private async Task <bool> ConditionalGetOrHeadIsValid(HttpContext httpContext)
{
_logger.LogInformation("Checking for conditional GET/HEAD.");
if (httpContext.Request.Method != HttpMethod.Get.ToString() &&
httpContext.Request.Method != HttpMethod.Head.ToString())
{
_logger.LogInformation("Not valid - method isn't GET or HEAD.");
return(false);
}
// we should check ALL If-None-Match values (can be multiple eTags) (if available),
// and the If-Modified-Since date (if available AND an eTag matches). See issue #2 @Github.
// So, this is a valid conditional GET/HEAD (304) if one of the ETags match and, if it's
// available, the If-Modified-Since date is larger than what's saved.
// if both headers are missing, we should
// always return false - we don't need to check anything, and
// can never return a 304 response
if (!httpContext.Request.Headers.Keys.Contains(HeaderNames.IfNoneMatch) &&
!httpContext.Request.Headers.Keys.Contains(HeaderNames.IfModifiedSince))
{
_logger.LogInformation("Not valid - no If-None-Match or If-Modified-Since headers.");
return(false);
}
// generate the request key
var storeKey = await _storeKeyGenerator.GenerateStoreKey(
ConstructStoreKeyContext(httpContext.Request, _validationModelOptions));
// find the validatorValue with this key in the store
var validatorValue = await _store.GetAsync(storeKey);
// if there is no validation value in the store, always
// return false - we have nothing to compare to, and can
// never return a 304 response
if (validatorValue?.ETag == null)
{
_logger.LogInformation("No saved response found in store.");
return(false);
}
if (httpContext.Request.Headers.Keys.Contains(HeaderNames.IfNoneMatch))
{
// check the ETags. If the Etag is present we should not check the If-Modified-Since header
// see issue https://github.com/KevinDockx/HttpCacheHeaders/issues/82
// cfr: "If none of the entity tags match, then the server MAY perform the requested method as if the
// If-None-Match header field did not exist, but MUST also ignore any If-Modified-Since header field(s)
// in the request. That is, if no entity tags match, then the server MUST NOT return a 304(Not Modified) response."
return(CheckIfNoneMatchIsValid(httpContext, validatorValue));
}
_logger.LogInformation("No If-None-Match header, don't check ETag.");
return(await CheckIfModifiedSinceIsValid(httpContext, validatorValue));
}
private async Task <bool> ConditionalGetOrHeadIsValid(HttpContext httpContext)
{
_logger.LogInformation("Checking for conditional GET/HEAD.");
if (httpContext.Request.Method != HttpMethod.Get.ToString() &&
httpContext.Request.Method != HttpMethod.Head.ToString())
{
_logger.LogInformation("Not valid - method isn't GET or HEAD.");
return(false);
}
// we should check ALL If-None-Match values (can be multiple eTags) (if available),
// and the If-Modified-Since date (if available AND an eTag matches). See issue #2 @Github.
// So, this is a valid conditional GET/HEAD (304) if one of the ETags match and, if it's
// available, the If-Modified-Since date is larger than what's saved.
// if both headers are missing, we should
// always return false - we don't need to check anything, and
// can never return a 304 response
if (!httpContext.Request.Headers.Keys.Contains(HeaderNames.IfNoneMatch) &&
!httpContext.Request.Headers.Keys.Contains(HeaderNames.IfModifiedSince))
{
_logger.LogInformation("Not valid - no If-None-Match or If-Modified-Since headers.");
return(false);
}
// generate the request key
var storeKey = await _storeKeyGenerator.GenerateStoreKey(
ConstructStoreKeyContext(httpContext.Request, _validationModelOptions));
// find the validatorValue with this key in the store
var validatorValue = await _store.GetAsync(storeKey);
// if there is no validation value in the store, always
// return false - we have nothing to compare to, and can
// never return a 304 response
if (validatorValue?.ETag == null)
{
_logger.LogInformation("No saved response found in store.");
return(false);
}
// check the ETags
// return the combined result of all validators.
return(CheckIfNoneMatchIsValid(httpContext, validatorValue) &&
await CheckIfModifiedSinceIsValid(httpContext, validatorValue));
}
// Key = generated from request URI & headers (if VaryBy is set, only use those headers)
public async Task <EntityTagHeaderValue> GenerateETag(HttpContext context)
{
var storeKey = (await _storeKeyGenerator.GenerateStoreKey(context)).ToString();
var requestKeyAsBytes = Encoding.UTF8.GetBytes(storeKey);
// combine both to generate an etag
var combinedBytes = GetETagValue(requestKeyAsBytes);
return(new ETag(_eTagType, combinedBytes).GetETag());
}