Struct DkimSigningStream 

pub struct DkimSigningStream<'a, T: SigningKey> { /* private fields */ }

A streaming DKIM1 signer, created by DkimSigner::sign_streaming.

Avoids loading the entire message into memory before signing. Headers are buffered until the header/body boundary (\r\n\r\n) is found; body content is then canonicalized and hashed as it arrives. The resulting Signature is identical to the one DkimSigner::sign produces for the same message and signing time, except that streaming fails with Error::NoHeadersFound when none of the listed headers is present, where sign signs them as empty.

Example

use mail_auth::{crypto::Ed25519Key, dkim::DkimSigner, headers::HeaderWriter};

let signer = DkimSigner::from_key(Ed25519Key::from_pkcs8_der(&pkcs8_der)?)
    .domain("example.com")
    .selector("default")
    .headers(["From", "To", "Subject"]);

let mut stream = signer.sign_streaming();
stream.write(b"From: sender@example.com\r\n");
stream.write(b"To: recipient@example.com\r\n");
stream.write(b"Subject: Test\r\n");
stream.write(b"\r\n");
stream.write(b"Body content here...");

let signature = stream.finish()?;
let header = signature.to_header();

Implementations

impl<T: SigningKey> DkimSigningStream<'_, T>

pub fn write(&mut self, chunk: &[u8])

Feeds the next chunk of raw message data to the signer.

Data must be provided in order, starting with the headers. Chunks may split lines, and the header/body boundary (\r\n\r\n), anywhere.

While reading headers, all data is buffered. Once the header/body boundary is detected, subsequent body data is streamed directly to the hasher.

pub fn finish(self) -> Result<Signature>

where <<T as SigningKey>::Hasher as HashImpl>::Context: HashContext,

Consumes the stream and returns the DKIM signature.

The current system time is used for t= (and as the base of x= when an expiration is set). A stream that never saw the header/body boundary is treated as a message with headers only and an empty body.

Errors

Returns Error::NoHeadersFound when none of the signer’s listed headers was found, or Error::Crypto when the signing operation fails.