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authorRasmus Dahlberg <rasmus.dahlberg@kau.se>2020-10-27 16:22:13 +0100
committerRasmus Dahlberg <rasmus.dahlberg@kau.se>2020-10-27 16:22:13 +0100
commit13dd306e69b26ab8b7aedcd6ed915df4b6672a01 (patch)
tree4b2b5456f5c979ce13f6419b676af165bb55fe3d
parentdd19521190f39a8b1704adb724f5f812040f91e4 (diff)
isolated chain and signature verification
-rw-r--r--reqres.go41
-rw-r--r--x509.go35
2 files changed, 46 insertions, 30 deletions
diff --git a/reqres.go b/reqres.go
index a725363..e1f97ee 100644
--- a/reqres.go
+++ b/reqres.go
@@ -4,8 +4,6 @@ import (
"fmt"
"strconv"
- "crypto/ecdsa"
- "crypto/rsa"
"crypto/x509"
"encoding/base64"
"encoding/json"
@@ -186,50 +184,33 @@ func VerifyAddEntryRequest(ld *LogParameters, r AddEntryRequest) ([]byte, []byte
leaf, err := tls.Marshal(item)
if err != nil {
return nil, nil, fmt.Errorf("failed tls marshaling StItem: %v", err)
- }
+ } // leaf is the serialized data that should be added to the tree
- certificate, err := base64.StdEncoding.DecodeString(r.Certificate)
+ c, err := base64.StdEncoding.DecodeString(r.Certificate)
if err != nil {
return nil, nil, fmt.Errorf("failed decoding certificate: %v", err)
}
- c, err := x509.ParseCertificate(certificate)
+ certificate, err := x509.ParseCertificate(c)
if err != nil {
return nil, nil, fmt.Errorf("failed decoding certificate: %v", err)
- }
- opts := x509.VerifyOptions{
- Roots: ld.AnchorPool,
- }
- chains, err := c.Verify(opts)
+ } // certificate is the end-entity certificate that signed leaf
+
+ chain, err := VerifyChain(ld, certificate)
if err != nil {
return nil, nil, fmt.Errorf("chain verification failed: %v", err)
- }
- if len(chains) == 0 {
- return nil, nil, fmt.Errorf("chain verification failed: no chain")
- }
- x509chain := chains[0]
+ } // chain is a valid path to some trust anchor
signature, err := base64.StdEncoding.DecodeString(r.Signature)
if err != nil {
return nil, nil, fmt.Errorf("failed decoding signature: %v", err)
}
+ if err := VerifySignature(leaf, signature, certificate); err != nil {
+ return nil, nil, fmt.Errorf("signature verification failed: %v", err)
+ } // signature is valid for certificate
- var algo x509.SignatureAlgorithm
- switch t := c.PublicKey.(type) {
- case *rsa.PublicKey:
- algo = x509.SHA256WithRSA
- case *ecdsa.PublicKey:
- algo = x509.ECDSAWithSHA256
- default:
- return nil, nil, fmt.Errorf("unsupported public key algorithm: %v", t)
- }
-
- if err := c.CheckSignature(algo, leaf, signature); err != nil {
- return nil, nil, fmt.Errorf("invalid signature: %v", err)
- }
// TODO: update doc of what signature "is", i.e., w/e x509 does
// TODO: doc in markdown/api.md what signature schemes we expect
-
- appendix, err := tls.Marshal(NewAppendix(x509chain, signature))
+ appendix, err := tls.Marshal(NewAppendix(chain, signature))
if err != nil {
return nil, nil, fmt.Errorf("failed tls marshaling appendix: %v", err)
}
diff --git a/x509.go b/x509.go
index cdcd523..4e5a4d6 100644
--- a/x509.go
+++ b/x509.go
@@ -3,6 +3,8 @@ package stfe
import (
"fmt"
+ "crypto/ecdsa"
+ "crypto/rsa"
"crypto/x509"
"encoding/pem"
"io/ioutil"
@@ -41,3 +43,36 @@ func LoadTrustAnchors(path string) ([]*x509.Certificate, *x509.CertPool, error)
}
return anchors, pool, nil
}
+
+func VerifyChain(ld *LogParameters, certificate *x509.Certificate) ([]*x509.Certificate, error) {
+ opts := x509.VerifyOptions{
+ Roots: ld.AnchorPool,
+ KeyUsages: []x509.ExtKeyUsage{x509.ExtKeyUsageAny}, // TODO: move to ld
+ } // TODO: add intermediates
+
+ chains, err := certificate.Verify(opts)
+ if err != nil {
+ return nil, fmt.Errorf("chain verification failed: %v", err)
+ }
+ if len(chains) == 0 {
+ return nil, fmt.Errorf("chain verification failed: no chain")
+ }
+ return chains[0], nil // if we found multiple paths just pick the first one
+}
+
+func VerifySignature(leaf, signature []byte, certificate *x509.Certificate) error {
+ var algo x509.SignatureAlgorithm
+ switch t := certificate.PublicKey.(type) {
+ case *rsa.PublicKey:
+ algo = x509.SHA256WithRSA
+ case *ecdsa.PublicKey:
+ algo = x509.ECDSAWithSHA256
+ default:
+ return fmt.Errorf("unsupported public key algorithm: %v", t)
+ }
+
+ if err := certificate.CheckSignature(algo, leaf, signature); err != nil {
+ return fmt.Errorf("invalid signature: %v", err)
+ }
+ return nil
+}