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I'm afraid the software of progress telerik fiddler web debugger does not have this capability.
Nick Iliev
Telerik team
 answered on 03 May 2021
2 answers
264 views

https://docs.telerik.com/fiddler/knowledge-base/fiddlerscript/modifyrequestorresponse?_ga=2.226810973.1912327690.1619085606-390831375.1615941114

 

I reviewed the content on this link. I added the nuget library. Why can't I use these codes? When using it with C #, I get an error as I mentioned in the appendix. "'oSession' does not exist in the current context" What is the cause of this error? I cannot use any code related to Fiddler. What causes the oSession error? I want to work on FiddlerCore, but I couldn't find a solution for this error.

Rosen Vladimirov
Telerik team
 answered on 29 Apr 2021
6 answers
774 views

I tried to redirect all traffic thru Fiddler by using redsocks and iptables. Plaintext HTTP seems to work fine, however HTTPS doesn't seem to work properly.

Initially I didn't want to use redsocks at all - however it seemed that Fiddler cannot work in the way similar to sniproxy: using iptables -j DNAT alone doesn't work at all.

Then, although redsocks supports http CONNECT proxy mode, Fiddler no longer shows domain names in intercepted CONNECT entries - IP addresses are shown instead. Fiddler also throws out certificate errors, even if I check the "ignore certificate errors" checkbox, the intercepted application (which already trusts FiddlerRoot certificate) still refuses to connect. I think this should be related to SNI.

I think if Fiddler could work in the way similar to sniproxy, this problem would no longer exist, probably.

Rosen Vladimirov
Telerik team
 answered on 26 Apr 2021
1 answer
11.7K+ views

Hello,

Is it possible to capture localhost (client and server) websockets communication?In my case, in the client side I am using javascript code to connect to the websocket server, that it is started using java language.

In fiddler I do not see anything...

 

Regards,

Ed

Rosen Vladimirov
Telerik team
 answered on 23 Apr 2021
6 answers
975 views
Hello,

Is there any way to decompress post data in Fiddler, sent from application? Post request to server contain headers like this:
Content-type: application/x-compressed-json
Content-length: 3xx

Sent JSON data is unreadable. Any ideas are welcome! 
Arthur
Top achievements
Rank 1
 answered on 21 Apr 2021
1 answer
163 views

Hi everyone. I'm using Fiddler Everywhere on mac to intercept calls from the smartphone app to the vaccum robot, so i can use those commands to integrate the robot into my home automation system (Home Assistant).
so I set up Fiddler Everywhere, set up the proxy in the ios wifi and installed the certificates, and correctly intercepted the commands sent.
however, there are some "parameters" that i can't intercept, let me explain with one of the cases as an example: the robot obviously drains the battery when it's working. when it finishes cleaning, it goes back to the charging base. keeping the mobile phone active during the robot charging process, I see that for every percentage point of charge acquired, a post call is sent, of which I see url, headers and payload, but there's absolutely no trace of that percentage value (or any other info related to the battery). however, obviously on the smartphone I see that variation, so somehow the information has to go through.
so the question is: what can be the case that I can't catch THAT particular detail? what tests can i perform?
I hope I've explained it well enough, if necessary I can provide screenshots (app screen and details of the intercepted traffic).

Thanks

Rosen Vladimirov
Telerik team
 answered on 21 Apr 2021
1 answer
157 views

hi 

telerik ... please help me 

what is it . fiddler cant capture this traffic ( from this software ). HTTPS / TLS  why ...  ??

what is solution  ??

Rosen Vladimirov
Telerik team
 answered on 21 Apr 2021
5 answers
1.6K+ views

I'm trying to capture HTTP requests from .Net code running within a website on my local IIS.  The calls are being made by proxy classes generated from a WSDL via a Connected Services reference.  The recipient of the calls is claiming that the requests contain invalid payloads and I want to see the raw outgoing request from my end.

The service my code is calling requires TLS 1.2 and a client certificate.  The code runs fine at runtime as long as I don't have Fiddler in the picture (other than the payload supposedly being incorrect).

I have configured the .Net web app to run through Fiddler as follows:

<defaultProxy enabled="true">
  <proxy proxyaddress="http://127.0.0.1:8888" bypassonlocal="false"  />
</defaultProxy>

 

In Fiddler I can see the CONNECT commands are failing.  I have the Fiddler HTTPS Protocols configured as "<client>;ssl3;tls1.0;tls1.1;tls1.2".  I have exported the client certificate from the certificate store as a .cer and have added the following code to the end of the OnBeforeRequest() method (hostname and cert name changed for illustrative purposes):

if (oSession.HTTPMethodIs("CONNECT"))
{     
    if (oSession.HostnameIs("service.hostname"))
    {
        oSession["https-Client-Certificate"] = "C:\\certs\\Fiddler\\serviceClientCert.cer";
    }     
}

 

The CONNECT request is as follows:

CONNECT service.hostname:443 HTTP/1.1
Host: service.hostname
 
A SSLv3-compatible ClientHello handshake was found. Fiddler extracted the parameters below.
 
Version: 3.3 (TLS/1.2)
Random: 60 6F C6 38 2E BC 87 BE 57 7C 55 C9 A7 B6 31 42 00 EE 66 35 37 A0 CD 4E 08 42 7D 45 4F 89 A4 CB
"Time": 3/8/2000 8:18:56 AM
SessionID: empty
Extensions:
    server_name service.hostname
    supported_groups    x25519 [0x1d], secp256r1 [0x17], secp384r1 [0x18]
    ec_point_formats    uncompressed [0x0]
    signature_algs  rsa_pss_rsae_sha256, rsa_pss_rsae_sha384, rsa_pss_rsae_sha512, rsa_pkcs1_sha256, rsa_pkcs1_sha384, rsa_pkcs1_sha1, ecdsa_secp256r1_sha256, ecdsa_secp384r1_sha384, ecdsa_sha1, dsa_sha1, rsa_pkcs1_sha512, ecdsa_secp521r1_sha512
    SessionTicket   empty
    extended_master_secret  empty
    renegotiation_info  00
Ciphers:
    [C02C]  TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384
    [C02B]  TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256
    [C030]  TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384
    [C02F]  TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256
    [009F]  TLS_DHE_RSA_WITH_AES_256_GCM_SHA384
    [009E]  TLS_DHE_RSA_WITH_AES_128_GCM_SHA256
    [C024]  TLS_ECDHE_ECDSA_WITH_AES_256_CBC_SHA384
    [C023]  TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA256
    [C028]  TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA384
    [C027]  TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256
    [C00A]  TLS_ECDHE_ECDSA_WITH_AES_256_CBC_SHA
    [C009]  TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA
    [C014]  TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA
    [C013]  TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA
    [009D]  TLS_RSA_WITH_AES_256_GCM_SHA384
    [009C]  TLS_RSA_WITH_AES_128_GCM_SHA256
    [003D]  TLS_RSA_WITH_AES_256_CBC_SHA256
    [003C]  TLS_RSA_WITH_AES_128_CBC_SHA256
    [0035]  TLS_RSA_WITH_AES_256_CBC_SHA
    [002F]  TLS_RSA_WITH_AES_128_CBC_SHA
    [000A]  SSL_RSA_WITH_3DES_EDE_SHA
 
Compression:
    [00]    NO_COMPRESSION

 

The CONNECT response is as follows:

HTTP/1.1 200 Connection Established
FiddlerGateway: Direct
StartTime: 20:12:56.601
Connection: close
 
fiddler.network.https> HTTPS handshake to service.hostname (for #5) failed. System.ComponentModel.Win32Exception The credentials supplied to the package were not recognized

 

I'm not sure why I'm getting the error or what I can do to rectify the problem.

 

Nick Iliev
Telerik team
 answered on 13 Apr 2021
1 answer
629 views

Hello im trying to change the root CA that fiddler uses, i generated my own using openssl-

openssl genrsa -out rootCA.key 2048

and then

openssl req -x509 -new -nodes -key rootCA.key -sha1 -days 2048 -out rootCA.crt

 

then i went to about:config- and changed the fiddler.certmaker.bc.cert to the data inside the newly generated

crt file, and same with the fiddler.certmaker.bc.key, however whenever i load fiddler for some reason it writes the original certificate back to

fiddler.certmaker.bc.cert- i even tried replacing it in the windows registry at Computer\HKEY_CURRENT_USER\Software\Microsoft\Fiddler2\Prefs\.default but again it just wrote the original certificate back into it.

 

Nick Iliev
Telerik team
 answered on 06 Apr 2021
2 answers
244 views
every time i try to open up fiddler it says this

---------------------------
Awww, Fiddlesticks!
---------------------------
Fiddler has encountered an unexpected problem. If you believe this is a bug in Fiddler, please copy this message by hitting CTRL+C, and submit a bug report at http://www.telerik.com/forums/fiddler.

Could not load file or assembly 'System.ComponentModel.Composition, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089' or one of its dependencies. The system cannot find the file specified.

Type: System.IO.FileNotFoundException
Source: Fiddler
   at Fiddler.Proxy.()

   at Fiddler.Proxy..ctor(Boolean isPrimary, ProxySettings upstreamProxySettings) in C:\Jenkins\Fiddler_Windows\workspace\FiddlerCore\FiddlerCore.Shared\Common\Core\Proxy.cs:line 210

   at Fiddler.frmViewer.‹•(String[] ˆ•) in C:\Jenkins\Fiddler_Windows\workspace\Fiddler2\Fiddler.Shared\Viewer.cs:line 3339

   at Fiddler.frmViewer.‡•(String[] ˆ•) in C:\Jenkins\Fiddler_Windows\workspace\Fiddler2\Fiddler.Shared\Viewer.cs:line 3164


Fiddler v5.0.20204.45441 (x64 AMD64) [.NET 4.0.30319.42000 on Microsoft Windows NT 10.0.15063.0] 
---------------------------
OK   
---------------------------


pls help
Leo
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 answered on 05 Apr 2021
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