[wip] do a little validation of commit event blocks

Cargo.lock

@@ -189,12 +189,24 @@ version = "0.2.11"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "4cbbc9d0964165b47557570cce6c952866c2678457aca742aafc9fb771d30270"
 
+[[package]]
+name = "base16ct"
+version = "0.2.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "4c7f02d4ea65f2c1853089ffd8d2787bdbc63de2f0d29dedbcf8ccdfa0ccd4cf"
+
 [[package]]
 name = "base64"
 version = "0.21.7"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "9d297deb1925b89f2ccc13d7635fa0714f12c87adce1c75356b39ca9b7178567"
 
+[[package]]
+name = "base64ct"
+version = "1.6.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "8c3c1a368f70d6cf7302d78f8f7093da241fb8e8807c05cc9e51a125895a6d5b"
+
 [[package]]
 name = "bindgen"
 version = "0.69.5"
@@ -288,17 +300,23 @@ dependencies = [
  "atrium-api",
  "bytes",
  "clap",
+ "ecdsa",
  "fastwebsockets",
  "http-body-util",
  "hyper",
  "hyper-util",
  "ipld-core",
+ "iroh-car",
+ "k256",
+ "multibase",
+ "p256",
  "pin-project-lite",
  "qstring",
  "rustls",
  "serde",
  "serde_ipld_dagcbor",
  "serde_json",
+ "sha2",
  "sled",
  "tokio",
  "tokio-rustls",
@@ -349,7 +367,7 @@ dependencies = [
  "multihash",
  "serde",
  "serde_bytes",
- "unsigned-varint",
+ "unsigned-varint 0.8.0",
 ]
 
 [[package]]
@@ -418,6 +436,12 @@ version = "1.0.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "5b63caa9aa9397e2d9480a9b13673856c78d8ac123288526c37d7839f2a86990"
 
+[[package]]
+name = "const-oid"
+version = "0.9.6"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "c2459377285ad874054d797f3ccebf984978aa39129f6eafde5cdc8315b612f8"
+
 [[package]]
 name = "core-foundation-sys"
 version = "0.8.7"
@@ -466,6 +490,18 @@ version = "0.8.20"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "22ec99545bb0ed0ea7bb9b8e1e9122ea386ff8a48c0922e43f36d45ab09e0e80"
 
+[[package]]
+name = "crypto-bigint"
+version = "0.5.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "0dc92fb57ca44df6db8059111ab3af99a63d5d0f8375d9972e319a379c6bab76"
+dependencies = [
+ "generic-array",
+ "rand_core",
+ "subtle",
+ "zeroize",
+]
+
 [[package]]
 name = "crypto-common"
 version = "0.1.6"
@@ -502,6 +538,17 @@ dependencies = [
  "syn 1.0.109",
 ]
 
+[[package]]
+name = "der"
+version = "0.7.9"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "f55bf8e7b65898637379c1b74eb1551107c8294ed26d855ceb9fd1a09cfc9bc0"
+dependencies = [
+ "const-oid",
+ "pem-rfc7468",
+ "zeroize",
+]
+
 [[package]]
 name = "digest"
 version = "0.10.7"
@@ -509,7 +556,9 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "9ed9a281f7bc9b7576e61468ba615a66a5c8cfdff42420a70aa82701a3b1e292"
 dependencies = [
  "block-buffer",
+ "const-oid",
  "crypto-common",
+ "subtle",
 ]
 
 [[package]]
@@ -518,12 +567,46 @@ version = "1.0.5"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "92773504d58c093f6de2459af4af33faa518c13451eb8f2b5698ed3d36e7c813"
 
+[[package]]
+name = "ecdsa"
+version = "0.16.9"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "ee27f32b5c5292967d2d4a9d7f1e0b0aed2c15daded5a60300e4abb9d8020bca"
+dependencies = [
+ "der",
+ "digest",
+ "elliptic-curve",
+ "rfc6979",
+ "signature",
+ "spki",
+]
+
 [[package]]
 name = "either"
 version = "1.13.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "60b1af1c220855b6ceac025d3f6ecdd2b7c4894bfe9cd9bda4fbb4bc7c0d4cf0"
 
+[[package]]
+name = "elliptic-curve"
+version = "0.13.8"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "b5e6043086bf7973472e0c7dff2142ea0b680d30e18d9cc40f267efbf222bd47"
+dependencies = [
+ "base16ct",
+ "crypto-bigint",
+ "digest",
+ "ff",
+ "generic-array",
+ "group",
+ "pem-rfc7468",
+ "pkcs8",
+ "rand_core",
+ "sec1",
+ "subtle",
+ "zeroize",
+]
+
 [[package]]
 name = "equivalent"
 version = "1.0.1"
@@ -560,6 +643,16 @@ dependencies = [
  "utf-8",
 ]
 
+[[package]]
+name = "ff"
+version = "0.13.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "ded41244b729663b1e574f1b4fb731469f69f79c17667b5d776b16cda0479449"
+dependencies = [
+ "rand_core",
+ "subtle",
+]
+
 [[package]]
 name = "fnv"
 version = "1.0.7"
@@ -591,6 +684,21 @@ version = "1.3.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "42703706b716c37f96a77aea830392ad231f44c9e9a67872fa5548707e11b11c"
 
+[[package]]
+name = "futures"
+version = "0.3.31"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "65bc07b1a8bc7c85c5f2e110c476c7389b4554ba72af57d8445ea63a576b0876"
+dependencies = [
+ "futures-channel",
+ "futures-core",
+ "futures-executor",
+ "futures-io",
+ "futures-sink",
+ "futures-task",
+ "futures-util",
+]
+
 [[package]]
 name = "futures-channel"
 version = "0.3.31"
@@ -598,6 +706,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "2dff15bf788c671c1934e366d07e30c1814a8ef514e1af724a602e8a2fbe1b10"
 dependencies = [
  "futures-core",
+ "futures-sink",
 ]
 
 [[package]]
@@ -606,6 +715,34 @@ version = "0.3.31"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "05f29059c0c2090612e8d742178b0580d2dc940c837851ad723096f87af6663e"
 
+[[package]]
+name = "futures-executor"
+version = "0.3.31"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "1e28d1d997f585e54aebc3f97d39e72338912123a67330d723fdbb564d646c9f"
+dependencies = [
+ "futures-core",
+ "futures-task",
+ "futures-util",
+]
+
+[[package]]
+name = "futures-io"
+version = "0.3.31"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "9e5c1b78ca4aae1ac06c48a526a655760685149f0d465d21f37abfe57ce075c6"
+
+[[package]]
+name = "futures-macro"
+version = "0.3.31"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "162ee34ebcb7c64a8abebc059ce0fee27c2262618d7b60ed8faf72fef13c3650"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "syn 2.0.89",
+]
+
 [[package]]
 name = "futures-sink"
 version = "0.3.31"
@@ -624,10 +761,16 @@ version = "0.3.31"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "9fa08315bb612088cc391249efdc3bc77536f16c91f6cf495e6fbe85b20a4a81"
 dependencies = [
+ "futures-channel",
  "futures-core",
+ "futures-io",
+ "futures-macro",
+ "futures-sink",
  "futures-task",
+ "memchr",
  "pin-project-lite",
  "pin-utils",
+ "slab",
 ]
 
 [[package]]
@@ -647,6 +790,7 @@ checksum = "85649ca51fd72272d7821adaf274ad91c288277713d9c18820d8499a7ff69e9a"
 dependencies = [
  "typenum",
  "version_check",
+ "zeroize",
 ]
 
 [[package]]
@@ -672,6 +816,17 @@ version = "0.3.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "d2fabcfbdc87f4758337ca535fb41a6d701b65693ce38287d856d1674551ec9b"
 
+[[package]]
+name = "group"
+version = "0.13.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "f0f9ef7462f7c099f518d754361858f86d8a07af53ba9af0fe635bbccb151a63"
+dependencies = [
+ "ff",
+ "rand_core",
+ "subtle",
+]
+
 [[package]]
 name = "h2"
 version = "0.4.7"
@@ -709,6 +864,15 @@ version = "0.3.9"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "d231dfb89cfffdbc30e7fc41579ed6066ad03abda9e567ccafae602b97ec5024"
 
+[[package]]
+name = "hmac"
+version = "0.12.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "6c49c37c09c17a53d937dfbb742eb3a961d65a994e6bcdcf37e7399d0cc8ab5e"
+dependencies = [
+ "digest",
+]
+
 [[package]]
 name = "home"
 version = "0.5.9"
@@ -856,6 +1020,22 @@ dependencies = [
  "serde_bytes",
 ]
 
+[[package]]
+name = "iroh-car"
+version = "0.5.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "cb7f8cd4cb9aa083fba8b52e921764252d0b4dcb1cd6d120b809dbfe1106e81a"
+dependencies = [
+ "anyhow",
+ "cid",
+ "futures",
+ "serde",
+ "serde_ipld_dagcbor",
+ "thiserror",
+ "tokio",
+ "unsigned-varint 0.7.2",
+]
+
 [[package]]
 name = "is_terminal_polyfill"
 version = "1.70.1"
@@ -895,6 +1075,20 @@ dependencies = [
  "wasm-bindgen",
 ]
 
+[[package]]
+name = "k256"
+version = "0.13.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "f6e3919bbaa2945715f0bb6d3934a173d1e9a59ac23767fbaaef277265a7411b"
+dependencies = [
+ "cfg-if",
+ "ecdsa",
+ "elliptic-curve",
+ "once_cell",
+ "sha2",
+ "signature",
+]
+
 [[package]]
 name = "langtag"
 version = "0.3.4"
@@ -1015,7 +1209,7 @@ checksum = "cc41f430805af9d1cf4adae4ed2149c759b877b01d909a1f40256188d09345d2"
 dependencies = [
  "core2",
  "serde",
- "unsigned-varint",
+ "unsigned-varint 0.8.0",
 ]
 
 [[package]]
@@ -1068,6 +1262,18 @@ version = "0.1.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "b15813163c1d831bf4a13c3610c05c0d03b39feb07f7e09fa234dac9b15aaf39"
 
+[[package]]
+name = "p256"
+version = "0.13.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "c9863ad85fa8f4460f9c48cb909d38a0d689dba1f6f6988a5e3e0d31071bcd4b"
+dependencies = [
+ "ecdsa",
+ "elliptic-curve",
+ "primeorder",
+ "sha2",
+]
+
 [[package]]
 name = "parking_lot"
 version = "0.11.2"
@@ -1122,6 +1328,15 @@ version = "1.0.15"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "57c0d7b74b563b49d38dae00a0c37d4d6de9b432382b2892f0574ddcae73fd0a"
 
+[[package]]
+name = "pem-rfc7468"
+version = "0.7.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "88b39c9bfcfc231068454382784bb460aae594343fb030d46e9f50a645418412"
+dependencies = [
+ "base64ct",
+]
+
 [[package]]
 name = "percent-encoding"
 version = "2.3.1"
@@ -1160,6 +1375,16 @@ version = "0.1.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "8b870d8c151b6f2fb93e84a13146138f05d02ed11c7e7c54f8826aaaf7c9f184"
 
+[[package]]
+name = "pkcs8"
+version = "0.10.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "f950b2377845cebe5cf8b5165cb3cc1a5e0fa5cfa3e1f7f55707d8fd82e0a7b7"
+dependencies = [
+ "der",
+ "spki",
+]
+
 [[package]]
 name = "ppv-lite86"
 version = "0.2.20"
@@ -1179,6 +1404,15 @@ dependencies = [
  "syn 2.0.89",
 ]
 
+[[package]]
+name = "primeorder"
+version = "0.13.6"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "353e1ca18966c16d9deb1c69278edbc5f194139612772bd9537af60ac231e1e6"
+dependencies = [
+ "elliptic-curve",
+]
+
 [[package]]
 name = "proc-macro2"
 version = "1.0.92"
@@ -1298,6 +1532,16 @@ version = "0.8.5"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "2b15c43186be67a4fd63bee50d0303afffcef381492ebe2c5d87f324e1b8815c"
 
+[[package]]
+name = "rfc6979"
+version = "0.4.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "f8dd2a808d456c4a54e300a23e9f5a67e122c3024119acbfd73e3bf664491cb2"
+dependencies = [
+ "hmac",
+ "subtle",
+]
+
 [[package]]
 name = "ring"
 version = "0.17.8"
@@ -1383,6 +1627,20 @@ version = "1.2.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "94143f37725109f92c262ed2cf5e59bce7498c01bcc1502d7b9afe439a4e9f49"
 
+[[package]]
+name = "sec1"
+version = "0.7.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d3e97a565f76233a6003f9f5c54be1d9c5bdfa3eccfb189469f11ec4901c47dc"
+dependencies = [
+ "base16ct",
+ "der",
+ "generic-array",
+ "pkcs8",
+ "subtle",
+ "zeroize",
+]
+
 [[package]]
 name = "serde"
 version = "1.0.215"
@@ -1460,6 +1718,17 @@ dependencies = [
  "digest",
 ]
 
+[[package]]
+name = "sha2"
+version = "0.10.8"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "793db75ad2bcafc3ffa7c68b215fee268f537982cd901d132f89c6343f3a3dc8"
+dependencies = [
+ "cfg-if",
+ "cpufeatures",
+ "digest",
+]
+
 [[package]]
 name = "sharded-slab"
 version = "0.1.7"
@@ -1484,6 +1753,16 @@ dependencies = [
  "libc",
 ]
 
+[[package]]
+name = "signature"
+version = "2.2.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "77549399552de45a898a580c1b41d445bf730df867cc44e6c0233bbc4b8329de"
+dependencies = [
+ "digest",
+ "rand_core",
+]
+
 [[package]]
 name = "simdutf8"
 version = "0.1.5"
@@ -1538,6 +1817,16 @@ version = "0.9.8"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "6980e8d7511241f8acf4aebddbb1ff938df5eebe98691418c4468d0b72a96a67"
 
+[[package]]
+name = "spki"
+version = "0.7.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d91ed6c858b01f942cd56b37a94b3e0a1798290327d1236e4d9cf4eaca44d29d"
+dependencies = [
+ "base64ct",
+ "der",
+]
+
 [[package]]
 name = "strsim"
 version = "0.11.1"
@@ -1751,6 +2040,12 @@ version = "1.0.14"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "adb9e6ca4f869e1180728b7950e35922a7fc6397f7b641499e8f3ef06e50dc83"
 
+[[package]]
+name = "unsigned-varint"
+version = "0.7.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "6889a77d49f1f013504cec6bf97a2c730394adedaeb1deb5ea08949a50541105"
+
 [[package]]
 name = "unsigned-varint"
 version = "0.8.0"

Cargo.toml

@@ -8,17 +8,23 @@ anyhow = "1.0.93"
 atrium-api = { version = "0.24.8", default-features = false, features = ["tokio"] }
 bytes = { version = "1.8.0", features = ["serde"] }
 clap = { version = "4.5.21", features = ["derive"] }
+ecdsa = { version = "0.16.9", features = ["verifying"] }
 fastwebsockets = { version = "0.8.0", features = ["hyper", "unstable-split", "upgrade"] }
 http-body-util = "0.1.2"
 hyper = { version = "1.5.1", features = ["client", "http1", "http2", "server"] }
 hyper-util = { version = "0.1.10", features = ["tokio", "server", "client", "http1", "http2"] }
 ipld-core = "0.4.1"
+iroh-car = "0.5.1"
+k256 = "0.13.4"
+multibase = "0.9.1"
+p256 = "0.13.2"
 pin-project-lite = "0.2.15"
 qstring = "0.7.2"
 rustls = "0.23.18"
 serde = { version = "1.0.215", features = ["derive"] }
 serde_ipld_dagcbor = "0.6.1"
 serde_json = "1.0.133"
+sha2 = "0.10.8"
 sled = { version = "0.34.7", features = ["compression"] }
 tokio = { version = "1.41.1", features = ["full"] }
 tokio-rustls = "0.26.0"

src/lib.rs

@@ -3,6 +3,7 @@ pub use app_state::*;
 
 pub mod http;
 pub mod relay;
+pub mod repo;
 pub mod sequencer;
 pub mod tls;
 pub mod user;

src/main.rs

@@ -25,6 +25,9 @@ struct Args {
     /// did:plc directory HTTPS host. defaults to plc.directory if unset
     #[arg(long)]
     plc_resolver: Option<String>,
+
+    #[arg(long)]
+    drop_user_cache: bool,
 }
 
 #[tokio::main]
@@ -43,6 +46,10 @@ async fn main() -> Result<()> {
         .open()
         .expect("Failed to open database");
 
+    if args.drop_user_cache {
+        let _ = db.drop_tree("users");
+    }
+
     let (event_tx, event_rx) = mpsc::channel(128);
 
     let mut server = RelayServer::new(db, event_tx);

src/relay/index.rs

@@ -14,6 +14,7 @@ use tokio_rustls::rustls::pki_types::ServerName;
 
 use crate::{
     http::{body_empty, HttpBody},
+    repo::validate_commit,
     tls::open_tls_stream,
     user::{fetch_user, lookup_user},
     wire_proto::{StreamEvent, StreamEventHeader, StreamEventPayload},
@@ -116,6 +117,11 @@ impl DataServerSubscription {
             return Ok(None);
         }
 
+        if let Err(e) = validate_commit(&user, &event.data).await {
+            tracing::warn!(did = %user.did, seq = %event.seq, err = ?e, "dropping commit that did not pass validation");
+            return Ok(None);
+        };
+
         Ok(Some(StreamEventPayload::Commit(event)))
     }
 

src/repo/mod.rs

@@ -0,0 +1,119 @@
+use std::collections::BTreeMap;
+
+use anyhow::{bail, Context, Result};
+use atrium_api::com::atproto::sync::subscribe_repos::CommitData;
+use bytes::Bytes;
+use ecdsa::signature::Verifier;
+use ipld_core::cid::Cid;
+use iroh_car::CarReader;
+use serde::{Deserialize, Serialize};
+use sha2::{Digest, Sha256};
+
+use crate::user::User;
+
+#[derive(Debug, Serialize, Deserialize)]
+pub struct UnsignedCommitNode {
+    pub did: String,
+    pub version: u8,
+    pub prev: Option<Cid>,
+    pub rev: String,
+    pub data: Cid,
+}
+
+#[derive(Debug, Serialize, Deserialize)]
+pub struct SignedCommitNode {
+    #[serde(flatten)]
+    pub node: UnsignedCommitNode,
+    pub sig: Bytes,
+}
+
+pub async fn validate_commit(user: &User, commit: &CommitData) -> Result<()> {
+    let mut car_reader = CarReader::new(commit.blocks.as_slice()).await?;
+    let car_header = car_reader.header().clone();
+
+    let mut blocks = BTreeMap::new();
+    while let Some((cid, cbor)) = car_reader.next_block().await? {
+        let (hash_type, hash_digest, hash_len) = cid.hash().into_inner();
+        if hash_type != 0x12 || hash_len != 32 {
+            bail!(
+                "unexpected cid type {:?} (expected sha-256 [id 18] with 32 bytes)",
+                cid
+            )
+        }
+
+        let cid_display = cid.to_string_of_base(multibase::Base::Base32Lower)?;
+
+        let record_hash = Sha256::digest(&cbor);
+        if &hash_digest[..32] != record_hash.as_slice() {
+            bail!("cid doesn't match cbor hash: {}", &cid_display)
+        }
+
+        blocks.insert(cid, cbor);
+    }
+
+    /*
+    let block_cids = blocks
+        .keys()
+        .filter_map(|cid| cid.to_string_of_base(multibase::Base::Base32Lower).ok())
+        .collect::<Vec<_>>();
+    dbg!(block_cids);
+    let root_cids = car_header
+        .roots()
+        .iter()
+        .filter_map(|cid| cid.to_string_of_base(multibase::Base::Base32Lower).ok())
+        .collect::<Vec<_>>();
+    dbg!(root_cids);
+     */
+
+    let signing_key = user
+        .signing_key()
+        .context("couldn't find signing key for user")?;
+    let (_, signing_key) = multibase::decode(signing_key).unwrap();
+
+    for root in car_header.roots() {
+        let cid_display = root.to_string_of_base(multibase::Base::Base32Lower)?;
+
+        let Some(block) = blocks.get(root) else {
+            bail!("block did not exist: {}", &cid_display)
+        };
+        let commit: SignedCommitNode = serde_ipld_dagcbor::from_slice(block)
+            .context("couldn't deserialize signed commit object")?;
+
+        if commit.node.did != user.did {
+            bail!("did in car doesn't match repo did {}", &cid_display)
+        }
+
+        let unsigned_data = serde_ipld_dagcbor::to_vec(&commit.node)?;
+        if commit.sig.len() != 64 {
+            bail!(
+                "unexpected signature length {} (expected 64)",
+                commit.sig.len()
+            );
+        }
+        let r: [u8; 32] = commit.sig[..32].try_into().unwrap();
+        let s: [u8; 32] = commit.sig[32..].try_into().unwrap();
+
+        match signing_key[..2] {
+            [0xe7, 0x01] => {
+                let key = k256::ecdsa::VerifyingKey::from_sec1_bytes(&signing_key[2..]).unwrap();
+                let sig = k256::ecdsa::Signature::from_scalars(r, s).unwrap();
+                key.verify(&unsigned_data, &sig)
+                    .context("failed to verify k256")
+            }
+            [0x80, 0x24] => {
+                let key = p256::ecdsa::VerifyingKey::from_sec1_bytes(&signing_key[2..]).unwrap();
+                let sig = p256::ecdsa::Signature::from_scalars(r, s).unwrap();
+                key.verify(&unsigned_data, &sig)
+                    .context("failed to verify p256")
+            }
+            _ => Err(anyhow::anyhow!(
+                "unknown signing key format {:?}",
+                &signing_key[..2]
+            )),
+        }?;
+
+        // TODO: dfs for cid from commit.node.data, error if cid is not in any signed root
+    }
+
+    Ok(())
+}

src/user.rs

@@ -1,4 +1,4 @@
-use anyhow::{bail, Context, Result};
+use anyhow::{anyhow, bail, Context, Result};
 use atrium_api::did_doc::DidDocument;
 use bytes::Buf;
 use http_body_util::BodyExt;
@@ -20,6 +20,32 @@ pub struct User {
     pub pds: Option<String>,
     #[serde(default)]
     pub handle: Option<String>,
+    #[serde(default)]
+    pub did_document: Option<DidDocument>,
+}
+
+impl User {
+    pub fn signing_key(&self) -> Result<&str> {
+        let did_doc = self
+            .did_document
+            .as_ref()
+            .context("no did document stored for user")?;
+        let verification_methods = did_doc
+            .verification_method
+            .as_ref()
+            .context("no verification method in did document")?;
+
+        let target_id = format!("{}#atproto", &self.did);
+        let method = verification_methods
+            .iter()
+            .find(|m| m.id == target_id)
+            .context("couldn't find signing key")?;
+        let key = method
+            .public_key_multibase
+            .as_ref()
+            .context("publicKeyMultibase missing")?;
+        Ok(key)
+    }
 }
 
 fn create_user_from_did_doc(did_doc: DidDocument) -> Result<User> {
@@ -33,19 +59,24 @@ fn create_user_from_did_doc(did_doc: DidDocument) -> Result<User> {
 
     let handle = did_doc
         .also_known_as
-        .and_then(|v| v.into_iter().next())
+        .as_ref()
+        .and_then(|v| v.iter().next())
         .and_then(|s| s.strip_prefix("at://").map(str::to_string));
-    let did = did_doc.id;
+    let did = did_doc.id.clone();
 
     // TODO: check if handle resolves to did and fill none otherwise
 
-    let user = User { pds, did, handle };
+    let user = User {
+        pds,
+        did,
+        handle,
+        did_document: Some(did_doc),
+    };
 
     Ok(user)
 }
 
-pub async fn fetch_user(server: &RelayServer, did: &str) -> Result<User> {
+pub async fn fetch_did_doc(server: &RelayServer, did: &str) -> Result<DidDocument> {
-    tracing::debug!(%did, "fetching user");
     if did.starts_with("did:plc:") {
         let domain: &str = &server.plc_resolver;
 
@@ -79,10 +110,7 @@ pub async fn fetch_user(server: &RelayServer, did: &str) -> Result<User> {
         let did_doc = serde_json::from_reader::<_, DidDocument>(body.reader())
             .context("Failed to parse plc DID doc as JSON")?;
 
-        let user = create_user_from_did_doc(did_doc)?;
+        Ok(did_doc)
-        store_user(server, &user)?;
-
-        Ok(user)
     } else if let Some(domain) = did.strip_prefix("did:web:") {
         let tcp_stream = TcpStream::connect((domain, 443)).await?;
         let domain_tls: ServerName<'_> = ServerName::try_from(domain.to_string())?;
@@ -114,15 +142,21 @@ pub async fn fetch_user(server: &RelayServer, did: &str) -> Result<User> {
         let did_doc = serde_json::from_reader::<_, DidDocument>(body.reader())
             .context("Failed to parse did:web document as JSON")?;
 
-        let user = create_user_from_did_doc(did_doc)?;
+        Ok(did_doc)
-        store_user(server, &user)?;
-
-        Ok(user)
     } else {
         bail!("unknown did type {did}");
     }
 }
 
+pub async fn fetch_user(server: &RelayServer, did: &str) -> Result<User> {
+    tracing::debug!(%did, "fetching user");
+    let did_doc = fetch_did_doc(server, did).await?;
+    let user = create_user_from_did_doc(did_doc)?;
+    store_user(server, &user)?;
+
+    Ok(user)
+}
+
 pub async fn lookup_user(server: &RelayServer, did: &str) -> Result<User> {
     if let Some(cached_user) = server.db_users.get(did)? {
         let cached_user = serde_ipld_dagcbor::from_slice::<User>(&cached_user)?;