HOST=https://api.paper.novig.com
KEY_ID=2c9a7e1d-5b3f-4e8a-a6d0-9f1b3c5e7a24
PEM=novig-api-key-mgmt-1.pem

REQ_PATH="/v3/time"
QUERY=""
BODY=''
TS=$(date +%s000)
HASH=$(printf %s "$BODY" \
  | openssl dgst -sha256 -r | cut -d" " -f1)

# openssl signs a file, not a pipe. base64 -A never wraps.
printf 'NOVIG-V3\n%s\nGET\n%s\n%s\n%s' \
  "$TS" "$REQ_PATH" "$QUERY" "$HASH" > canon.bin
SIG=$(openssl pkeyutl -sign -rawin -inkey "$PEM" \
  -in canon.bin | openssl base64 -A)

curl -s -X GET "$HOST$REQ_PATH${QUERY:+?$QUERY}" \
  -H "Novig-Key-Id: $KEY_ID" \
  -H "Novig-Timestamp: $TS" \
  -H "Novig-Signature: $SIG"

use base64::prelude::*;
use ed25519_dalek::pkcs8::DecodePrivateKey;
use ed25519_dalek::{Signer, SigningKey};
use reqwest::blocking::{Client, Request};
use reqwest::{Method, Url};
use sha2::{Digest, Sha256};
use std::time::{SystemTime, UNIX_EPOCH};

const HOST: &str = "https://api.paper.novig.com";
const KEY_ID: &str =
    "2c9a7e1d-5b3f-4e8a-a6d0-9f1b3c5e7a24";
const PEM: &str = "novig-api-key-mgmt-1.pem";

fn main() -> anyhow::Result<()> {
    let key = Key::load(KEY_ID, PEM)?;
    let client = Client::new();
    let path = "/v3/time";
    let url = format!("{HOST}{path}");
    let req = client
        .get(url)
        .build()?
        .sign(&key)?;
    println!("{}", client.execute(req)?.text()?);
    Ok(())
}

/// An API key: the id the server looks up, and the
/// private half that signs.
struct Key {
    id: &'static str,
    signer: SigningKey,
}

impl Key {
    fn load(id: &'static str, pem: &str) -> anyhow::Result<Self> {
        let signer =
            SigningKey::read_pkcs8_pem_file(pem)?;
        Ok(Self { id, signer })
    }
}

/// Signs a built request over the method, path, query and
/// body it will send, so the two can never disagree.
trait Sign: Sized {
    fn sign(self, key: &Key) -> anyhow::Result<Self>;
}

impl Sign for Request {
    fn sign(mut self, key: &Key) -> anyhow::Result<Self> {
        let ts = SystemTime::now()
            .duration_since(UNIX_EPOCH)?
            .as_millis()
            .to_string();
        let body = self.body().and_then(|b| b.as_bytes());
        let body = body.unwrap_or_default();
        let canon = Canonical::new(
            &ts,
            self.method(),
            self.url(),
            body,
        );
        let sig = key.signer.sign(canon.0.as_bytes());
        let sig = BASE64_STANDARD.encode(sig.to_bytes());
        let headers = self.headers_mut();
        headers.insert("Novig-Key-Id", key.id.parse()?);
        headers.insert("Novig-Timestamp", ts.parse()?);
        headers.insert("Novig-Signature", sig.parse()?);
        Ok(self)
    }
}

/// The six NOVIG-V3 lines, joined by LF.
struct Canonical(String);

impl Canonical {
    fn new(
        ts: &str,
        method: &Method,
        url: &Url,
        body: &[u8],
    ) -> Self {
        let query =
            Query::from(url.query().unwrap_or(""));
        let hash = format!("{:x}", Sha256::digest(body));
        let method = method.as_str();
        let path = url.path();
        let lines = [
            "NOVIG-V3", ts, method, path, &query.0, &hash,
        ];
        Self(lines.join("\n"))
    }
}

/// Each part decoded and re-encoded, then sorted by
/// name and value.
struct Query(String);

impl From<&str> for Query {
    fn from(raw: &str) -> Self {
        let mut pairs = raw
            .split('&')
            .filter(|pair| !pair.is_empty())
            .map(|pair| {
                pair.split_once('=').unwrap_or((pair, ""))
            })
            .map(|(k, v)| {
                (Self::encode(k), Self::encode(v))
            })
            .collect::<Vec<_>>();
        pairs.sort();
        let pairs =
            pairs.iter().map(|(k, v)| format!("{k}={v}"));
        Self(pairs.collect::<Vec<_>>().join("&"))
    }
}

impl Query {
    fn encode(part: &str) -> String {
        Self::decode(part)
            .iter()
            .map(|&b| match b {
                b'-' | b'.' | b'_' | b'~' => {
                    (b as char).to_string()
                }
                _ if b.is_ascii_alphanumeric() => {
                    (b as char).to_string()
                }
                _ => format!("%{b:02X}"),
            })
            .collect()
    }

    /// Only `%XX` decodes. A bare `+` stays a `+`.
    fn decode(part: &str) -> Vec<u8> {
        let raw = part.as_bytes();
        let mut out = Vec::with_capacity(raw.len());
        let mut i = 0;
        while i < raw.len() {
            let escape =
                raw.get(i + 1..i + 3).and_then(Self::hex);
            match (raw[i], escape) {
                (b'%', Some(byte)) => {
                    out.push(byte);
                    i += 3;
                }
                (byte, _) => {
                    out.push(byte);
                    i += 1;
                }
            }
        }
        out
    }

    fn hex(pair: &[u8]) -> Option<u8> {
        let hi = (pair[0] as char).to_digit(16)?;
        let lo = (pair[1] as char).to_digit(16)?;
        Some((hi * 16 + lo) as u8)
    }
}

import base64, hashlib, time, urllib.request
from cryptography.hazmat.primitives.serialization import (
    load_pem_private_key)

HOST = "https://api.paper.novig.com"
KEY_ID = "2c9a7e1d-5b3f-4e8a-a6d0-9f1b3c5e7a24"
PEM = "novig-api-key-mgmt-1.pem"

path = "/v3/time"
query = ""
body = b""

ts = str(int(time.time() * 1000))
canon = "\n".join(["NOVIG-V3", ts, "GET", path, query,
                   hashlib.sha256(body).hexdigest()])
key = load_pem_private_key(open(PEM, "rb").read(), None)
headers = {
    "Novig-Key-Id": KEY_ID,
    "Novig-Timestamp": ts,
    "Novig-Signature": base64.b64encode(
        key.sign(canon.encode())).decode(),
}
url = f"{HOST}{path}"
req = urllib.request.Request(
    url, data=body or None,
    method="GET", headers=headers)
print(urllib.request.urlopen(req).read().decode())

import {
  createHash, createPrivateKey, sign,
} from "node:crypto";
import { readFileSync } from "node:fs";

const HOST = "https://api.paper.novig.com";
const KEY_ID = "2c9a7e1d-5b3f-4e8a-a6d0-9f1b3c5e7a24";
const PEM = "novig-api-key-mgmt-1.pem";

const path = "/v3/time";
const query = "";
const body = "";

const ts = Date.now().toString();
const hash =
  createHash("sha256").update(body).digest("hex");
const canon = [
  "NOVIG-V3", ts, "GET", path, query, hash,
].join("\n");
const key = createPrivateKey(readFileSync(PEM));
const headers: Record<string, string> = {
  "Novig-Key-Id": KEY_ID,
  "Novig-Timestamp": ts,
  "Novig-Signature": sign(null, Buffer.from(canon), key)
    .toString("base64"),
};
const url = `${HOST}${path}`;
const r = await fetch(url, {
  method: "GET",
  headers,
});
console.log(await r.text());

{
  "ts": 1756512000000
}

{
  "code": "SIGNATURE_REJECTED",
  "message": "signature verification failed"
}

{
  "code": "SCOPE_INSUFFICIENT",
  "message": "api key scope is insufficient for this route"
}

{
  "code": "RATE_LIMIT_EXCEEDED",
  "message": "Rate limit exceeded. Please wait before retrying."
}