Bug in API Management set-header policy when using UTF-8 characters

Gert Vloo 26

Hi, I think I found a bug in APIM set-header policy.

When I use a UTF-8 'dash' (–) character as input for set-header I get the error: "Expression value is invalid. Specified value has invalid Control characters."

The first error is thrown at 11-6-2021 07:01:04.722Z

Are there more people having this problem?

Mike Urnun 9,666 Reputation points Microsoft Employee

2021-06-24T22:05:52.547+00:00

Hello @Gert Vloo - I'd like to reproduce and validate. Could you share the policy snippet you used and any repro steps that might help?

Gert Vloo 26

Hi Mike,

Here is the simplified policy I used:

 <inbound>
        <set-variable name="requestBody" value="@{return context.Request.Body.As<string>(preserveContent: true);}" />
        <set-variable name="CUSTOMER_STATUS" value="@{return System.Xml.XPath.Extensions.XPathSelectElements(XDocument.Parse((string)context.Variables["requestBody"]), "//CONTACT_LOG_DETAIL[ATTRIBUTE='CUSTOMER_STATUS']/VALUE").FirstOrDefault()?.Value;}" />
        <set-header name="CUSTOMER_STATUS" exists-action="override">
            <value>@(context.Variables.GetValueOrDefault<string>("CUSTOMER_STATUS")?.ToUpper())</value>
        </set-header>
    </inbound>

And here is the test request:

        <CONTACT_LOG>
            <CONTACT_LOG_DETAILS>
                <CONTACT_LOG_DETAIL>
                    <ATTRIBUTE>CUSTOMER_STATUS</ATTRIBUTE>
                    <VALUE>HOLD 108 – OK</VALUE>
                </CONTACT_LOG_DETAIL>
            </CONTACT_LOG_DETAILS>
        </CONTACT_LOG>

Mike Urnun 9,666 Reputation points Microsoft Employee

2021-06-25T16:26:43.773+00:00

Thanks, @Gert Vloo ! I'll review and get back to you with my findings.

1 answer

Mike Urnun 9,666 Reputation points Microsoft Employee

2021-06-29T21:16:59.107+00:00

Hello @Gert Vloo

I have run this by the APIM team and they have confirmed that this is not a bug but an expected behavior that honors the RFC2616 spec for the header value as *TEXT, which is an 8-bit sequence of data excluding control characters: https://datatracker.ietf.org/doc/html/rfc2616#page-16

I hope this brings clarity and helps you proceed with your project.
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