Merged PR 32088: Merged PR 32017: [7.0] Fix regression loading null-p…

…assword encrypted PFX certificates

When decrypting the payload with empty string and null passwords, try reading the payload with the Asn reader to ensure the header matches the expected format. If that succeeds, then proceed with the iteration counting. This guards against a false-positive match that previously caused our iteration count work to throw/abort, thus preventing some null-password encrypted payloads from being loaded.

src/libraries/Common/src/System/Security/Cryptography/Asn1/Pkcs12/PfxAsn.manual.cs

@@ -249,6 +249,12 @@ private static ArraySegment<byte> DecryptContentInfo(ContentInfoAsn contentInfo,
                         default,
                         encryptedData.EncryptedContentInfo.EncryptedContent.Value.Span,
                         destination);
+
+                    // When padding happens to be as expected (false-positive), we can detect gibberish and prevent unexpected failures later
+                    // This extra check makes it so it's very unlikely we'll end up with false positive.
+                    AsnValueReader outerSafeBag = new AsnValueReader(destination.AsSpan(0, written), AsnEncodingRules.BER);
+                    AsnValueReader safeBagReader = outerSafeBag.ReadSequence();
+                    outerSafeBag.ThrowIfNotEmpty();
                 }
                 catch
                 {
@@ -259,6 +265,12 @@ private static ArraySegment<byte> DecryptContentInfo(ContentInfoAsn contentInfo,
                         default,
                         encryptedData.EncryptedContentInfo.EncryptedContent.Value.Span,
                         destination);
+
+                    // When padding happens to be as expected (false-positive), we can detect gibberish and prevent unexpected failures later
+                    // This extra check makes it so it's very unlikely we'll end up with false positive.
+                    AsnValueReader outerSafeBag = new AsnValueReader(destination.AsSpan(0, written), AsnEncodingRules.BER);
+                    AsnValueReader safeBagReader = outerSafeBag.ReadSequence();
+                    outerSafeBag.ThrowIfNotEmpty();
                 }
             }
             finally