Move expires timestamp in SignatureV4 to be generated before startTimestamp #1325

daum · 2017-07-06T23:18:51Z

As described in issue #1322 an edge case of using exactly 1 week expiration when a second rolls between
the startTimestamp calculation via time() and the expires timestamp can cause incorrect exceptions. This
occurs when the second rolls over (ie 12:01:01.9999999 to 12:02:02.00000) between the startTime (time())
and endTime conversion from strtotime(). This causes the exception of the expiration must be less than a week
to be thrown. By moving the endTime to be converted before startTime this guarantees that will never occur.

…mestamp for edge case of second roll overs. As described in issue aws#1322 an edge case of using exactly 1 week expiration when a second rolls between the startTimestamp calculation via time() and the expires timestamp can cause incorrect exceptions. This occurs when the second rolls over (ie 12:01:01.9999999 to 12:02:02.00000) between the startTime (time()) and endTime conversion from strtotime(). This causes the exception of the expiration must be less than a week to be thrown. By moving the endTime to be converted before startTime this guarantees that will never occur.

…nt expiration timestamp formats so it only uses public API.

codecov-io · 2017-07-07T10:15:17Z

Codecov Report

Merging #1325 into master will increase coverage by <.01%.
The diff coverage is 100%.

@@             Coverage Diff              @@
##             master    #1325      +/-   ##
============================================
+ Coverage     91.87%   91.87%   +<.01%     
- Complexity     2465     2466       +1     
============================================
  Files           142      142              
  Lines          7518     7523       +5     
============================================
+ Hits           6907     6912       +5     
  Misses          611      611

Impacted Files	Coverage Δ	Complexity Δ
src/Signature/SignatureV4.php	`100% <100%> (ø)`	`45 <6> (+1)`	⬆️

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imshashank · 2017-07-10T18:44:25Z

tests/Signature/SignatureV4Test.php

-        );
+        list($request, $credentials, $signature) = $this->getFixtures();
+        $credentials = new Credentials('foo', 'bar', '123');
+        $url = (string) $signature->presign($request,$credentials,new \DateTime('December 11, 2013 00:00:00 UTC'))->getUri();


Please break this into lines less than 80 characters in length.

imshashank · 2017-07-10T18:44:30Z

tests/Signature/SignatureV4Test.php

-        );
+        list($request, $credentials, $signature) = $this->getFixtures();
+        $credentials = new Credentials('foo', 'bar', '123');
+        $url = (string) $signature->presign($request,$credentials,'December 11, 2013 00:00:00 UTC')->getUri();


Please break this into lines less than 80 characters in length.

daum · 2017-07-11T07:36:41Z

@imshashank All set just updated those lines.

kstich

I think this will end up requiring a deeper change to convertExpires or convertToTimestamp to handle a start time to guarantee this is a fix.

kstich · 2017-07-13T17:22:33Z

.changes/nextrelease/signatureExpiratinoEdgeCaseFix.json

+    {
+        "type": "bugfix",
+        "category": "Signature",
+        "description": "Fixed edgecase in expiration duration check on signature when seconds roll between implicit startime and relative end time.."


Non-blocker: double . at the end.

All set, removed.

kstich · 2017-07-13T18:14:48Z

src/Signature/SignatureV4.php

@@ -82,6 +82,7 @@ public function presign(
        $expires,
        array $options = []
    ) {
+        $expiresTimestamp = $this->convertToTimestamp($expires);


Isn't this still susceptible to being incorrect? The only way to guarantee the strtotime case for convertExpires() will be in coordination with the $startTimestamp is to pass in a $now.

Consider the case:
1:23:45.9999 - $expiresTimestamp generated from '+1 week'
1:23:46.0005 - $startTimestamp generated via time()
1:23:46:0100 - convertExpires() is called, generating 604799

You'd technically get a different duration however it won't throw an error. Assuming that server times are synced up noone could request it in historical time (requiring the extra second of duration). The goal of this PR is to fix the opposite case where the second rolls and you fall past the 1 week allow duration and it throws an error, even though the initial request is valid.

It does fix the issue of throwing an exception on the calculation, but not the correctness of the relative time cases. For instance, the tests for the AuthTokenGenerator detect an explicit expires length. Actually, it looks like these are already failing very infrequently.

We could take this PR as is and supply another fix for relative times, though it'd be preferable to fix both at the same time. The change for this would be using convertToTimestamp in convertExpires for the non-strtotime cases and passing the $startTimestamp to strtotime's second param. strtotime will properly ignore being given a $now parameter when not using a relative time. This would be in lieu of doing a convertToTimestamp before sending in to convertExpires.

@kstich Not sure I follow what the fix for both scenarios would be. I think part of the issue is that if the SDK allows any relative timestamp to be passed there will always be scenarios when the duration for the expires length could be off. The reason for that is that the thread could be paused/roll over a second at any given point, so unless the caller of presign includes a "now" parameter (options perhaps?) there is always the possibility of a slight skew.

We could add that as an option to pass, if passed any strtotime in the convertToTimestamp will use the "now" as the second parameter for the time it is based on.

This would solve any specific duration requests from possibly being off by a tiny amount. We could maintain BC by making it an optional parameter, so if it isn't passed it will just use the current time that the createSign is invoked, which majority of the time would be the same time.

Let me know if that makes sense. I think the change to the existing PR would be fairly minimal. I'd update convertToTimestamp to take a second parameter, which would be passed to the strtotime conversion in it. Then in the options array it'd check for the "now" parameter, if non-existent it'd take current time. What do you think the option should be? "relativeTimeBase" could be more descriptive than now?

@daum Thanks for working through this with us. I think we're both on the same page with regards to the problem and that the solution being worked towards both fixes the issues at hand and maintains our contracts.

For a relative expires, which will be the only used case for an optional $relativeTimeBase in convertToTimestamp, we'll already have $startTimestamp and the intent of the contract is the relative expires is based on that. The default/non-existent value should just be null, as that will have strtotime use its own default if we're not overriding. This should probably also warrant a new test on the relative time handling of SignatureV4 of the '+6 days' the suite is set up for; you'll have to pass in the 'start_time' based on the 'aws_time' as an option.

Ok sounds good, will try to update the PR with the additional test + other changes either later today or tomorrow hopefully.

daum · 2017-07-24T15:37:41Z

@kstich @imshashank Just wanted to check in on this to see if you think it will be integrated soon or if there are other questions.

… timestamps on a presign request. Defaults to current time.

kstich · 2017-08-03T21:22:13Z

src/Signature/SignatureV4.php

@@ -82,7 +82,9 @@ public function presign(
        $expires,
        array $options = []
    ) {
-        $startTimestamp = isset($options['start_time']) ? $this->convertToTimestamp($options['start_time']) : time();
+        $relativeTimeBase = isset($options['relativeTimeBase']) ? $options['relativeTimeBase'] : time();
+        $expiresTimestamp = $this->convertToTimestamp($expires,$relativeTimeBase);


Thanks for making these updates @daum!

It seems like I was unclear previously when talking about this section, apologies. I don't think there needs to be a separate relativeTimeBase option, but instead use the $startTimestamp we already have for this line passed to $relativeTimeBase of convertToTimestamp when generating $expiresTimestamp. I can't think of any cases where someone would want 'relativeTimeBase' to not be the same as 'start_time', let me know if I'm missing something.

And a small formatting update: please add a space after the , in this function call.

Just updated to use the startTimestamp. Let me know if you are ok with that ternary in the strtotime function for the convertTimestamp, wasn't sure if you'd prefer that or a nested if/else.

The ternary located here isn't actually needed. strtotime will use its own default ($now = time()) on being passed null and will correctly ignore the $now when passed a non-relative $time string.

$time = time(); $date = date(DATE_ATOM, $time); echo strtotime($date); // 1501704830 echo strtotime($date, null); // 1501704830 echo strtotime($date, $time); // 1501704830 echo strtotime('+15 minutes', $time); // 1501705730

@kstich I think the segfault on the builds is coming from the precise to trusty upgrade, I can't replicate locally. It also appears this is a change Travis made recently: https://blog.travis-ci.com/2017-07-11-trusty-as-default-linux-is-coming . There were no segfaults before the upgrade, I can add the precise variable into the travis config if you want. Let me know how you want to proceed.

@kstich Actually that's a fun PHP gotcha, here is what happens if I send it a null when using a relative timestamp (see last test case):

$time = time(); $date = date(DATE_ATOM, $time); echo strtotime($date)."\n"; // 1501704830 echo strtotime($date, null)."\n"; // 1501704830 echo strtotime($date, $time)."\n"; // 1501704830 echo strtotime('+15 minutes', $time)."\n"; // 1501705730 echo strtotime('+15 minutes', null)."\n"; // 900

The second parameter has to default to time() or a valid int otherwise it starts at 0 which is what you see in my last example.

That's lovely, this should stay a ternary then. Sorry for the misdirection!

#1339 will temporarily take care of the Travis issue and we'll rerun these jobs.

Ok - will wait for you guys to merge that, then will merge those updates into this branch.

#1339 has been merged in.

imshashank

Minor formatting fixes. Besides that LGTM

imshashank · 2017-08-03T23:21:11Z

src/Signature/SignatureV4.php

@@ -82,7 +82,9 @@ public function presign(
        $expires,
        array $options = []
    ) {
-        $startTimestamp = isset($options['start_time']) ? $this->convertToTimestamp($options['start_time']) : time();
+
+        $startTimestamp = isset($options['start_time']) ? $this->convertToTimestamp($options['start_time'], null) : time();


Please break this into multiple lines. We try to keep all line length to be of less than 80 characters in the PHP SDK.

Similar to my other comment - how would you like the ternary broken up. If you would prefer I could also switch it to a if/else which would have a shorter line length.

An example of what our 3 line ternary looks like can be found here.

imshashank · 2017-08-03T23:21:16Z

src/Signature/SignatureV4.php

    {
        if ($dateValue instanceof \DateTime) {
            $timestamp = $dateValue->getTimestamp();
        } elseif (!is_numeric($dateValue)) {
-            $timestamp = strtotime($dateValue);
+            $timestamp = strtotime($dateValue, $relativeTimeBase === null ? time() : $relativeTimeBase );


Please break this into multiple lines. We try to keep all line length to be of less than 80 characters in the PHP SDK.

How do you want to break the ternary statements? I personally think they are much more readable on one line like this but understand the 80 character comment, was just following other examples in the code like https://github.com/daum/aws-sdk-php/blob/6cd12a2744b9da9813faf1f7d6bf3f52d336c67a/src/Signature/SignatureV4.php#L39

Can you just give me an example of how you'd like the ternary formatted for the multiple lines and I'll get that fixed up asap.

For this case, the ternary can be one line but the arguments would be separated.

strtotime( $dateValue, $relativeTimeBase === null ? time() : $relativeTimeBase );

Thanks just updated

imshashank

LGTM

kstich · 2017-08-04T20:59:52Z

Thanks again for this work @daum!

daum added 2 commits July 6, 2017 19:12

Added changelog document

e98a955

daum mentioned this pull request Jul 6, 2017

Edge Case Error: Valid 1 week expiration throws error #1322

Closed

Updated Signature Presign tests to not use reflection to test differe…

6e7ac7c

…nt expiration timestamp formats so it only uses public API.

imshashank requested a review from kstich July 7, 2017 17:28

imshashank reviewed Jul 11, 2017

View reviewed changes

Updated line spacing on test to be under 80 characters

30d6c8b

kstich requested changes Jul 13, 2017

View reviewed changes

Removed extra period in sentence in change doc.

12cc59e

Added relativeTimeBase option to specify a base time for all relative…

880c3e1

… timestamps on a presign request. Defaults to current time.

kstich requested changes Aug 3, 2017

View reviewed changes

daum added 2 commits August 3, 2017 17:32

Removed relativeTimeBase option and instead uses startTime as base.

de105ed

Merge branch 'master' into bugfix-signature-expiration-second-break

6cd12a2

kstich approved these changes Aug 3, 2017

View reviewed changes

imshashank reviewed Aug 3, 2017

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Formatting update for line breaks

851c29f

imshashank reviewed Aug 4, 2017

View reviewed changes

kstich merged commit e49a541 into aws:master Aug 4, 2017

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Move expires timestamp in SignatureV4 to be generated before startTimestamp #1325

Move expires timestamp in SignatureV4 to be generated before startTimestamp #1325

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Move expires timestamp in SignatureV4 to be generated before startTimestamp #1325

Move expires timestamp in SignatureV4 to be generated before startTimestamp #1325

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