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zeekay
046717e828
Red-team review found a real fail-open: Go's Verify ACCEPTED a cap with an unknown caveat kind (e.g. 0x42424242) while the Rust verifier REJECTED the identical bytes. A caveat is a RESTRICTION; accepting an unrecognized one silently ignores a constraint the issuer intended (privilege escalation). SPEC §2.3 line 106 mandates fail-closed. Verify (and via it VerifyChain) now refuses kinds > CaveatNonceHash with ErrUnknownCaveat. +2 regression tests.
65 lines
2.1 KiB
Go
65 lines
2.1 KiB
Go
package cap
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import (
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"errors"
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"testing"
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)
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// TestUnknownCaveatKindFailsClosed pins SPEC §2.3 line 106: a verifier MUST
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// refuse a cap carrying an unknown CaveatKind (fail-closed). A caveat is a
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// restriction; an unrecognized one cannot be evaluated, so accepting the cap
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// would silently ignore a constraint the issuer intended.
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//
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// This was a real cross-language divergence found by red-team review: Go's
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// Verify formerly ACCEPTED an unknown caveat kind while the Rust verifier
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// REJECTED the identical bytes. Go now matches Rust + the spec.
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func TestUnknownCaveatKindFailsClosed(t *testing.T) {
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signer := mustSigner(t)
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const unknownKind = 0x42424242 // NOT in {0x00..0x09}
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c, err := Issue(Issuance{
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Kind: uint32(KindKMSAccess),
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Permissions: 0xFF,
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IssuedAt: 1700000000,
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ExpiresAt: 2000000000,
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Caveats: []Caveat{
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{Kind: CaveatKind(unknownKind), Value: []byte("must-not-be-ignored")},
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},
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}, signer)
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if err != nil {
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t.Fatalf("Issue: %v", err)
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}
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v := Verifier{IssuerKey: issuerKeyFn(signer)}
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if verr := v.Verify(c, 1700000001); !errors.Is(verr, ErrUnknownCaveat) {
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t.Fatalf("Verify: want ErrUnknownCaveat (fail-closed), got %v", verr)
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}
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// VerifyChain must reject it too (it calls Verify on the leaf + each link).
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if cerr := v.VerifyChain(c, nil, 0x01, c.Target(), c.Holder(), 1700000001); !errors.Is(cerr, ErrUnknownCaveat) {
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t.Fatalf("VerifyChain: want ErrUnknownCaveat, got %v", cerr)
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}
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}
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// TestKnownCaveatKindsAccepted is the positive control: every defined kind
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// (0x00..0x09) must still pass the kind gate.
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func TestKnownCaveatKindsAccepted(t *testing.T) {
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signer := mustSigner(t)
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for kind := CaveatExpiresAt; kind <= CaveatNonceHash; kind++ {
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c, err := Issue(Issuance{
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Kind: uint32(KindKMSAccess),
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Permissions: 0xFF,
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IssuedAt: 1700000000,
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ExpiresAt: 2000000000,
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Caveats: []Caveat{{Kind: kind, Value: []byte("ok")}},
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}, signer)
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if err != nil {
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t.Fatalf("Issue kind %#x: %v", kind, err)
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}
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v := Verifier{IssuerKey: issuerKeyFn(signer)}
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if err := v.Verify(c, 1700000001); errors.Is(err, ErrUnknownCaveat) {
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t.Fatalf("Verify rejected KNOWN caveat kind %#x as unknown", kind)
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}
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}
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}
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