Smuggler - An HTTP Request Smuggling / Desync Testing Tool

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  • An HTTP Request Smuggling / Desync testing tool written in Python 3
    A special thanks to James Kettle for his research and methods into HTTP desyncs
    And a special thanks to Ben Sadeghipour for beta testing Smuggler and for allowing me to discuss my work at Nahamcon 2020
    This tool does not guarantee no false-positives or false-negatives. Just because a mutation may report OK does not mean there isn't a desync issue, but more importantly just because the tool indicates a potential desync issue does not mean there definitely exists one. The script may encounter request processors from large entities (i.e. Google/AWS/Yahoo/Akamai/etc..) that may show false positive results.

    1. git clone
    2. cd smuggler
    3. python3 -h
      Example Usage
      Single Host:
    python3 -u <URL>  

    List of hosts:

    cat list_of_hosts.txt | python3  


    usage: [-h] [-u URL] [-v VHOST] [-x] [-m METHOD] [-l LOG] [-q]  
    [-t TIMEOUT] [--no-color] [-c CONFIGFILE]  
    optional arguments:  
    -h, --help            show this help message and exit  
    -u URL, --url URL     Target URL with Endpoint  
    -v VHOST, --vhost VHOST  
    Specify a virtual host  
    -x, --exit_early      Exit scan on first finding  
    -m METHOD, --method METHOD  
    HTTP method to use (e.g GET, POST) Default: POST  
    -l LOG, --log LOG     Specify a log file  
    -q, --quiet           Quiet mode will only log issues found  
    -t TIMEOUT, --timeout TIMEOUT  
    Socket timeout value Default: 5  
    --no-color            Suppress color codes  
    -c CONFIGFILE, --configfile CONFIGFILE  
    Filepath to the configuration file of payloads  

    Smuggler at a minimum requires either a URL via the -u/--url argument or a list of URLs piped into the script via stdin. If the URL specifies https:// then Smuggler will connect to the host:port using SSL/TLS. If the URL specifies http:// then no SSL/TLS will be used at all. If only the host is specified, then the script will default to https://
    Use -v/--vhost <host> to specify a different host header from the server address
    Use -x/--exit_early to exit the scan of a given server when a potential issue is found. In piped mode smuggler will just continue to the next host on the list
    Use -m/--method <method> to specify a different HTTP verb from POST (i.e GET/PUT/PATCH/OPTIONS/CONNECT/TRACE/DELETE/HEAD/etc...)
    Use -l/--log <file> to write output to file as well as stdout
    Use -q/--quiet reduce verbosity and only log issues found
    Use -t/--timeout <value> to specify the socket timeout. The value should be high enough to conclude that the socket is hanging, but low enough to speed up testing (default: 5)
    Use --no-color to suppress the output color codes printed to stdout (logs by default don't include color codes)
    Use -c/--configfile <configfile> to specify your smuggler mutation configuration file (default:
    Config Files
    Configuration files are python files that exist in the ./config directory of smuggler. These files describe the content of the HTTP requests and the transfer-encoding mutations to test.
    Here is example content of

    def render_template(gadget):  
    RN = "\r\n"  
    p = Payload()  
    p.header  = "__METHOD__ __ENDPOINT__?cb=__RANDOM__ HTTP/1.1" + RN  
    # p.header += "Transfer-Encoding: chunked" +RN	  
    p.header += gadget + RN  
    p.header += "Host: __HOST__" + RN  
    p.header += "User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/78.0.3904.87 Safari/537.36" + RN  
    p.header += "Content-type: application/x-www-form-urlencoded; charset=UTF-8" + RN  
    p.header += "Content-Length: __REPLACE_CL__" + RN  
    return p  
    mutations["nameprefix1"] = render_template(" Transfer-Encoding: chunked")  
    mutations["tabprefix1"] = render_template("Transfer-Encoding:\tchunked")  
    mutations["tabprefix2"] = render_template("Transfer-Encoding\t:\tchunked")  
    mutations["space1"] = render_template("Transfer-Encoding : chunked")  
    for i in [0x1,0x4,0x8,0x9,0xa,0xb,0xc,0xd,0x1F,0x20,0x7f,0xA0,0xFF]:  
    mutations["midspace-%   02x"%i] = render_template("Transfer-Encoding:%cchunked"%(i))  
    mutations["postspace-%02x"%i] = render_template("Transfer-Encoding%c: chunked"%(i))  
    mutations["prespace-%02x"%i] = render_template("%cTransfer-Encoding: chunked"%(i))  
    mutations["endspace-%02x"%i] = render_template("Transfer-Encoding: chunked%c"%(i))  
    mutations["xprespace-%02x"%i] = render_template("X: X%cTransfer-Encoding: chunked"%(i))  
    mutations["endspacex-%02x"%i] = render_template("Transfer-Encoding: chunked%cX: X"%(i))  
    mutations["rxprespace-%02x"%i] = render_template("X: X\r%cTransfer-Encoding: chunked"%(i))  
    mutations["xnprespace-%02x"%i] = render_template("X: X%c\nTransfer-Encoding: chunked"%(i))  
    mutations["endspacerx-%02x"%i] = render_template("Transfer-Encoding: chunked\r%cX: X"%(i))  
    mutations["endspacexn-%02x"%i] = render_template("Transfer-Encoding: chunked%c\nX: X"%(i))

    There are no input arguments yet on specifying your own customer headers and user-agents. It is recommended to create your own configuration file based on and modify it to your liking.
    Smuggler comes with 3 configuration files: (fast), (niche, slow), (very slow) is the fastest because it contains less mutations.
    specify configuration files using the -c/--configfile <configfile> command line option
    Payloads Directory
    Inside the Smuggler directory is the payloads directory. When Smuggler finds a potential CLTE or TECL desync issue, it will automatically dump a binary txt file of the problematic payload in the payloads directory. All payload filenames are annotated with the hostname, desync type and mutation type. Use these payloads to netcat directly to the server or to import into other analysis tools.
    Helper Scripts
    After you find a desync issue feel free to use my Turbo Intruder desync scripts found Here: and are great scripts to help stage a desync attack
    These scripts are released under the MIT license. See LICENSE.
    Download Smuggler

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