forked from cavaliergopher/rpm
/
gpgcheck.go
212 lines (181 loc) · 5.39 KB
/
gpgcheck.go
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package rpm
import (
"bytes"
"crypto/md5"
"fmt"
"io"
"golang.org/x/crypto/openpgp"
"golang.org/x/crypto/openpgp/errors"
"golang.org/x/crypto/openpgp/packet"
)
// see: https://github.com/rpm-software-management/rpm/blob/3b1f4b0c6c9407b08620a5756ce422df10f6bd1a/rpmio/rpmpgp.c#L51
var gpgPubkeyTbl = map[packet.PublicKeyAlgorithm]string{
packet.PubKeyAlgoRSA: "RSA",
packet.PubKeyAlgoRSASignOnly: "RSA(Sign-Only)",
packet.PubKeyAlgoRSAEncryptOnly: "RSA(Encrypt-Only)",
packet.PubKeyAlgoElGamal: "Elgamal",
packet.PubKeyAlgoDSA: "DSA",
packet.PubKeyAlgoECDH: "Elliptic Curve",
packet.PubKeyAlgoECDSA: "ECDSA",
}
// Map Go hashes to rpm info name
// See: https://golang.org/src/crypto/crypto.go?s=#L23
// https://github.com/rpm-software-management/rpm/blob/3b1f4b0c6c9407b08620a5756ce422df10f6bd1a/rpmio/rpmpgp.c#L88
var gpgHashTbl = []string{
"Unknown hash algorithm",
"MD4",
"MD5",
"SHA1",
"SHA224",
"SHA256",
"SHA384",
"SHA512",
"MD5SHA1",
"RIPEMD160",
"SHA3_224",
"SHA3_256",
"SHA3_384",
"SHA3_512",
"SHA512_224",
"SHA512_256",
}
// GPGSignature is the raw byte representation of a package's signature.
type GPGSignature []byte
func (b GPGSignature) String() string {
pkt, err := packet.Read(bytes.NewReader(b))
if err != nil {
return ""
}
switch sig := pkt.(type) {
case *packet.SignatureV3:
algo, ok := gpgPubkeyTbl[sig.PubKeyAlgo]
if !ok {
algo = "Unknown public key algorithm"
}
hasher := gpgHashTbl[0]
if int(sig.Hash) < len(gpgHashTbl) {
hasher = gpgHashTbl[sig.Hash]
}
ctime := sig.CreationTime.UTC().Format(RPMDate)
return fmt.Sprintf("%v/%v, %v, Key ID %x", algo, hasher, ctime, sig.IssuerKeyId)
}
return ""
}
// Predefined checksum errors.
var (
// ErrMD5ValidationFailed indicates that a RPM package failed checksum
// validation.
ErrMD5ValidationFailed = fmt.Errorf("MD5 checksum validation failed")
// ErrGPGValidationFailed indicates that a RPM package failed GPG signature
// validation.
ErrGPGValidationFailed = fmt.Errorf("GPG signature validation failed")
// ErrGPGUnknownSignature indicates that the RPM package signature tag is of
// an unknown type.
ErrGPGUnknownSignature = fmt.Errorf("unknown signature type")
)
// rpmReadSigHeader reads the lead and signature header of a rpm package and
// returns a pointer to the signature header.
func rpmReadSigHeader(r io.Reader) (*Header, error) {
// read package lead
lead, err := ReadPackageLead(r)
if err != nil {
return nil, err
}
// check signature type
if lead.SignatureType != 5 { // RPMSIGTYPE_HEADERSIG
return nil, fmt.Errorf("Unsupported signature type: 0x%x", lead.SignatureType)
}
// read signature header
hdr, err := ReadPackageHeader(r)
if err != nil {
return nil, err
}
// pad to next header
pad := (8 - (hdr.Length % 8)) % 8
if pad > 0 {
if _, err := io.ReadFull(r, padBuf[:pad]); err != nil {
return nil, fmt.Errorf("Error seeking to next header: %v", err)
}
}
return hdr, nil
}
// GPGCheck validates the integrity of a RPM package file read from the given
// io.Reader. Public keys in the given keyring are used to validate the package
// signature.
//
// If validation succeeds, nil is returned. If validation fails,
// ErrGPGValidationFailed is returned.
//
// This function is an expensive operation which reads the entire package file.
func GPGCheck(r io.Reader, keyring openpgp.KeyRing) (string, error) {
// read signature header
sigheader, err := rpmReadSigHeader(r)
if err != nil {
return "", err
}
tags := []int{
1002, // RPMSIGTAG_PGP
1006, // RPMSIGTAG_PGP5
1005, // RPMSIGTAG_GPG
}
// get signature bytes
var sigval []byte
for _, tag := range tags {
if sigval = sigheader.Indexes.BytesByTag(tag); sigval != nil {
break
}
}
if sigval == nil {
return "", fmt.Errorf("Package signature not found")
}
// check signature
signer, err := openpgp.CheckDetachedSignature(keyring, r, bytes.NewReader(sigval))
if err == errors.ErrUnknownIssuer {
return "", ErrGPGValidationFailed
} else if err != nil {
return "", err
}
// get signer identity
for id := range signer.Identities {
return id, nil
}
return "", fmt.Errorf("No identity found in public key")
}
// MD5Check validates the integrity of a RPM package file read from the given
// io.Reader. An MD5 checksum is computed for the package payload and compared
// with the checksum value specified in the package header.
//
// If validation succeeds, nil is returned. If validation fails,
// ErrMD5ValidationFailed is returned.
//
// This function is an expensive operation which reads the entire package file.
func MD5Check(r io.Reader) error {
// read signature header
sigheader, err := rpmReadSigHeader(r)
if err != nil {
return err
}
// get expected payload size
payloadSize := sigheader.Indexes.IntByTag(1000) // RPMSIGTAG_SIZE
if payloadSize == 0 {
return fmt.Errorf("RPMSIGTAG_SIZE tag not found in signature header")
}
// get expected payload md5 sum
sigmd5 := sigheader.Indexes.BytesByTag(1004) // RPMSIGTAG_MD5
if sigmd5 == nil {
return fmt.Errorf("RPMSIGTAG_MD5 tag not found in signature header")
}
// compute payload sum
h := md5.New()
if n, err := io.Copy(h, r); err != nil {
return fmt.Errorf("Error reading payload: %v", err)
} else if n != payloadSize {
return ErrMD5ValidationFailed
}
// compare sums
payloadmd5 := h.Sum(nil)
if !bytes.Equal(payloadmd5, sigmd5) {
return ErrMD5ValidationFailed
}
return nil
}