Initial commit

challenge/js-pow-sha256/runtime/.gitignore

@@ -0,0 +1 @@
+*.wasm

challenge/js-pow-sha256/runtime/runtime.go

@@ -0,0 +1,92 @@
+package main
+
+import (
+	"crypto/sha256"
+	"crypto/subtle"
+	"encoding/binary"
+	"encoding/hex"
+	"encoding/json"
+	"git.gammaspectra.live/git/go-away/challenge"
+	"strconv"
+	"strings"
+)
+
+//go:generate tinygo build -target wasip1 -buildmode=c-shared -scheduler=none -gc=leaking -o runtime.wasm runtime.go
+func main() {
+
+}
+
+func getChallenge(key []byte, params map[string]string) ([]byte, uint64) {
+	difficulty := uint64(5)
+	var err error
+	if diffStr, ok := params["difficulty"]; ok {
+		difficulty, err = strconv.ParseUint(diffStr, 10, 64)
+		if err != nil {
+			panic(err)
+		}
+	}
+	hasher := sha256.New()
+	hasher.Write(binary.LittleEndian.AppendUint64(nil, difficulty))
+	hasher.Write(key)
+	return hasher.Sum(nil), difficulty
+}
+
+//go:wasmexport MakeChallenge
+func MakeChallenge(in challenge.Allocation) (out challenge.Allocation) {
+	return challenge.MakeChallengeDecode(func(in challenge.MakeChallengeInput, out *challenge.MakeChallengeOutput) {
+		type Result struct {
+			Challenge  string `json:"challenge"`
+			Difficulty uint64 `json:"difficulty"`
+		}
+
+		challenge, difficulty := getChallenge(in.Key, in.Parameters)
+
+		data, err := json.Marshal(Result{
+			Challenge:  hex.EncodeToString(challenge),
+			Difficulty: difficulty,
+		})
+		if err != nil {
+			panic(err)
+		}
+		out.Data = data
+		out.Headers.Set("Content-Type", "text/javascript; charset=utf-8")
+	}, in)
+}
+
+//go:wasmexport VerifyChallenge
+func VerifyChallenge(in challenge.Allocation) (out challenge.VerifyChallengeOutput) {
+	return challenge.VerifyChallengeDecode(func(in challenge.VerifyChallengeInput) challenge.VerifyChallengeOutput {
+		c, difficulty := getChallenge(in.Key, in.Parameters)
+
+		type Result struct {
+			Hash  string `json:"hash"`
+			Nonce uint64 `json:"nonce"`
+		}
+		var result Result
+		err := json.Unmarshal(in.Result, &result)
+
+		if err != nil {
+			panic(err)
+		}
+
+		if !strings.HasPrefix(result.Hash, strings.Repeat("0", int(difficulty))) {
+			return challenge.VerifyChallengeOutputFailed
+		}
+
+		resultBinary, err := hex.DecodeString(result.Hash)
+		if err != nil {
+			panic(err)
+		}
+
+		buf := make([]byte, 0, len(c)+8)
+		buf = append(buf, c[:]...)
+		buf = binary.LittleEndian.AppendUint64(buf, result.Nonce)
+		calculated := sha256.Sum256(buf)
+
+		if subtle.ConstantTimeCompare(resultBinary, calculated[:]) != 1 {
+			return challenge.VerifyChallengeOutputFailed
+		}
+
+		return challenge.VerifyChallengeOutputOK
+	}, in)
+}