feat: implement clock skew interceptor #972
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| { | ||
| "id": "6de10487-c3a0-4c63-929a-ba11a415ea8f", | ||
| "type": "feature", | ||
| "description": "Detect and automatically correct clock skew to prevent signing errors" | ||
| } |
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| /* | ||
| * Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved. | ||
| * SPDX-License-Identifier: Apache-2.0 | ||
| */ | ||
| package aws.smithy.kotlin.runtime.awsprotocol | ||
|
|
||
| import aws.smithy.kotlin.runtime.ErrorMetadata | ||
| import aws.smithy.kotlin.runtime.SdkBaseException | ||
| import aws.smithy.kotlin.runtime.ServiceErrorMetadata | ||
| import aws.smithy.kotlin.runtime.client.ProtocolRequestInterceptorContext | ||
| import aws.smithy.kotlin.runtime.client.ResponseInterceptorContext | ||
| import aws.smithy.kotlin.runtime.http.interceptors.HttpInterceptor | ||
| import aws.smithy.kotlin.runtime.http.operation.HttpOperationContext | ||
| import aws.smithy.kotlin.runtime.http.request.HttpRequest | ||
| import aws.smithy.kotlin.runtime.http.response.HttpResponse | ||
| import aws.smithy.kotlin.runtime.http.response.header | ||
| import aws.smithy.kotlin.runtime.telemetry.logging.logger | ||
| import aws.smithy.kotlin.runtime.time.Instant | ||
| import aws.smithy.kotlin.runtime.time.until | ||
| import aws.smithy.kotlin.runtime.util.get | ||
| import kotlinx.atomicfu.* | ||
| import kotlin.coroutines.coroutineContext | ||
| import kotlin.time.Duration | ||
| import kotlin.time.Duration.Companion.minutes | ||
|
|
||
| /** | ||
| * An interceptor used to detect clock skew (difference between client and server clocks) and apply a correction. | ||
| */ | ||
| public class ClockSkewInterceptor : HttpInterceptor { | ||
| public companion object { | ||
| /** | ||
| * How much must the clock be skewed before attempting correction | ||
| */ | ||
| public val CLOCK_SKEW_THRESHOLD: Duration = 4.minutes | ||
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|
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| /** | ||
| * Determine whether the client's clock is skewed relative to the server. | ||
| * @return true if the service's response represents a definite clock skew error | ||
| * OR a *possible* clock skew error AND the skew exists. false otherwise. | ||
| * @param responseCodeDescription the server's response code description | ||
| * @param serverTime the server's time | ||
| */ | ||
| internal fun Instant.isSkewed(serverTime: Instant, responseCodeDescription: String?): Boolean = | ||
| responseCodeDescription?.let { | ||
| CLOCK_SKEW_ERROR_CODES.contains(it) || (POSSIBLE_CLOCK_SKEW_ERROR_CODES.contains(it) && until(serverTime).absoluteValue >= CLOCK_SKEW_THRESHOLD) | ||
| } ?: false | ||
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|
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| // Errors definitely caused by clock skew | ||
| private val CLOCK_SKEW_ERROR_CODES = listOf( | ||
| "RequestTimeTooSkewed", | ||
| "RequestExpired", | ||
| "RequestInTheFuture", | ||
| ) | ||
|
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| // Errors possibly caused by clock skew | ||
| private val POSSIBLE_CLOCK_SKEW_ERROR_CODES = listOf( | ||
| "PriorRequestNotComplete", | ||
| "RequestTimeout", | ||
| "RequestTimeoutException", | ||
| "InternalError", | ||
| ) | ||
|
There was a problem hiding this comment. Correctness: These don't appear to be related to clock skew. Looks like Java considers There was a problem hiding this comment. 🤦 Good catch. I took the wrong list of exceptions from Java and then convinced myself they could be caused by clock skew. |
||
| } | ||
|
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| // Clock skew to be applied to all requests | ||
| private val _currentSkew: AtomicRef<Duration?> = atomic(null) | ||
|
|
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| /** | ||
| * Apply the previously-computed skew, if it's set, to the execution context before signing | ||
| */ | ||
| public override suspend fun modifyBeforeSigning(context: ProtocolRequestInterceptorContext<Any, HttpRequest>): HttpRequest { | ||
| val logger = coroutineContext.logger<ClockSkewInterceptor>() | ||
|
|
||
| val skew = _currentSkew.value | ||
| skew?.let { | ||
| logger.info { "applying clock skew $skew to client" } | ||
| context.executionContext[HttpOperationContext.ClockSkew] = skew | ||
| } | ||
|
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| context.executionContext[HttpOperationContext.ClockSkewApproximateSigningTime] = Instant.now() | ||
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| return context.protocolRequest | ||
| } | ||
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| /** | ||
| * After receiving a response, check if the client clock is skewed and apply a correction if necessary. | ||
| */ | ||
| public override suspend fun modifyBeforeAttemptCompletion(context: ResponseInterceptorContext<Any, Any, HttpRequest, HttpResponse?>): Result<Any> { | ||
| val logger = coroutineContext.logger<ClockSkewInterceptor>() | ||
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| val serverTime = context.protocolResponse?.header("Date")?.let { | ||
| Instant.fromRfc5322(it) | ||
| } ?: run { | ||
| logger.debug { "service did not return \"Date\" header, skipping skew calculation" } | ||
| return context.response | ||
| } | ||
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| val clientTime = context.protocolRequest.headers["Date"]?.let { | ||
| Instant.fromRfc5322(it) | ||
| } ?: context.protocolRequest.headers["x-amz-date"]?.let { | ||
| Instant.fromIso8601(it) | ||
| } ?: context.executionContext[HttpOperationContext.ClockSkewApproximateSigningTime] | ||
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| val ex = (context.response.exceptionOrNull() as? SdkBaseException) ?: return context.response | ||
| val errorCode = ex.sdkErrorMetadata.attributes.getOrNull(ServiceErrorMetadata.ErrorCode) | ||
|
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||
| if (clientTime.isSkewed(serverTime, errorCode)) { | ||
| val skew = clientTime.until(serverTime) | ||
| logger.warn { "client clock ($clientTime) is skewed $skew from the server ($serverTime), applying correction" } | ||
| _currentSkew.getAndSet(skew) | ||
| context.executionContext[HttpOperationContext.ClockSkew] = skew | ||
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| // Mark the exception as retryable | ||
| ex.sdkErrorMetadata.attributes[ErrorMetadata.Retryable] = true | ||
| return Result.failure(ex) | ||
| } | ||
|
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| return context.response | ||
| } | ||
| } | ||
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nit:
responseCodeDescription->errorCodeAlso
responseCodeDescriptionshould probably be non-nullable since this always returns false otherwise which means it's really a required parameter for determining if a clock is skewed.