Split termination of secure communication sessions with mutual certificate-based authentication
A method and apparatus are provided for split-terminating a secure client-server communication connection when the client and server perform mutual authentication by exchanging certificates, such as within a Lotus Notes environment. When the client submits a certificate to the server, an intermediary device intercepts the certificate and submits to the server a substitute client certificate generated by that intermediary. A certificate authority's private key is previously installed on the intermediary to enable it to generate public keys, private keys and digital certificates. With the private key corresponding to the substitute certificate, the intermediary extracts a temporary key from a subsequent server message. The intermediary uses the temporary key to read a session key issued later by the server. Thereafter, the intermediary shares the session key with another intermediary, and together they use the session keys to access and optimize (e.g., accelerate) messages sent by the client and the server.
1. A method of facilitating split-termination of a secure communication connection between a client computing device and a server computing device that perform mutual authentication, the method comprising, at a first intermediate network device situated in a communication path between the client and the server:
intercepting a client digital certificate transmitted toward the server by the client;
generating a substitute digital certificate in a name of the client, wherein said generating comprises:
constructing a substitute client private key and a substitute client public key; and
signing the substitute digital certificate with a private key of a certificate authority recognized by the server;
transmitting the substitute digital certificate to the server;
intercepting a message addressed to the client and issued by the server after the server receives the substitute digital certificate;
decrypting the message with a key associated with the substitute digital certificate;
extracting a ticket from the message;
re-encrypting the message with a key associated with the client digital certificate;
forwarding the re-encrypted message toward the client;
extracting a temporary key from the ticket; and
using the temporary key to retrieve a session key from a subsequent message issued by the server and addressed to the client.
2. The method of claim 1 , further comprising, prior to said generating:
storing a private key of the certificate authority recognized by the server.
3. The method of claim 2 , wherein the client digital certificate was issued by the certificate authority.
4. The method of claim 1 , wherein:
the message was encrypted with the substitute client public key.
5. The method of claim 1 , further comprising:
storing the ticket to facilitate a subsequent authentication of the client to the server.
6. The method of claim 1 , further comprising:
deleting the substitute digital certificate after said retrieving a session key.
7. The method of claim 1 , further comprising:
intercepting a second client digital certificate transmitted toward the server by a second client;
altering the substitute digital certificate to include a name of the second client in place of a name of the client;
re-signing the substitute digital certificate with the private key of the certificate authority; and
transmitting the substitute digital certificate to the server.
8. The method of claim 1 , further comprising:
storing a public key of the first intermediate network device on the server.
9. The method of claim 8 , further comprising:
intercepting a second client digital certificate transmitted toward the server by a second client;
constructing a second substitute client private key and a second substitute client public key;
signing a second substitute digital certificate with a private key of the first intermediate network device; and
transmitting the second substitute digital certificate to the server in place of the second client digital certificate.
10. The method of claim 1 , wherein the first intermediate network device is configured to operate with a second intermediate network device to optimize communications between the client and the server, wherein the second intermediate network device is also situated in a communication path between the client and the server.
11. The method of claim 1 , further comprising, after said retrieving a session key:
transmitting the session key from the first intermediate network device to a second intermediate network device situated in closer proximity to the client than the first intermediate network device.
12. The method of claim 11 , further comprising:
at the second intermediate network device:
receiving a message from the client directed toward the server;
decrypting the message with the session key;
encrypting the message with an intermediary key shared between the first intermediate network device and the second intermediate network device; and
transmitting the message toward the first intermediate network device; and
at the first intermediate network device:
decrypting the message with the shared intermediary key;
encrypting the message with the session key; and
transmitting the message toward the server.
13. The method of claim 12 , further comprising:
at the first intermediate network device:
receiving from the server a response directed toward the client;
decrypting the message with the session key;
encrypting the message with the shared intermediary key; and
transmitting the message toward the second intermediate network device; and
at the second intermediate network device:
decrypting the message with the shared intermediary key;
encrypting the message with the session key; and
transmitting the message toward the client.
14. A non-transitory computer-readable medium storing instructions that, when executed by a first intermediate network device, cause the first intermediate network device to perform a method of facilitating split-termination of a secure communication connection between a client computing device and a server computing device that perform mutual authentication, the method comprising:
intercepting a client digital certificate transmitted toward the server by the client;
generating a substitute digital certificate in a name of the client, wherein said generating comprises:
constructing a substitute client private key and a substitute client public key; and signing the substitute digital certificate with a private key of a certificate authority recognized by the server;
transmitting the substitute digital certificate to the server;
intercepting a message addressed to the client and issued by the server after the server receives the substitute digital certificate;
decrypting the message with a key associated with the substitute digital certificate;
extracting a ticket from the message;
re-encrypting the message with a key associated with the client digital certificate;
forwarding the re-encrypted message toward the client;
extracting a temporary key from the ticket; and
using the temporary key to retrieve a session key from a subsequent message issued by the server and addressed to the client.
15. A hardware apparatus situated in a path of communication between a client and server, wherein the client is configured to authenticate the server using a digital certificate associated with the server and the server is configured to authenticate the client using a digital certificate associated with the client, the hardware apparatus comprising:
at least one microprocessor; and
memory storing logic for execution by the at least one processor, the logic including:
first intercept logic for intercepting a client digital certificate transmitted toward the server by the client;
key logic for generating a substitute public key and a substitute private key;
certificate logic for generating a substitute client digital certificate encompassing a name of the client and the substitute public key, wherein generating the substitute client digital certificate comprises:
constructing a substitute client private key and a substitute client public key; and
signing the substitute digital certificate with a private key of a certificate authority recognized by the server;
authentication logic for transmitting the substitute client digital certificate toward the server in place of the client digital certificate;
second intercept logic for intercepting messages addressed to the client by the server; and
encryption/decryption logic for:
decrypting a first intercepted from the server with the substitute private key, to retrieve a temporary key;
re-encrypting the first intercepted message with a public key corresponding to the intercepted client digital certificate, for transmission toward the client; and
decrypting a second intercepted message from the server with the temporary key, to retrieve a client-server session key, wherein the client-server session key is shared between the server, the client, and the hardware apparatus.
16. The hardware apparatus of claim 15 , the memory further including:
storage logic for storing a private key of the certificate authority trusted by the server.
17. The hardware apparatus of claim 15 ,
wherein the apparatus does not comprise the certificate authority.
18. The hardware apparatus of claim 15 , wherein the apparatus is configured to operate cooperatively with a second apparatus situated in the path of communications to optimize communications between the client and the server.