Administrators can configure a Network Decoder to decrypt incoming network packets. This capability is currently supported with encrypted communications to managed servers using TLS 1.2 or earlier and certain cipher suites, which are described in Supported Cipher Suites . The following figure illustrates the supported configuration of a Network Decoder deployed as a passive network device where it captures network traffic for managed servers. The Network Decoder is able to decrypt the traffic by using private keys uploaded to it from the managed servers .
As the network traffic is collected and passed through the system, the encrypted packets are stored as captured even if the system has been able to decrypt them. As the Decoder parses the encrypted traffic, it uses any private keys that have been uploaded, and determines if the network traffic can be decrypted. If the Decoder is able to decrypt the traffic, it generates an additional meta key, defined as tls.premaster, which contains the decryption key for that particular session. Whether the traffic is decrypted or not, the metadata service is tagged as 443 or SSL/TLS traffic, as the Decoder is port agnostic, even though it is marked with the default port number. The following figure shows the basic progression through the NetWitness platform as the packets are being decrypted and the session metadata is generated.
Follow the steps below to configure the Network Decoder to natively decrypt this network traffic.
- Step 1: Validate That The Network Decoder Captures Encrypted Traffic
- Step 2: Obtain Private Keys from Managed Servers
- Step 3: Validate That The Private Key Cipher Suite is Supported
- Step 4: Confirm HTTPS Parser is Enabled on Decoders
- Step 5: Upload the Supported Private Keys to Decoders
- Step 6: Reload HTTPS Parser on Decoders
- Step 7: View Decrypted Sessions
Note: Currently, you cannot review the decypted payloads directly in the in the user interface. However, you can review them using the RESTful API interface and the NwConsole. However, the Decoders being able to decrypt traffic enables them to detect and generate potentially malicious communications that would otherwise not be detected.
See Troubleshooting for resolving any issues you might encounter while performing these steps.
Step 1: Validate That The Network Decoder Captures Encrypted Traffic
First, make sure the Decoder is actually capturing the SSL/TLS traffic from the managed servers that you want to use to gain visibility into the encrypted sessions. You can do this by searching in the Investigate views (Navigate or Events) using the IP addresses of the servers as the destination IP addresses, and the service as SSL/TLS.
For example, if you are searching for HTTPS traffic to 192.168.1.2 and 192.168.1.3, you can run the following query:
service = 443 && ip.dst = 192.168.1.2, 192.168.1.3
Conduct this search on the Concentrator that aggregates metadata from the Decoder that is expected to capture this network segment, or on a Broker that may have access to all collected metadata.
Step 2: Obtain Private Keys from Managed Servers
Private keys are the asymmetric keys generated by services that accept TLS traffic. They are normally stored in PEM files. These keys are used during the TLS handshake to encrypt the premaster symmetric key that is used for the rest of the payload encryption.
Note: The method to export private keys from web servers (from which to decrypt traffic) varies depending on the product. Refer to the product documentation for instructions for exporting private keys.
Step 3: Validate That The Private Key Cipher Suite is Supported
As a passive collection device, the Network Decoder can only decrypt ciphers that use the RSA key exchange. The list of supported keys, and whether the keys are FIPS compliant, are listed in Supported Cipher Suites and Unsupported Cipher Suites . If you are expecting to decrypt less-secure channels of communication, you might need to disable FIPS. However, this is a system change to the entire Decoder, not just the parsing of captured traffic, so take caution before disabling FIPS. If you require more-secure cipher suites for the managed server communications, search for "SSL decrypt" in our third party partner integrations section at RSA Ready Community (https://community.rsa.com/community/products/rsa-ready).
Note: If FIPS is enabled, the list of ciphers for decryption is restricted to only those that are FIPS-compliant.
Supported Cipher Suites
The following table lists which cipher-suites are supported using private keys.
|Cipher Suite Name (RFC)||Name (OpenSSL)||Cipher Suite||TLS Version||KeyExch.||FIPS|
Unsupported Cipher Suites
The following table lists which cipher-suites are not supported using private keys.
|Cipher Suite Name (RFC)||Name (OpenSSL)||Cipher Suite||TLS Version||KeyExch.||FIPS|
Step 4: Confirm HTTPS Parser is Enabled on Decoders
The decryption process requires the native HTTPS parser to be enabled to examine the TLS handshake and to compare the uploaded encryption keys to determine if they decrypt the traffic. This can be validated in (Admin) > Services > Decoder > Config > Parsers Configuration panel as shown in the following figure.
Step 5: Upload the Supported Private Keys to Decoders
The sslKeys command provides a way to upload premaster or private keys to the Decoder, so that captured encrypted packets that match the keys can be decrypted before parsing. Administrators configure the Decoder by entering the sslKeys command using the NwConsole command line interface or the Decoder RESTful interface. After upload, you must issue a parser reload command so that the newly installed key becomes visible to the HTTPS parser. Now, all TLS handshakes that use that private key will be able to be decrypted by the Decoder.
For information about how to use the NwConsole command line interface, see the NwConsole User Guide for RSA NetWitness Platform. For information about how to use the RESTful interface, see the RESTful API User Guide for RSA NetWitness Platform. Go to the Master Table of Contents to find all RSA NetWitness Platform 11.x documents.
The RESTful interface form at the path /decoder/sslkeys allows uploading a single PEM-encoded private key, a single file containing multiple private keys concatenated together, or a single file of multiple premaster keys.
Upload Multiple Premaster and Private Keys
Note: As of 11.5, uploading premaster keys is not officially supported yet for real-time capture, but can be used to validate that decryption is functioning properly on the Decoder.
You can use the RESTful interface form to facilitate uploading of multiple keys, both premaster and private at the same time.
Open the RESTful API in your browser and navigate to this path on the Decoder that you want to configure: /decoder/sslkeys.
- Next to Upload File 1, click Choose File and locate the premaster key file or PEM file that you want to upload on your local file system.
(Optional) Repeat for Upload File 2 and Upload File 3.
The files are uploaded to the Decoder and results are displayed in the form.
Parameters for Managing Keys
The sslKeys command has several parameters for managing premaster and private keys. This is the full list of parameters:
|clear||Removes all premaster keys from memory. Does not delete any PEM files installed on the system.|
|maxKeys||Changes the maximum number of premaster keys that are stored in memory.|
|listPems||Returns a list of all installed private key PEM files.|
|deletePem||Deletes the named PEM file from the file system. You can pass this parameter more than once to remove multiple files.|
|random||The random hash used to identify the premaster key.|
|premaster||The premaster key that will be installed for the previous random parameter. They must show up in pairs and random must be first.|
Most sslKeys commands return name/value pairs of statistics about the premaster keys in memory. The statistics are listed in the following table.
|added||The number of premaster keys just added during this command.|
|total||The total number of premaster keys loaded in memory.|
|agedOut||The total number of premaster keys that were removed during this command; this is not a lifetime stat.|
|maxKeys||The current maximum allowed premaster keys|
The sslKeys command accepts two types of encryption keys:
- Premaster key: the symmetric key used in the TLS payload stream for encryption and decryption.
- Private key: the asymmetric private key used during the TLS handshake that encrypts the premaster.
The premaster key is generated randomly and is ephemeral for the life of one specific TLS session. Normally, there is not a good way to get premaster keys to a Decoder in time for the parsing step. However, both Chrome and Firefox can write the premaster keys they generate to a file. This is useful for testing purposes. To configure your browser to do this, create an environment variable called SSLKEYLOGFILE and assign it the pathname of a file to which the keys will be written. The Decoder will accept the file exactly as written and will use all the decryption keys in the file for any encrypted traffic it captures.
This is a sample NwConsole script that uploads the file to a Decoder:
login <decoder>:50004 <username> <password>
send /decoder sslKeys --file-data=SSLKeys.txt
This is an example using a curl command (with the RESTful port) to upload the file to a Decoder:
curl -u "<username>:<password>" -H "Content-Type: application/octet-stream" --data-binary @"/path/SSLKeys.txt" -X POST "http://<hostname>:50104/decoder?msg=sslKeys"
After the symmetric keys are uploaded, they will immediately be used for any necessary decryption. Symmetric keys are stored in memory and there is a limit to how many can be stored at any point in time. As more keys are added, the earliest keys will be aged out. You can also add premaster keys by just passing the random and premaster parameters to sslKeys.
Private Keys or PEM Files
Private keys are normally stored in PEM files and are the asymmetric keys generated by services that accept TLS traffic. These keys are used during the TLS handshake to encrypt the premaster symmetric key that will be used for the rest of the payload encryption.
For example, if you have a web server whose traffic you want visibility into, you need to upload the private key it uses to encrypt traffic. You only need to do this once, as it is stored permanently (or until removed by a delete command). Private keys are automatically encrypted before storing to protect them. After upload, you must issue a parser reload command so that the newly installed key becomes visible to the HTTPS parser. Now, all TLS handshakes that use that private key will be able to be decrypted by the Decoder.
Note: Not all ciphers suites use a "known" private key (for example, Ephemeral Diffie Hellman). Encrypted traffic with those ciphers cannot be decrypted unless the premaster key is uploaded to the Decoder before the session is parsed.
These are some sample commands that upload a PEM file to be used for decryption.
send /decoder sslKeys pemFilename=MyKey.pem --file-data=/path/MyKey.pem
Using the RESTful interface (you must provide the pemFilename parameter in the URL):
curl -u "<username>:<password>" -H "Content-Type: application/octet-stream" --data-binary @"/path/MyKey.pem" -X POST "http://<hostname>:50104/decoder?msg=sslKeys&pemFilename=MyKey.pem"
Step 6: Reload HTTPS Parser on Decoders
After uploading the private keys, you must issue a parser reload command so that the newly-installed key becomes visible to the HTTPS parser. All TLS handshakes that use that private key are now able to be decrypted by the Decoder.
To issue a parser reload command:
- Go to (Admin) > Services and select the Decoder.
- Click > View > Explore > decoder, right-click parsers and select Properties.
- In the Properties for Decoder (DECODER) /decoder/parsers pane, select reload from the drop-down menu and click Send.
Step 7: View Decrypted Sessions
All storage of the packets is still encrypted, so when you search for any decrypted traffic, your query should still focus on service=443 or HTTPS (HTTP over SSL/TLS). If any packets were able to be decrypted, tls.premaster metadata is associated with the session that has the premaster key required for decrypting that session. The session will also have crypto metadata denoting the cipher suite, with crypto formated as tls.premaster.
Viewing Unencrypted Traffic
If packets are decrypted during the parse stage, encrypted packets are written to disk, and the matching premaster key used for decrypting is written to the tls.premaster meta key, analysts can view the unencrypted packets using the tls.premaster meta key.
One Decoder API that you can use to see the unencrypted packets is the /sdk/content RESTful service. You need to know the Session ID of the encrypted packets and the flags parameter masked to the value 128 (or 0x80 in hex). Point your browser to the Decoder RESTful interface and type in the following command, substituting the actual Session ID for <id>:
The Decoder returns a simple web page showing the packets after they are decrypted.
If you want to see what the packets look like encrypted, type in one of the following commands, substituting the Session ID for <id>:
For more information on the /sdk/content service, see the manual page for /sdk content.
Alternatively, you can use the NetWitness Investigator thick client to decrypt and display the network sessions, as it can communicate to a Concentrator or have PCAPs and private keys loaded locally.
If you are not able to view the encrypted sessions, check Troubleshooting. However, if you are able to see the tls.premaster metadata, that confirms that the Decoder is able to see inside the encrypted session, which enables parsers to see the unencrypted packet payload and create metadata accordingly. For these decrypted sessions, look for additional metadata around usernames, passwords, or HTTP body content that would be obfuscated when encrypted, which would result in metadata not being generated.
If you are still not able to decrypt or view the decrypted payloads after attempting the steps above, try these steps.
- Validate that your private key is using an acceptable cipher-suite.
- Make sure your Network Decoder is capturing the traffic matching the server for which you have the private key. To check, you can upload the private key and PCAP into Wireshark and see if it is able to decrypt it.
Decryption of Secure SMTP
In version 11.3, NetWitness Platform supports opportunistic SSL/TLS decryption, which addresses RFC 3207 (https://tools.ietf.org/html/rfc3207). You can add an HTTPS parser option that provides a .csv list of destination ports of the session where the STARTTLS command will be searched, with at least one encryption key that has been uploaded. This enables the STARTTLS functionality.
Note: The .csv list must include all the destination ports of a session. If a destination port is not in the list, the search for STARTTLS will not be started.
The STARTTLS search is limited to the first 1024 bytes of the session's payload, to prevent performance degradation. If STARTTLS is found, the parser uses the next client packet with payload as the start of a TLS negotiation.
To add an HTTPS parser option for secure SMTP decryption:
- In the NetWitness Platform User Interface, go to (Admin) > Services.
- Select a Log Decoder service and click > View > Explore.
- In the left panel, select decoder > parsers > config.
In parsers.options, enter an HTTPS parser option in the following format that provides a .csv list of the destination ports of the session where the STARTTLS command is searched:
The following image shows an example of an HTTPS parser option for secure SMTP decryption.
Decrypting packets in real time requires extra work in the parsing stage. Before implementing this feature, plan carefully to ensure the incoming traffic bandwidth does not overwhelm the available compute power. You may need more Decoders to decrypt traffic than you would need if not decrypting.
Packets captured on a Decoder normally have a timeout of ~60 seconds in the assembly stage before they are sent to the parsing step. If the Decoder is under memory pressure due to very high bandwidth, the lifetime of the packets in Assembler may be shortened. To alleviate this situation, you can configure a longer timeout value and increase the amount of memory available to hold packets in Assembly. Also, in order to perform decryption of the packets, the Decoder must receive the decryption key before the parsing stage.
Note: Currently, only TLS 1.2 and earlier protocols can be decrypted
With no feeds loaded, the following parsers enabled, and 50% of the sessions being decrypted, a Decoder can process traffic at 3 Gbps .
|GeoIP||Geographic data based on ip.src and ip.dst|
|GeoIP2||Geographic data by default based on IPv4 (ip.src, ip.dst) and IPv6 (ipv6.src, ipv6.dst) meta keys|
|HTTP||Hyper Text Transport Protocol (HTTP)|
|HTTP_Lua||Hyper Text Transport Protocol (HTTP) Lua|
|FTP||File Transfer Protocol (FTP)|
Simple Mail Transport Protocol (SMTP)
|POP3||Post Office Protocol (POP3)|
Network News Transport Protocol (NNTP)
|DNS||Domain Name Service (DNS)|
Secure Socket Layer (SSL) Protocol
|Standard E-Mail Format (RFC822)|
Extracts VCARD fullname and email information
|PGP||Identifies PGP blocks within network traffic|
Identifies SMIME blocks within network traffic
|SSH||Secure Shell (SSH)|
Trivial File Transfer Protocol (TFTP)
|DHCP||Dynamic Host Configuration Protocol (DHCP and BOOTP)|
Extracts NETBIOS computer name information.
|SNMP||Simple Network Management Protocol (SNMP)|
Network File System (NFS) protocol
|RIP||Routing Information Protocol (RIP).|
|TDS||MSSQL and Sybase database protocol (TDS)|
Oracle database protocol (TNS)
|IRC||Internet Relay Chat (IRC) protocol|
Real Time Protocol (RTP) for audio/video
|SIP||Session Initiation Protocol (SIP)|
H.323 Teleconferencing protocol
|SCCP||Cisco Skinny Client Control Protocol|
Google Talk (GTalk)
|VlanGre||Vlan ID and GRE/EtherIP tunnel addresses|
BitTorrent File Sharing Protocol
|FIX||Financial Information eXchange Protocol|
Gnutella file sharing protocol
|IMAP||Internet Message Access Protocol|
Microsoft Remote Procedure Call protocol
|RDP||Remote Desktop Protocol|
Command Shell Identification
A parser that extracts search terms
|FeedParser||External Feed Parser|
TLS Certificate Hashing
The Network Decoder can produce hashes of certificates that are seen in the packet stream. These hashes are the SHA-1 value of any DER-encoded certificate encountered during a TLS handshake. The hashes produced can be used to compare network traffic with hashes from public SSL blacklists, such as the one from sslbl.abuse.ch.
The TLS Certificate hashing feature is disabled by default. To enable TLS Certificate hashing:
- Go to (Admin) > Services, select a Network Decoder service and > View > Explore.
- Select decoder > parsers > config.
- In the values column next to parsers.options, type HTTPS="cert.sha1=true".
When this option is enabled, the SHA-1 is stored as a text value in the cert.thumbprint meta key.
- The change takes effect on parser reload. In the left panel, right-click parsers and click Properties. In the drop-down menu, select reload and then click Send
The SHA-256 hash of the certificate can be enabled by adding the parser option:
to a Network Decoder's /decoder/parsers/config/parsers.options configuration.
When this option is enabled, SHA-256 is stored as a text value in the meta keys:
JA3 and JA3S TLS Fingerprints
The Network Decoder can produce the JA3 value of TLS clients and the JA3S value of TLS servers that are observed in a Network session. The values that are produced conform to the values generated by the open source JA3 tools (https://github.com/salesforce/ja3). The JA3 features are disabled by default.
To enable JA3 features:
- In the NetWitness Platform User Interface, go to (Admin) > Services.
- Select a Decoder service and click > View > Explore.
- In the left panel, select decoder > parsers > config.
In parsers.options, add HTTPS="ja3=true ja3s=true".
In the left panel, right click on parsers and select properties.
In the right panel, in the lower pane, set the value in the first drop down to Reload.
JA3 and JA3S can be enabled independently using these options. When enabled, the JA3 is stored as a text value in the meta key ja3. The JA3S is stored as a text value in the meta key ja3s.
Additional meta keys are activated using a mechanism similar to the JA3S and JA3S meta items. For example, ja3.orig is enabled by adding ja3.orig=true to the HTTPS parser options. This is also true for ja3s.orig, tls.extensionlen, and tls.cipherlen.
ja3.orig, tls.extensionlen, and tls.cipherlen are only created if JA3 is enabled.
ja3s.orig is only created if JA3S is enabled.
The Network Decoder generates Community ID flow hash values that are compatible with the Community ID specification defined by https://github.com/corelight/community-id-spec.
The Community ID is written to a text-formatted meta key named community.
The Community ID is generated on sessions containing TCP over IPv4, TCP over IPv6, UDP over IPV4, and UDP over IPV6.