feat: HTTP Signatureの署名器を実装

src/main/kotlin/dev/usbharu/hideout/service/signature/HttpSignatureSigner.kt

@@ -0,0 +1,16 @@
+package dev.usbharu.hideout.service.signature
+
+import io.ktor.http.*
+
+interface HttpSignatureSigner {
+    suspend fun sign(
+        url: String,
+        method: HttpMethod,
+        headers: Headers,
+        requestBody: String,
+        keyPair: Key,
+        signHeaders: List<String>
+    ): SignedRequest
+
+    suspend fun signRaw(signString: String, keyPair: Key, signHeaders: List<String>): Sign
+}

src/main/kotlin/dev/usbharu/hideout/service/signature/HttpSignatureSignerImpl.kt

@@ -0,0 +1,78 @@
+package dev.usbharu.hideout.service.signature
+
+import dev.usbharu.hideout.util.Base64Util
+import io.ktor.http.*
+import io.ktor.util.*
+import org.springframework.stereotype.Component
+import java.net.URL
+import java.security.Signature
+
+@Component
+class HttpSignatureSignerImpl : HttpSignatureSigner {
+    override suspend fun sign(
+        url: String,
+        method: HttpMethod,
+        headers: Headers,
+        requestBody: String,
+        keyPair: Key,
+        signHeaders: List<String>
+    ): SignedRequest {
+        val sign = signRaw(
+            signString = buildSignString(
+                url = URL(url),
+                method = method,
+                headers = headers,
+                signHeaders = signHeaders
+            ),
+            keyPair = keyPair,
+            signHeaders = signHeaders
+        )
+        return SignedRequest(
+            url = url,
+            method = method,
+            headers = headers,
+            requestBody = requestBody,
+            sign = sign
+        )
+    }
+
+    override suspend fun signRaw(signString: String, keyPair: Key, signHeaders: List<String>): Sign {
+        val signer = Signature.getInstance("SHA256withRSA")
+        signer.initSign(keyPair.privateKey)
+        signer.update(signString.toByteArray())
+        val sign = signer.sign()
+        val signature = Base64Util.encode(sign)
+        return Sign(
+            signature,
+            """keyId="${keyPair.keyId}",algorithm="${signHeaders.joinToString(" ")}",signature="$signature""""
+        )
+    }
+
+    private fun buildSignString(
+        url: URL,
+        method: HttpMethod,
+        headers: Headers,
+        signHeaders: List<String>
+    ): String {
+        headers.toMap().map { it.key.lowercase() to it.value }.toMap()
+        val result = signHeaders.map {
+            if (it.startsWith("(")) {
+                specialHeader(it, url, method)
+            } else {
+                generalHeader(it, headers.get(it)!!)
+            }
+        }.joinToString("\n")
+        return result
+    }
+
+    private fun specialHeader(fieldName: String, url: URL, method: HttpMethod): String {
+        if (fieldName != "(request-target)") {
+            throw IllegalArgumentException(fieldName + "is unsupported type")
+        }
+        return "(request-target): ${method.value.lowercase()} ${url.path}"
+    }
+
+    private fun generalHeader(fieldName: String, value: String): String {
+        return "$fieldName: $value"
+    }
+}

src/main/kotlin/dev/usbharu/hideout/service/signature/Key.kt

@@ -0,0 +1,10 @@
+package dev.usbharu.hideout.service.signature
+
+import java.security.PrivateKey
+import java.security.PublicKey
+
+data class Key(
+    val keyId: String,
+    val privateKey: PrivateKey,
+    val publicKey: PublicKey
+)

src/main/kotlin/dev/usbharu/hideout/service/signature/Sign.kt

@@ -0,0 +1,6 @@
+package dev.usbharu.hideout.service.signature
+
+data class Sign(
+    val signature: String,
+    val signatureHeader: String
+)

src/main/kotlin/dev/usbharu/hideout/service/signature/SignedRequest.kt

@@ -0,0 +1,23 @@
+package dev.usbharu.hideout.service.signature
+
+import io.ktor.client.request.*
+import io.ktor.http.*
+
+data class SignedRequest(
+    val url: String,
+    val method: HttpMethod,
+    val headers: Headers,
+    val requestBody: String,
+    val sign: Sign
+) {
+    fun toRequestBuilder(): HttpRequestBuilder {
+        val httpRequestBuilder = HttpRequestBuilder()
+        httpRequestBuilder.url(this.url)
+        httpRequestBuilder.method = this.method
+        httpRequestBuilder.headers {
+            this.appendAll(headers)
+        }
+        httpRequestBuilder.setBody(requestBody)
+        return httpRequestBuilder
+    }
+}