# pssh-box
This crate defines Rust data structures allowing you to store, parse and serialize Protection System
Specific Header (**PSSH**) boxes, which provide data for the initialization of a Digital Rights
Management (DRM) system.
[](https://crates.io/crates/pssh-box)
[](https://docs.rs/pssh-box/)
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[](https://deps.rs/repo/github/emarsden/pssh-box-rs)
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PSSH boxes are used:
- in an MP4 box of type `pssh` in an MP4 fragment (CMAF/MP4/ISOBMFF containers)
- in a `<cenc:pssh>` element in a DASH MPD manifest
- in DRM initialization data passed to the Encrypted Media Extension of a web browser
- in an EXT-X-SESSION-KEY field of an m3u8 playlist.
A PSSH box includes information for a single DRM system. This library supports the PSSH data formats
for the following DRM systems:
- Widevine, owned by Google, widely used for DASH streaming
- PlayReady, owned by Microsoft, widely used for DASH streaming
- WisePlay, owned by Huawei
- Irdeto
- Marlin
- Nagra
- The unofficial variant of Apple FairPlay that is used for DASH-like streaming by Netflix
- Common Encryption
PSSH boxes contain (depending on the DRM system) information on the key_ID for which to obtain a
content key, the encryption scheme used (e.g. cenc, cbc1, cens or cbcs), the URL of the licence
server, and checksum data.
## Features
This crate provides the following functionality:
- **parse PSSH boxes** from binary buffers (as found in an MP4 fragment), or from a base64-encoded
string (as found in a `<cenc:pssh>` element in an MPD manifest), or from a hex-encoded string.
- **scan** a binary buffer for the location of a PSSH box, using the function `find_iter`.
- pretty print a PSSH, using function `pprint`.
- serialize a PSSH box to binary, base64 or hexadecimal (base 16) formats, using methods
`to_bytes()`, `to_base64()` and `to_hex()` on a `PsshBox` struct.
A **commandline utility** for decoding PSSH boxes and PSSH data in various formats is available in
`example/decode-pssh.rs`.
If you wish to use this functionality in web applications, you may be interested in the
[pssh-box-wasm](https://github.com/emarsden/pssh-box-wasm/) library, which provides functionality
for using this code as WebAssembly.
## Usage
```
let boxes = from_base64("AAAAZ3Bzc2gAAAAA7e+LqXnWSs6jyCfc1R0h7QAAAEcSEKqL5HpT2ymw4FM7KEUKHLsaA3NmciIkYWE4YmU0N2EtNTNkYi0yOWIwLWUwNTMtM2IyODQ1MGExY2JiKgJTREjj3JWbBg==")
.unwrap();
assert_eq!(boxes.len(), 1);
let pssh = &boxes[0];
assert_eq!(pssh.system_id, WIDEVINE_SYSTEM_ID);
if let PsshData::Widevine(ref pd) = pssh.pssh_data {
assert!(pd.provider.clone().is_some_and(|p| p.eq("sfr")));
assert_eq!(pd.key_id[0], hex::decode("aa8be47a53db29b0e0533b28450a1cbb").unwrap());
assert_eq!(pd.content_id, Some(hex::decode("61613862653437612d353364622d323962302d653035332d336232383435306131636262").unwrap()));
}
```
## Build
The protoc compiler is used during the build process to translate the protobuf interface definition
for Widevine PSSH data into Rust structs. This happens in the `build.rs` file. The default
configuration uses a **prebuilt protobuf compiler**, which must be locally installed (from Debian
package `protobuf-compiler`, for example).
As an alternative if the `vendored-protoc` feature is enabled, the `protobuf-src` crate is used to
build a vendored version of the protoc compiler. This requires a working C++ compiler and cmake
support, and tends to be rather unreliable (in particular, the abseil-cpp component of protobuf
often causes build failures on any mildly unusual platform). To build on Windows, the simplest
solution seems to be the UCRT64 environment of [MSYS2](https://www.msys2.org/); see our GitHub
continuous integration workflow for one recipe that works.
## License
This project is licensed under the MIT license. For more information, see the `LICENSE` file.