package getproviders import ( "bytes" "crypto/sha256" "encoding/hex" "fmt" "io" "log" "os" "strings" "golang.org/x/crypto/openpgp" openpgpArmor "golang.org/x/crypto/openpgp/armor" openpgpErrors "golang.org/x/crypto/openpgp/errors" ) type packageAuthenticationResult int const ( verifiedChecksum packageAuthenticationResult = iota officialProvider partnerProvider communityProvider ) // PackageAuthenticationResult is returned from a PackageAuthentication // implementation. It is a mostly-opaque type intended for use in UI, which // implements Stringer and includes an optional Warning field. // // A failed PackageAuthentication attempt will return an "unauthenticated" // result, which is represented by nil. type PackageAuthenticationResult struct { result packageAuthenticationResult Warning string } func (t *PackageAuthenticationResult) String() string { if t == nil { return "unauthenticated" } return []string{ "verified checksum", "official provider", "partner provider", "community provider", }[t.result] } // SigningKey represents a key used to sign packages from a registry, along // with an optional trust signature from the registry operator. These are // both in ASCII armored OpenPGP format. // // The JSON struct tags represent the field names used by the Registry API. type SigningKey struct { ASCIIArmor string `json:"ascii_armor"` TrustSignature string `json:"trust_signature"` } // PackageAuthentication is an interface implemented by the optional package // authentication implementations a source may include on its PackageMeta // objects. // // A PackageAuthentication implementation is responsible for authenticating // that a package is what its distributor intended to distribute and that it // has not been tampered with. type PackageAuthentication interface { // AuthenticatePackage takes the local location of a package (which may or // may not be the same as the original source location), and returns a // PackageAuthenticationResult, or an error if the authentication checks // fail. // // The local location is guaranteed not to be a PackageHTTPURL: a remote // package will always be staged locally for inspection first. AuthenticatePackage(localLocation PackageLocation) (*PackageAuthenticationResult, error) } type packageAuthenticationAll []PackageAuthentication // PackageAuthenticationAll combines several authentications together into a // single check value, which passes only if all of the given ones pass. // // The checks are processed in the order given, so a failure of an earlier // check will prevent execution of a later one. // // The returned result is from the last authentication, so callers should // take care to order the authentications such that the strongest is last. func PackageAuthenticationAll(checks ...PackageAuthentication) PackageAuthentication { return packageAuthenticationAll(checks) } func (checks packageAuthenticationAll) AuthenticatePackage(localLocation PackageLocation) (*PackageAuthenticationResult, error) { var authResult *PackageAuthenticationResult for _, check := range checks { var err error authResult, err = check.AuthenticatePackage(localLocation) if err != nil { return authResult, err } } return authResult, nil } type archiveHashAuthentication struct { WantSHA256Sum [sha256.Size]byte } // NewArchiveChecksumAuthentication returns a PackageAuthentication // implementation that checks that the original distribution archive matches // the given hash. // // This authentication is suitable only for PackageHTTPURL and // PackageLocalArchive source locations, because the unpacked layout // (represented by PackageLocalDir) does not retain access to the original // source archive. Therefore this authenticator will return an error if its // given localLocation is not PackageLocalArchive. func NewArchiveChecksumAuthentication(wantSHA256Sum [sha256.Size]byte) PackageAuthentication { return archiveHashAuthentication{wantSHA256Sum} } func (a archiveHashAuthentication) AuthenticatePackage(localLocation PackageLocation) (*PackageAuthenticationResult, error) { archiveLocation, ok := localLocation.(PackageLocalArchive) if !ok { // A source should not use this authentication type for non-archive // locations. return nil, fmt.Errorf("cannot check archive hash for non-archive location %s", localLocation) } f, err := os.Open(string(archiveLocation)) if err != nil { return nil, err } defer f.Close() h := sha256.New() _, err = io.Copy(h, f) if err != nil { return nil, err } gotHash := h.Sum(nil) if !bytes.Equal(gotHash, a.WantSHA256Sum[:]) { return nil, fmt.Errorf("archive has incorrect SHA-256 checksum %x (expected %x)", gotHash, a.WantSHA256Sum[:]) } return &PackageAuthenticationResult{result: verifiedChecksum}, nil } type matchingChecksumAuthentication struct { Document []byte Filename string WantSHA256Sum [sha256.Size]byte } // NewMatchingChecksumAuthentication returns a PackageAuthentication // implementation that scans a registry-provided SHA256SUMS document for a // specified filename, and compares the SHA256 hash against the expected hash. // This is necessary to ensure that the signed SHA256SUMS document matches the // declared SHA256 hash for the package, and therefore that a valid signature // of this document authenticates the package. // // This authentication always returns a nil result, since it alone cannot offer // any assertions about package integrity. It should be combined with other // authentications to be useful. func NewMatchingChecksumAuthentication(document []byte, filename string, wantSHA256Sum [sha256.Size]byte) PackageAuthentication { return matchingChecksumAuthentication{ Document: document, Filename: filename, WantSHA256Sum: wantSHA256Sum, } } func (m matchingChecksumAuthentication) AuthenticatePackage(location PackageLocation) (*PackageAuthenticationResult, error) { // Find the checksum in the list with matching filename. The document is // in the form "0123456789abcdef filename.zip". filename := []byte(m.Filename) var checksum []byte for _, line := range bytes.Split(m.Document, []byte("\n")) { parts := bytes.Fields(line) if len(parts) > 1 && bytes.Equal(parts[1], filename) { checksum = parts[0] break } } if checksum == nil { return nil, fmt.Errorf("checksum list has no SHA-256 hash for %q", m.Filename) } // Decode the ASCII checksum into a byte array for comparison. var gotSHA256Sum [sha256.Size]byte if _, err := hex.Decode(gotSHA256Sum[:], checksum); err != nil { return nil, fmt.Errorf("checksum list has invalid SHA256 hash %q: %s", string(checksum), err) } // If the checksums don't match, authentication fails. if !bytes.Equal(gotSHA256Sum[:], m.WantSHA256Sum[:]) { return nil, fmt.Errorf("checksum list has unexpected SHA-256 hash %x (expected %x)", gotSHA256Sum, m.WantSHA256Sum[:]) } // Success! But this doesn't result in any real authentication, only a // lack of authentication errors, so we return a nil result. return nil, nil } type signatureAuthentication struct { Document []byte Signature []byte Keys []SigningKey } // NewSignatureAuthentication returns a PackageAuthentication implementation // that verifies the cryptographic signature for a package against any of the // provided keys. // // The signing key for a package will be auto detected by attempting each key // in turn until one is successful. If such a key is found, there are three // possible successful authentication results: // // 1. If the signing key is the HashiCorp official key, it is an official // provider; // 2. Otherwise, if the signing key has a trust signature from the HashiCorp // Partners key, it is a partner provider; // 3. If neither of the above is true, it is a community provider. // // Any failure in the process of validating the signature will result in an // unauthenticated result. func NewSignatureAuthentication(document, signature []byte, keys []SigningKey) PackageAuthentication { return signatureAuthentication{ Document: document, Signature: signature, Keys: keys, } } func (s signatureAuthentication) AuthenticatePackage(location PackageLocation) (*PackageAuthenticationResult, error) { // Find the key that signed the checksum file. This can fail if there is no // valid signature for any of the provided keys. signingKey, err := s.findSigningKey() if err != nil { return nil, err } // Verify the signature using the HashiCorp public key. If this succeeds, // this is an official provider. hashicorpKeyring, err := openpgp.ReadArmoredKeyRing(strings.NewReader(HashicorpPublicKey)) if err != nil { return nil, fmt.Errorf("error creating HashiCorp keyring: %s", err) } _, err = openpgp.CheckDetachedSignature(hashicorpKeyring, bytes.NewReader(s.Document), bytes.NewReader(s.Signature)) if err == nil { return &PackageAuthenticationResult{result: officialProvider}, nil } // If the signing key has a trust signature, attempt to verify it with the // HashiCorp partners public key. if signingKey.TrustSignature != "" { hashicorpPartnersKeyring, err := openpgp.ReadArmoredKeyRing(strings.NewReader(HashicorpPartnersKey)) if err != nil { return nil, fmt.Errorf("error creating HashiCorp Partners keyring: %s", err) } authorKey, err := openpgpArmor.Decode(strings.NewReader(signingKey.ASCIIArmor)) if err != nil { return nil, fmt.Errorf("error decoding signing key: %s", err) } trustSignature, err := openpgpArmor.Decode(strings.NewReader(signingKey.TrustSignature)) if err != nil { return nil, fmt.Errorf("error decoding trust signature: %s", err) } _, err = openpgp.CheckDetachedSignature(hashicorpPartnersKeyring, authorKey.Body, trustSignature.Body) if err != nil { return nil, fmt.Errorf("error verifying trust signature: %s", err) } return &PackageAuthenticationResult{result: partnerProvider}, nil } // We have a valid signature, but it's not from the HashiCorp key, and it // also isn't a trusted partner. This is a community provider. // FIXME: we may want to add a more detailed warning here explaining the // difference between partner and community providers. return &PackageAuthenticationResult{result: communityProvider}, nil } // findSigningKey attempts to verify the signature using each of the keys // returned by the registry. If a valid signature is found, it returns the // signing key. // // Note: currently the registry only returns one key, but this may change in // the future. func (s signatureAuthentication) findSigningKey() (*SigningKey, error) { for _, key := range s.Keys { keyring, err := openpgp.ReadArmoredKeyRing(strings.NewReader(key.ASCIIArmor)) if err != nil { return nil, fmt.Errorf("error decoding signing key: %s", err) } entity, err := openpgp.CheckDetachedSignature(keyring, bytes.NewReader(s.Document), bytes.NewReader(s.Signature)) // If the signature issuer does not match the the key, keep trying the // rest of the provided keys. if err == openpgpErrors.ErrUnknownIssuer { continue } // Any other signature error is terminal. if err != nil { return nil, fmt.Errorf("error checking signature: %s", err) } log.Printf("[DEBUG] Provider signed by %s", entityString(entity)) return &key, nil } // If none of the provided keys issued the signature, this package is // unsigned. This is currently a terminal authentication error. return nil, fmt.Errorf("authentication signature from unknown issuer") } // entityString extracts the key ID and identity name(s) from an openpgp.Entity // for logging. func entityString(entity *openpgp.Entity) string { if entity == nil { return "" } keyID := "n/a" if entity.PrimaryKey != nil { keyID = entity.PrimaryKey.KeyIdString() } var names []string for _, identity := range entity.Identities { names = append(names, identity.Name) } return fmt.Sprintf("%s %s", keyID, strings.Join(names, ", ")) }