fix possible RegexMatchTimeoutException

[mus65]

6bda890 introduced a Timeout on RegEx compilation. We hit this timeout a few times since this change.

Removed the timeout so it uses the default like before.

Stacktrace:

System.Text.RegularExpressions.RegexMatchTimeoutException: The Regex engine has timed out while trying to match a pattern to an input string. This can occur for many reasons, including very large inputs or excessive backtracking caused by nested quantifiers, back-references and other factors.
   at System.Text.RegularExpressions.RegexRunner.<CheckTimeout>g__ThrowRegexTimeout|25_0()
   at Regex5_TryMatchAtCurrentPosition(RegexRunner, ReadOnlySpan`1)
   at Regex5_Scan(RegexRunner, ReadOnlySpan`1)
   at System.Text.RegularExpressions.Regex.RunAllMatchesWithCallback[TState](String inputString, ReadOnlySpan`1 inputSpan, Int32 startat, TState& state, MatchCallback`1 callback, RegexRunnerMode mode, Boolean reuseMatchObject)
   at System.Text.RegularExpressions.RegexReplacement.ReplaceSimpleText(Regex regex, String input, String replacement, Int32 count, Int32 startat)
   at System.Text.RegularExpressions.Regex.Replace(String input, String replacement)
   at Microsoft.OpenApi.Validations.Rules.OpenApiPathsRules.<>c.<get_PathMustBeUnique>b__4_0(IValidationContext context, OpenApiPaths item)
   at Microsoft.OpenApi.Validations.ValidationRule`1.Evaluate(IValidationContext context, Object item)
   at Microsoft.OpenApi.Validations.OpenApiValidator.Validate(Object item, Type type)
   at Microsoft.OpenApi.Validations.OpenApiValidator.Validate[T](T item)
   at Microsoft.OpenApi.Validations.OpenApiValidator.Visit(OpenApiPaths item)
   at Microsoft.OpenApi.Services.OpenApiWalker.Walk(OpenApiPaths paths)
   at Microsoft.OpenApi.Services.OpenApiWalker.<>c__DisplayClass4_0.<Walk>b__2()
   at Microsoft.OpenApi.Services.OpenApiWalker.Walk(String context, Action walk)
   at Microsoft.OpenApi.Services.OpenApiWalker.Walk(OpenApiDocument doc)
   at Microsoft.OpenApi.Services.OpenApiWalker.Walk(IOpenApiElement element)
   at Microsoft.OpenApi.Extensions.OpenApiElementExtensions.Validate(IOpenApiElement element, ValidationRuleSet ruleSet)
   at Microsoft.OpenApi.Readers.OpenApiYamlDocumentReader.Read(YamlDocument input, OpenApiDiagnostic& diagnostic)
   at Microsoft.OpenApi.Readers.OpenApiTextReaderReader.Read(TextReader input, OpenApiDiagnostic& diagnostic)
   at Microsoft.OpenApi.Readers.OpenApiStringReader.Read(String input, OpenApiDiagnostic& diagnostic)

[baywet]

Hi @mus65,
Thanks for the contribution.
The timeout is a security requirement here. Depending on where the library is used, attackers could inject an extremely long path to DDoS a service if there was no timeout.
Instead of removing the timeout, I encourage you to explore the following route:

• replace the regex by string operations (index of, substring, etc)
• remove captures (if not necessary)
• reduce back-propagation.

[mus65]

@baywet replaced the regex with IndexOf/Substring and rebased to take #1504 into account.

[baywet]

Thanks for the update, here are a few recommendations

[mus65]

@microsoft-github-policy-service agree company="TIS GmbH"

[baywet]

thanks for making the changes

[baywet]

@MaggieKimani1 for final review and merge