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fix(x402): base-sepolia USDC EIP-712 domain name is "USDC", with offline guards
Base-Sepolia USDC (FiatTokenV2_2) signs its EIP-712 domain under name "USDC", not the mainnet "USD Coin" — verified: the on-chain DOMAIN_SEPARATOR() equals the domain built with "USDC". chains.go advertised "USD Coin", so the 402 a standalone seller emits made every host-side EIP-3009 signature fail a REAL facilitator (the cluster buyer buy.py and the catalog renderer already hardcoded "USDC", which is why only host-side buyers broke and the stub facilitator masked it). Two offline guards so it cannot recur — the recurring root cause was the name being hand-maintained in several independent places that drifted: TestUSDCDomainSeparatorsMatchOnChain pins each chain to its captured on-chain DOMAIN_SEPARATOR (via the same apitypes path the signer uses); TestCatalogUSDCMatchesVerifierChain pins the catalog renderer and the x402 registry to each other. Surfaced by flows/p2p-surface-smoke.sh against a live x402-rs facilitator.
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3 files changed

Lines changed: 135 additions & 6 deletions

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‎internal/serviceoffercontroller/usdc_domain_consistency_test.go‎

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package serviceoffercontroller
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import (
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"testing"
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"github.com/ObolNetwork/obol-stack/internal/x402"
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)
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// TestCatalogUSDCMatchesVerifierChain guards against the EIP-712 USDC domain
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// name (and version) drifting between the TWO independent Go sources that must
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// agree: the catalog renderer's defaultUSDCForNetwork (what /api/services.json
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// advertises) and x402's chain registry (what the 402 advertises and the buyer
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// signs under). They disagreed once — chains.go said "USD Coin" for base-sepolia
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// while the catalog already said the correct "USDC" — which silently broke
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// host-side EIP-3009 signatures against a real facilitator and kept recurring
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// because each source was hand-maintained.
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//
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// x402's TestUSDCDomainSeparatorsMatchOnChain pins the registry to the on-chain
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// value; this test pins the catalog and the registry to EACH OTHER, so a future
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// edit to one without the other fails offline at `go test`.
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func TestCatalogUSDCMatchesVerifierChain(t *testing.T) {
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for _, net := range []string{"base", "base-sepolia", "ethereum"} {
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t.Run(net, func(t *testing.T) {
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cat, ok := defaultUSDCForNetwork(net)
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if !ok || cat.EIP712Domain == nil {
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t.Fatalf("catalog has no USDC EIP-712 domain for %q", net)
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}
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ci, err := x402.ResolveChainInfo(net)
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if err != nil {
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t.Fatalf("x402.ResolveChainInfo(%q): %v", net, err)
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}
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if cat.EIP712Domain.Name != ci.EIP3009Name {
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t.Errorf("%s EIP-712 name drift: catalog=%q vs verifier=%q — both must equal the on-chain token domain (base-sepolia is \"USDC\", mainnet is \"USD Coin\")",
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net, cat.EIP712Domain.Name, ci.EIP3009Name)
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}
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if cat.EIP712Domain.Version != ci.EIP3009Version {
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t.Errorf("%s EIP-712 version drift: catalog=%q vs verifier=%q",
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net, cat.EIP712Domain.Version, ci.EIP3009Version)
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}
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})
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}
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}

‎internal/x402/chains.go‎

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@@ -66,12 +66,19 @@ var (
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}
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ChainBaseSepolia = ChainInfo{
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Name: "base-sepolia",
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NetworkID: "base-sepolia",
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CAIP2Network: "eip155:84532",
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USDCAddress: "0x036CbD53842c5426634e7929541eC2318f3dCF7e",
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Decimals: 6,
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EIP3009Name: "USD Coin",
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Name: "base-sepolia",
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NetworkID: "base-sepolia",
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CAIP2Network: "eip155:84532",
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USDCAddress: "0x036CbD53842c5426634e7929541eC2318f3dCF7e",
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Decimals: 6,
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// Base-Sepolia USDC is FiatTokenV2_2 whose EIP-712 domain name is "USDC"
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// (verified: on-chain DOMAIN_SEPARATOR() == keccak of the domain built
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// with "USDC"), NOT the mainnet "USD Coin". Advertising "USD Coin" makes
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// every EIP-3009 signature fail FiatToken's SignatureChecker against a
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// REAL facilitator — the recurring base-sepolia "name" bug that the stub
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// facilitator silently masked. TestUSDCDomainSeparatorsMatchOnChain pins
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// this so it can never regress.
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EIP3009Name: "USDC",
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EIP3009Version: "2",
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}
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‎internal/x402/chains_domain_test.go‎

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package x402
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import (
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"testing"
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gethmath "github.com/ethereum/go-ethereum/common/math"
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"github.com/ethereum/go-ethereum/signer/core/apitypes"
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)
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// goldenUSDCDomainSeparators pins each chain's USDC EIP-712 DOMAIN_SEPARATOR as
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// read from the live token contract:
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//
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// cast call <USDCAddress> "DOMAIN_SEPARATOR()(bytes32)" --rpc-url <chain-rpc>
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//
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// The domain separator is a deterministic function of the four fields a buyer
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// signs under — (name, version, chainId, verifyingContract). Pinning it turns
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// the recurring base-sepolia "USD Coin" vs "USDC" EIP-712 *name* bug into an
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// OFFLINE `go test` failure: a wrong name yields a different separator, so an
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// EIP-3009 signature built from this registry would be rejected by a real
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// facilitator (FiatToken's SignatureChecker). The bug bit ~repeatedly because
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// nothing tied the hand-maintained name string to the on-chain domain; this
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// closes that loop. Capture and add a chain's value here as you verify it.
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var goldenUSDCDomainSeparators = []struct {
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name string
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chain ChainInfo
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golden string
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}{
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// Base-Sepolia USDC is FiatTokenV2_2 — domain name "USDC", NOT "USD Coin".
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{"base-sepolia", ChainBaseSepolia, "0x71f17a3b2ff373b803d70a5a07c046c1a2bc8e89c09ef722fcb047abe94c9818"},
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}
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func TestUSDCDomainSeparatorsMatchOnChain(t *testing.T) {
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for _, tc := range goldenUSDCDomainSeparators {
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t.Run(tc.name, func(t *testing.T) {
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got, err := usdcDomainSeparator(tc.chain)
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if err != nil {
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t.Fatalf("compute domain separator: %v", err)
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}
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if got != tc.golden {
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t.Errorf("%s USDC EIP-712 domain separator = %s, want on-chain %s\n"+
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" registry has EIP3009Name=%q version=%q addr=%s — the name almost certainly\n"+
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" disagrees with the on-chain token domain (base-sepolia FiatTokenV2_2 is \"USDC\",\n"+
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" mainnet USDC is \"USD Coin\"). A real facilitator will reject signatures built here.",
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tc.name, got, tc.golden, tc.chain.EIP3009Name, tc.chain.EIP3009Version, tc.chain.USDCAddress)
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}
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})
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}
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}
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// usdcDomainSeparator computes the EIP-712 domain separator a buyer signs under
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// for ci's USDC via the SAME apitypes path SignExactPayment uses, so this guards
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// the exact value that reaches a facilitator — not a re-derivation that could
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// drift from the signer.
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func usdcDomainSeparator(ci ChainInfo) (string, error) {
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chainID, err := chainIDFromNetwork(ci.CAIP2Network)
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if err != nil {
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return "", err
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}
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td := apitypes.TypedData{
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Types: apitypes.Types{
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"EIP712Domain": {
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{Name: "name", Type: "string"},
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{Name: "version", Type: "string"},
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{Name: "chainId", Type: "uint256"},
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{Name: "verifyingContract", Type: "address"},
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},
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},
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Domain: apitypes.TypedDataDomain{
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Name: ci.EIP3009Name,
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Version: ci.EIP3009Version,
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ChainId: gethmath.NewHexOrDecimal256(chainID),
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VerifyingContract: ci.USDCAddress,
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},
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}
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sep, err := td.HashStruct("EIP712Domain", td.Domain.Map())
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if err != nil {
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return "", err
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}
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return sep.String(), nil
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}

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