Questions on Fiddler Forum

4 answers

4.0K+ views

How to use Fiddler to block outgoing requests

Hi everyone, I normally wouldn't post something like this but I couldn't find it anywhere in the docs.

What I'm trying to do right now is block a specific outgoing request to a URL. Basically the site I'm testing sends a request to a URL to complete something, and to test it properly I need to block that request from ever getting sent.

Is there anyway to do this in Fiddler? The guy who's code it is assures me that I can but he forgot how. :p

Fiddler Classic

answered on 16 May 2017

0 answers

215 views

Extension of Text Wizard possible?

I can't find any documentation on how to extend the text wizard with new decode options, is it possible?

I would like to add decode of JWT access tokens into more readable form (with dates converted and such). The built in base64 decode is useable but dates are epoch based.

Any pointers? I did find an example of a customized inspector which I got working but wanted to include in text wizard as well

Extensions and Customization

asked on 12 May 2017

12 answers

2.6K+ views

HTTPS issues with Windows system proxy

Posting this here as a last resort. I've been using Fiddler for years, but sometime in the past few months, it stopped decrypting all HTTPS traffic using the system proxy. I see the same issue on both my office computer running Win7 and my home machine running Win10. This is with Fiddler4. I suspect it was the result of a recent Fiddler update?

Chrome gives the error page: "Your connection is not private" NET::ERR_CERT_AUTHORITY_INVALID

I've spent many hours trying every solution I could find online:

- Resetting all certificates with the reset button
- Unchecking 'decrypt HTTP traffic', removing certs, restart Fiddler, check 'decrypt' again
- Generating certs with different generators (CertEnroll, MakeCert)
- Exporting root cert and manually importing into certmgr
- Manually importing into Chrome cert settings

I see the certificate in the Trusted Root Certificates folder in certmgr. I feel like I've tried everything. Have I missed something?

Windows

answered on 11 May 2017

0 answers

106 views

Run the same set of API tests against different hosts

What is the best way to do this?

If it is by simply prompting in BeforeTestList(), then how would you prompt for, say, which host out of 4 choices to use on a particular run?

Also, is there any way to directly edit the API tests themselves, other than just view them readonly with the Inspect Baseline option?

Extensions and Customization

asked on 10 May 2017

3 answers

799 views

Not able to capture the HTTPS traffic from IOS

I was able to capture the traffic from IOS and andriod 2 weeks back but from 2 days back getting the below error.

11:51:43:8688 !SecureClientPipeDirect failed: System.Security.Authentication.AuthenticationException A call to SSPI failed, see inner exception. < The certificate chain was issued by an authority that is not trusted for pipe (CN=xxx-xxx.com, O=DO_NOT_TRUST_BC, OU=Created by http://www.fiddler2.com).
11:51:44:0193 !SecureClientPipeDirect failed: System.Security.Authentication.AuthenticationException A call to SSPI failed, see inner exception. < The certificate chain was issued by an authority that is not trusted for pipe (CN=xxxx.apple.com, O=DO_NOT_TRUST_BC, OU=Created by http://www.fiddler2.com).

Mobile

answered on 08 May 2017

1 answer

87 views

Forum search function not working?

Hi!

This is really puzzling to me. It seems like the forum search function is not working. I just tried to search for "mozroots" in the search bar, and it returned 0 results, even though there is a thread containing the word mozroots on the front page.

I'm attaching a screenshot.

Linux

answered on 05 May 2017

1 answer

875 views

FiddlerScript customization throws and error in Scriptbase.cs:919

Hi, I'm trying to proxy and cache some responses that are being redownloaded over and over.

To do that I wrote this simple customization in FiddlerScript:

static function OnBeforeResponse(oSession: Session) {

var captureRequests = false;

var targetHost = "api.nuget.org";

var captureFolder = "c:\\Projects\\Fiddler\\api.nuget.org";

// Capture traffic

if (captureRequests && oSession.host.toLowerCase() == targetHost)

{

var targetFile = captureFolder + oSession.PathAndQuery.Split('?')[0].Replace('/','\\');

oSession.oResponse["X-oSession-PathAndQuery"] = targetFile;

var fi = new FileInfo(targetFile);

Directory.CreateDirectory(fi.DirectoryName)

if(!File.Exists(fi.FullName))

{

File.WriteAllBytes(fi.FullName, oSession.ResponseBody);

}

// // Replay captured

var replayRequests = true;

if (replayRequests&& oSession.host.toLowerCase() == targetHost)

{

var targetFile = captureFolder +"\\" + oSession.PathAndQuery.Split('?')[0].Replace('/','\\');

var fi = new FileInfo(targetFile);

if(!File.Exists(fi.FullName))

{

oSession["x-replywithfile"] = fi.FullName;

}

And presumably it should work - when captureRequests=true - fiddler captures requests from a particular domain into a folder, preserving path and file name

When replayRequests = true - it simply replays existing files.

The problem here that even if I just capturing the data (I suspect I may be replaying too late - fiddler would call http already by that time...) - fiddler throws a lot of errors with this text:

---------------------------

FiddlerScript OnBeforeResponse() failed.

---------------------------

There was a problem with your FiddlerScript.

The given path's format is not supported.

at System.Security.Permissions.FileIOPermission.EmulateFileIOPermissionChecks(String fullPath)

at System.Security.Permissions.FileIOPermission.QuickDemand(FileIOPermissionAccess access, String fullPath, Boolean checkForDuplicates, Boolean needFullPath)

at System.IO.FileInfo.Init(String fileName, Boolean checkHost)

at Fiddler.ScriptNamespace.Handlers.OnBeforeResponse(Session oSession)

at Fiddler.ScriptBase.(Session ) in C:\JenkinsHome\jobs\FiddlerReleaseBuild\workspace\Fiddler2\Common\Application\Scripting\ScriptBase.cs:line 919

---------------------------

OK

---------------------------

I tried to investigate it by playing with code and identified that for some reason a typical file path like `c:\Projects\Fiddler\api.nuget.org\v3\registration1-gz\analytics\index.json` causes an error. Or that code is somehow not thread safe and competing requests simply break it (and visual studio starts them in parallel so there is a high chance of some kind of race).

Can anyone suggest what am I doing wrong here or maybe advice on better solution to the problem.

Extensions and Customization

answered on 04 May 2017

0 answers

415 views

cannot see headers

Hello,

I hope this is the correct forum for my question.

I am learning to use Fiddler (for debugging API's issues) hence I could be asking a question which is very basic or non-sensical, in this case I apologise upfront.

I would like Fiddler to show the streams going to Shopify using their API's:- in this example I have a simple GET Customers coded in Microsoft Dotnet. The API works 100% and it returns the expected XML list of current Shopify Customers.

However, when I look at the Fiddler data, it does NOT show the Authentication Headers:- I was expecting to see my Shopify API Key and Password.

Would anyone be able to explain why Fiddler states there isno Authorization Header where I used it in the API call?

Thanks

Fiddler Classic

asked on 04 May 2017

0 answers

152 views

Radio button prompting in rules

Is there a way to do a radio button effect that I can leverage in the custom rules.

I want to prompt for which one of a small set of choices should be used as the Session[i].hostname to run the selected tests.

Select host:

- localhost

- xxx.yyy.com

-aaa.bbb.com

Or if there is a better more in-built way to dynamically change the hostname for all selected sessions per run.

Extensions and Customization

asked on 03 May 2017

0 answers

289 views

HTTPS Handshake failure: AuthenticationException

I am receiving an error from Fiddler when attempting to decrypt HTTPS traffic from a specific site. Other HTTPS sites seem to be working Ok.

The error is "fiddler.network.https> HTTPS handshake to login.nbnco.net.au"

URL : https://login.nbnco.net.au/portal-login

Fiddler Version :

v4.6.20171.14978
Built: Tuesday, 21 March 2017
64-bit AMD64, VM: 110.0mb, WS: 90.0mb
.NET 4.6.2 WinNT 6.1.7601 SP1

HTTPS protocols being used : <client>;ssl3;tls1.0

Browsers used :

Chrome Latest - Version 58.0.3029.96 (64-bit)

Internet Explorer : Version 11.0.9600.18638

Fiddler Log :

11:46:38:4535 fiddler.network.https> HTTPS handshake to login.nbnco.net.au (for #1136) failed. System.Security.Authentication.AuthenticationException A call to SSPI failed, see inner exception. < The message received was unexpected or badly formatted

Win32 (SChannel) Native Error Code: 0x80090326

Can anyone tell me what is happening here? And any steps I can take to rectify?

I have already followed other advice I have seen regarding Resetting Certificates, and restarting Fiddler.

Much thanks!!!

Chris

Windows