Selectively performing man in the middle decryption

1. A method performed by data processing apparatus, the method comprising:

receiving, at a network gateway from a client device within a network, a first request to access a first resource hosted by a server outside the network, the first request including a first universal resource identifier that identifies the first resource;

determining, based on one or more policies in a policy group associated with the client device, whether requests from the client device to access the first resource outside the network should be inspected;

selecting, from a plurality of candidate man-in-the-middle gateways, a man-in-the-middle gateway for use; and

providing, based on determining that requests from the client device to access the first resource outside the network are to be inspected, a redirect response to the client device, the redirect response including a second universal resource identifier, the second universal resource identifier comprising a domain associated with the man-in-the-middle gateway and further comprising at least a portion of the first universal resource identifier, such that the client device displays at least the domain associated with the man-in-the-middle gateway to a user of the client device in response to receiving, from the user, input to navigate to the first universal resource identifier.

2. The method of claim 1 , the method further comprising:

receiving, from the client device, a second request to access the first resource, the second request including the second universal resource identifier;

establishing, based on receiving the second request, a first encrypted connection between the client device and the man-in-the-middle gateway, and a second encrypted connection between the man-in-the-middle gateway and the server hosting the first resource, to facilitate encrypted communication traffic between the client device and the server hosting the first resource; and

decrypting and inspecting the encrypted communication traffic passing between the client device and the server hosting the first resource.

3. The method of claim 2 , wherein the inspecting comprises applying one or more first security policies to the decrypted communication traffic, the first security policies being included in the policy group.

4. The method of claim 3 , further comprising blocking communication traffic between the client device and the server hosting the first resource upon determining that one or more second security policies have been violated, the second security policies being included in the policy group.

5. The method of claim 3 , further comprising modifying communication traffic between the client device and the server hosting the first resource based on content of the communication traffic.

6. The method of claim 3 , wherein:

the providing comprises appending one or more client device parameters to the redirect response, the client device parameters identifying one of the client device and the policy group;

the receiving the second request to access the first resource comprises receiving the client device parameters from the client device; and

the inspecting comprises identifying the policy group using the client device parameters and selecting the first security policies from the policy group.

7. The method of claim 3 , wherein:

the providing comprises sending a cookie to the client device;

the receiving the second request to access the first resource comprises receiving one or more parameters included in the cookie from the client device; and

the inspecting comprises identifying the policy group using the parameters from the cookie and selecting the first security policies from the policy group.

8. The method of claim 3 , wherein the inspecting comprises identifying the policy group associated with the client device based on the internet protocol address of the client device and selecting the first security policies from the policy group.

9. The method of claim 2 , wherein the encrypted communication traffic between the client device and the server hosting the first resource passes through the man-in-the-middle gateway.

10. The method of claim 1 , wherein the receiving the first request, the determining and the providing are performed by a web gateway device.

11. The method of claim 10 , wherein the man-in-the-middle gateway comprises a proxy server device separate from the web gateway device.

12. The method of claim 1 , wherein:

each candidate man-in-the-middle gateway inspects based on an associated one of a plurality of inspection levels; and

selecting, from a plurality of candidate man-in-the-middle gateways, a man-in-the-middle gateway for use comprises selecting a man-in-the-middle gateway based on an associated one of a plurality of inspection levels.

13. The method of claim 1 , wherein selecting, from a plurality of candidate man-in-the-middle gateways, a man-in-the-middle gateway for use comprises selecting a man-in-the-middle gateway based on a classification of the first resource.

14. A non-transitory computer storage medium encoded with instructions that, when executed by one or more computers, cause the one or more computers to perform operations comprising:

receiving, at a network gateway from a client device within a network, a first request to access a first resource hosted by a server outside the network, the first request including a first universal resource identifier that identifies the first resource;

determining, based on one or more policies in a policy group associated with the client device, whether requests from the client device to access the first resource outside the network should be inspected;

selecting, from a plurality of candidate man-in-the-middle gateways, a man-in-the-middle gateway for use; and

providing, based on determining that requests from the client device to access the first resource outside the network are to be inspected, a redirect response to the client device, the redirect response including a second universal resource identifier, the second universal resource identifier comprising a domain associated with the man-in-the-middle gateway and further comprising at least a portion of the first universal resource identifier, such that the client device displays at least the domain associated with the man-in-the-middle gateway to a user of the client device in response to receiving, from the user, input to navigate to the first universal resource identifier.

15. A system comprising:

one or more computers and one or more storage devices storing instructions that are operable, when executed by the one or more computers, to cause the one or more computers to perform operations comprising:

receiving, at a network gateway from a client device within a network, a first request to access a first resource hosted by a server outside the network, the first request including a first universal resource identifier that identifies the first resource;

determining, based on one or more policies in a policy group associated with the client device, whether requests from the client device to access the first resource outside the network should be inspected;

selecting, from a plurality of candidate man-in-the-middle gateways, a man-in-the-middle gateway for use; and

providing, based on determining that requests from the client device to access the first resource outside the network are to be inspected, a redirect response to the client device, the redirect response including a second universal resource identifier, the second universal resource identifier comprising a domain associated with the man-in-the-middle gateway and further comprising at least a portion of the first universal resource identifier, such that the client device displays at least the domain associated with the man-in-the-middle gateway to a user of the client device in response to receiving, from the user, input to navigate to the first universal resource identifier.

16. The system of claim 15 , the operations further comprising:

receiving, from the client device, a second request to access the first resource, the second request including the second universal resource identifier;

establishing, based on receiving the second request, a first encrypted connection between the client device and the man-in-the-middle gateway, and a second encrypted connection between the man-in-the-middle gateway and the server hosting the first resource, to facilitate encrypted communication traffic between the client device and the server hosting the first resource; and

decrypting and inspecting the encrypted communication traffic passing between the client device and the server hosting the first resource.

17. The system of claim 16 , wherein the inspecting comprises applying one or more first security policies to the decrypted communication traffic, the first security policies being included in the policy group.

18. The system of claim 17 , further comprising blocking communication traffic between the client device and the server hosting the first resource upon determining that one or more second security policies have been violated, the second security policies being included in the policy group.

19. The system of claim 17 , the operations further comprising modifying communication traffic between the client device and the server hosting the first resource based on content of the communication traffic.

20. The system of claim 17 , wherein:

the providing comprises appending one or more client device parameters to the redirect response, the client device parameters identifying one of the client device and the policy group;

the receiving the second request to access the first resource comprises receiving the client device parameters from the client device; and

the inspecting comprises identifying the policy group using the client device parameters and selecting the first security policies from the policy group.

21. The system of claim 17 , wherein:

the providing comprises sending a cookie to the client device;

the receiving the second request to access the first resource comprises receiving one or more parameters included in the cookie from the client device; and

the inspecting comprises identifying the policy group using the parameters from the cookie and selecting the first security policies from the policy group.

22. The system of claim 17 , wherein the inspecting comprises identifying the policy group associated with the client device based on the internet protocol address of the client device and selecting the first security policies from the policy group.

23. The system of claim 16 , wherein the encrypted communication traffic between the client device and the server hosting the first resource passes through the man-in-the-middle gateway.

24. The system of claim 15 , wherein the receiving the first request, the determining and the providing are performed by a web gateway device.

25. The system of claim 24 , wherein the man-in-the-middle gateway comprises a proxy server device separate from the web gateway device.

26. The system of claim 15 , wherein:

each candidate man-in-the-middle gateway inspects based on an associated one of a plurality of inspection levels; and

selecting, from a plurality of candidate man-in-the-middle gateways, a man-in-the-middle gateway for use comprises selecting a man-in-the-middle gateway based on an associated one of a plurality of inspection levels.

27. The system of claim 15 , wherein selecting, from a plurality of candidate man-in-the-middle gateways, a man-in-the-middle gateway for use comprises selecting a man-in-the-middle gateway based on a classification of the first resource.