Enhanced authentication for secure communications
A server obtains a challenge from another computer system during a negotiation with a client according to a protocol. The server injects the challenge into a message of the protocol to the client. The client uses the challenge in an authentication request. The server submits the authentication request to the other computer system for verification. The other computer system verifies the authentication request using a key registered to the client. The server operations are further dependent at least in part on whether verification of the authentication request was successful.
1. A computer-implemented method comprising:
obtaining a challenge value from an authentication service;
subsequent to performing a cryptographic key exchange with a client computer in accordance with a cryptographic protocol that includes an authentication phase, sending, to the client computer using the cryptographic protocol, the challenge value within a field that is not reserved by the cryptographic protocol for the challenge value, wherein the field is in a handshake message, the handshake message in accordance with the cryptographic protocol, transmitted as part of a handshake of the cryptographic protocol; and
authenticating a response to the challenge value based at least in part on the challenge value.
2. The computer-implemented method of claim 1 , further comprising:
receiving the challenge value from a server; and
wherein authenticating the response to the challenge value comprises transmitting the response to the challenge value to the server to be authenticated.
3. The computer-implemented method of claim 1 , wherein the response to the challenge value comprises a digital signature.
4. The computer-implemented method of claim 1 , wherein:
the computer-implemented method is performed by a first system;
authenticating the response comprises transmitting the response to a second system to cause the second system to perform a cryptographic operation to authenticate the response; and
the cryptographic operation is performed using a cryptographic key that is inaccessible to the first system.
5. The computer-implemented method of claim 1 , wherein the challenge value comprises a randomly generated value.
6. A system, comprising:
one or more processors; and
memory storing instructions that, if executed by the one or more processors, cause the system to:
perform, before an authentication phase of a cryptographic protocol, a key exchange with a client computer, the key exchange being a condition of the cryptographic protocol;
send, to the client computer in accordance with the cryptographic protocol, a challenge value within a field that is not reserved by the cryptographic protocol for the challenge value, the challenge value obtained from an authentication service, the field in a handshake message sent as part of a handshake of the cryptographic protocol; and
authenticate a response, from the client computer, to the challenge value based at least in part on the challenge value.
7. The system of claim 6 , wherein the challenge value is generated by another system.
8. The system of claim 6 , wherein:
the response comprises a digital signature; and
the system authenticates the response by verifying the digital signature using a message of the cryptographic protocol that comprises the challenge value.
9. The system of claim 6 , wherein the system authenticates the response by at least:
transmitting over a network a request to authenticate the response; and
receiving, over the network, an indication of whether the response is successfully authenticated.
10. The system of claim 6 , wherein the cryptographic protocol is to establish a cryptographically protected communications session.
11. The system of claim 6 , wherein the instructions, if executed, further cause the system to provide access to computing resources as a result of successful authentication of the response.
12. The system of claim 6 , wherein the field is optionally populated according to the cryptographic protocol.
13. A non-transitory computer-readable storage medium storing thereon instructions that, if executed by one or more processors of a computer system, cause the computer system to:
obtain, after exchanging a key with a first computer in accordance with a cryptographic protocol that includes an authentication phase, a challenge value from the first computer within a field that is not reserved by the cryptographic protocol for the challenge value, the field in a handshake message transmitted as part of a handshake of the cryptographic protocol;
send a response to the challenge value; and
obtain an indication from the first computer whether the response to the challenge value has been verified by an authentication service.
14. The non-transitory computer-readable storage medium of claim 13 , the field is optionally populated according to the cryptographic protocol.
15. The non-transitory computer-readable storage medium of claim 13 , wherein the field is reserved by the cryptographic protocol for another value.
16. The non-transitory computer-readable storage medium of claim 13 , wherein the cryptographic protocol is to establish a cryptographically protected communications session.
17. The non-transitory computer-readable storage medium of claim 13 , whether the instructions, if executed, further cause the computer system to generate the response by at least computing a digital signature over information that comprises a message of the cryptographic protocol that comprises the challenge value.