Automatic login to social-network from executable

1. A computer-implemented method comprising, by a server computer:

receiving, from a client device, a request to download an application, wherein the client device is logged-in to a session associated with a user account in a communications system;

transmitting, to the client device, an installer file in response to the request; and

causing a login information associated with the user account and authentication information to be injected into the installer file;

appending, in response to the request, a downloader module executable file with the login information and the authentication information; and

transmitting, to the client device, the downloader module executable file,

wherein the transmitting the installer file is performed in response to a second request from the downloader module executable file.

2. The method of claim 1 , wherein the server computer injects the login information and the authentication information before transmitting the installer file.

3. The method of claim 1 , further comprising generating a login nonce, wherein,

the login information comprises a login identifier and the login nonce, and

the authentication information comprises a first hash message authentication code (HMAC), the HMAC generated based on the login nonce and an internet protocol (IP) address of the client device.

4. The method of claim 3 , further comprising:

receiving, from the client device, a login request, the login request comprising the login nonce;

computing a second HMAC based on the received login nonce and the client device's IP address;

verifying that the second HMAC is equal to the first HMAC; and

transmitting a notification, to the client device, that the login request was successful.

5. The method of claim 1 , wherein the appending the downloader module executable file further comprises updating a signature size field in the header of the downloader module executable file.

6. The method of claim 1 , wherein the communications system comprises a social-networking system.

7. A computer-implemented method comprising, by a client device:

receiving a user input to download an application;

transmitting, to a server computer, a request to download the application, wherein the client device is logged-in to a session associated with a user account in a communications system;

receiving, from the server computer, a downloader module for execution on the client device;

executing, by the client device, the downloader module;

transmitting, by the downloader module to the server computer, a request for an installer executable file;

injecting a login information associated with the user account and authentication information into the installer executable file; and

executing the installer executable file to install the application.

8. The method of claim 7 , further comprising:

transmitting a login request, the login request comprising a login nonce.

9. The method of claim 8 , further comprising:

receiving a notification that the login request was successful; and

presenting, on a user interface of the client device, an option to login to the communications system with the user account without entering user account information.

10. The method of claim 8 , further comprising:

receiving a notification that the login nonce was unsuccessful; and

prompting, on the user interface of the client device, for user login information to login to the communications system.

11. The method of claim 7 , wherein the injecting a login information associated with the user account and authentication information into the installer executable file comprises passing the login information and authentication information as parameters when executing the installer executable file.

12. The method of claim 7 , wherein the communications system comprises a social-networking system.

13. One or more computer-readable non-transitory storage media embodying software that is operable when executed to:

receive, from a client device, a request to download an application, wherein the client device is logged-in to a session associated with a user account in a communications system;

transmit, to the client device, an installer file in response to the request; and

cause a login information associated with the user account and authentication information to be injected into the installer file; and

wherein the software is further operable when executed to:

append, in response to the request, a downloader module executable file with the login information and the authentication information;

transmit, to the client device, the downloader module executable file; and

wherein the software is further operable when executed to transmit the installer file in response to a second request from the downloader module executable file.

14. The storage media of claim 13 , wherein the software is further operable to inject the login information and the authentication information before transmitting the installer file.

15. The storage media of claim 13 , wherein the software is further operable when executed to generate a login nonce, wherein,

the login information comprises a login identifier and the login nonce, and

the authentication information comprises a first hash message authentication code (MAC), the HMAC generated based on the login nonce and an internet protocol (IP) address of the client device.

16. The storage media of claim 15 , wherein the software is further operable when executed to:

receive, from the client device, a login request, the login request comprising the login nonce;

compute a second HMAC based on the received login nonce and the client device's IP address;

verify that the second HMAC is equal to the first HMAC; and

transmit, to the client device, a notification the login request was successful.

17. The storage media of claim 13 , wherein the software is further operable when executed to append the downloader module executable file by updating a signature size field in the header of the downloader module executable file.

18. The storage media of claim 13 , wherein the communications system comprises a social-networking system.