Force 'now' to be in UTC for signing requests (#1975)

Fix signing request during DST change

Author: JonathanFinch-awin

CHANGELOG.md

@@ -20,6 +20,7 @@
 ### Fixed
 
 - Buffer the response in temporary file to avoid issues when stream is used by another request's body
+- SignerV4: Fix signing request during DST change
 
 ## 1.27.1
 

src/Signer/SignerV4.php

@@ -62,7 +62,7 @@ public function __construct(string $scopeName, string $region)
 
     public function presign(Request $request, Credentials $credentials, RequestContext $context): void
     {
-        $now = $context->getCurrentDate() ?? new \DateTimeImmutable();
+        $now = $context->getCurrentDate() ?? new \DateTimeImmutable('now', new \DateTimeZone('UTC'));
 
         // Signer date have to be UTC https://docs.aws.amazon.com/general/latest/gr/sigv4-date-handling.html
         $now = $now->setTimezone(new \DateTimeZone('UTC'));
@@ -73,7 +73,7 @@ public function presign(Request $request, Credentials $credentials, RequestConte
 
     public function sign(Request $request, Credentials $credentials, RequestContext $context): void
     {
-        $now = $context->getCurrentDate() ?? new \DateTimeImmutable();
+        $now = $context->getCurrentDate() ?? new \DateTimeImmutable('now', new \DateTimeZone('UTC'));
 
         // Signer date have to be UTC https://docs.aws.amazon.com/general/latest/gr/sigv4-date-handling.html
         $now = $now->setTimezone(new \DateTimeZone('UTC'));