Name: Netronome SSL Inspector

Text: NtONOME

WHITE PAPEk

Lommunication
NetronomeSS1 Inspector"
Solution Overview
SSL USECASES
SSL has become the ubiquitous choice to secure Web-based transactions. That fact,
coupled with the flexibility that SSL provides, has made it the obvious choice for securing a host of additional applications and to enable new services where SSL is used as a
secure tunneling mechanism.
Specifically, for end users, SSL has long been used to secure Web-based transactions to enable e-commerce and online banking. Over time, the simplicity that SSL
provides has made it the perfect vehlcle to migrate many applications to a Web-based
model for new online services like viewing medical records, ordering prescriptions,
filing federal, state, and local tax returns and other government uses. In addition
new cloud based and enterprise applications such as Salesforce.com, Exchange,
Sharepoint and most of the web based email applicationson the market such as Gmail,
Yahoo, Zimbra etc.
In the enterprise, SSL is most often used to encrypt traffic leaving the enterprise to
provide data security between remote locations across a public network.. SSL is also
used inside the enterprise to secure sensitive transmissions, such as human resource
data, between departments or groups and to ensure privacy for corporate activities,
such as business development, mergers and acquisitions. Enterprises also require
encrypted communications to individual mobile users who need remote access and
therefore SSL-based VPNs are a fast-growing technology for remote-access VPNs.

SSL GROWTH

While
solves many security Table I . SSL Deployment and Use
problems, encrypting sensitive
transactions can allow them to
pass through security measures
unchecked. This fact is exacerbated considering that SSLencrypted communications constitute a significant and growing percentage of the traffic in enterprise LAN and WAN.
Surveys have shown that between 2535% of enterprise traffic is SSL-encrypted, and can
be as hgh as 70% in select verticals.

,

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PROBLEM POSEDBY SSL
It is clear that there are legitimate needs for encrypted data within, to and from the
enterprise. But this encrypted traffic poses a security risk as SSL also provides a
mechanism for more nefarious applications. As many IT managers are aware, the
privacy benefits provided by SSL encryption can be overshadowed by the risks SSL
brings to the enterprise network. While SSL encryption provides privacy and can
protect both corporate and individual user information by ensuring that data is useless
to potential interceptors, it can also make it difficult or impossible for network
administrators to enforce corporate acceptable-use policies. SSL also makes it difficult

SSL traffic (encrypted traffic) in the enterprise is growing rapidly due to the enterprise-wide usage of applications, such as
Sharepoint, Exchange, WebEx, Salesforce.com and GoogleApps. Additionally,
most e-mail applications, such as Gmail,
Yahoo and Zimbra, all use SSL to encrypt
communications.
Although this enuyptedtrafficprotects
end user data, it also creates security "blind
spots." The security infrastructure put in
place to protect your enterprise is blind to
SSL traffic, thus causing risks for traffic destined to the enterprise. The same SSL encryption methods used to protect your data
provide an easy vehiclefor criminals to hide
their cyber attack activities, as in the case of
several recent well-publicizedattack
In addition to the risks of incoming
threats hiding over SSL channelsbypassing
security architectures, outbound enterprise
traffic is now a growing problem. This is becoming quite a "hot 6utton"for security applications that tackle data loss prevention
(DLP), compliancereporting and lawful intercept solutions that could, at one time,
see what was outgoing, but are suddenly "in
the dark" to SSL traffic
This paper explores the drivers behind
the increase in SSL usage and the methods
used by enterprisesto confront the security
challengesthat SSL creates.TheNetronome
SSL Inspector offers enterprisesecurity appliances or applicationsunparalleledaccess
to the unenuyptedplaintext of SSL flows for
theseapplications to be succerrful.

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NETRONOME

Figure l . Network appliances have failed to keep pace with improvements in network performance.

NO VISIBILITY

INCREASED VISIBILITY

I

I
GlGABlT ETHERNET
REDUCED THROUGHPUT
for IT organizations to ensure that threats, like viruses, spam and
malware, are stopped before they reach individual users. Without the ability to examine the contents of SSL communications,
network operators leave open the possibility for information to
be accidentally leaked out of the enterprise or worse, stolen.
Regulatory compliance requirements, including identifying
accidental or intentional leakage of confidential information, are
also virtually impossible to meet because of SSL encryption.
In many instances, there are conflicting requirements to
both encrypt and examine data within the enterprise. In typical
installations, these seemingly incompatible requirements cannot
both be met with acceptable performance. This SSL conundrum
has wreaked havoc for organizations subjected to industry and
government compliance mandates, such as Health Insurance
Portability and Accounting Act (HIPAA) and Sarbanes-Oxley
(SOX), which require intrusion protection and detection to
ensure that only authorized individuals have access to hardware
and software resources within the network infrastructure. Other
compliance mandates require all organizations with publicly
accessible networks to be able to provide law enforcement
agencies with documentation of network activity, thus requiring
that all traffic be unencrypted.

SSL CONTROL
APPROACHES
Network operators already deploy an array of network and
security a p p h c e s to protect their enterprises, enforce internal
corporate acceptable use policies and satisfy external government regulation. These devices provide solutions for detecting
rogue applications, controlling unrestricted Web surfing, firewalling traffic, VPNs, network access control (NAC), intrusion
detection (IDS), intrusion prevention (IPS), unified threat management (UTM), regulatory compliance, virus protection and
spam control, amongst others. These appliances work almost
entirely by providing deep packet inspection and flow analysis,
looking for known patterns of mischievous activity and blocking or recording it. Unfortunately, these network and security
appliances, in many instances, can only inspect plaintext traffic
and are unable to inspect SSL-encrypted communications for
attack signatures. These solutions are thus becoming less and
less effective, as the amount of encrypted SSL communications
and traffic continues to grow.
Network operators previously faced two extremes in
confronting the issues associated with SSL communications.
They could take a draconian approach by blockung SSL
communications entirely or, alternatively, allowing SSL com-

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munications transparently without inspection (by leaving port
443 open on their security infrastructure), thereby greatly
reducing the effectiveness of their network and security appliances that are unable to examine the encrypted flows. Neither of
these alternatives is a viable option for enterprise networks.
Besides simply passing all SSL-encrypted payloads or blocking encrypted traffic entirely, several other approaches have been
used. These methods share a common goal of providing plaintext inspection of SSL-encrypted flows, enabling the content of
encrypted traffic that does not meet corporate acceptable-use
policies to be dropped or the logging of suspected attacks to a
management station. Just as importantly, these methods also
need to identify and permit SSL in legitimate use cases. In many
instances, these methods are successful at examining encrypted
SSL, but they typically suffer other major problems that limit
their effectiveness.

SSL PROXIES
Today, in most cases, network operators permit encrypted communications, but only through SSL proxies that allow the IT
organization to examine and inspect SSL-encrypted content
before entering or exiting the enterprise. These proxies provide
the opportunity to examine the contents of network traffic, yet
still offer encryption prior to leaving the enterprise.
Unfortunately, traditional SSL proxies create additional
problems that become trade-offs to the security benefits that they
offer. They are inserted in the network path and create congestion as the performance of the network appliance fails to keep
pace with the rate of expansion of network capacity and
bandwidth at Gigabitdsecond and beyond. The network VO,
memory and CPU utilization of these systems all strain at these
new performance levels. As a result, these network appliances
are rated for use by some amount of aggregate bandwidth or a
number of users, sessions and/or flows. When any of these
metrics are exceeded, the appliance becomes a bottleneck
that can only be relieved by adding capacity with yet another
network appliance($.
SSL proxies also require network IP address configuration
and likely need network topology changes to engineer the
appliance into the network as an active network element.
As an active network element with IP addresses on the in-line
interfaces, these SSL proxies are now vulnerable to all attacks
just as any other host, server, switch or router would be.
Careful consideration needs to be given to the security of the
SSL proxy configuration itself in both the data plane and
management plane.

ExaminingSSL-encrypted Communications

2

Another issue with network designs based on SSL proxies
is that these assume that all SSL traffic is blocked except that
which goes through the proxy. Network devices redirect traffic
on port 443 to the proxy SSL proxies are incapable of detecting
hidden SSL flows on different (non-443) port numbers because
such traffic is not directed to the proxy.
TraditionalSSL proxies also force costly changes to network
topology, firewall and policy configuration, as well as modification of clientlserver stations and their SSL-capable applications
in the enterprise. Applications using SSL require the proxy
server's information, such as IP address, port number and,
potentially, other security settings.

nt balance
seaurity
ce.

TRANSPARENT
SSL PROXIES
As network bandwidths expand and the complexity of
applications and attacks increases, more networks are employing a multitude of network and security appliances and IP-based
applications and services. Accordingly, interest in the use of
SSL proxies has surged once again. Despite this and the
existence of many SSL products in the market, few solutions
exist that can provide a high level of security with little or no effect upon management and performance.
The ultimate solution in ensuring the confidendty and protection of SSL traffic balances performance, control and security
While solutions exist to meet each objective independently, it is
difficult to satisfy them simultaneously resulting in one or more of
these critical areas failing to meet expectations.Increasingsecurity
at the expense of network performance or compliance is no more
acceptable than meeting application bandwidth and compliance
requirements while ignoringsecurit)!To date, it has been difficult,
if not impossible, to satisfy all three of these objectives.
A new class of SSL proxy is entering the market that
provides many of the benefits of existing SSL proxies, yet also
removes or mitigates the negative impacts that are currently
associated with them. These devices, known as transparent
SSL proxies, are deployed in the IP network where encrypted
SSL traffic can be inspected as plaintext before it enters or exits

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the LAN, WAN or data center. Their transparency is defined by
the fact that they are deployed as a "bump-in-the-wire,"meaning they are not active endpoints in the network. As a result,
they do not require any IP address assignment or configuration,
removing any complicated configuration requirementsor P network topology changes. They can easily be added or removed
from the network by simply connecting or disconnecting their
input and output network connections. The transparency also
means that the SSL proxy function is hidden from the end user,
removing the need for time-consuming and costly client device
and application configuration.
Transparent SSL proxies see all network traffic, not just SSL,
and, thereby, require line-rate network performance and the ability to cut-through non-SSL flows. An effective transparent SSL
proxy solution provides great performance at both the network
and application levels as well as multiple-interface support for
applications to tap into SSL streams. By providmg applications
with access to the plaintext in SSL streams, the transparent proxy
enables IT managers to implement policy control and regulate
network users-often necessary for compliance.

Examining SSL-encrypted Communications

3

Netronome SSL Inspector"

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-3

TransparentSSL Proxy
The Netronome SSL Inspector is the industryk hlghestperformance h-ansparrnt proxy for Secure Sockets Layer (SSL) network communications,providing applicationswith access to the
plaintext in SSL-encrypted connections. Beyond industrydefining performance, the Netronome SSL Inspector is the first
transparent SSL proxy that both increases network security and
sipficantly minimizes deployment and operational costs by
removing costly user and network configuration. The SSL Inspector was designed for secunty and network appliance manufacturers, enterprise IT organizations and system integrators to
provide industry-leading performance at a fraction of the cost of
other solutions. Without compromising any aspect of enterprise
or government-regulated compliance, the SSL Inspector allows
network appliances to be deployed with the hghest levels of flow
analysis while still maintaining multi-gigabit, line-rate network
performance.
The Netronome SSL Inspector enables existing security and
network applications to obtain access to the plaintext wthin
SSL-secured flows, thereby extending the benefits of their
applications to SSL-encrypted traffic. Unmodified applications
r u m g on the same platform as the Netronome SSL Inspector,
or on adjacent appliances, can gam visibility into the content of
SSL traffic. Netronome's network processing and cryptography
acceleration hardware are leveraged to forward non-SSL traffic at
multi-Gbitls rates.
The SSL Inspector can be deployed as a "bump-m-the-wire"
fully transparent proxy, el~minatingthe need for costly reconfiguration of network elements. This transparency removes any
needed configuration of clients and servers to make them direct
SSL traffic towards the proxy The SSL Inspector just needs to
be located in-line so that all network flows (mcluding SSL flows)
pass through it.
The SSL Inspector can also be deployed in a passive mode
of operation with the appliance connected to a span port, tap or
mirrored interface where the SSL Inspector is receiving a copy
of all network traffic for classification, flow identification and
decryption.This mode permits SSL inspection without the need
to place an apphnce in-line.
Netronome's solutions enable the identification and elirnination of risks, such as remlatory compliance violations,
virusdmalware and intrusio;attem;ts
no&ally hidden within
SSL. The privacy and integrity of SSL-encrypted communications are maintained by making the plainte
able only w i h n a controlled environment
while also exempting certain traffic from inspection based on user preference.

PRODUCTOFFERINGS
The SSL Inspector is offered as a complete
work appliance and can be used byenterprises or
pnvate-labeled for OEMs. As an appliance, the SSL Inspector is
deployed adjacent to existing security and networlung apphnces
to provide there devices with visibility into SSL flows. The plaintext of SSL flows can be fed to exlsting applications via a de&NETRONOME WHITE PAPER

cated gigabit Ethemet link while non-SSL flows are mirrored to the
security appliance, firewalled or cut-through, bypassing the security appliance altogether.T h enables SSL visibility to be added to
existing network security infrastructurewith no integration effort.
The product provides network and security appliance manufacturers with access to plaintext traffic immediately as a two-box solution. The system is configured and managed via a Web-b+ed
graphical user interface.

OPERATINGMODES
In the network security appliance space, due to its nascent
nature, the market segmentation is somewhat malleable as the
market is still developing. New threats emerge, security and
compliance requirements evolve and enabling technologies
adapt. This is visible today, considering the numerous categories
of network and content security appliances available on the
market. Some of the more common products (and product categories) include firewalls, intrusion detection systems, intrusion
prevention systems, anti-virus scanners, unified threat management systems, network capture, network monitoring, network
forensics, network analysis, network access control, sparnlsand Web filters. There are also as many analysis techniques employed as there are product categoriesin the content and security
appliance space. These systems use methods like packet filters,
signature detection, traflidpacket anomaly detection, protocol
monitoring and packet capture to alleviate security threats.
Even though the network security appliance market is
complex and constantly changing, these devices share several
common deployment modes. They are either installed in-line
with respect to traffic flow, and actively filter traffic to block
attacks, or they are deployed on a mirrored interface, span port
or tap port and only monitor network traffic as it passes through
the network to identify attacks or record traffic. These device
configurations are referred to in the SSL Inspector as filtering
and sniffing configurations, respectively.
The SSL Inspector is either deployed in-line to offer the
plaintext of SSL-encrypted communications to sniffing or filtering applications for analysis, or it can be installed in a passive
or "offline" mode for packet capture applications. The choice
between
modes
is a global system setting configured by the
.
.
network administrator.

Figun

Nmonome

sSL

Examining SSL-encryptedCommunications

4

Sniffing//OS In-line Mode
In sniffing in-line mode, also known as IDS inline, the SSL
Inspector sits as a "bump-in-the-wire" and will receive all
inbound and outbound traffic to/from the computing resources
behind it. The Netronome SSL Inspector forwards all traffic to
the egress network port while simultaneously copying both
non-SSL flows and decrypted plaintext to an attached sniffing
application for examinatiodoggmg.
SSL plaintext flows may be marked by the SSL Inspector
with either a configurable source MAC, VLAN ID or DSCP to
identify plaintext decrypted flows from non-SSL flows sent to
the attached security appliance. It is assumed that the sniffing
device is monitoring only and, therefore, no data will be
transferred from the IDS or sniffing application back to the SSL
Inspector.
Sniffing //OS Passive Mode
In passive mode, the SSL Inspector is deployed off a span port,
tap or mirrored interface where the appliance is receiving a copy
of all network traffic for classification, flow identification and
decryption. Packets are classified and based on policy are
forwarded to an adjacent packet capture security appliance, such
as an IDS or network forensics appliance. In passive configuration, no data is ever forwarded back toward the network;
the SSL Inspector and adjacent security appliance are capturing
traffic for analysis.
Filtering //PS Mode
In filtering mode, both the SSL Inspector and filtering appliance
are in-line and all network traffic may traverse both devices.
Similar to IDS in-he mode, the SSL Inspector will receive inbound traffic and can pass both non-SSL flows and unencrypted
plaintext to the host applicat~onor adjacent filteringdevice. SSL
plaintext flows will be marked by the SSL Inspector with either
source MAC, DSCP or VLAN ID to distinguish decrypted
plaintext flows from non-SSL flows sent to the IPS. The filtering
applicatiodappliancewill parse the plaintext and non-SSL flows
against its signature database to identlfy and counteract threats
andlor data leakage.
Unlike sniffing mode, in a filtering configuration, there is
an active communications path back from the security appliance. For each SSL packet, a plaintext packet will be generated
and sent to the filtering appliance where it will be bridged and
sent back. The original encrypted SSL data packets of inspected
flows will be held back in a queue in the SSL Inspector appliance. If the flow is validated by the security appliance and packets are received back by the Netronome SSL Inspector, the
returned plaintext packet will trigger the release of the original
SSL data packet, which has been re-encrypted, to the egress network interface. Any non-SSL traffic received back from the security appliance is cut-through to the egress port of the SSL
Inspector.
If the attached IPS device decides to drop the flow, it will
send a TCP RST and/or silently drop all packets of the flow. The
Netronome SSL Inspector assumes that all buffered flows are
invalid until their packet headers are returned from the IPS. After
a timeout period, the buffered flows are discarded under the
assumption that the security application has blocked them.

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SSL POLICIES
The main function of the SSL Inspector is to expose the plaintext
of encrypted flows to thlrd-party security appliances or applications. In addtion to processing SSL traffic, the SSL Inspector can
act as an intelligent and programmable traffic-capturing and mirroring device, optionally reducing load on the attached security
appliance and/or replacing costly network switch span ports.
There are several policy and filtering stages that control access to
overall SSL inspection.
Traffic Diversion Policy
The Traffic Diversion Policy (TDP) is a list of global rules in the
form of 7-tuple IP filters and associated actions. The goal of the
TCAM-based rules table is to reduce the processing requirements
on the Netronome SSL Inspector system and the associated
security appliance or application by providing a classification,
filtering and fonvard~ngmechanism for flows to be steered to
the IPMDS, cut-through to the egress interface or other actions
to be performed (such as drop). These rules are applied to all
incoming flows (SSL and non-SSL) via basic 7-tuple classification
rules that allow the IT administrator to invoke policies, such as
"never decrypt traffic from host w.x.yz, or network w.x.O.0."
The Netronome SSL Inspector system defaults to a single TDP
wildcard rule that indicates that all packets should be cutthrough and not mirrored at system startup.
SSL Inspection Policy
An integral part of the SSL Inspector is identifying SSL traffic in
order to separate it from non-SSL traffic. SSL traffic is identified
based on content (pre-SSL, SSL Handshake and SSL Data) and
does not rely on it being on port 443. Based on the SSL Inspection Policy, MIC
is optionally decrypted and forwarded as plaintext to an external IPSADS network appliance. The SSL
Inspection Policy provides the network operator with a quick
and easy way to alert the SSL Inspector to valid or acceptable
uses of SSL encryption that should not be decrypted further,
such as personal banking or other online transactions. Once
identified,these flows are immediately cut through to the egress
network interface without further inspection. Indvidual SSL site
URLs can be specified as exempt and set to be cut through or
marked for inspection. The SSL Inspection Policy contains a
default entry for all flows. The default SSL Inspection Policy is
that all flows are exempt from further SSL processingldecryption and should be cut-through at system stamp. Adrninistraton must specifically enable SSL inspection.
SSL Session Log
The SSL Inspector Session Log provides a mecharmm for l o ~ n g
all SSL communications through the system. It contains the
learned information that was passively gathered from the flows
through the system. This database is for the network administrator to view details of SSL flows so that certain trends or
patterns can be identified as data traverses the system. The SSL
Inspector Session Log is a repository where data detailing the
SSL flows through the system is maintained and can be accessed
by the network administrator.
SSL Session Log Classification Fields

The SSL Session Log contains data from flows that are being
actively inspected, as well as those that are not. These flows are
uniquely identified so that the network administrator can

ExaminingSSL-encryptedCommunications

identify activity that needs to be inspected. The flow identification is based on classificationof the certificate fingerprint. From
the fingerprint, fields of interest are:
Certificate Subject
Certificate Issuer
5-tuple
Fingerprint Hex
Date
Time
Flow Start Time
Flow End Time
SSL-Inspect-WOff (status)
Traffic Mirroring
In sniffing mode, inbound traffic has the option of being
mirrored to the connected security appliance or application.
Traffic Mirroring is necessary to configure the profile of non-SSL
traffic to be forwarded to the security appliance and other
traffic that should be cut-through without further examination.
Traffic Bypass
In filtering mode, inbound traffic can be classified and passed
directly from the ingress to egress network-facing interfaces in
hardware to bypass the filtering appliance entirely for flows not
requiring further inspection. Thls bypass mechanism saves
resources on the filtering appliance. It also allows the security
appliance to be removed from service or updated without
affecting network throughput and availability

SSL CONNECTIONESTABLISHMENT
Oftentimes, SSL connections are passively ignored or actively
dropped by "bump-in-the-wire" security appliances. To decrypt
SSL, the Netronome SSL Inspector sits inline and acts a transparent proxy to SSL flows traversing the system to provide plaintext of encrypted SSL sessions to adjacent security appliances.
As previously described, the SSL Inspector Appliance is deployed as a "bump-in-the-wire" directly inline with flows to and
from protected computing resources. This transparent proxy
does not require IP interface configurationon the SSL Inspector's
Ethemet interfaces. This allows the original IP address of the
client to communicate with the original IP address of the server
without further admmstrative intervention, such as SSL proxy
configuration on clients. The SSL Inspector acts as a "man in the
middle" and intercepts SSL sessions as they are establishedlnegotiated between the SSL client and server.
By intercepting these sessions, the SSL Inspector transparently establishes two SSL sessions: one between the SSL client
and the SSL Inspector; and another between the SSL Inspector
and SSL server.
Each individual SSL session terminates on the SSL Inspector,
but TCP connections are retained end-to-end via TCP splicing.
The SSL stream is parsed, terminated, decoded and regenerated
on the other side. The TCP ACK loop continues to operate between the main client and server, not to the SSL Inspection app h c e . Terminating and re-oripting SSL allows the appliance
to get hold of the plaintext in the encrypted payload whch can
be sent to the adjacent security appliance in a valid, regenerated
S
can be made available via an internal
TCP stream. T ~ Istream
API, sent to a host interface (VNIC) or sent to an attached security appliance. Although the u n m d i e d d i g or filtering application d l see the contents of the unencrypted SSL flows, the
data remains encrypted on both the connection from the client to
the SSL Inspector and from the SSL Inspector to the Web server.

Figure 4. Security appliances cannot inspect encrypted SSL flows
and has no access to decrypted plaintext.
SECURITY
APPLIANCE

WEB BROWSER

WEB
(mSERVER
Server)

(SSL Client)

Figure 5a. TheSSL Inspector can be deployed in-line. The adjacent
security appliance is passed plaintext of decrypted SSL flows and
(optionally)non-SSL data for analytic
SKURITY

;lir
WEB BROWSER
(XLUient)

4

WEB SW R S
(SSL Servers)

k

Figure 56. TheSSL Inspector can also be deployed in apassive mode
of operationconnected to a span port, tap or mirrored interface.

SPAN PORXTAP

ORMIRROR WEBSERMRS
(SSL Sewer9

Figure 6. TheNetronomeSSL Inspector supports the foI!ogna
ciphers and encryption standards:
- --. - .

-.
.-

Encryption.. ................... .TLS 1.0,TLS 1 .l, SSU, partial SSU
Proxy Mode.. ........................................ .Transparent !
Public Key Algorithms ....................................RSA, DH l
--

Symmetric Key Algorithms.. ................. AES, 3DES, DES, RC4
-

-

Hash~ngAlgor~thm~ ..............................MD5, SHA-1 ,
RSA Keys ..... p?;. ..............512,1024,2048,4096,8172
bits
-p

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l

Q

Examining SSL-encrypted Communications

... -.

: ;

i

*

:-

._cc

6

Certificates
During SSL session establishment, the SSL Inspector appliance
acts as a Certificate Authority (CA). The server certificate that
would be usually stored in the server and transmitted to the client
as part of the SSL protocol is transparently re-signed by the SSL
Inspector. The name of the server in the certificate remains unchanged, but the signature of the CA belonging to the SSL
Inspector is applied. A key is maintained for the SSL server in
which all of the details are known to the SSL Inspector appliance. The modified certificate is transmitted to the SSL client.
Instead of the original server key a different key is used between
the SSL Inspector and SSL client. Since the private key associated with the modified certificate a known to the Netronome
SSL Inspector, the whole SSL handshake can proceed successfully If the SSL clients are configured to use the Netronome SSL
Inspector as a trusted Certificate Authority the SSL client dsee
the server ceruficate as a valid CA-signed certificate. This process
is called "re-signing,"and allows the Netronome SSL Inspector to
transparently intercept SSL communications.

SSL PROXYMODES
The Netronome SSL Inspector can work simultaneously in
two modes with respect to SSL certificates and private keys. These
modes are called "server-controlled and "client-controlled."
The primary difference between these modes is the location of
the SSL Inspector Appliance relating to the SSL clientkrver.
Client-controlled
Also known as "re-sign mode" or "outbound SSL recrypt" in
client-controlled operation, the SSL client and the SSL Inspector
Appliance are under common administration by an enterprise IT
organization. The SSL Inspector would be deployed to inspect
outgoing client traffic to protect confidential information from
leaking out of the enterprise. In this mode, the SSL Inspector
does not have access to the destination SSL server private key(s).
Instead, the certificate key that the SSL server would store and
transmit to the client as part of the SSL protocol handshake is
intercepted and transparently re-signed by a Certificate Authority (CA) in the SSL Inspector Appliance. The name of the SSL
server in the certificate remains unchanged, but the signature of
the CA belonging to the SSL Inspector is applied. A key for the
SSL server is maintained in the SSL Inspector.
When the SSL Inspector intercepts a connection, it presents a "re-signed server certificate to the SSL client. Provided
that the ceruficate issued by the Netronome SSL Inspector is
installed as a trusted root in the SSL client's certificate store, the
SSL connection proceeds normally. If the certificate was not
imported by the client, the client browser issues a security
window to the user because the browser does not trust the
certificate issuer. The user could accept the security waming
pop-up box in the browser for the SSL connection to proceed.
The a h t r a t o r does not need to have access to the server
private key; he only needs to make the modification to the SSL
client by installing the CA certificate to be used for re-signing
(which is a common one-time configuration task for IT organizations). Optionally, a CA certificate that is a subordinate to
the Root CA within the enterprise Public Key Infrastructure may
be used for re-signing. This enables minimal administration if
the Root CA certificate has already been installed in the client
certificate store.
During resigning, the SSL Inspector Appliance will only
modify the CA that issued the sitek certificate. All other attributes
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present in the re-signed certificate are retained from the origmal
certificate. In the case that a certificate that has expired, or contains a common name that does not match the host to which
the certificate was issued, the client will be presented with a
warning as though the SSL Inspector Appliance were not in-line.
Server-controlled
In the server-controlled mode, or "key-known mode," the SSL
server(s) and the SSL Inspector Appliance are in the same
administrative domain. In this mode of operation, the SSL
Inspector can be deployed to protect e-commerce or other SSLserver infrastructure from incoming web threats, as well as protect enterprise resources from threats originating over SSL-based
VPNs. In server-controlled mode, the SSL-server private key is
installed directly in the SSL Inspector Appliance. This allows
the SSL Inspector to participate transparently during SSL session
estabhhment between the SSL client and the SSL server.

HIGHAVAILABILITY
In order to ensure network uptime and allow the SSL Inspector to
be installed and removed from the system with minimal network
disruption, various forms of hgh availability measures are s u p
ported in the SSL Inspector system. The system supports both
hardware and software features to reduce network downtime.
Network Interface High Availability
The SSL Inspector Appliance was designed to ensure that
organizations retain network connectivity and guarantee traffic
flow in failure scenarios, including loss of power to the appliance. Available with both copper- and fiber-based SFPs, the
SSL Inspector supports a hardware relay-based interface card
that can connect ingress and egress ports in case of power loss
or any other failure of the SSL Inspector. Failure monitoring
is accomplished by means of an active heartbeat from the
NFE-i8000 and CPU to the Ethemet relay interface card. If the
heartbeat packets are no longer received, the Ethemet relay card
will revert to one of two modes of operation:
"Fail to close" or "fail to wire," where ingress and egress
ports are connected via mechanical relay when a failure is
detected in the SSL Inspector system. This will allow traffic
to continue flowing and bypass the SSL Inspector Appliance, as well as any connected security appliances. The
system defaults to a "fail to wire" configuration.
"Fail to open," where the ingress and egress ports are no
longer connected during a failure. Fail to open is the
preferred failure mode for highly secure applications that
would prefer that no traffic be sent across the network
(through the SSL Inspector appliance) when the adjacent
application is unavailable to manage or inspect traffic.
System High Availability
NPU-based Bypass
The SSL Inspector supports bypass of all traffic received by the
system, based on a Traffic Diversion Policy rule-set that assures
that all traffic is cut-through the system and not forwarded to
the attached IDS or IPS device entirely. This wd1 allow traffic to
continue flowing in the network in case of a failure in the
attached security appliances. These pre-defined TDP rules do
not protect from a failure in the Netronome SSL Inspector itself,
but rather can be quickly applied to the SSL Inspector to keep
traffic flowing in case of a failure of an attached security appliance. They also allow changes to be made to an attached
network security appliance with minimal network disruption.

Examining SSL-encgrpted Communications

7

Link State Control
Ethemet link status is a common method used to identify
network mfrastructure failures from fiber cuts to system hardware or software problems. If Ethemet lmk or "canier" is flagged
as down, the network device connected to the interface reporting the error is unreachable. When an interface's link state
changes, it is useful to report these state changes to adjacent
devices. Inserting the SSL Inspector into the network architecture as a "bumpin-the-wire" allows it to report link failures on
the network-connected ports, as well as state changes to and
from the adjacent security appliance (filteringor sniffingmodes).
The SSL Inspector supports configurablebehavior to mirror link
state between pairs of ports that form a virtual "bump-in-thewire." This enables the system to function in high availability
deployment scenarios which rely on detecting the link state to
determine the path through the system.
The SSL Inspector allows the administrator to remotely control the link state to force link down or enable auto-detection of
each GigE interface through the Web UI. In addition to manually
controlling link state through the user interface, the SSL Inspector supports several link state mirroring modes where state on an
interface can optionally be indicated on adjacent interfaces.
Link State Mirroring Modes
Mirroring by Direct Coupling: In direct coupling mode,
when link is lost on one GigE interface, link is immediately
forced down on the paired GigE interface. Link indication
will always mirror the state of the paired interface.
Latching Mirroring: In latching mode, when link is lost,
h k is immediately forced down on the paired GigE
interface. An adrmnistrator must manually configure the
interface to again automaticallysense link.
Mirroring with Hysteresis: to avoid needlessly propagating
a fluctuating link state, when llnk on an interface goes
down, the system waits for a configurable time before
bringing the paired link down. Once the link on an interface
is restored, the system waits for an additional configurable
time before configuring the paired link to automatically
sense link state again.

PERFORMANCE
Usmg SSL to encrypt data over a network ensures that the data
was only read by its intended recipient and not intercepted
during transmission. The SSL protocol is computationally
intensive, though. Depending on the cipher suite chosen, SSL
can slow down a Web server or application substantially
The SSL protocol is slow because public key cryptography is
extremely CPU intensive. The time and number of CPU cycles
required to estabhsh an SSL session and encryptldecrypt data
are much hgher than similar metrics for symmetricencryption
and certainly for an unencrypted TCP connection.
Accordingly in-line SSL decryption is a potential bottleneck
in network performance. Most SSL proxy devices in the industry only operate at hundreds of Mbps. Consideringthat they are

almost exclusively deployed in-line on Gigabit Ethemet interfaces, it takes many devices operating in parallel to keep up
with network speeds, not to mention the additional hardware
required to optionally load-balance flows across a large number
of SSL proxies.
SSL Inspection Performance
The Netronome SSL Inspector is the industry's highest performance Transparent SSL proxy, supporting line-rate network
performance, scalable flow-based processing, flexible cipher
support and extremely high connection rates; metrics that
allow the SSL Inspector to be installed in a network without becoming a bottleneck adversely affecting network ~erforrnance.

.....
-

.:

.;

CONCLUSION
With the amount of SSL-encrypted traffic forecasted to continue
to increase, IT network operators are lookmg for new solutions
that satisfy their need for information security for the enterprise
and individual users, as well as the requirement for corporate
compliance, acceptable use policies and government regulations
for both security and privacy. The solution must also be provided without impact to network performance, because providing compliance at the expense of throughput is no more
acceptable than meeting user and application bandwidth requirements whde ignoring security:To date, it has been difficult,
if not impossible,to satisfy these competing requirements for security performance and control. Thankfully, for enterprise network operators,a next ggneration of high-speed, transparent SSL
proxies is now poised to deliver it.
The Netronome SSL Inspector is the industryS highestperformance SSL proxy qi any type, providing IT administrators
with vislb~lityinto the i'ontents of encrypted flows at the
highest speeds, largest n~;$ber of flows and highest connection
rate. Beyond industry-d~finingperformance, the Netronome
SSL Inspector is unique y bemg the first transparent SSL Proxy
that both increases se-unty and significantly minimizes
ldeployment and operatiyn costs by removing costly user and
network configuration.

o 'Intelhgent to the Core",NetronomeSS1

All other trademarks are the property of then respective
owners
0 2010 Netmnome Systems, Inc All r~ghtsresewed
Spertficatlonsare subject to change wthout nouce (2-10)

..,.

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;,...1 Gbps
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. .- . .. .. I,QOQ,OO~
T w ! FIOWS ,..:.......... :...........,.......................
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SSL FIOWS:. ................................................:50
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SSL Flow Setups/Teardowns Per Second ..I;. .-:. ,.I.. :.....
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Traffic Diversion Policies..........,
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SSL %ssioi( L Q .........................
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@ Netmnome a a regmered trademark and The

or and
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t Neuonome SSL Inspector Logo are
,Netmnome
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emarks
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of Netmnome Systems, Inc

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Figure 7. Netronome SSL lnspedor Perl

NETRONOME
intelligent to the Corem

9 :

Netronomehas
operations in:
USA (Pittsburgh [HQ],
Santa Clara & Boston),
UK (Cambridge),
Malaysia (Penang),
South Africa (Centurion)and
China (Shenzhen, Hong Kong)
[email protected]
+l 8776387629
ssCinspector.com

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