office-crypto

Pure Rust library to decrypt password-protected MS Office files.

https://docs.rs/office-crypto

Example

This crate exposes two functions: decrypt_from_file and decrypt_from_bytes, which do exactly what they say they do. The resulting bytes can then be interpreted by any MS Office parser like docx-rs or calamine.

use docx_rs::read_docx;
use office_crypto::decrypt_from_file;

let path = "protected.docx";
let decrypted = decrypt_from_file(path, "Password1234_").unwrap(); 
let docx = read_docx(&decrypted).unwrap();

Formats

• ECMA-376 (Agile Encryption/Standard Encryption)
  • MS-DOCX (OOXML) (Word 2007-Present)
  • MS-XLSX (OOXML) (Excel 2007-Present)
  • MS-PPTX (OOXML) (PowerPoint 2007-Present)
• [-] Office Binary Document RC4 CryptoAPI
  • MS-DOC (Word 2002, 2003, 2004)
  • MS-XLS (Excel 2002, 2003, 2004)
  • MS-PPT (PowerPoint 2002, 2003, 2004)
• ECMA-376 (Extensible Encryption)

Non-SHA512 hash functions are not yet implemented. This only affects Agile encrypted files, but I have yet to find one that doesn't use SHA512.

Performance

Measured on an M4 Max:

test bench_agile_sha512        ... bench:  15,029,308 ns/iter (+/- 372,423)
test bench_agile_sha512_large  ... bench:  45,220,041 ns/iter (+/- 3,078,352)
test bench_standard            ... bench:   3,080,678 ns/iter (+/- 95,020)
test bench_doc97_rc4_cryptoapi ... bench:      42,690 ns/iter (+/- 1,393)

File sizes for tests:

• bench_agile_sha512 => 25 KB
• bench_agile_sha512_large => 7.1 MB
• bench_standard => 7 KB
• bench_doc97_rc4_cryptoapi => 23 KB

Note that the latest version of Word will create an Agile encrypted document.

Acknowledgements

This crate is essentially a port of the OOXML-specific features from msoffcrypto and olefile.