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/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at https://mozilla.org/MPL/2.0/. */
use std::io::Cursor;
use thin_vec::ThinVec;
pub mod types;
use types::HpkeConfig;
use types::Report;
use types::ReportID;
use types::ReportMetadata;
use types::TaskID;
use types::Time;
pub mod prg;
use prg::PrgAes128Alt;
use prio::codec::Encode;
use prio::codec::{encode_u32_items, Decode};
use prio::field::Field128;
use prio::flp::types::Sum;
use prio::vdaf::prio3::Prio3;
use prio::vdaf::Client;
use prio::vdaf::VdafError;
use crate::types::HpkeCiphertext;
type Prio3Aes128SumAlt = Prio3<Sum<Field128>, PrgAes128Alt, 16>;
extern "C" {
pub fn dapHpkeEncryptOneshot(
aKey: *const u8,
aKeyLength: u32,
aInfo: *const u8,
aInfoLength: u32,
aAad: *const u8,
aAadLength: u32,
aPlaintext: *const u8,
aPlaintextLength: u32,
aOutputEncapsulatedKey: &mut ThinVec<u8>,
aOutputShare: &mut ThinVec<u8>,
) -> bool;
}
pub fn new_prio(num_aggregators: u8, bits: u32) -> Result<Prio3Aes128SumAlt, VdafError> {
if bits > 64 {
return Err(VdafError::Uncategorized(format!(
"bit length ({}) exceeds limit for aggregate type (64)",
bits
)));
}
Prio3::new(num_aggregators, Sum::new(bits as usize)?)
}
enum Role {
Leader = 2,
Helper = 3,
}
/// A minimal wrapper around the FFI function which mostly just converts datatypes.
fn hpke_encrypt_wrapper(
plain_share: &Vec<u8>,
aad: &Vec<u8>,
info: &Vec<u8>,
hpke_config: &HpkeConfig,
) -> Result<HpkeCiphertext, Box<dyn std::error::Error>> {
let mut encrypted_share = ThinVec::<u8>::new();
let mut encapsulated_key = ThinVec::<u8>::new();
unsafe {
if !dapHpkeEncryptOneshot(
hpke_config.public_key.as_ptr(),
hpke_config.public_key.len() as u32,
info.as_ptr(),
info.len() as u32,
aad.as_ptr(),
aad.len() as u32,
plain_share.as_ptr(),
plain_share.len() as u32,
&mut encapsulated_key,
&mut encrypted_share,
) {
return Err(Box::from("Encryption failed."));
}
}
Ok(HpkeCiphertext {
config_id: hpke_config.id,
enc: encapsulated_key.to_vec(),
payload: encrypted_share.to_vec(),
})
}
/// Pre-fill the info part of the HPKE sealing with the constants from the standard.
fn make_base_info() -> Vec<u8> {
let mut info = Vec::<u8>::new();
const START: &[u8] = "dap-02 input share".as_bytes();
info.extend(START);
const FIXED: u8 = 1;
info.push(FIXED);
info
}
/// This function creates a full report - ready to send - for a measurement.
///
/// To do that it also needs the HPKE configurations for the endpoints and some
/// additional data which is part of the authentication.
fn get_dap_report_internal(
leader_hpke_config_encoded: &ThinVec<u8>,
helper_hpke_config_encoded: &ThinVec<u8>,
measurement: u32,
task_id: &[u8; 32],
time_precision: u64,
) -> Result<Report, Box<dyn std::error::Error>> {
let leader_hpke_config = HpkeConfig::decode(&mut Cursor::new(leader_hpke_config_encoded))?;
let helper_hpke_config = HpkeConfig::decode(&mut Cursor::new(helper_hpke_config_encoded))?;
let prio = new_prio(2, 2)?;
let (public_share, input_shares) = prio.shard(&(measurement as u128))?;
debug_assert_eq!(input_shares.len(), 2);
debug_assert_eq!(public_share, ());
let public_share = Vec::new(); // the encoding wants an empty vector not ()
let metadata = ReportMetadata {
report_id: ReportID::generate(),
time: Time::generate(time_precision),
extensions: vec![],
};
// This quote from the standard describes which info and aad to use for the encryption:
// enc, payload = SealBase(pk,
// "dap-02 input share" || 0x01 || server_role,
// task_id || metadata || public_share, input_share)
// https://www.ietf.org/archive/id/draft-ietf-ppm-dap-02.html#name-upload-request
let mut info = make_base_info();
let mut aad = Vec::from(*task_id);
metadata.encode(&mut aad);
encode_u32_items(&mut aad, &(), &public_share);
info.push(Role::Leader as u8);
let leader_payload = hpke_encrypt_wrapper(
&input_shares[0].get_encoded(),
&aad,
&info,
&leader_hpke_config,
)?;
*info.last_mut().unwrap() = Role::Helper as u8;
let helper_payload = hpke_encrypt_wrapper(
&input_shares[1].get_encoded(),
&aad,
&info,
&helper_hpke_config,
)?;
Ok(Report {
task_id: TaskID(*task_id),
metadata,
public_share,
encrypted_input_shares: vec![leader_payload, helper_payload],
})
}
/// Wraps the function above with minor C interop.
/// Mostly it turns any error result into a return value of false.
#[no_mangle]
pub extern "C" fn dapGetReport(
leader_hpke_config_encoded: &ThinVec<u8>,
helper_hpke_config_encoded: &ThinVec<u8>,
measurement: u32,
task_id: &ThinVec<u8>,
time_precision: u64,
out_report: &mut ThinVec<u8>,
) -> bool {
assert_eq!(task_id.len(), 32);
if let Ok(report) = get_dap_report_internal(
leader_hpke_config_encoded,
helper_hpke_config_encoded,
measurement,
&task_id.as_slice().try_into().unwrap(),
time_precision,
) {
let encoded_report = report.get_encoded();
out_report.extend(encoded_report);
true
} else {
false
}
}
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