Rework how keys are represented, named, and bound

.gitignore

@@ -17,6 +17,7 @@
 /node_modules/
 /versioned/
 Gemfile.lock
+__pycache__/
 archive.json
 draft-richer-oauth-httpsig.xml
 package-lock.json

tools/examples/content-digest.hdr

@@ -1 +1,4 @@
-Content-Digest: sha-256=:4fEzRVTGqfZg7lqf/d3oxXu837pvb3L0GN24+F1VkZk=:
+NOTE: '\' line wrapping per RFC 8792
+
+Content-Digest: sha-256=:4fEzRVTGqfZg7lqf/d3oxXu837pvb3L0GN24+F\
+  1VkZk=:

tools/examples/present-request-signed.http

@@ -5,7 +5,7 @@ Host: example.com
 Date: Mon, 20 Apr 2026 02:07:55 GMT
 Authorization: HTTPSig 2340897.34j123-134uh2345n
 Signature-Input: sig1=("@method" "@target-uri" "authorization")\
-  ;created=1776650875;keyid="j-0Ny45NWmqGq6G4UxLjGjNuloktugtOW4jfGCCg\
-  efQ";nonce="k9Jyxempel2305Nmx7Rk";tag="httpsig-oauth"
-Signature: sig1=:kFJC2WoBbrQc8tsKiowIb8oeIA533qmKvzdKf8kndJ7kaLxGmm2v\
-  9+IPB8kLE0WUea8KryJGSV7ji1apLkeKBg==:
+  ;created=1776650875;nonce="k9Jyxempel2305Nmx7Rk"\
+  ;tag="httpsig-oauth"
+Signature: sig1=:uvIxaaJED8BxpYUL6cBd1v5uy24SptQnVQ35oKxWflg8GumiH77\
+  60va6P2qWxadrLodjGmIFna3bS70KxYv7CQ==:

tools/examples/rs-request-signed.http

@@ -5,7 +5,7 @@ Host: example.com
 Date: Mon, 20 Apr 2026 02:07:55 GMT
 Authorization: HTTPSig 2340897.34j123-134uh2345n
 Signature-Input: sig1=("@method" "@target-uri" "authorization")\
-  ;created=1776650875;keyid="test-key-ecdsa-p256"\
-  ;nonce="k9Jyxempel2305Nmx7Rk";tag="httpsig-oauth"
-Signature: sig1=:ggBLokBFCW7NcE4z1P5zV1wn7vmnRADiMcpAVFb1q8kOQ3nlhXqQ\
-  c9LPWdz1h4FGRtImK9LqNdDdpn9G4o9zRw==:
+  ;created=1776650875;nonce="k9Jyxempel2305Nmx7Rk"\
+  ;tag="httpsig-oauth"
+Signature: sig1=:iIwwgqVdmaneSVYJaLAMCf9yz8SnvNfUPZgeyWdkEjsO3+29XB0\
+  OLVBsR0w9Q+uw04yOVV1JeogdVvpyBhw3ZA==:

tools/examples/rs-sig-base.sigbase

@@ -4,5 +4,5 @@ NOTE: '\' line wrapping per RFC 8792
 "@target-uri": https://example.com/foo
 "authorization": HTTPSig 2340897.34j123-134uh2345n
 "@signature-params": ("@method" "@target-uri" "authorization")\
-  ;created=1776650875;keyid="test-key-ecdsa-p256"\
-  ;nonce="k9Jyxempel2305Nmx7Rk";tag="httpsig-oauth"
+  ;created=1776650875;nonce="k9Jyxempel2305Nmx7Rk"\
+  ;tag="httpsig-oauth"

tools/examples/token-request-prereg-signed.http

@@ -0,0 +1,16 @@
+NOTE: '\' line wrapping per RFC 8792
+
+POST /token HTTP/1.1
+Host: server.example.com
+Authorization: Basic czZCaGRSa3F0MzpnWDFmQmF0M2JW
+Content-Type: application/x-www-form-urlencoded
+Content-Digest: sha-256=:4fEzRVTGqfZg7lqf/d3oxXu837pvb3L0GN24+F\
+  1VkZk=:
+Signature-Input: sig1=("@method" "@target-uri" "content-digest" \
+  "authorization");created=1618884473;keyid="j-0Ny45NWmqGq6GQ"\
+  ;nonce="b3k2pp5k7z-50gnX1b06";tag="httpsig-oauth-token-request"
+Signature: sig1=:blPeRn3D3nkYqc1RNzCzge9E0n/Guf9yA1BBOeMFOOeSwuDdrVN\
+  cc5KSUKSOabdVHXVExQT0v6J+e3QDc3zzBA==:
+
+grant_type=authorization_code&code=SplxlOBeZQQYbYS6WxSbIA&redirect_u\
+  ri=https%3A%2F%2Fclient%2Eexample%2Ecom%2Fcb

tools/examples/token-request-signed.http

@@ -4,14 +4,14 @@ POST /token HTTP/1.1
 Host: server.example.com
 Authorization: Basic czZCaGRSa3F0MzpnWDFmQmF0M2JW
 Content-Type: application/x-www-form-urlencoded
-Content-Digest: sha-256=:4fEzRVTGqfZg7lqf/d3oxXu837pvb3L0GN24+F1VkZk=:
+Content-Digest: sha-256=:4fEzRVTGqfZg7lqf/d3oxXu837pvb3L0GN24+F\
+  1VkZk=:
 Signature-Input: sig1=("@method" "@target-uri" "content-digest" \
-  "authorization");created=1618884473;keyid="j-0Ny45NWmqGq6G4UxLjGjNu\
-  loktugtOW4jfGCCgefQ";alg="ed25519";nonce="b3k2pp5k7z-50gnX1b06"\
-  ;tag="httpsig-oauth-token-request";pub_key_a=:iuemcj/GhRHmY/yCsMlDN\
-  p3BQgPZDdG00VRsg/BgU3s=:
-Signature: sig1=:ikilCUkL+BjDRXdC7m4eNgU/4dQtijp4BTgehqYRxJX+sPr394dx\
-  qGAPzV99eUVDhN1cgAk2VFXvN2pNfpFTBA==:
+  "authorization");created=1618884473;alg="ed25519"\
+  ;nonce="b3k2pp5k7z-50gnX1b06";tag="httpsig-oauth-token-request"\
+  ;pub=:iuemcj/GhRHmY/yCsMlDNp3BQgPZDdG00VRsg/BgU3s=:
+Signature: sig1=:W1jjnCpI59MI13gajmWP9DViwQHXhQdQ8r8q+h+Drp2JbJyu/md\
+  QrMMkGuiMvkWWY/noYbi9L4cW/lTOZigsCQ==:
 
-grant_type=authorization_code&code=SplxlOBeZQQYbYS6WxSbIA&redirect_ur\
-  i=https%3A%2F%2Fclient%2Eexample%2Ecom%2Fcb
+grant_type=authorization_code&code=SplxlOBeZQQYbYS6WxSbIA&redirect_u\
+  ri=https%3A%2F%2Fclient%2Eexample%2Ecom%2Fcb

tools/genexamples.sh

@@ -17,8 +17,8 @@ py() { python3 "$gensig" "$@"; }
 
 # --- Token request (runtime Ed25519 key) -----------------------------------
 # #2 Content-Digest of the form body and #3 the signed token request.
-# The runtime key is embedded as pub_key_a + keyid params (no Signature-Key
-# header); the alg param is forced on by --runtime-key.
+# The runtime key is embedded in the pub param; --runtime-key forces the alg
+# param on and drops keyid.
 py "$ex/token-request.http" \
     --key "$ex/token-key.jwk" \
     --covered @method @target-uri content-digest authorization \
@@ -29,12 +29,26 @@ py "$ex/token-request.http" \
     --out-digest "$ex/content-digest.hdr" \
     --out-signed "$ex/token-request-signed.http"
 
-# --- Presenting the bound token (Ed25519, keyid only) ----------------------
-# #7 (also reused verbatim for #8). Token is already bound, so no key is
-# embedded here.
+# --- Token request (pre-registered Ed25519 key) ----------------------------
+# The key is selected by keyid from the client's registered key set, so no
+# alg or pub parameter appears; the algorithm comes from the JWK.
+py "$ex/token-request.http" \
+    --key "$ex/token-key.jwk" \
+    --key-id j-0Ny45NWmqGq6GQ \
+    --covered @method @target-uri content-digest authorization \
+    --content-digest \
+    --tag httpsig-oauth-token-request \
+    --nonce b3k2pp5k7z-50gnX1b06 \
+    --created 1618884473 \
+    --out-signed "$ex/token-request-prereg-signed.http"
+
+# --- Presenting the bound token (Ed25519) ----------------------------------
+# #7 (also reused verbatim for #8). The token is already bound, so neither the
+# key nor an identifier for it appears on the wire.
 py "$ex/rs-request.http" \
     --key "$ex/token-key.jwk" \
     --covered @method @target-uri authorization \
+    --no-keyid \
     --tag httpsig-oauth \
     --nonce k9Jyxempel2305Nmx7Rk \
     --created 1776650875 \
@@ -46,6 +60,7 @@ py "$ex/rs-request.http" \
     --key "$ex/test-key-ecdsa-p256.pem" \
     --key-id test-key-ecdsa-p256 \
     --covered @method @target-uri authorization \
+    --no-keyid \
     --tag httpsig-oauth \
     --nonce k9Jyxempel2305Nmx7Rk \
     --created 1776650875 \

tools/gensig.py

@@ -70,7 +70,8 @@ def _wrap_at_column(text: str, max_len: int) -> str:
     indent = CONTINUATION_INDENT
     lines = []
     while len(text) > max_len:
-        bp = _adjust_for_short_tail(max_len, text)
+        # -1 leaves room for the trailing "\" that joins the fold
+        bp = _adjust_for_short_tail(max_len - 1, text)
         if bp >= len(text):
             break  # single trailing character: don't break
         lines.append(text[:bp])
@@ -142,7 +143,8 @@ def wrap_structured_field(line: str, max_len: int = 69) -> str:
     indent = CONTINUATION_INDENT
     parts = []
     while len(line) > max_len:
-        bp = _adjust_for_short_tail(_find_structured_break(line, max_len), line)
+        # -1 leaves room for the trailing "\" that joins the fold
+        bp = _adjust_for_short_tail(_find_structured_break(line, max_len - 1), line)
         if bp >= len(line):
             break  # single trailing character: don't break
         parts.append(line[:bp])
@@ -479,30 +481,23 @@ def parse_http_request(text: str) -> HTTPRequest:
 # ---------------------------------------------------------------------------
 
 def runtime_key_params(public_pem: bytes, algorithm: type) -> "collections.OrderedDict":
-    """Map a public key into HTTP Message Signature parameters per {#embed-keys}.
+    """Map a public key into the `pub` signature parameter per {#embed-keys}.
 
     Returns an OrderedDict of parameter name -> bytes (serialized as a Byte
-    Sequence by http_sfv). Covers EC (pub_key_x/pub_key_y), Ed25519
-    (pub_key_a), and RSA (pub_key_n/pub_key_e).
+    Sequence by http_sfv). EC keys use the SEC1 uncompressed point form
+    (0x04 || X || Y); Ed25519 uses the raw 32-octet public key A. RSA is out
+    of scope for the inline representation.
     """
-    from cryptography.hazmat.primitives.asymmetric import ec, ed25519, rsa
+    from cryptography.hazmat.primitives.asymmetric import ec, ed25519
 
     pub = load_pem_public_key(public_pem)
     params: "collections.OrderedDict[str, bytes]" = collections.OrderedDict()
 
-    if algorithm in (sig_algorithms.ECDSA_P256_SHA256,) or isinstance(pub, ec.EllipticCurvePublicKey):
-        numbers = pub.public_numbers()
-        size = (pub.curve.key_size + 7) // 8
-        params["pub_key_x"] = numbers.x.to_bytes(size, "big")
-        params["pub_key_y"] = numbers.y.to_bytes(size, "big")
+    if isinstance(pub, ec.EllipticCurvePublicKey):
+        params["pub"] = pub.public_bytes(Encoding.X962,
+                                         PublicFormat.UncompressedPoint)
     elif isinstance(pub, ed25519.Ed25519PublicKey):
-        params["pub_key_a"] = pub.public_bytes(Encoding.Raw, PublicFormat.Raw)
-    elif isinstance(pub, rsa.RSAPublicKey):
-        numbers = pub.public_numbers()
-        n_len = (numbers.n.bit_length() + 7) // 8
-        e_len = (numbers.e.bit_length() + 7) // 8
-        params["pub_key_n"] = numbers.n.to_bytes(n_len, "big")
-        params["pub_key_e"] = numbers.e.to_bytes(e_len, "big")
+        params["pub"] = pub.public_bytes(Encoding.Raw, PublicFormat.Raw)
     else:
         raise ValueError(f"Cannot embed public key of type {type(pub).__name__}")
 
@@ -515,15 +510,22 @@ class InspectableSigner(HTTPMessageSigner):
     If ``extra_params`` is set, those parameters are merged into every
     signature's parameters so they appear in Signature-Input and are covered
     by the signature base (used for runtime public-key embedding).
+
+    If ``drop_keyid`` is set, the keyid parameter the library always emits is
+    removed. The draft omits keyid for runtime key introduction and for token
+    presentation.
     """
 
     def __init__(self, *args, **kwargs):
         super().__init__(*args, **kwargs)
         self.last_sig_base: Optional[str] = None
         self.last_sig_elements: Optional[dict] = None
         self.extra_params: Optional[dict] = None
+        self.drop_keyid: bool = False
 
     def _build_signature_base(self, message, *, covered_component_ids, signature_params):
+        if self.drop_keyid:
+            signature_params.pop("keyid", None)
         if self.extra_params:
             signature_params.update(self.extra_params)
         result = super()._build_signature_base(
@@ -637,9 +639,11 @@ def build_arg_parser() -> argparse.ArgumentParser:
     p.add_argument("--include-alg-param", action="store_true",
                    help="Include the 'alg' parameter in Signature-Input")
     p.add_argument("--runtime-key", action="store_true",
-                   help="Embed the public key as signature parameters per the "
-                        "draft's Embedding a Public Key Value section "
-                        "(pub_key_*). Implies --include-alg-param.")
+                   help="Embed the public key in the 'pub' signature parameter "
+                        "per the draft's Embedding a Public Key Value section. "
+                        "Implies --include-alg-param and --no-keyid.")
+    p.add_argument("--no-keyid", action="store_true",
+                   help="Omit the 'keyid' parameter from Signature-Input")
     p.add_argument("--output", "-o", type=Path, default=None,
                    help="Output file (default: stdout)")
     p.add_argument("--width", "-w", type=int, default=69,
@@ -693,6 +697,11 @@ def main() -> None:
         key_resolver=key.as_resolver(),
     )
 
+    # The draft omits keyid whenever the key is not identified by reference:
+    # runtime key introduction carries pub instead, and presentation to the RS
+    # relies on the access token binding.
+    signer.drop_keyid = args.no_keyid or args.runtime_key
+
     if args.runtime_key:
         if key.public_pem is None:
             raise SystemExit("--runtime-key requires a key with public material")