Function read_encrypted_segment

nodedb/src/storage/segment.rs:271–326

Read and decrypt a segment file's data portion. For encrypted segments, reads the 16-byte `SEGP` preamble at the start of the file to recover the epoch, then uses it for nonce reconstruction. Returns the plaintext data (footer is stripped and validated separately).

(
    path: &Path,
    key: Option<&nodedb_wal::crypto::WalEncryptionKey>,
)

/// the file to recover the epoch, then uses it for nonce reconstruction.
/// Returns the plaintext data (footer is stripped and validated separately).
pub fn read_encrypted_segment(
    path: &Path,
    key: Option<&nodedb_wal::crypto::WalEncryptionKey>,
) -> crate::Result<Vec<u8>> {
    let raw = std::fs::read(path)?;

    if let Some(key) = key {
        // Encrypted layout: [preamble(16)] [ciphertext] [footer(58)]
        let min_len = PREAMBLE_SIZE + nodedb_wal::crypto::AUTH_TAG_SIZE + FOOTER_SIZE;
        if raw.len() < min_len {
            return Err(crate::Error::SegmentCorrupted {
                detail: "encrypted segment file too small".into(),
            });
        }

        // Read and validate the preamble.
        let preamble_bytes: [u8; PREAMBLE_SIZE] = raw[..PREAMBLE_SIZE]
            .try_into()
            .expect("slice is PREAMBLE_SIZE bytes");
        let preamble =
            SegmentPreamble::from_bytes(&preamble_bytes, &SEG_PREAMBLE_MAGIC).map_err(|e| {
                crate::Error::SegmentCorrupted {
                    detail: format!("invalid segment preamble: {e}"),
                }
            })?;

        // Footer is at the end.
        let footer_bytes: [u8; FOOTER_SIZE] = raw[raw.len() - FOOTER_SIZE..]
            .try_into()
            .expect("slice is FOOTER_SIZE bytes");
        let footer = SegmentFooter::from_bytes(&footer_bytes)?;

        // Ciphertext is between preamble and footer.
        let ciphertext = &raw[PREAMBLE_SIZE..raw.len() - FOOTER_SIZE];

        // Decrypt: epoch from preamble, nonce input is min_lsn.
        key.decrypt_aad(
            preamble.epoch(),
            footer.min_lsn.as_u64(),
            &preamble_bytes,
            ciphertext,
        )
        .map_err(|e| crate::Error::Storage {
            engine: "segment".into(),
            detail: format!("segment decryption failed: {e}"),
        })
    } else {
        // Unencrypted layout: [data] [footer(58)]
        if raw.len() < FOOTER_SIZE {
            return Err(crate::Error::SegmentCorrupted {
                detail: "file too small".into(),
            });
        }
        Ok(raw[..raw.len() - FOOTER_SIZE].to_vec())
    }
}

#[cfg(test)]