feat: add signing for chunk trailing headers (#60)

.changes/5c32e493-2c13-4eef-9ffc-3c3a2326bcf6.json

@@ -0,0 +1,8 @@
+{
+    "id": "5c32e493-2c13-4eef-9ffc-3c3a2326bcf6",
+    "type": "feature",
+    "description": "Implement signChunkTrailer",
+    "issues": [
+        "awslabs/aws-sdk-kotlin/#747"
+    ]
+}

src/common/src/aws/sdk/kotlin/crt/auth/signing/AwsSigner.kt

@@ -5,6 +5,7 @@
 
 package aws.sdk.kotlin.crt.auth.signing
 
+import aws.sdk.kotlin.crt.http.Headers
 import aws.sdk.kotlin.crt.http.HttpRequest
 
 public expect object AwsSigner {
@@ -13,4 +14,6 @@ public expect object AwsSigner {
     public suspend fun sign(request: HttpRequest, config: AwsSigningConfig): AwsSigningResult
 
     public suspend fun signChunk(chunkBody: ByteArray, prevSignature: ByteArray, config: AwsSigningConfig): AwsSigningResult
+
+    public suspend fun signChunkTrailer(trailingHeaders: Headers, prevSignature: ByteArray, config: AwsSigningConfig): AwsSigningResult
 }

src/common/src/aws/sdk/kotlin/crt/auth/signing/AwsSigningConfig.kt

@@ -18,7 +18,8 @@ public enum class AwsSignatureType(public val value: Int) {
     HTTP_REQUEST_VIA_HEADERS(0),
     HTTP_REQUEST_VIA_QUERY_PARAMS(1),
     HTTP_REQUEST_CHUNK(2),
-    HTTP_REQUEST_EVENT(3);
+    HTTP_REQUEST_EVENT(3),
+    HTTP_REQUEST_TRAILING_HEADERS(6);
 }
 
 public object AwsSignedBodyValue {

src/common/test/aws/sdk/kotlin/crt/auth/signing/SigningTest.kt

@@ -8,6 +8,7 @@ package aws.sdk.kotlin.crt.auth.signing
 import aws.sdk.kotlin.crt.*
 import aws.sdk.kotlin.crt.auth.credentials.StaticCredentialsProvider
 import aws.sdk.kotlin.crt.auth.credentials.build
+import aws.sdk.kotlin.crt.http.Headers
 import aws.sdk.kotlin.crt.http.HttpRequest
 import aws.sdk.kotlin.crt.http.HttpRequestBodyStream
 import aws.sdk.kotlin.crt.http.headers
@@ -193,4 +194,36 @@ class SigningTest : CrtTest() {
             assertTrue(signedRequest.headers["Authorization"]!!.contains(prefix), signedRequest.headers["Authorization"])
         }
     }
+
+    @Test
+    fun testSigningChunkTrailingHeaders() = runSuspendTest {
+        StaticCredentialsProvider.build {
+            accessKeyId = "AKID"
+            secretAccessKey = "SECRET"
+        }.use { provider ->
+
+            val creds = provider.getCredentials()
+
+            val signingConfig = AwsSigningConfig.build {
+                algorithm = AwsSigningAlgorithm.SIGV4
+                signatureType = AwsSignatureType.HTTP_REQUEST_TRAILING_HEADERS
+                region = "foo"
+                service = "bar"
+                date = 1651022625000
+                credentialsProvider = provider
+                credentials = creds
+            }
+
+            val trailingHeaders = Headers.build {
+                append("x-amz-checksum-crc32", "AAAAAA==")
+                append("x-amz-arbitrary-header-with-value", "test")
+            }
+
+            val previousSignature = "106d0654706e3e8dde144d69ca9882ea38d4d72576056c724ba763f8ed3074f3".encodeToByteArray()
+
+            val signature = AwsSigner.signChunkTrailer(trailingHeaders, previousSignature, signingConfig).signature.decodeToString()
+            val expectedSignature = "24f8ed01c7add645b75e65d2382fae5233b97526fdd1a2c4094933b93f6a08bf" // validated using DefaultAwsSigner
+            assertEquals(expectedSignature, signature)
+        }
+    }
 }

src/jvm/src/aws/sdk/kotlin/crt/auth/signing/AwsSignerJVM.kt

@@ -12,6 +12,7 @@ import aws.sdk.kotlin.crt.http.from
 import aws.sdk.kotlin.crt.http.into
 import kotlinx.coroutines.future.await
 import software.amazon.awssdk.crt.auth.credentials.Credentials
+import software.amazon.awssdk.crt.http.HttpHeader
 import java.util.function.Predicate
 import software.amazon.awssdk.crt.auth.signing.AwsSigner as AwsSignerJni
 import software.amazon.awssdk.crt.auth.signing.AwsSigningConfig as AwsSigningConfigJni
@@ -68,6 +69,30 @@ public actual object AwsSigner {
             AwsSigningResult(null, jniResult.signature)
         }
     }
+
+    /**
+     * Signs a chunk consisting of trailing headers
+     * @param trailingHeaders the trailing headers to be signed
+     * @param prevSignature the signature of the previous component of the request (in most cases, this will be the signature
+     * of the final data chunk, since the trailing header chunk is always sent last)
+     * @param config the signing configuration to use
+     * @return signing result, which provides access to all signing-related result properties
+     */
+    public actual suspend fun signChunkTrailer(trailingHeaders: Headers, prevSignature: ByteArray, config: AwsSigningConfig): AwsSigningResult {
+        if (trailingHeaders.isEmpty()) {
+            throw IllegalArgumentException("can't sign empty trailing headers")
+        }
+
+        // canonicalize the headers
+        val headers: List<HttpHeader> = trailingHeaders.entries().sortedBy { e -> e.key.lowercase() }
+            .map { e -> HttpHeader(e.key.lowercase(), e.value.joinToString(",") { v -> v.trim() }) }
+
+        return asyncCrtJniCall {
+            val signFuture = AwsSignerJni.sign(headers, prevSignature, config.into())
+            val jniResult = signFuture.await()
+            AwsSigningResult(null, jniResult.signature)
+        }
+    }
 }
 
 private fun AwsSigningConfig.into(): AwsSigningConfigJni {