Merge branch 'design' of github.com:system-transparency/stfe into design

1 files changed, 188 insertions, 0 deletions

diff --git a/types/http.go b/types/http.go
new file mode 100644
index 0000000..8bbe26d
--- /dev/null
+++ b/types/http.go
@@ -0,0 +1,188 @@
+package types
+
+import (
+	"bytes"
+	"encoding/hex"
+	"fmt"
+	"net/http"
+	"strconv"
+	"strings"
+)
+
+const (
+	// HeaderPrefix is the start of every ST log HTTP header key
+	HeaderPrefix = "stlog-"
+
+	// New leaf
+	HeaderShardHint            = HeaderPrefix + "shard_hint"
+	HeaderChecksum             = HeaderPrefix + "checksum"
+	HeaderSignatureOverMessage = HeaderPrefix + "signature_over_message"
+	HeaderVerificationKey      = HeaderPrefix + "verification_key"
+	HeaderDomainHint           = HeaderPrefix + "domain_hint"
+
+	// Inclusion proof
+	HeaderLeafHash      = HeaderPrefix + "leaf_hash"
+	HeaderLeafIndex     = HeaderPrefix + "leaf_index"
+	HeaderInclusionPath = HeaderPrefix + "inclusion_path"
+
+	// Consistency proof
+	HeaderNewSize         = HeaderPrefix + "new_size"
+	HeaderOldSize         = HeaderPrefix + "old_size"
+	HeaderConsistencyPath = HeaderPrefix + "consistency_path"
+
+	// Range of leaves
+	HeaderStartSize = HeaderPrefix + "start_size"
+	HeaderEndSize   = HeaderPrefix + "end_size"
+
+	// Tree head
+	HeaderTimestamp = HeaderPrefix + "timestamp"
+	HeaderTreeSize  = HeaderPrefix + "tree_size"
+	HeaderRootHash  = HeaderPrefix + "root_hash"
+
+	// Signature and signer identity
+	HeaderSignature = HeaderPrefix + "signature"
+	HeaderKeyHash   = HeaderPrefix + "key_hash"
+)
+
+// ToHTTP returns a signed tree-head as HTTP key-value pairs
+func (sth *SignedTreeHead) ToHTTP() ([]byte, error) {
+	hdr := http.Header{}
+	hdr.Add(HeaderTimestamp, strconv.FormatUint(sth.Timestamp, 10))
+	hdr.Add(HeaderTreeSize, strconv.FormatUint(sth.TreeSize, 10))
+	hdr.Add(HeaderRootHash, hex.EncodeToString(sth.RootHash[:]))
+	for _, sigident := range sth.SigIdent {
+		hdr.Add(HeaderSignature, hex.EncodeToString(sigident.Signature[:]))
+		hdr.Add(HeaderKeyHash, hex.EncodeToString(sigident.KeyHash[:]))
+	}
+	return headerToBytes(hdr)
+}
+
+// ToHTTP returns a consistency proof as HTTP key-value pairs
+func (p *ConsistencyProof) ToHTTP() ([]byte, error) {
+	hdr := http.Header{}
+	hdr.Add(HeaderNewSize, strconv.FormatUint(p.NewSize, 10))
+	hdr.Add(HeaderOldSize, strconv.FormatUint(p.OldSize, 10))
+	for _, hash := range p.Path {
+		hdr.Add(HeaderConsistencyPath, hex.EncodeToString(hash[:]))
+	}
+	return headerToBytes(hdr)
+}
+
+// ToHTTP returns an inclusion proof as HTTP key-value pairs
+func (p *InclusionProof) ToHTTP() ([]byte, error) {
+	hdr := http.Header{}
+	hdr.Add(HeaderTreeSize, strconv.FormatUint(p.TreeSize, 10))
+	hdr.Add(HeaderLeafIndex, strconv.FormatUint(p.LeafIndex, 10))
+	for _, hash := range p.Path {
+		hdr.Add(HeaderInclusionPath, hex.EncodeToString(hash[:]))
+	}
+	return headerToBytes(hdr)
+}
+
+// ToHTTP returns a leaf as HTTP key-value pairs
+func (l *Leaf) ToHTTP() ([]byte, error) {
+	hdr := http.Header{}
+	hdr.Add(HeaderShardHint, strconv.FormatUint(l.ShardHint, 10))
+	hdr.Add(HeaderChecksum, hex.EncodeToString(l.Checksum[:]))
+	hdr.Add(HeaderSignature, hex.EncodeToString(l.Signature[:]))
+	hdr.Add(HeaderKeyHash, hex.EncodeToString(l.KeyHash[:]))
+	return headerToBytes(hdr)
+}
+
+// SignedTreeHeadFromHTTP parses a signed tree head from HTTP key-value pairs
+func SignedTreeHeadFromHTTP(buf []byte) (*SignedTreeHead, error) {
+	hdr, err := headerFromBuf(buf)
+	if err != nil {
+		return nil, fmt.Errorf("headerFromBuf(): %v", err)
+	}
+
+	// TreeHead
+	var sth SignedTreeHead
+	sth.Timestamp, err = strconv.ParseUint(hdr.Get(HeaderTimestamp), 10, 64)
+	if err != nil {
+		return nil, fmt.Errorf("invalid timestamp: %v", err)
+	}
+	sth.TreeSize, err = strconv.ParseUint(hdr.Get(HeaderTreeSize), 10, 64)
+	if err != nil {
+		return nil, fmt.Errorf("invalid tree size: %v", err)
+	}
+	if err := decodeHex(hdr.Get(HeaderRootHash), sth.RootHash[:]); err != nil {
+		return nil, fmt.Errorf("decodeHex(): %v", err)
+	}
+
+	// SigIdent
+	signatures := hdr.Values(HeaderSignature)
+	keyHashes := hdr.Values(HeaderKeyHash)
+	if len(signatures) == 0 {
+		return nil, fmt.Errorf("no signer")
+	}
+	if len(signatures) != len(keyHashes) {
+		return nil, fmt.Errorf("mismatched signature-signer count")
+	}
+	for i := 0; i < len(signatures); i++ {
+		var sigident SigIdent
+		if err := decodeHex(signatures[i], sigident.Signature[:]); err != nil {
+			return nil, fmt.Errorf("decodeHex(): %v", err)
+		}
+		if err := decodeHex(keyHashes[i], sigident.KeyHash[:]); err != nil {
+			return nil, fmt.Errorf("decodeHex(): %v", err)
+		}
+		sth.SigIdent = append(sth.SigIdent, sigident)
+	}
+	return &sth, nil
+}
+
+// ConsistencyProofFromHTTP parses a consistency proof from HTTP key-value pairs
+func ConsistencyProofFromHTTP(buf []byte) (*ConsistencyProof, error) {
+	return nil, nil // TODO
+}
+
+// InclusionProofFromHTTP parses an inclusion proof from HTTP key-value pairs
+func InclusionProofFromHTTP(buf []byte) (*InclusionProof, error) {
+	return nil, nil // TODO
+}
+
+// LeavesFromHTTP parses a list of leaves from HTTP key-value pairs
+func LeavesFromHTTP(buf []byte) ([]*Leaf, error) {
+	return nil, nil // TODO
+}
+
+// headerFromBuf parses ST log HTTP header key-value pairs from a response body
+func headerFromBuf(buf []byte) (http.Header, error) {
+	hdr := http.Header{}
+	lines := strings.Split(string(buf), "\r\n")
+	lines = lines[:len(lines)-1] // skip the final empty line
+	for _, line := range lines {
+		split := strings.Split(line, ":")
+		if len(split) != 2 {
+			return nil, fmt.Errorf("invalid ST log HTTP header: %s", line)
+		}
+		if !strings.HasPrefix(strings.ToLower(split[0]), HeaderPrefix) {
+			return nil, fmt.Errorf("invalid ST log HTTP header prefix: %s", line)
+		}
+		hdr.Add(split[0], strings.TrimSpace(split[1]))
+	}
+	return hdr, nil
+}
+
+// decodeHex decodes a hex-encoded string into a fixed-size output slice
+func decodeHex(str string, out []byte) error {
+	buf, err := hex.DecodeString(str)
+	if err != nil {
+		return fmt.Errorf("hex.DecodeString(): %v", err)
+	}
+	if len(buf) != len(out) {
+		return fmt.Errorf("invalid length: %v", len(buf))
+	}
+	copy(out, buf)
+	return nil
+}
+
+// headerToBytes encodes a header as HTTP key-value pairs
+func headerToBytes(hdr http.Header) ([]byte, error) {
+	buf := bytes.NewBuffer(nil)
+	if err := hdr.Write(buf); err != nil {
+		return nil, fmt.Errorf("hdr.Write(): %v", err) // should not happen
+	}
+	return buf.Bytes(), nil
+}