88 lines
30 KiB
Plaintext
88 lines
30 KiB
Plaintext
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rust
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Öt #rustc 1.96.0 (ac68faa20 2026-05-25)ÁíàÄTËŸ ÜJîÄ)'ß\¥! -3d1337db07d0b3aeÁ ¤°ð ¾ä-±($²ï=©Ã -7e98a21bfd32b0edÁ‰ í inputÁ × 'aÁ ÷ is_emptyÁ ‘ read_allÁ — £ – as_slice_less_safeÁ
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,½ Q Q Ù S± ÐÀŸX‰• ÷ › ö ±C ‘ ,Š tƒ Q � — üÏH § $ô › ,à › d ± 4 $Bí ”,™' G >åT' [ @å \ @Å4¹' ( Aü‚å& ü‚H E untrusted.rs: Safe, fast, zero-panic, zero-crashing, zero-allocationÁ üË( % parsing of untrusted inputs in Rust.Á ôú üøB ? <code>git clone https://github.com/briansmith/untrusted</code>Á »ú ü¿E B untrusted.rs goes beyond Rust's normal safety guarantees by alsoÁ ü…< 9 guaranteeing that parsing will be panic-free, as long asÁ üÂK H `untrusted::Input::as_slice_less_safe()` is not used. It avoids copyingÁ üŽ K H data and heap allocation and strives to prevent common pitfalls such asÁ üÚ K H accidentally parsing input bytes multiple times. In order to meet theseÁ ü¦
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O L goals, untrusted.rs is limited in functionality such that it works best forÁ üö
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N K input languages with a small fixed amount of lookahead such as ASN.1, TLS,Á üÅ L I TCP/IP, and many other networking, IPC, and related protocols. LanguagesÁ ü’ L I that require more lookahead and/or backtracking require some significantÁ üß O L contortions to parse using this framework. It would not be realistic to useÁ ü¯
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: 7 it for parsing programming language code, for example.Á ê
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2 / The overall pattern for using untrusted.rs is:Á ¡ú ü¥O L 1. Write a recursive-descent-style parser for the input language, where theÁ üõJ G input data is given as a `&mut untrusted::Reader` parameter to eachÁ üÀN K function. Each function should have a return type of `Result<V, E>` forÁ ü�O L some value type `V` and some error type `E`, either or both of which mayÁ üßJ G be `()`. Functions for parsing the lowest-level language constructsÁ üªN K should be defined. Those lowest-level functions will parse their inputsÁ üùF C using `::read_byte()`, `Reader::peek()`, and similar functions.Á üÀF C Higher-level language constructs are then parsed by calling theÁ ü‡) & lower-level functions in sequence.Á ±ú üµF C 2. Wrap the top-most functions of your recursive-descent parser inÁ üüI F functions that take their input data as an `untrusted::Input`. TheÁ üÆK H wrapper functions should call the `Input`'s `read_all` (or a variantÁ ü’N K thereof) method. The wrapper functions are the only ones that should beÁ üá+ ( exposed outside the parser's module.Á �ú ü‘P M 3. After receiving the input data to parse, wrap it in an `untrusted::Input`Á üâF C using `untrusted::Input::from()` as early as possible. Pass theÁ ü©O L `untrusted::Input` to the wrapper functions when they need to be parsed.Á ùú üýP M In general parsers built using `untrusted::Reader` do not need to explicitlyÁ üÎO L check for end-of-input unless they are parsing optional constructs, becauseÁ üžH E `Reader::read_byte()` will return `Err(EndOfInput)` on end-of-input.Á üçN K Similarly, parsers using `untrusted::Reader` generally don't need to checkÁ ü¶O L for extra junk at the end of the input as long as the parser's API uses theÁ ü†O L pattern described above, as `read_all` and its variants automatically checkÁ üÖN K for trailing junk. `Reader::skip_to_end()` must be used when any remainingÁ ü¥ ? < unread input should be ignored without triggering an error.Á å ú üé I F untrusted.rs works best when all processing of the input data is doneÁ ü³ D A through the `untrusted::Input` and `untrusted::Reader` types. InÁ üø J G particular, avoid trying to parse input data using functions that takeÁ üà M J byte slices. However, when you need to access a part of the input data asÁ ü‘ D A a slice to use a function that isn't written using untrusted.rs,Á üÖ . + `Input::as_slice_less_safe()` can be used.Á … ú ü‰ H E It is recommend to use `use untrusted;` and then `untrusted::Input`,Á üÒ N K `untrusted::Reader`, etc., instead of using `use untrusted::*`. QualifyingÁ ü¡!M J the names with `untrusted` helps remind the reader of the code that it isÁ üï!# dealing with *untrusted* input.Á “"ú t—" # ExamplesÁ ¦"ú üª"K H [*ring*](https://github.com/briansmith/ring)'s parser for the subset ofÁ üö"% " ASN.1 DER it needs to understand,Á üœ#N K [`ring::der`](https://github.com/briansmith/ring/blob/main/src/io/der.rs),Á üë#O L is built on top of untrusted.rs. *ring* also uses untrusted.rs to parse ECCÁ ü»$K H public keys, RSA PKCS#1 1.5 padding, and for all other parsing it does.Á ‡%ú ü‹%L I All of [webpki](https://github.com/briansmith/webpki)'s parsing of X.509Á üØ%= : certificates (also ASN.1 DER) is done using untrusted.rs.Á https://briansmith.org/rustdoc/Álž& $Bí ” G
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8 5 Construct a new `Input` for the given input `bytes`.Á$¸ Ë
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Á±!ô‚ ü²= : Returns `true` if the input is empty and false otherwise.ÁD‰ l lÇ ’
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Á$“ Ô… üÌ& # Returns the length of the `Input`.Á Œ m mÇ �
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Á$‘ ü‹Š üÆI F Calls `read` with the given input as a `Reader`, ensuring that `read`Á ü”K H consumed the entire input. If `read` does not consume the entire input,Á üä" `incomplete_read` is returned.ÁD’ o oÇ –—Ö¿Ù¿ Ú¿« Û¿ˆ Ü¿ Ý¿Þ¿ˆ ‚†f|Â
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ÁÉAœBÄA$¥ incomplete_readÁ|« readÁ$¿ ÒÔ ÏÑ ÌÎ üÿ, üêH E Access the input as a slice so it can be processed by functions thatÁ ü·5 2 are not written using the Input/Reader framework.Á”† p pÇ Ë
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