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Define constants for `AuthClient` field lengths. 

These are used in multiple places (and will also be used by the HS
descriptor encoder later on), so let's make them named constants.

Signed-off-by: Gabriela Moldovan <gabi@torproject.org>
This commit is contained in:
Gabriela Moldovan 2023-03-17 20:19:22 +00:00
parent 1394a81142
commit 89ca965d2a
2 changed files with 19 additions and 7 deletions
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11
crates/tor-netdoc/src/doc/hsdesc/desc_enc.rs
View File

@ -41,13 +41,22 @@ pub(super) struct HsDescEncryption<'a> {
pub(super) string_const: &'a [u8],
}
/// The length of a client ID.
pub(crate) const HS_DESC_MIDDLE_CLIENT_ID_LEN: usize = 8;
/// The length of the the `AuthClient` IV.
pub(crate) const HS_DESC_MIDDLE_IV_LEN: usize = 16;
/// The length of an `N_hs_desc_enc` nonce (also known as a "descriptor cookie").
pub(crate) const HS_DESC_MIDDLE_ENC_NONCE_LEN: usize = 16;
/// A value used in deriving the encryption key for the inner (encryption) layer
/// of onion service encryption.
///
/// This is `N_hs_desc_enc` in the spec, where sometimes we also call it a
/// "descriptor cookie".
#[derive(derive_more::AsRef, derive_more::From)]
pub(super) struct HsDescEncNonce([u8; 16]);
pub(super) struct HsDescEncNonce([u8; HS_DESC_MIDDLE_ENC_NONCE_LEN]);
/// Length of our cryptographic salt.
const SALT_LEN: usize = 16;

15
crates/tor-netdoc/src/doc/hsdesc/middle.rs
View File

@ -12,7 +12,10 @@ use crate::parse::{keyword::Keyword, parser::SectionRules};
use crate::types::misc::B64;
use crate::{Pos, Result};
use super::desc_enc::{HsDescEncNonce, HsDescEncryption};
use super::desc_enc::{
HsDescEncNonce, HsDescEncryption, HS_DESC_MIDDLE_CLIENT_ID_LEN, HS_DESC_MIDDLE_ENC_NONCE_LEN,
HS_DESC_MIDDLE_IV_LEN,
};
use super::DecryptionError;
/// A more-or-less verbatim representation of the middle document of an onion
@ -67,7 +70,7 @@ impl HsDescMiddle {
}
/// Use a `ClientDescAuthSecretKey` (`KS_hsc_desc_enc`) to see if there is any `auth-client`
/// entry for us (a client who holds that secret key) in this descriptor.
/// entry for us (a client who holds that secret key) in this descriptor.
/// If so, decrypt it and return its
/// corresponding "Descriptor Cookie" (`N_hs_desc_enc`)
///
@ -135,11 +138,11 @@ struct AuthClient {
/// A check field that clients can use to see if this [`AuthClient`] entry corresponds to a key they hold.
///
/// This is the first part of the `auth-client` line.
client_id: CtByteArray<8>,
client_id: CtByteArray<HS_DESC_MIDDLE_CLIENT_ID_LEN>,
/// An IV used to decrypt `encrypted_cookie`.
///
/// This is the second item on the `auth-client` line.
iv: [u8; 16],
iv: [u8; HS_DESC_MIDDLE_IV_LEN],
/// An encrypted value used to find the descriptor cookie `N_hs_desc_enc`,
/// which in turn is
/// needed to decrypt the [HsDescMiddle]'s `encrypted_body`.
@ -147,7 +150,7 @@ struct AuthClient {
/// This is the third item on the `auth-client` line. When decrypted, it
/// reveals a `DescEncEncryptionCookie` (`N_hs_desc_enc`, not yet so named
/// in the spec).
encrypted_cookie: [u8; 16],
encrypted_cookie: [u8; HS_DESC_MIDDLE_ENC_NONCE_LEN],
}
impl AuthClient {
@ -203,7 +206,7 @@ impl HsDescMiddle {
Ok(result)
}
/// Extract an HsDescMiddle from a reader.
/// Extract an HsDescMiddle from a reader.
///
/// The reader must contain a single HsDescOuter; we return an error if not.
fn take_from_reader(reader: &mut NetDocReader<'_, HsMiddleKwd>) -> Result<HsDescMiddle> {