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Add the ability to specify certificate identity via a regular expression #236

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merged 2 commits into from
Jul 24, 2024
Merged

Add the ability to specify certificate identity via a regular expression #236

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7c0ed51
Add the ability to specify certificate identity via a regular expression
steiza Jul 18, 2024
777cbac
Create IssuerMatcher to mirror SubjectAlternativeNameMatcher
steiza Jul 23, 2024
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4 changes: 2 additions & 2 deletions cmd/conformance/main.go
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Original file line number Diff line number Diff line change
Expand Up @@ -284,7 +284,7 @@ func main() {

identityPolicies := []verify.PolicyOption{}
if *certOIDC != "" || *certSAN != "" {
certID, err := verify.NewShortCertificateIdentity(*certOIDC, *certSAN, "")
certID, err := verify.NewShortCertificateIdentity(*certOIDC, "", *certSAN, "")
if err != nil {
fmt.Println(err)
os.Exit(1)
Expand Down Expand Up @@ -333,7 +333,7 @@ func main() {
// Configure verification options
identityPolicies := []verify.PolicyOption{}
if *certOIDC != "" || *certSAN != "" {
certID, err := verify.NewShortCertificateIdentity(*certOIDC, *certSAN, "")
certID, err := verify.NewShortCertificateIdentity(*certOIDC, "", *certSAN, "")
if err != nil {
fmt.Println(err)
os.Exit(1)
Expand Down
2 changes: 1 addition & 1 deletion cmd/sigstore-go/main.go
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Expand Up @@ -120,7 +120,7 @@ func run() error {
verifierConfig = append(verifierConfig, verify.WithOnlineVerification())
}

certID, err := verify.NewShortCertificateIdentity(*expectedOIDIssuer, *expectedSAN, *expectedSANRegex)
certID, err := verify.NewShortCertificateIdentity(*expectedOIDIssuer, "", *expectedSAN, *expectedSANRegex)
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if err != nil {
return err
}
Expand Down
4 changes: 2 additions & 2 deletions docs/verification.md
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Expand Up @@ -95,7 +95,7 @@ Then, we need to prepare the expected artifact digest. Note that this option has
In this case, we also need to prepare the expected certificate identity. Note that this option has an alternative option `WithoutIdentitiesUnsafe`. This is a failsafe to ensure that the caller is aware that simply verifying the bundle is not enough, you must also verify the contents of the bundle against a specific identity. If your bundle was signed with a key, and thus does not have a certificate identity, a better choice is to use the `WithKey` option.

```go
certID, err := verify.NewShortCertificateIdentity("https://token.actions.githubusercontent.com", "", "^https://github.com/sigstore/sigstore-js/")
certID, err := verify.NewShortCertificateIdentity("https://token.actions.githubusercontent.com", "", "", "^https://github.com/sigstore/sigstore-js/")
if err != nil {
panic(err)
}
Expand Down Expand Up @@ -221,7 +221,7 @@ func main() {
panic(err)
}

certID, err := verify.NewShortCertificateIdentity("https://token.actions.githubusercontent.com", "", "^https://github.com/sigstore/sigstore-js/")
certID, err := verify.NewShortCertificateIdentity("https://token.actions.githubusercontent.com", "", "", "^https://github.com/sigstore/sigstore-js/")
if err != nil {
panic(err)
}
Expand Down
2 changes: 1 addition & 1 deletion examples/oci-image-verification/main.go
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Expand Up @@ -134,7 +134,7 @@ func run() error {
}

if *expectedOIDIssuer != "" || *expectedSAN != "" || *expectedSANRegex != "" {
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certID, err := verify.NewShortCertificateIdentity(*expectedOIDIssuer, *expectedSAN, *expectedSANRegex)
certID, err := verify.NewShortCertificateIdentity(*expectedOIDIssuer, "", *expectedSAN, *expectedSANRegex)
if err != nil {
return err
}
Expand Down
32 changes: 26 additions & 6 deletions pkg/verify/certificate_identity.go
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Expand Up @@ -30,6 +30,7 @@ type SubjectAlternativeNameMatcher struct {

type CertificateIdentity struct {
SubjectAlternativeName SubjectAlternativeNameMatcher `json:"subjectAlternativeName"`
IssuerRegexp *regexp.Regexp
certificate.Extensions
}

Expand Down Expand Up @@ -116,15 +117,19 @@ func (s SubjectAlternativeNameMatcher) Verify(actualCert certificate.Summary) er
return nil
}

func NewCertificateIdentity(sanMatcher SubjectAlternativeNameMatcher, extensions certificate.Extensions) (CertificateIdentity, error) {
func NewCertificateIdentity(sanMatcher SubjectAlternativeNameMatcher, issuerRegexp *regexp.Regexp, extensions certificate.Extensions) (CertificateIdentity, error) {
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if sanMatcher.SubjectAlternativeName == "" && sanMatcher.Regexp.String() == "" {
return CertificateIdentity{}, errors.New("when verifying a certificate identity, there must be subject alternative name criteria")
}

certID := CertificateIdentity{SubjectAlternativeName: sanMatcher, Extensions: extensions}
certID := CertificateIdentity{
SubjectAlternativeName: sanMatcher,
IssuerRegexp: issuerRegexp,
Extensions: extensions,
}

if certID.Issuer == "" {
return CertificateIdentity{}, errors.New("when verifying a certificate identity, the Issuer field can't be empty")
if certID.Issuer == "" && issuerRegexp == nil {
return CertificateIdentity{}, errors.New("when verifying a certificate identity, must specify Issuer criteria")
}

return certID, nil
Expand All @@ -133,13 +138,23 @@ func NewCertificateIdentity(sanMatcher SubjectAlternativeNameMatcher, extensions
// NewShortCertificateIdentity provides a more convenient way of initializing
// a CertificiateIdentity with a SAN and the Issuer OID extension. If you need
// to check more OID extensions, use NewCertificateIdentity instead.
func NewShortCertificateIdentity(issuer, sanValue, sanRegex string) (CertificateIdentity, error) {
func NewShortCertificateIdentity(issuer, issuerRegex, sanValue, sanRegex string) (CertificateIdentity, error) {
var r *regexp.Regexp
var err error

if issuerRegex != "" {
r, err = regexp.Compile(issuerRegex)
if err != nil {
return CertificateIdentity{}, err
}
}

sanMatcher, err := NewSANMatcher(sanValue, sanRegex)
if err != nil {
return CertificateIdentity{}, err
}

return NewCertificateIdentity(sanMatcher, certificate.Extensions{Issuer: issuer})
return NewCertificateIdentity(sanMatcher, r, certificate.Extensions{Issuer: issuer})
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}

// Verify verifies the CertificateIdentities, and if ANY of them match the cert,
Expand All @@ -164,5 +179,10 @@ func (c CertificateIdentity) Verify(actualCert certificate.Summary) error {
if err = c.SubjectAlternativeName.Verify(actualCert); err != nil {
return err
}
if c.IssuerRegexp != nil {
if !c.IssuerRegexp.MatchString(actualCert.Extensions.Issuer) {
return fmt.Errorf("expected issuer value to match regex \"%s\", got \"%s\"", c.IssuerRegexp.String(), actualCert.Extensions.Issuer)
}
}
return certificate.CompareExtensions(c.Extensions, actualCert.Extensions)
}
47 changes: 35 additions & 12 deletions pkg/verify/certificate_identity_test.go
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Expand Up @@ -15,6 +15,7 @@
package verify

import (
"regexp"
"testing"

"github.com/sigstore/sigstore-go/pkg/fulcio/certificate"
Expand All @@ -23,6 +24,7 @@ import (

const (
ActionsIssuerValue = "https://token.actions.githubusercontent.com"
ActionsIssuerRegex = "githubusercontent.com$"
SigstoreSanValue = "https://github.com/sigstore/sigstore-js/.github/workflows/release.yml@refs/heads/main"
SigstoreSanRegex = "^https://github.com/sigstore/sigstore-js/"
)
Expand Down Expand Up @@ -57,32 +59,39 @@ func TestCertificateIdentityVerify(t *testing.T) {
}

// First, let's test happy paths:
issuerOnlyID, _ := certIDForTesting("", "", ActionsIssuerValue, "")
issuerOnlyID, _ := certIDForTesting("", "", ActionsIssuerValue, "", "")
assert.NoError(t, issuerOnlyID.Verify(actualCert))

sanValueOnly, _ := certIDForTesting(SigstoreSanValue, "", "", "")
issuerOnlyRegex, _ := certIDForTesting("", "", "", ActionsIssuerRegex, "")
assert.NoError(t, issuerOnlyRegex.Verify(actualCert))

sanValueOnly, _ := certIDForTesting(SigstoreSanValue, "", "", "", "")
assert.NoError(t, sanValueOnly.Verify(actualCert))

sanRegexOnly, _ := certIDForTesting("", SigstoreSanRegex, "", "")
sanRegexOnly, _ := certIDForTesting("", SigstoreSanRegex, "", "", "")
assert.NoError(t, sanRegexOnly.Verify(actualCert))

// multiple values can be specified
sanRegexAndIssuer, _ := certIDForTesting("", SigstoreSanRegex, ActionsIssuerValue, "github-hosted")
sanRegexAndIssuer, _ := certIDForTesting("", SigstoreSanRegex, ActionsIssuerValue, "", "github-hosted")
assert.NoError(t, sanRegexAndIssuer.Verify(actualCert))

// unhappy paths:
// wrong issuer
sanRegexAndWrongIssuer, _ := certIDForTesting("", SigstoreSanRegex, "https://token.actions.example.com", "")
sanRegexAndWrongIssuer, _ := certIDForTesting("", SigstoreSanRegex, "https://token.actions.example.com", "", "")
errCompareExtensions := &certificate.ErrCompareExtensions{}
assert.ErrorAs(t, sanRegexAndWrongIssuer.Verify(actualCert), &errCompareExtensions)
assert.Equal(t, "expected Issuer to be \"https://token.actions.example.com\", got \"https://token.actions.githubusercontent.com\"", errCompareExtensions.Error())

// bad san regex
badRegex, _ := certIDForTesting("", "^badregex.*", "", "")
badRegex, _ := certIDForTesting("", "^badregex.*", "", "", "")
errSANValueRegexMismatch := &ErrSANValueRegexMismatch{}
assert.ErrorAs(t, badRegex.Verify(actualCert), &errSANValueRegexMismatch)
assert.Equal(t, "expected SAN value to match regex \"^badregex.*\", got \"https://github.com/sigstore/sigstore-js/.github/workflows/release.yml@refs/heads/main\"", errSANValueRegexMismatch.Error())

// bad issuer regex
badIssuerRegex, _ := certIDForTesting("", "", "", "^badregex$", "")
assert.Error(t, badIssuerRegex.Verify(actualCert))

// if we have an array of certIDs, only one needs to match
ci, err := CertificateIdentities{sanRegexAndWrongIssuer, sanRegexAndIssuer}.Verify(actualCert)
assert.NoError(t, err)
Expand All @@ -105,24 +114,38 @@ func TestCertificateIdentityVerify(t *testing.T) {
}

func TestThatCertIDsAreFullySpecified(t *testing.T) {
_, err := NewShortCertificateIdentity("", "", "")
_, err := NewShortCertificateIdentity("", "", "", "")
assert.Error(t, err)

_, err = NewShortCertificateIdentity("foobar", "", "", "")
assert.Error(t, err)

_, err = NewShortCertificateIdentity("foobar", "", "")
_, err = NewShortCertificateIdentity("", ActionsIssuerRegex, "", "")
assert.Error(t, err)

_, err = NewShortCertificateIdentity("", "", SigstoreSanRegex)
_, err = NewShortCertificateIdentity("", "", "", SigstoreSanRegex)
assert.Error(t, err)

_, err = NewShortCertificateIdentity("foobar", "", SigstoreSanRegex)
_, err = NewShortCertificateIdentity("foobar", "", "", SigstoreSanRegex)
assert.Nil(t, err)

_, err = NewShortCertificateIdentity("", ActionsIssuerRegex, "", SigstoreSanRegex)
assert.Nil(t, err)
}

func certIDForTesting(sanValue, sanRegex, issuer, runnerEnv string) (CertificateIdentity, error) {
func certIDForTesting(sanValue, sanRegex, issuer, issuerRegex, runnerEnv string) (CertificateIdentity, error) {
san, err := NewSANMatcher(sanValue, sanRegex)
if err != nil {
return CertificateIdentity{}, err
}

return CertificateIdentity{SubjectAlternativeName: san, Extensions: certificate.Extensions{Issuer: issuer, RunnerEnvironment: runnerEnv}}, nil
var r *regexp.Regexp
if issuerRegex != "" {
r, err = regexp.Compile(issuerRegex)
if err != nil {
return CertificateIdentity{}, err
}
}

return CertificateIdentity{SubjectAlternativeName: san, IssuerRegexp: r, Extensions: certificate.Extensions{Issuer: issuer, RunnerEnvironment: runnerEnv}}, nil
}
10 changes: 5 additions & 5 deletions pkg/verify/signed_entity_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -210,7 +210,7 @@ func TestEntityWithOthernameSan(t *testing.T) {
digest, err := hex.DecodeString("bc103b4a84971ef6459b294a2b98568a2bfb72cded09d4acd1e16366a401f95b")
assert.NoError(t, err)

certID, err := verify.NewShortCertificateIdentity("http://oidc.local:8080", "foo!oidc.local", "")
certID, err := verify.NewShortCertificateIdentity("http://oidc.local:8080", "", "foo!oidc.local", "")
assert.NoError(t, err)
res, err := v.Verify(entity, verify.NewPolicy(verify.WithArtifactDigest("sha256", digest), verify.WithCertificateIdentity(certID)))
assert.NoError(t, err)
Expand All @@ -220,7 +220,7 @@ func TestEntityWithOthernameSan(t *testing.T) {
assert.Equal(t, res.VerifiedIdentity.SubjectAlternativeName.SubjectAlternativeName, "foo!oidc.local")

// an email address doesn't verify
certID, err = verify.NewShortCertificateIdentity("http://oidc.local:8080", "foo@oidc.local", "")
certID, err = verify.NewShortCertificateIdentity("http://oidc.local:8080", "", "foo@oidc.local", "")
assert.NoError(t, err)
_, err = v.Verify(entity, verify.NewPolicy(verify.WithArtifactDigest("sha256", digest), verify.WithCertificateIdentity(certID)))
assert.Error(t, err)
Expand All @@ -235,7 +235,7 @@ func TestVerifyPolicyOptionErors(t *testing.T) {
verifier, err := verify.NewSignedEntityVerifier(tr, verify.WithTransparencyLog(1), verify.WithObserverTimestamps(1))
assert.Nil(t, err)

goodCertID, err := verify.NewShortCertificateIdentity(verify.ActionsIssuerValue, "", verify.SigstoreSanRegex)
goodCertID, err := verify.NewShortCertificateIdentity(verify.ActionsIssuerValue, "", "", verify.SigstoreSanRegex)
assert.Nil(t, err)

digest, _ := hex.DecodeString("46d4e2f74c4877316640000a6fdf8a8b59f1e0847667973e9859f774dd31b8f1e0937813b777fb66a2ac67d50540fe34640966eee9fc2ccca387082b4c85cd3c")
Expand Down Expand Up @@ -326,8 +326,8 @@ func TestEntitySignedByPublicGoodWithCertificateIdentityVerifiesSuccessfully(t *
tr := data.PublicGoodTrustedMaterialRoot(t)
entity := data.SigstoreJS200ProvenanceBundle(t)

goodCI, _ := verify.NewShortCertificateIdentity(verify.ActionsIssuerValue, "", verify.SigstoreSanRegex)
badCI, _ := verify.NewShortCertificateIdentity(verify.ActionsIssuerValue, "BadSANValue", "")
goodCI, _ := verify.NewShortCertificateIdentity(verify.ActionsIssuerValue, "", "", verify.SigstoreSanRegex)
badCI, _ := verify.NewShortCertificateIdentity(verify.ActionsIssuerValue, "", "BadSANValue", "")

verifier, err := verify.NewSignedEntityVerifier(tr, verify.WithTransparencyLog(1), verify.WithObserverTimestamps(1))

Expand Down
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