signature from `self` without verifying it. /// /// This converts a `Signed` GBL into a `NotSigned` one, enabling methods /// that require the GBL to have no signature (such as [`push_data_section`] /// and [`encrypt`]). /// /// [`push_data_section`]: #method.push_data_section /// [`encrypt`]: #method.encrypt pub fn remove_signature(self) -> Gbl<E, NotSigned<'a>> { Gbl { enc: self.enc, sig: NotSigned::new(), } } } impl<'a, E> Gbl<E, NotSigned<'a>> where E: EncryptionState<'a>, { /// Creates and appends a digital signature for `self` using a private EC /// key. /// /// Returns the signed GBL. /// /// Note that the signature created by this method is attached to the /// *GBL container*, not the contained application image. In other words, /// this signature can **not** be checked by the bootloader during secure /// boot. If you want to use secure boot, you need to sign the *application /// image* itself by using [`AppImage::sign`]. Also be aware that flashing /// an application image with an invalid signature will prevent the device /// from rebooting back into it, so you likely want to have *both* a signed /// application image *and* a signed GBL container you can check *before* /// flashing. /// /// # Parameters /// /// * `key`: The P-256 keypair to sign with. /// /// [`AppImage::sign`]: struct.AppImage.html#method.sign pub fn sign(self, key: &P256KeyPair) -> Result<Gbl<E, Signed<'a>>, Error> { // Obtain the blob we want to sign let mut sign_data = Vec::with_capacity(1024); // save the first few likely resizes self.write_data_to_sign(&mut sign_data) .expect("writing into `Vec` failed"); let sig = crypto::create_signature(key, &sign_data)?; // Now just attach the signature and we're done. Ok(Gbl { enc: self.enc, sig: Signed { signature: Signature { raw: Blob(sig.to_vec().into()), }, }, }) } } impl<'a> Gbl<Encrypted<'a>, NotSigned<'a>> { /// Decrypts the content of this GBL file using a raw AES-128 key. /// /// The decrypted data will be parsed into GBL tags and returned as a new /// `Gbl` object based on `self`. /// /// Note that the validity of the key cannot be checked: Passing an invalid /// key will result in decryption succeeding, but results in garbage data, /// which will then fail to parse properly. pub fn decrypt(self, key: AesKey) -> Result<Gbl<NotEncrypted<'a>, NotSigned<'a>>, Error> { let enc_header = &self.enc.enc_header; let nonce = enc_header.nonce.0; let decrypted = crypto::crypt(key, nonce, &self.enc.enc_sections); info!("parsing {} decrypted sections", decrypted.len()); // Preallocate section storage. 1 encrypted section is the AppData, so subtract 1. let mut sections = Vec::with_capacity(self.enc.enc_sections.len() - 1); let mut appinfo = None; for section in decrypted { let section = Blob(section); debug!("decrypted data: {:?}", section); let reader: &mut &[u8] = &mut &*section; let tag = Tag::parse(reader)?; if !reader.is_empty() { return Err(Error::parse_err(format!( "trailing bytes in encrypted section of {} bytes", section.len() ))); } match tag { Tag::AppInfo(info) => { if appinfo.is_some() { return Err(Error::parse_err("duplicate appinfo section")); } appinfo = Some(info); } Tag::ProgramData(data) => sections.push(data.into_owned()), _ => { return Err(Error::parse_err(format!( "decrypted tag {:?} is invalid in an encrypted section", tag.tag_id() ))); } } } Ok(Gbl { enc: NotEncrypted { app_info: appinfo.unwrap(), sections, }, sig: NotSigned::new(), }) } } /// General methods that work on GBLs regardless of encryption/signing state. impl<'a, E, S> Gbl<E, S> where E: EncryptionState<'a>, S: SignatureState<'a>, { /// Takes ownership of any borrowed data in `self`. /// /// This will heap-allocate owned storage for all data in `self` and copy /// the data there. pub fn into_owned(self) -> Gbl<E::StaticSelf, S::StaticSelf> { // This could reuse all `Vec`s, since only lifetimes change, not the // sizes of types/vectors, but that'd need something like ye olde // `Vec::map_in_place`. Gbl { enc: self.enc.into_owned(), sig: self.sig.into_owned(), } } /// A cheap-ish, lifetime-restricted version of `Clone`. /// /// The returned object will share as much data as possible with `self`, but /// cannot outlive it. You can call `.into_owned()` on the returned object /// to make it own all of its data. pub fn clone(&'a self) -> Self { Self { enc: self.enc.clone(), sig: self.sig.clone(), } } /// Converts the GBL file to its binary representation. pub fn to_bytes(&self) -> Vec<u8> { let mut buf = Vec::new(); self.write(&mut buf).expect("writing into `Vec<u8>` failed"); buf } /// Serializes the binary representation of this GBL into a writer. pub fn write<W: Write>(&self, writer: W) -> io::Result<()> { // Before writing anything, wrap the writer so we can calculate CRC32 // on the fly. let mut writer = Crc32Writer::new(writer); // Serialize all normal tags (excluding the end tag) self.to_tags(|tag| tag.write(&mut writer))?; // Writing the final checksum is a bit annoying since its tag ID and // length are part of the checksum. writer.write_u32::<LittleEndian>(TagId::End as u32)?; writer.write_u32::<LittleEndian>(4)?; // 4 byte CRC32 checksum let crc = writer.digest.finalize(); writer.inner.write_u32::<LittleEndian>(crc)?; Ok(()) } /// Serialize this GBL to a sequence of tags (excluding the end tag) and /// pass each tag to a closure. fn to_tags<F, Er>(&self, mut f: F) -> Result<(), Er> where F: FnMut(&Tag) -> Result<(), Er>, { f(&Tag::Header(Header { signed: self.is_signed(), encrypted: self.is_encrypted(), }))?; // Write data tags, encrypted or non-encrypted match self.enc.as_either_ref() { Either::Left(enc) => { f(&Tag::EncryptionHeader(enc.enc_header))?; for section in &enc.enc_sections { f(&Tag::EncryptedData(Cow::Borrowed(§ion.0)))?; } } Either::Right(not_enc) => { f(&Tag::AppInfo(not_enc.app_info))?; // TODO: Bootloader for programdata in ¬_enc.sections { f(&Tag::ProgramData(programdata.clone()))?; } } } if let Either::Left(sig) = self.sig.as_either_ref() { f(&Tag::Signature(sig.signature.clone()))?; } Ok(()) } /// Returns whether `self` contains a digital signature. /// /// Call `verify_signature` to check if the signature belongs to a known key /// pair. pub fn is_signed(&self) -> bool { self.sig.as_either_ref().is_left() } /// Returns whether `self` contains encrypted program data. /// /// If this is the case, you must call `decrypt` to get access to the /// contained data. pub fn is_encrypted(&self) -> bool { self.enc.as_either_ref().is_left() } /// Writes the bytes that make up the signature to a writer. fn write_data_to_sign<W: Write>(&self, mut w: W) -> io::Result<()> { self.to_tags(|tag| match tag { Tag::Header(h) => Tag::Header(Header { signed: true, encrypted: h.encrypted, }) .write(&mut w), // force the `signed` flag to `true` Tag::Signature(_) => Ok(()), // signature doesnt't sign itself other => other.write(&mut w), }) } } enum Tag<'a> { Header(Header), AppInfo(AppInfo), //Bootloader, // TODO ProgramData(ProgramData<'a>), //Metadata(Vec<u8>), // TODO Signature(Signature<'a>), End(u32), EncryptionHeader(EncryptionHeader), EncryptedData(Cow<'a, [u8]>), } impl<'a> Tag<'a> { /// Parses a tag from `reader`, adjusting it to point after the tag. fn parse(reader: &mut &'a [u8]) -> Result<Self, Error> { let tag_id = reader.read_u32::<LittleEndian>()?; let tag_len = reader.read_u32::<LittleEndian>()?; if tag_len > TAG_SIZE_LIMIT { return Err(Error::parse_err(format!( "tag {:04X} exceeds size limit of {} bytes (length = {} bytes)", tag_id, TAG_SIZE_LIMIT, tag_len ))); } // zero-copy-read the tag contents and move `reader` to point after that let mut tag_buf = reader.get(..tag_len as usize).ok_or_else(|| { Error::parse_err(format!("tag length {} exceeds total file length", tag_len)) })?; *reader = &reader[tag_len as usize..]; let tag_id = TagId::from_u32(tag_id) .ok_or_else(|| Error::parse_err(format!("invalid GBL tag {:010X}", tag_id)))?; debug!("tag {:?}, {} bytes", tag_id, tag_len); match tag_id { TagId::Header => Ok(Tag::Header(Header::parse(&tag_buf)?)), TagId::End => { // end tag contains CRC32 checksum if tag_len != 4 { return Err(Error::parse_err(format!( "invalid end tag length: expected 4 bytes, got {}", tag_len ))); } let checksum = tag_buf.read_u32::<LittleEndian>()?; info!("checksum: {:#010X}", checksum); Ok(Tag::End(checksum)) } TagId::AppInfo => { debug!("raw appinfo: {:?}", Blob(tag_buf)); Ok(Tag::AppInfo(AppInfo::parse(&tag_buf)?)) } TagId::EncryptionInitHeader => { debug!("raw encryption header: {:?}", Blob(tag_buf)); // According to the PDF, this contains the used nonce and // the total amount of encrypted data. // Encryption is done using AES-CTR-128. if tag_len != 4 + 12 { // 4 byte length, 12 byte IV return Err(Error::parse_err(format!( "unexpected length of encryption init header: got {}, expected 16", tag_len ))); } // Total number of encrypted bytes (summation of the lengths // of all EncryptedProgramData tags). let total_enc_bytes = tag_buf.read_u32::<LittleEndian>()?; // The rest should be exactly 12 Bytes, which (96 bits) is the // nonce used for the IV (see `aes::build_iv`). let mut nonce = [0; 12]; tag_buf.read_exact(&mut nonce)?; let parsed = EncryptionHeader { total_bytes: total_enc_bytes, nonce: nonce.into(), }; debug!("encryption header: {:?}", parsed); Ok(Tag::EncryptionHeader(parsed)) } TagId::ProgramData | TagId::ProgramData2 => { let data = if tag_len > 64 { &tag_buf[..64] } else { &tag_buf }; debug!("raw program data: {:?}", Blob(data)); // The raw data to be programmed is prefixed by its offset // into flash memory. let flash_addr = tag_buf.read_u32::<LittleEndian>()?; Ok(Tag::ProgramData(ProgramData { flash_addr, data: Blob(tag_buf.into()), })) } TagId::EncryptedProgramData => Ok(Tag::EncryptedData(tag_buf.into())), TagId::Signature => { debug!("raw signature: {:?}", Blob(tag_buf)); if tag_len != 64 { return Err(Error::parse_err(format!( "signature is {} Bytes, expected 64", tag_len ))); } Ok(Tag::Signature(Signature { raw: Blob(tag_buf.into()), })) } TagId::Bootloader | TagId::Metadata => { if cfg!(fuzzing) { // When fuzzing, we don't want to panic Err(Error::parse_err("NYI: bootloader/metadata tag")) } else { unimplemented!() } } } } fn tag_id(&self) -> TagId { match self { Tag::Header(_) => TagId::Header, Tag::AppInfo(_) => TagId::AppInfo, Tag::ProgramData(_) => TagId::ProgramData2, Tag::Signature(_) => TagId::Signature, Tag::End(_) => TagId::End, Tag::EncryptionHeader(_) => TagId::EncryptionInitHeader, Tag::EncryptedData(_) => TagId::EncryptedProgramData, } } /// Writes this tag, along with tag ID and length, into a GBL file stream. fn write<W: Write>(&self, writer: &mut W) -> io::Result<()> { let mut buf = Vec::new(); self.write_raw(&mut buf) .expect("writing into a Vec<u8> failed"); writer.write_u32::<LittleEndian>(self.tag_id() as u32)?; writer.write_u32::<LittleEndian>(buf.len() as u32)?; writer.write_all(&buf)?; Ok(()) } /// Writes this tag into a writer, without its tag ID and length. fn write_raw<W: Write>(&self, writer: &mut W) -> io::Result<()> { match self { Tag::Header(hdr) => { writer.write_u32::<LittleEndian>(0x03000000)?; writer.write_u8(if hdr.encrypted { 1 } else { 0 })?; writer.write_u8(if hdr.signed { 1 } else { 0 })?; writer.write_u8(0)?; writer.write_u8(0)?; } Tag::AppInfo(appinfo) => { appinfo.write(writer)?; } Tag::ProgramData(data) => { writer.write_u32::<LittleEndian>(data.flash_addr)?; writer.write_all(&data.data)?; } Tag::Signature(sig) => { writer.write_all(&sig.raw)?; } Tag::End(crc) => { writer.write_u32::<LittleEndian>(*crc)?; } Tag::EncryptionHeader(hdr) => { writer.write_u32::<LittleEndian>(hdr.total_bytes)?; writer.write_all(&hdr.nonce)?; } Tag::EncryptedData(data) => { writer.write_all(data)?; } } Ok(()) } } #[derive(FromPrimitive, Debug)] #[repr(u32)] enum TagId { Header = 0x03A617EB, AppInfo = 0xF40A0AF4, Bootloader = 0xF50909F5, ProgramData = 0xFE0101FE, ProgramData2 = 0xFD0303FD, // alternate Tag ID for program data Metadata = 0xF60808F6, Signature = 0xF70A0AF7, End = 0xFC0404FC, EncryptionInitHeader = 0xFA0606FA, EncryptedProgramData = 0xF90707F9, } #[derive(Debug, Copy, Clone)] struct Header { signed: bool, encrypted: bool, } impl Header { fn parse(mut bytes: &[u8]) -> Result<Self, Error> { debug!("raw header: {:?}", bytes); if bytes.len() != 8 { return Err(Error::parse_err(format!( "got {} header bytes, expected 8", bytes.len() ))); } // The first 4 bytes of the header tag are apparently always "0 0 0 3" let mut fixed = [0u8; 4]; bytes.read_exact(&mut fixed)?; if fixed != [0, 0, 0, 3] { return Err(Error::parse_err(format!( "invalid or unknown header format: {:?}", fixed ))); } // The next 4 bytes contain flags // First byte: 1=encrypted, 0=unencrypted // Second byte: 1=signed, 0=not signed // Rest: Unknown (always 0) let encrypted = match bytes.read_u8()? { 0 => false, 1 => true, invalid => { return Err(Error::parse_err(format!( "invalid value for encryption byte: {:#04X} (expected 0 or 1)", invalid ))); } }; let signed = match bytes.read_u8()? { 0 => false, 1 => true, invalid => { return Err(Error::parse_err(format!( "invalid value for sign byte: {:#04X} (expected 0 or 1)", invalid ))); } }; let zero = bytes.read_u16::<LittleEndian>()?; if zero != 0 { return Err(Error::parse_err(format!( "invalid trailing word in header (expected 0, got {:#06X})", zero ))); } Ok(Header { signed, encrypted }) } } /// A chunk of program data to be programmed to a specified flash address. #[derive(Debug)] pub struct ProgramData<'a> { // FIXME: On EFR32xG1 devices, the first part of flash is the bootloader. // Does that mean this can overwrite it? flash_addr: u32, data: Blob<Cow<'a, [u8]>>, } impl<'a> ProgramData<'a> { /// Creates a new `ProgramData` section for flashing `data` at `addr`. /// /// It is the users responsibility to ensure that no `ProgramData` section /// writes out of bounds of flash memory. pub fn new<D>(addr: u32, data: D) -> Self where D: Into<Cow<'a, [u8]>>, { Self { flash_addr: addr, data: Blob(data.into()), } } /// Returns the target address in the device flash. pub fn start_addr(&self) -> u32 { self.flash_addr } /// Returns the bytes to be written. pub fn bytes(&self) -> &[u8] { &self.data } /// Converts `self` into another `ProgramData` instance that fully owns its /// contents. /// /// This does basically the same operation as `clone`, but the resulting /// type reflects that fact in its `'static` lifetime. fn into_owned(self) -> ProgramData<'static> { ProgramData { flash_addr: self.flash_addr, data: Blob(self.data.0.into_owned().into()), } } /// Cheaply creates another `ProgramData` struct borrowing the data from /// `self`. /// /// This can be used as a cheap `clone` replacement when the lifetime of the /// result may be shorter than that of `self`. fn clone(&'a self) -> Self { ProgramData { flash_addr: self.flash_addr, data: Blob(Cow::Borrowed(&self.data.0)), } } } impl<'a> From<AppImage<'a>> for ProgramData<'a> { fn from(image: AppImage<'a>) -> Self { Self { flash_addr: 0, data: Blob(image.into_raw()), } } } /// An ECDSA-P256 signature. /// /// The signature is computed over all preceding data in the file. It uses /// ECDSA-P256. The P-256 curve is the same as the `secp256r1` curve, which in /// turn is called `prime256v1` by OpenSSL. #[derive(Debug)] struct Signature<'a> { /// Raw signature blob. Always contains 64 Bytes. raw: Blob<Cow<'a, [u8]>>, // WE (probably still) WANT CONST GENERICS! } impl<'a> Signature<'a> { fn into_owned(self) -> Signature<'static> { Signature { raw: Blob(self.raw.0.into_owned().into()), } } fn clone(&'a self) -> Self { Signature { raw: Blob(Cow::Borrowed(&self.raw.0)), } } } /// Contains initialization info for encrypted blocks. #[derive(Debug, Copy, Clone)] struct EncryptionHeader { /// Total number of encrypted bytes. /// /// This is the sum of the lengths of all `EncryptedProgramData` blocks. total_bytes: u32, /// The nonce for the IV of the AES-CTR-128 encryption. nonce: Blob<[u8; 12]>, }