Decrypting BIG-IP Packet Captures without iRules

Dammit JRahm now you have ruined my entire weekend - I just had to get a Bash version working 🤣

I don't know how you do it but these ideas are awesome and I just love the challenge trying to keep up with your Python (some would might call it an addiction 😋).

The overall concept wasn't the difficult part, getting curl to consume the json payload was! I wasn't able to create a one-liner with the timeout + tcpdump parameters. Either curl complained about the "--f5" option inside the json body or the BigIP complained about it not being a proper formated json, so I gave up and put the body in a file instead. If you have an idea on how to make the right sequence of escaping, please let me know.

During my scritpting sessions I added the option to fetch a VS in another partition and some error catching around different scenarios. You could probably put more catching in there but I'm out of weekend 😆

I also played with the idea of extracting the VS' as a list and then make it a selection but if you have thousands of services this wouldn't scale well. So, I settled for some checking if the return value indead was an IP address.

#!/bin/bash

# Utility functions. It takes two parameters, first is the text and the second is the default value.
# If no default value is supplied it will loop until something is entered.
function prompt_user {
    read -p "${1} (default: [${2}]): " input
    echo "${input:-${2}}"
}

function prompt_bigip_address {
    read -p "BIG-IP address [default: https://10.1.1.10]: " BIGIP
    # Assign a default value if nothing is entered
    BIGIP="${BIGIP:-https://10.1.1.10}"
    # Make sure that the address is prefixed with https if only an IP address is entered
    BIGIP="https://${BIGIP#https://}"
}

function prompt_credentials {
    read -p "BIG-IP username [default: admin]: " USER
    USER="${USER:-admin}"
    read -s -p "BIG-IP password: " PASS
    echo ""
}

function get_token {
     # Authenticate and get auth token
    TOKEN=$(curl -skf -H "Content-Type: application/json" -d '{"username":"'$USER'","password":"'$PASS'","loginProviderName":"tmos"}' "$BIGIP/mgmt/shared/authn/login" | grep -oP '(?<="token":")[^"]+')

}

function delete_token {
    # Delete token
    curl -sk -H "X-F5-Auth-Token: $TOKEN" -X DELETE "$BIGIP/mgmt/shared/authz/tokens/$TOKEN"| jq -r  '.|{"Deleted token": .token}'    
}

function toggle_ssl_provider {
    # Toggle the "sys db tcpdump.sslprovider" variable
    local value=${1}
    curl -sk -X PATCH -H "Content-Type: application/json" -H "X-F5-Auth-Token: $TOKEN" "$BIGIP/mgmt/tm/sys/db/tcpdump.sslprovider" -d '{"value": "'$value'"}'
}

function download_file {
    # Download the pcap file from the filesystem "/share/images/encrypt_autocap_*.pcap"
    local file="${1}" message="${2}"
    curl -skf -H "X-F5-Auth-Token: $TOKEN" "$BIGIP/mgmt/cm/autodeploy/software-image-downloads/$file" -o "$file"
    if [ "$?" -eq 0 ]; then
      echo -e "\t$message"
    else
      echo -e "\tDOWNLOAD FAILED!!!"
    fi
}

function delete_file {
    # Delete the pcap file from the filesystem "/share/images/encrypt_autocap_*.pcap"
    local file="${1}" message="${2}"
    curl -skf -X POST -H "X-F5-Auth-Token: $TOKEN" -H "Content-Type: application/json" "$BIGIP/mgmt/tm/util/unix-rm" -d '{"command": "run", "utilCmdArgs": "/shared/images/'$file'"}'
    if [ "$?" -eq 0 ]; then
      echo -e "\t$message"
    else
      echo -e "\tDELETE FAILED!!!"
    fi
}

# Main function
function main {
    # Get user inputs
    partition=$(prompt_user "Which partition: " "Common")
    
    vip_name=""
    while [[ -z $vip_name ]]; do
        vip_name=$(prompt_user "Virtual name" "")
    done
    
    duration=$(prompt_user "Duration in seconds for capture: " "30")
    filters=$(prompt_user "Capture filters in addition to vip [ex. \"and (port 80 or port 443)\"]: ")
       
    
    # Prep variables for execution
    datestring=$(date +%Y%m%d-%H%M%S)
    tcpdump_file="autocap_$datestring.pcap"
    tcpdump_file_encrypt="encrypt_$tcpdump_file"
    tcpdump_file_decrypt="decrypt_$tcpdump_file"
    pms_file="pms_$datestring.key"
    payload="payload.json"
    
    # Regular expression to match an IP address
    IP_REGEX='^((25[0-5]|2[0-4][0-9]|1?[0-9]{1,2})\.){3}(25[0-5]|2[0-4][0-9]|1?[0-9]{1,2})$'

    # Get the IP of the virtual server
    virtual_ip=$(curl -skf -H "X-F5-Auth-Token: $TOKEN" "$BIGIP/mgmt/tm/ltm/virtual/~$partition~$vip_name" | jq -r '.destination | split(":") | .[0]'|awk -F/ '{print $3}')
    # Check if virtual IP is a valid IP address
    if [[ ! $virtual_ip =~ $IP_REGEX ]]; then
      echo "Error: virtual IP '$virtual_ip' is not a valid IP address - Did you spell the VS correctly?"
      exit 1
    fi
    
    # Build command execution string and dump it into a payload file as a json array to be read by curl
    tcpdump_bash_string=(timeout -s SIGKILL $duration tcpdump -s0 -nni 0.0:nnnp --f5 ssl:v host $virtual_ip $filters -w /shared/images/$tcpdump_file_encrypt)
    echo "{\"command\":\"run\",\"utilCmdArgs\":\"-c '${tcpdump_bash_string[@]}'\"}" > $payload

    # Run tcpdump
    echo -e "\tStarting tcpdump...please reproduce your issue now."
    output=$(curl -sk -X POST -H "Content-Type: application/json" -H "X-F5-Auth-Token: $TOKEN" "$BIGIP/mgmt/tm/util/bash" -d @$payload)

    #curl -skf -X POST -H "Content-Type: application/json" -H "X-F5-Auth-Token: $TOKEN" "$BIGIP/mgmt/tm/util/bash" -d '{"command":"run","utilCmdArgs":"-c "'${tcpdump_bash_string[@]}'""}'
    sleep 5
    echo -e "\ttcpdump complete...continuing."
    

    # Download tcpdump capture from BIG-IP
    echo -e "\nDownloading tcpdump capture from BIG-IP..."
    download_file $tcpdump_file_encrypt "\tDownload complete!"
    
    # Delete tcpdump capture on BIG-IP
    echo -e "\nDeleting tcpdump capture on BIG-IP..."
    delete_file $tcpdump_file_encrypt "\tDeletion complete!"
    
    # Extract session keys from tcpdump capture
    echo -e "\nExtracting session keys from tcpdump capture..."
    tshark -r $tcpdump_file_encrypt -Y f5ethtrailer.tls.keylog -Tfields -e f5ethtrailer.tls.keylog > $pms_file
    echo -e "\tSession keys extracted!"
    
    # Create a decrypted tcpdump capture from the encrypted capture + session keys file
    echo -e "\nCreating decrypted tcpdump capture..."
    editcap --inject-secrets tls,$pms_file $tcpdump_file_encrypt $tcpdump_file_decrypt
    echo -e "\tDecrypted tcpdump capture created!"

    echo -e "\nCleanup..."
    rm -f $payload $pms_file
    echo -e "\nComplete!"
}

prompt_bigip_address
prompt_credentials
get_token
main
delete_token

 I'm open to feedback and ideas. This concept of remote "tcpdumping" and decrypting is extremely useful and I can see a lot of applications for it.

This looks very promising! I am definitely trying this out in my lab.

Nice work Jason - this is good stuff 👍

Great job !

lnxgeek that's awesome! Always love to see alternate versions so community members have choices in implementation.