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edhoc: new structure for message 4
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Added test_handshake for 3 and 4 messages to derive prk_exporter in both cases
Added a function completed_without_message4 for handshake with 3 messages
Removed the trait for Done
Fix minor mistakes
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@ElsaLopez133
ElsaLopez133 committed Nov 2, 2024
1 parent 0fac1f0 commit 457f378
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Showing 7 changed files with 146 additions and 170 deletions.
2 changes: 1 addition & 1 deletion examples/coap/src/bin/coapclient.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -60,7 +60,7 @@ fn client_handshake() -> Result<(), EDHOCError> {
let initiator = initiator.verify_message_2(valid_cred_r)?;

let mut msg_3 = Vec::from(c_r.as_cbor());
let (mut initiator, message_3, prk_out, prk_out_exporter) =
let (mut initiator, message_3, prk_out) =
initiator.prepare_message_3(CredentialTransfer::ByReference, &None)?;
msg_3.extend_from_slice(message_3.as_slice());
println!("message_3 len = {}", msg_3.len());
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9 changes: 4 additions & 5 deletions examples/coap/src/bin/coapserver-coaphandler.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -182,11 +182,10 @@ impl coap_handler::Handler for EdhocHandler {
.expect("Static credential is not processable");
let valid_cred_i =
credential_check_or_fetch(Some(cred_i), id_cred_i).map_err(render_error)?;
let (responder, prk_out, prk_exporter) =
responder.verify_message_3(valid_cred_i).map_err(|e| {
println!("EDHOC processing error: {:?}", e);
render_error(e)
})?;
let (responder, prk_out) = responder.verify_message_3(valid_cred_i).map_err(|e| {
println!("EDHOC processing error: {:?}", e);
render_error(e)
})?;

let ead_4 = None;
let (mut responder, message_4) = responder.prepare_message_4(&ead_4).unwrap();
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7 changes: 2 additions & 5 deletions examples/coap/src/bin/coapserver.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -108,14 +108,11 @@ fn main() {
};
let cred_i = Credential::parse_ccs(CRED_I.try_into().unwrap()).unwrap();
let valid_cred_i = credential_check_or_fetch(Some(cred_i), id_cred_i).unwrap();
let Ok((mut responder, prk_out, prk_exporter)) =
responder.verify_message_3(valid_cred_i)
else {
let Ok((mut responder, prk_out)) = responder.verify_message_3(valid_cred_i) else {
println!("EDHOC error at verify_message_3: {:?}", valid_cred_i);
continue;
};
let ead_4 = None;
let (mut responder, message_4) = responder.prepare_message_4(&ead_4).unwrap();
let (mut responder, message_4) = responder.prepare_message_4(&None).unwrap();
// send empty ack back
response.message.payload = b"".to_vec();

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2 changes: 1 addition & 1 deletion examples/lakers-nrf52840/src/bin/initiator.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -94,7 +94,7 @@ async fn main(spawner: Spawner) {
let valid_cred_r = credential_check_or_fetch(Some(cred_r), id_cred_r).unwrap();
let initiator = initiator.verify_message_2(valid_cred_r).unwrap();

let (mut initiator, message_3, i_prk_out, i_prk_out_exporter) = initiator
let (mut initiator, message_3, i_prk_out) = initiator
.prepare_message_3(CredentialTransfer::ByReference, &None)
.unwrap();
let pckt_3 =
Expand Down
3 changes: 1 addition & 2 deletions examples/lakers-nrf52840/src/bin/responder.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -121,8 +121,7 @@ async fn main(spawner: Spawner) {
Credential::parse_ccs(common::CRED_I.try_into().unwrap()).unwrap();
let valid_cred_i =
credential_check_or_fetch(Some(cred_i), id_cred_i).unwrap();
let Ok((responder, r_prk_out, r_prk_exporter)) =
responder.verify_message_3(valid_cred_i)
let Ok((responder, r_prk_out)) = responder.verify_message_3(valid_cred_i)
else {
info!("EDHOC error at parse_message_3");
continue;
Expand Down
110 changes: 28 additions & 82 deletions lib/src/edhoc.rs
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Original file line number Diff line number Diff line change
@@ -1,68 +1,7 @@
use lakers_shared::{Crypto as CryptoTrait, *};

pub trait Done {
fn get_prk_exporter(&self) -> &[u8; SHA256_DIGEST_LEN];
fn get_prk_out(&self) -> &[u8; SHA256_DIGEST_LEN];
fn update_keys(
&mut self,
new_prk_out: &[u8; SHA256_DIGEST_LEN],
new_prk_exporter: &[u8; SHA256_DIGEST_LEN],
);
}

impl Done for WaitM4 {
fn get_prk_exporter(&self) -> &[u8; SHA256_DIGEST_LEN] {
&self.prk_exporter
}
fn get_prk_out(&self) -> &[u8; SHA256_DIGEST_LEN] {
&self.prk_out
}
fn update_keys(
&mut self,
new_prk_out: &[u8; SHA256_DIGEST_LEN],
new_prk_exporter: &[u8; SHA256_DIGEST_LEN],
) {
self.prk_out.copy_from_slice(new_prk_out);
self.prk_exporter.copy_from_slice(new_prk_exporter);
}
}

impl Done for Completed {
fn get_prk_exporter(&self) -> &[u8; SHA256_DIGEST_LEN] {
&self.prk_exporter
}
fn get_prk_out(&self) -> &[u8; SHA256_DIGEST_LEN] {
&self.prk_out
}
fn update_keys(
&mut self,
new_prk_out: &[u8; SHA256_DIGEST_LEN],
new_prk_exporter: &[u8; SHA256_DIGEST_LEN],
) {
self.prk_out.copy_from_slice(new_prk_out);
self.prk_exporter.copy_from_slice(new_prk_exporter);
}
}

impl Done for ProcessedM3 {
fn get_prk_exporter(&self) -> &[u8; SHA256_DIGEST_LEN] {
&self.prk_exporter
}
fn get_prk_out(&self) -> &[u8; SHA256_DIGEST_LEN] {
&self.prk_out
}
fn update_keys(
&mut self,
new_prk_out: &[u8; SHA256_DIGEST_LEN],
new_prk_exporter: &[u8; SHA256_DIGEST_LEN],
) {
self.prk_out.copy_from_slice(new_prk_out);
self.prk_exporter.copy_from_slice(new_prk_exporter);
}
}

pub fn edhoc_exporter(
state: &impl Done,
state: &Completed,
crypto: &mut impl CryptoTrait,
label: u8,
context: &BytesMaxContextBuffer,
Expand All @@ -71,7 +10,7 @@ pub fn edhoc_exporter(
) -> BytesMaxBuffer {
edhoc_kdf(
crypto,
state.get_prk_exporter(),
&state.prk_exporter,
label,
context,
context_len,
Expand All @@ -80,39 +19,34 @@ pub fn edhoc_exporter(
}

pub fn edhoc_key_update(
state: &mut impl Done,
state: &mut Completed,
crypto: &mut impl CryptoTrait,
context: &BytesMaxContextBuffer,
context_len: usize,
) -> BytesHashLen {
// Calculate new PRK_out
// new PRK_out
let prk_new_buf = edhoc_kdf(
crypto,
state.get_prk_out(),
&state.prk_out,
11u8,
context,
context_len,
SHA256_DIGEST_LEN,
);
let mut new_prk_out = [0u8; SHA256_DIGEST_LEN];
new_prk_out.copy_from_slice(&prk_new_buf[..SHA256_DIGEST_LEN]);
state.prk_out[..SHA256_DIGEST_LEN].copy_from_slice(&prk_new_buf[..SHA256_DIGEST_LEN]);

// Calculate new PRK_exporter
let prk_exporter_buf = edhoc_kdf(
// new PRK_exporter
let prk_new_buf = edhoc_kdf(
crypto,
&new_prk_out,
&state.prk_out,
10u8,
&[0x00; MAX_KDF_CONTEXT_LEN],
0,
SHA256_DIGEST_LEN,
);
let mut new_prk_exporter = [0u8; SHA256_DIGEST_LEN];
new_prk_exporter.copy_from_slice(&prk_exporter_buf[..SHA256_DIGEST_LEN]);
state.prk_exporter[..SHA256_DIGEST_LEN].copy_from_slice(&prk_new_buf[..SHA256_DIGEST_LEN]);

// Update state with new keys
state.update_keys(&new_prk_out, &new_prk_exporter);

new_prk_out
state.prk_out
}

pub fn r_process_message_1(
Expand Down Expand Up @@ -250,7 +184,7 @@ pub fn r_verify_message_3(
state: &mut ProcessingM3,
crypto: &mut impl CryptoTrait,
valid_cred_i: Credential,
) -> Result<(ProcessedM3, BytesHashLen, BytesHashLen), EDHOCError> {
) -> Result<(ProcessedM3, BytesHashLen), EDHOCError> {
// compute salt_4e3m
let salt_4e3m = compute_salt_4e3m(crypto, &state.prk_3e2m, &state.th_3);

Expand Down Expand Up @@ -316,7 +250,6 @@ pub fn r_verify_message_3(
prk_exporter: prk_exporter,
},
prk_out,
prk_exporter,
))
} else {
Err(EDHOCError::MacVerificationFailed)
Expand All @@ -341,6 +274,13 @@ pub fn r_prepare_message_4(
))
}

pub fn r_complete_without_message_4(state: &ProcessedM3) -> Result<Completed, EDHOCError> {
Ok(Completed {
prk_out: state.prk_out,
prk_exporter: state.prk_exporter,
})
}

pub fn i_prepare_message_1(
state: &InitiatorStart,
crypto: &mut impl CryptoTrait,
Expand Down Expand Up @@ -464,7 +404,7 @@ pub fn i_prepare_message_3(
cred_i: Credential,
cred_transfer: CredentialTransfer,
ead_3: &Option<EADItem>, // FIXME: make it a list of EADItem
) -> Result<(WaitM4, BufferMessage3, BytesHashLen, BytesHashLen), EDHOCError> {
) -> Result<(WaitM4, BufferMessage3, BytesHashLen), EDHOCError> {
let id_cred_i = match cred_transfer {
CredentialTransfer::ByValue => cred_i.by_value()?,
CredentialTransfer::ByReference => cred_i.by_kid()?,
Expand Down Expand Up @@ -522,7 +462,6 @@ pub fn i_prepare_message_3(
},
message_3,
prk_out,
prk_exporter,
))
}

Expand All @@ -547,6 +486,13 @@ pub fn i_process_message_4(
}
}

pub fn i_complete_without_message_4(state: &WaitM4) -> Result<Completed, EDHOCError> {
Ok(Completed {
prk_out: state.prk_out,
prk_exporter: state.prk_exporter,
})
}

fn encode_ead_item(ead_1: &EADItem) -> Result<EdhocMessageBuffer, EDHOCError> {
let mut output = EdhocMessageBuffer::new();

Expand Down Expand Up @@ -960,7 +906,7 @@ fn decrypt_message_4(
th_4: &BytesHashLen,
message_4: &BufferMessage4,
) -> Result<BufferPlaintext4, EDHOCError> {
// decode message_3
// decode message_4
let bytestring_length: usize;
let prefix_length;
// FIXME: Reuse CBOR decoder
Expand Down
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