450 lines
11 KiB
Go
450 lines
11 KiB
Go
package protocol
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import (
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"bytes"
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"crypto"
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"crypto/ecdsa"
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"crypto/elliptic"
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"crypto/rand"
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"crypto/rsa"
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"crypto/tls"
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"crypto/x509"
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"crypto/x509/pkix"
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"encoding/asn1"
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"errors"
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"fmt"
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"io/ioutil"
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"net/http"
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"time"
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asn "github.com/InfiniteLoopSpace/go_S-MIME/asn1"
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oid "github.com/InfiniteLoopSpace/go_S-MIME/oid"
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)
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// SignedDataContent returns SignedData if ContentType is SignedData.
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func (ci ContentInfo) SignedDataContent() (*SignedData, error) {
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if !ci.ContentType.Equal(oid.SignedData) {
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return nil, ErrWrongType
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}
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sd := new(SignedData)
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if rest, err := asn.Unmarshal(ci.Content.Bytes, sd); err != nil {
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return nil, err
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} else if len(rest) > 0 {
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return nil, ErrTrailingData
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}
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return sd, nil
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}
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// SignedData ::= SEQUENCE {
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// version CMSVersion,
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// digestAlgorithms DigestAlgorithmIdentifiers,
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// encapContentInfo EncapsulatedContentInfo,
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// certificates [0] IMPLICIT CertificateSet OPTIONAL,
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// crls [1] IMPLICIT RevocationInfoChoices OPTIONAL,
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// signerInfos SignerInfos }
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type SignedData struct {
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Version int `` // CMSVersion ::= INTEGER { v0(0), v1(1), v2(2), v3(3), v4(4), v5(5) }
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DigestAlgorithms []pkix.AlgorithmIdentifier `asn1:"set"` //DigestAlgorithmIdentifiers ::= SET OF DigestAlgorithmIdentifier //DigestAlgorithmIdentifier ::= AlgorithmIdentifier
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EncapContentInfo EncapsulatedContentInfo `` //
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Certificates []asn1.RawValue `asn1:"optional,set,tag:0"` // CertificateSet ::= SET OF CertificateChoices
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CRLs []RevocationInfoChoice `asn1:"optional,set,tag:1"` // RevocationInfoChoices ::= SET OF RevocationInfoChoice
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SignerInfos []SignerInfo `asn1:"set"` // SignerInfos ::= SET OF SignerInfo
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}
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// CertificateChoices ::= CHOICE {
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// certificate Certificate,
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// extendedCertificate [0] IMPLICIT ExtendedCertificate, -- Obsolete
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// v1AttrCert [1] IMPLICIT AttributeCertificateV1, -- Obsolete
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// v2AttrCert [2] IMPLICIT AttributeCertificateV2,
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// other [3] IMPLICIT OtherCertificateFormat }
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type CertificateChoices struct {
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Cert x509.Certificate `asn1:"optional"`
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V2AttrCert asn1.RawValue `asn1:"optional,tag:2"`
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Other OtherCertificateFormat `asn1:"optional,tag:3"`
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}
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// OtherCertificateFormat ::= SEQUENCE {
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// otherCertFormat OBJECT IDENTIFIER,
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// otherCert ANY DEFINED BY otherCertFormat }
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type OtherCertificateFormat struct {
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OtherCertFormat asn1.ObjectIdentifier
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OtherCert asn1.RawValue
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}
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// RevocationInfoChoice ::= CHOICE {
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// crl CertificateList,
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// other [1] IMPLICIT OtherRevocationInfoFormat }
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type RevocationInfoChoice struct {
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Crl pkix.CertificateList `asn1:"optional"`
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Other OtherRevocationInfoFormat `asn1:"optional,tag:1"`
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}
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// OtherRevocationInfoFormat ::= SEQUENCE {
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// otherRevInfoFormat OBJECT IDENTIFIER,
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// otherRevInfo ANY DEFINED BY otherRevInfoFormat }
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type OtherRevocationInfoFormat struct {
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OtherRevInfoFormat asn1.ObjectIdentifier
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OtherRevInfo asn1.RawValue
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}
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// NewSignedData creates a new SignedData.
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func NewSignedData(eci EncapsulatedContentInfo) (*SignedData, error) {
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// The version is picked based on which CMS features are used. We only use
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// version 1 features, except for supporting non-data econtent.
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version := 1
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if !eci.IsTypeData() {
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version = 3
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}
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return &SignedData{
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Version: version,
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DigestAlgorithms: []pkix.AlgorithmIdentifier{},
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EncapContentInfo: eci,
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SignerInfos: []SignerInfo{},
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}, nil
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}
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// AddSignerInfo adds a SignerInfo to the SignedData.
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func (sd *SignedData) AddSignerInfo(keypPair tls.Certificate, attrs []Attribute) (err error) {
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for _, cert := range keypPair.Certificate {
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if err = sd.AddCertificate(cert); err != nil {
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return
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}
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}
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signer := keypPair.PrivateKey.(crypto.Signer)
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cert := keypPair.Leaf
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ias, err := NewIssuerAndSerialNumber(cert)
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if err != nil {
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return err
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}
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sid := SignerIdentifier{ias, nil}
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var signerOpts crypto.SignerOpts
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digestAlgorithm := digestAlgorithmForPublicKey(cert.PublicKey)
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signatureAlgorithm, ok := oid.PublicKeyAlgorithmToSignatureAlgorithm[keypPair.Leaf.PublicKeyAlgorithm]
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if isRSAPSS(cert) {
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h := oid.DigestAlgorithmToHash[digestAlgorithm.Algorithm.String()]
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signatureAlgorithm, signerOpts, err = newPSS(h, cert.PublicKey.(*rsa.PublicKey))
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}
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if !ok {
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return errors.New("unsupported certificate public key algorithm")
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}
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si := SignerInfo{
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Version: 1,
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SID: sid,
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DigestAlgorithm: digestAlgorithm,
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SignedAttrs: nil,
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SignatureAlgorithm: signatureAlgorithm,
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Signature: nil,
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UnsignedAttrs: nil,
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}
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// Get the message
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content := sd.EncapContentInfo.EContent
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if err != nil {
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return err
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}
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if content == nil {
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return errors.New("already detached")
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}
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// Digest the message.
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hash, err := si.Hash()
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if err != nil {
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return err
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}
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if !isRSAPSS(cert) {
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signerOpts = hash
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}
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md := hash.New()
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if _, err = md.Write(content); err != nil {
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return err
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}
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// Build our SignedAttributes
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mdAttr, err := NewAttribute(oid.AttributeMessageDigest, md.Sum(nil))
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if err != nil {
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return err
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}
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ctAttr, err := NewAttribute(oid.AttributeContentType, sd.EncapContentInfo.EContentType)
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if err != nil {
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return err
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}
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sTAttr, err := NewAttribute(oid.AttributeSigningTime, time.Now())
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if err != nil {
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return err
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}
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si.SignedAttrs = append(si.SignedAttrs, mdAttr, ctAttr, sTAttr)
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si.SignedAttrs = append(si.SignedAttrs, attrs...)
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sm, err := asn.MarshalWithParams(si.SignedAttrs, `set`)
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if err != nil {
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return err
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}
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smd := hash.New()
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if _, errr := smd.Write(sm); errr != nil {
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return errr
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}
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if si.Signature, err = signer.Sign(rand.Reader, smd.Sum(nil), signerOpts); err != nil {
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return err
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}
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sd.addDigestAlgorithm(si.DigestAlgorithm)
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sd.SignerInfos = append(sd.SignerInfos, si)
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return nil
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}
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// algorithmsForPublicKey takes an opinionated stance on what algorithms to use
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// for the given public key.
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func digestAlgorithmForPublicKey(pub crypto.PublicKey) pkix.AlgorithmIdentifier {
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if ecPub, ok := pub.(*ecdsa.PublicKey); ok {
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switch ecPub.Curve {
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case elliptic.P384():
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return pkix.AlgorithmIdentifier{Algorithm: oid.DigestAlgorithmSHA384}
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case elliptic.P521():
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return pkix.AlgorithmIdentifier{Algorithm: oid.DigestAlgorithmSHA512}
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}
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}
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return pkix.AlgorithmIdentifier{Algorithm: oid.DigestAlgorithmSHA256}
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}
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// ClearCertificates removes all certificates.
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func (sd *SignedData) ClearCertificates() {
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sd.Certificates = []asn1.RawValue{}
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}
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// AddCertificate adds a *x509.Certificate.
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func (sd *SignedData) AddCertificate(cert []byte) error {
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for _, existing := range sd.Certificates {
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if bytes.Equal(existing.Bytes, cert) {
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return errors.New("certificate already added")
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}
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}
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var rv asn1.RawValue
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if _, err := asn.Unmarshal(cert, &rv); err != nil {
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return err
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}
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sd.Certificates = append(sd.Certificates, rv)
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return nil
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}
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// addDigestAlgorithm adds a new AlgorithmIdentifier if it doesn't exist yet.
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func (sd *SignedData) addDigestAlgorithm(algo pkix.AlgorithmIdentifier) {
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for _, existing := range sd.DigestAlgorithms {
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if existing.Algorithm.Equal(algo.Algorithm) {
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return
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}
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}
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sd.DigestAlgorithms = append(sd.DigestAlgorithms, algo)
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}
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// X509Certificates gets the certificates, assuming that they're X.509 encoded.
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func (sd *SignedData) X509Certificates() (map[string]*x509.Certificate, error) {
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// Certificates field is optional. Handle missing value.
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if sd.Certificates == nil {
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return nil, nil
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}
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certs := map[string]*x509.Certificate{}
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// Empty set
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if len(sd.Certificates) == 0 {
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return certs, nil
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}
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for _, raw := range sd.Certificates {
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if raw.Class != asn1.ClassUniversal || raw.Tag != asn1.TagSequence {
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return nil, ErrUnsupported
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}
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x509, err := x509.ParseCertificate(raw.FullBytes)
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if err != nil {
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return nil, err
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}
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iasString, err := IASstring(x509)
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certs[iasString] = x509
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if err != nil {
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return nil, err
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}
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}
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return certs, nil
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}
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// ContentInfo returns the SignedData wrapped in a ContentInfo packet.
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func (sd *SignedData) ContentInfo() (ContentInfo, error) {
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var nilCI ContentInfo
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der, err := asn.Marshal(*sd)
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if err != nil {
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return nilCI, err
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}
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return ContentInfo{
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ContentType: oid.SignedData,
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Content: asn1.RawValue{
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Class: asn1.ClassContextSpecific,
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Tag: 0,
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Bytes: der,
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IsCompound: true,
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},
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}, nil
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}
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// Verify checks the signature
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func (sd *SignedData) Verify(Opts x509.VerifyOptions, detached []byte) (chains [][][]*x509.Certificate, err error) {
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certs, _ := sd.X509Certificates()
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opts := Opts
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for _, c := range certs {
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opts.Intermediates.AddCert(c)
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intermediates, fetchErr := fetchIntermediates(c.IssuingCertificateURL)
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for _, e := range fetchErr {
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fmt.Printf("Error while fetching intermediates: %s\n", e)
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}
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for _, i := range intermediates {
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opts.Intermediates.AddCert(i)
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}
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}
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eContent := detached
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if eContent == nil {
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eContent = sd.EncapContentInfo.EContent
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}
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for _, signer := range sd.SignerInfos {
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//Find and check signer Certificate:
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sidxxx, _ := signer.SID.IAS.RawValue()
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sid := fmt.Sprintf("%x", sidxxx.Bytes)
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cert, exist := certs[sid]
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if !exist {
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err = errors.New("Could not find a Certificate for signer with sid : " + sid)
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return
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}
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var signingTime time.Time
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signingTime, err = signer.GetSigningTimeAttribute()
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if err != nil {
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opts.CurrentTime = time.Now()
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}
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opts.CurrentTime = signingTime
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var chain [][]*x509.Certificate
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chain, err = cert.Verify(opts)
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if err != nil {
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// return
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}
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signedMessage := eContent
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if signer.SignedAttrs != nil {
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//Hash message:
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var hash crypto.Hash
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hash, err = signer.Hash()
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if err != nil {
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return nil, err
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}
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md := hash.New()
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_, err = md.Write(eContent)
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if err != nil {
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return nil, err
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}
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h := md.Sum(nil)
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var messageDigestAttr []byte
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messageDigestAttr, err = signer.GetMessageDigestAttribute()
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if err != nil {
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return
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}
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if !bytes.Equal(messageDigestAttr, h) {
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err = errors.New("Signed hash does not match the hash of the message")
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return
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}
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signedMessage, err = asn.MarshalWithParams(signer.SignedAttrs, `set`)
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if err != nil {
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return
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}
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}
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var sigAlg x509.SignatureAlgorithm
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sigAlg, err = signer.X509SignatureAlgorithm()
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if err != nil {
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return
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}
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switch signer.SignatureAlgorithm.Algorithm.String() {
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case oid.SignatureAlgorithmRSASSAPSS.String():
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default:
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err = cert.CheckSignature(sigAlg, signedMessage, signer.Signature)
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}
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if err != nil {
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return
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}
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chains = append(chains, chain)
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}
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return
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}
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func fetchIntermediates(urls []string) (certificates []*x509.Certificate, errs []error) {
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for _, url := range urls {
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var resp *http.Response
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resp, err := http.Get(url)
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if err != nil {
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errs = append(errs, err)
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continue
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}
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defer resp.Body.Close()
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issuerBytes, err := ioutil.ReadAll(resp.Body)
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if err != nil {
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errs = append(errs, err)
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continue
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}
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issuerCert, err := x509.ParseCertificate(issuerBytes)
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if err != nil {
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errs = append(errs, err)
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continue
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}
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//Prevent infinite loop
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if len(certificates) > 50 {
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err = errors.New("To many issuers")
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errs = append(errs, err)
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return
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}
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certificates = append(certificates, issuerCert)
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//Recusively fetch issuers
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issuers, fetchErrs := fetchIntermediates(issuerCert.IssuingCertificateURL)
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certificates = append(certificates, issuers...)
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errs = append(errs, fetchErrs...)
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}
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return
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}
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