Vitamin C Normalize

Normalized equality terms for the plaintext data model of vitaminc-aead. Part of the Vitamin C framework.

An equality index derives a key from a value. Two values that are equal must derive the same key whichever width, scale or spelling wrote them, and two values that merely look alike (a date and the integer it is stored as, a uuid and the same sixteen bytes) must not. This crate decides both: each scalar kind that can be indexed has a frozen domain label and a normalization to bytes, and everything else has no term.

There is no cryptography here and no PAE: the crate's own dependencies are the Unicode tables. (It builds on vitaminc-aead for the data model, which brings that crate's dependencies with it.) The encodings are its own, including the decimal one, which is ported from the frozen orderable-bytes release and checked against it byte for byte. A PRF crate such as vitaminc-prf takes a [Normalized] and derives under its domain.

One scalar

use vitaminc_normalize::{domain, normalize};
use vitaminc_aead::{Int, Logical, Physical};
use vitaminc_protected::Controlled;

// Every integer width is one term.
let a = normalize(None, Physical::Int(Int::I8(34)))?;
let b = normalize(None, Physical::Int(Int::U64(34)))?;
assert_eq!(a.domain, domain::INTEGER);
assert_eq!(a.bytes.risky_ref(), b.bytes.risky_ref());

// A date is not the integer it is stored as.
let day = normalize(Some(Logical::Date), Physical::Int(Int::I32(34)))?;
assert_eq!(day.domain, domain::DATE);
assert_ne!(day.bytes.risky_ref(), a.bytes.risky_ref());
# Ok::<(), vitaminc_normalize::NormalizeError>(())

Logical types opt in: a date, a timestamp, a decimal and a uuid have domains of their own. A null, a boolean, an undefined and a logical type this crate does not know have no term, and normalize refuses them with [NormalizeError::NoDomain].

A whole value, beside encryption

[Terms] is a sink that collects one [Term] per indexable scalar, with the path to it. Teed with the encrypting sink it sees the same walk, so the terms are complete before any cipher call:

use std::collections::BTreeMap;
use vitaminc_normalize::{domain, encrypt_with_terms, Step};
# use vitaminc_aead::{seal::Cipher, Context};
# use vitaminc_protected::{Controlled, Protected};
# /// Keeps the plaintext in the clear, for the example. Any `Cipher` will do.
# struct Clear;
# impl Cipher for Clear {
#     type Leaf = Vec<u8>;
#     type Error = core::convert::Infallible;
#     fn seal(&self, plaintext: Protected<Vec<u8>>, _: &Context<'_>) -> Result<Vec<u8>, Self::Error> {
#         Ok(plaintext.risky_unwrap())
#     }
#     fn open(&self, leaf: Vec<u8>, _: &Context<'_>) -> Result<Protected<Vec<u8>>, Self::Error> {
#         Ok(Protected::new(leaf))
#     }
# }
# let cipher = Clear;

let mut user = BTreeMap::new();
user.insert("email", "ada@example.com");
user.insert("name", "Ada");

let (ciphertext, terms) = encrypt_with_terms(user, &cipher, "users/v1")?;
assert_eq!(terms.len(), 2);
assert_eq!(terms[0].path.steps(), [Step::Key("email".into())]);
assert_eq!(terms[0].normalized.domain, domain::TEXT);
# Ok::<(), vitaminc_aead::EncryptError<core::convert::Infallible>>(())

encrypt_with_terms_async does the same through an async cipher and has every term before its first await. plan_with_terms walks without sealing at all, and terms collects the terms with no encryption in the walk.

terms refuses every value encryption refuses, for the same reason and at the same path, so an index never holds terms for a value that cannot be stored. It keeps the same shape rules, through the same code: no duplicate key, no value nested too deep, every scalar valid for its logical type, every passthrough framable, and something sealed in every container with children, even though it seals nothing itself. Read such a refusal with TermsError::refusal; encryption reports the same one as EncryptError::Shape.

A scalar whose kind has no domain (a null, a boolean, an undefined) produces no term and does not stop the walk; passthrough subtrees get none either. A scalar whose logical type has no domain, one from a newer client, stops the walk: encrypting it with no term and no error would leave an index silently incomplete. That refusal and an unassigned code point arrive as EncryptError::Source carrying a TermError (from terms, as TermsError::term), which holds the NormalizeError and the path to the refused field. Downcast to TermError; the NormalizeError is also its source(), so a reporter that walks the error chain reaches it. The message names neither the field nor the value, because map keys can be user data; read the path with TermError::path.

Encodings

These are protocol data. Changing any of them, or a domain label, means a new label.

Text normalization is variable-time. The integer and float paths use no floating-point arithmetic.