yotta/data/example-tls-client/README.md - security/mbedtls - Rivoreo Source Code Repositories

 # HTTPS File Download Example for TLS Client

 This application downloads a file from an HTTPS server (developer.mbed.org) and looks for a specific string in that file.

 This example is implemented as a logic class (HelloHTTPS) wrapping a TCP socket and a TLS context. The logic class handles all events, leaving the main loop to just check if the process has finished.

 ## Pre-requisites

 To build and run this example you must have:

 * A computer with the following software installed:
   * [CMake](http://www.cmake.org/download/).
   * [yotta](https://github.com/ARMmbed/yotta). Please note that **yotta has its own set of dependencies**, listed in the [installation instructions](http://armmbed.github.io/yotta/#installing-on-windows).
   * [Python](https://www.python.org/downloads/).
   * [The ARM GCC toolchain](https://launchpad.net/gcc-arm-embedded).
   * A serial terminal emulator (Like screen, pySerial and cu).
 * An [FRDM-K64F](http://developer.mbed.org/platforms/FRDM-K64F/) development board, or another board supported by mbed OS (in which case you'll have to substitute frdm-k64f-gcc with the appropriate target in the instructions below).
 * A micro-USB cable.
 * An Ethernet connection to the internet.
 * An Ethernet cable.
 * If your OS is Windows, please follow the installation instructions [for the serial port driver](https://developer.mbed.org/handbook/Windows-serial-configuration).

 ## Getting started

 1. Connect the FRDM-K64F to the internet using the Ethernet cable.

 2. Connect the FRDM-K64F to the computer with the micro-USB cable, being careful to use the "OpenSDA" connector on the target board.

 3. Navigate to the mbedtls directory supplied with your release and open a terminal.

 4. Set the yotta target:

     ```
     yotta target frdm-k64f-gcc
     ```

 5. Build mbedtls and the examples. This will take a long time if it is the first time:

     ```
     $ yotta build
     ```

 6. Copy `build/frdm-k64f-gcc/test/mbedtls-test-example-tls-client.bin` to your mbed board and wait until the LED next to the USB port stops blinking.

 7. Start the serial terminal emulator and connect to the virtual serial port presented by FRDM-K64F.

 	Use the following settings:

 	* 115200 baud (not 9600).
 	* 8N1.
 	* No flow control.

 8. Press the Reset button on the board.

 9. The output in the terminal window should look similar to this:

     ```
     {{timeout;120}}
     {{host_test_name;default}}
     {{description;mbed TLS example HTTPS client}}
     {{test_id;MBEDTLS_EX_HTTPS_CLIENT}}
     {{start}}

     Client IP Address is 192.168.0.2
     Starting DNS lookup for developer.mbed.org
     DNS Response Received:
     developer.mbed.org: 217.140.101.30
     Connecting to 217.140.101.30:443
     Connected to 217.140.101.30:443
     Starting the TLS handshake...
     TLS connection to developer.mbed.org established
     Server certificate:
         cert. version     : 3
         serial number     : 11:21:4E:4B:13:27:F0:89:21:FB:70:EC:3B:B5:73:5C:FF:B9
         issuer name       : C=BE, O=GlobalSign nv-sa, CN=GlobalSign Organization Validation CA - SHA256 - G2
         subject name      : C=GB, ST=Cambridgeshire, L=Cambridge, O=ARM Ltd, CN=*.mbed.com
         issued  on        : 2015-03-05 10:31:02
         expires on        : 2016-03-05 10:31:02
         signed using      : RSA with SHA-256
         RSA key size      : 2048 bits
         basic constraints : CA=false
         subject alt name  : *.mbed.com, *.mbed.org, mbed.org, mbed.com
         key usage         : Digital Signature, Key Encipherment
         ext key usage     : TLS Web Server Authentication, TLS Web Client Authentication
     Certificate verification passed

     HTTPS: Received 473 chars from server
     HTTPS: Received 200 OK status ... [OK]
     HTTPS: Received 'Hello world!' status ... [OK]
     HTTPS: Received message:

     HTTP/1.1 200 OK
     Server: nginx/1.7.10
     Date: Tue, 18 Aug 2015 18:34:04 GMT
     Content-Type: text/plain
     Content-Length: 14
     Connection: keep-alive
     Last-Modified: Fri, 27 Jul 2012 13:30:34 GMT
     Accept-Ranges: bytes
     Cache-Control: max-age=36000
     Expires: Wed, 19 Aug 2015 04:34:04 GMT
     X-Upstream-L3: 172.17.42.1:8080
     X-Upstream-L2: developer-sjc-indigo-2-nginx
     X-Upstream-L1-next-hop: 217.140.101.86:8001
     X-Upstream-L1: developer-sjc-indigo-border-nginx

     Hello world!
     {{success}}
     {{end}}
     ```

 ## Debugging the TLS connection

 If you are experiencing problems with this example, you should first rule out network issues by making sure the [simple HTTP file downloader example](https://github.com/ARMmbed/mbed-example-network-private/tree/master/test/helloworld-tcpclient) for the TCP module works as expected. If not, please follow the debug instructions for the HTTP file example before proceeding with the instructions below.

 To print out more debug information about the TLS connection, edit the file `source/main.cpp` and change the definition of `DEBUG_LEVEL` (near the top of the file) from 0 to a positive number:

 * Level 1 only prints non-zero return codes from SSL functions and information about the full certificate chain being verified.

 * Level 2 prints more information about internal state updates.

 * Level 3 is intermediate.

 * Level 4 (the maximum) includes full binary dumps of the packets.


 If the TLS connection is failing with an error similar to:

     ```
     mbedtls_ssl_write() failed: -0x2700 (-9984): X509 - Certificate verification failed, e.g. CRL, CA or signature check failed
     Failed to fetch /media/uploads/mbed_official/hello.txt from developer.mbed.org:443
     ```

 it probably means you need to update the contents of the `SSL_CA_PEM` constant (this can happen if you modify `HTTPS_SERVER_NAME`, or when `developer.mbed.org` switches to a new CA when updating its certificate).

 Another reason for this error may be a proxy providing a different certificate. Proxies can be used in some network configurations or for performing man-in-the-middle attacks. If you choose to ignore this error and proceed with the connection anyway, you can change the definition of `UNSAFE` near the top of the file from 0 to 1. **Warning:** this removes all security against a possible active attacker, therefore use at your own risk, or for debugging only!
	# HTTPS File Download Example for TLS Client

	This application downloads a file from an HTTPS server (developer.mbed.org) and looks for a specific string in that file.

	This example is implemented as a logic class (HelloHTTPS) wrapping a TCP socket and a TLS context. The logic class handles all events, leaving the main loop to just check if the process has finished.

	## Pre-requisites

	To build and run this example you must have:

	* A computer with the following software installed:
	* [CMake](http://www.cmake.org/download/).
	* [yotta](https://github.com/ARMmbed/yotta). Please note that yotta has its own set of dependencies, listed in the [installation instructions](http://armmbed.github.io/yotta/#installing-on-windows).
	* [Python](https://www.python.org/downloads/).
	* [The ARM GCC toolchain](https://launchpad.net/gcc-arm-embedded).
	* A serial terminal emulator (Like screen, pySerial and cu).
	* An [FRDM-K64F](http://developer.mbed.org/platforms/FRDM-K64F/) development board, or another board supported by mbed OS (in which case you'll have to substitute frdm-k64f-gcc with the appropriate target in the instructions below).
	* A micro-USB cable.
	* An Ethernet connection to the internet.
	* An Ethernet cable.
	* If your OS is Windows, please follow the installation instructions [for the serial port driver](https://developer.mbed.org/handbook/Windows-serial-configuration).

	## Getting started

	1. Connect the FRDM-K64F to the internet using the Ethernet cable.

	2. Connect the FRDM-K64F to the computer with the micro-USB cable, being careful to use the "OpenSDA" connector on the target board.

	3. Navigate to the mbedtls directory supplied with your release and open a terminal.

	4. Set the yotta target:

	```
	yotta target frdm-k64f-gcc
	```

	5. Build mbedtls and the examples. This will take a long time if it is the first time:

	```
	$ yotta build
	```

	6. Copy `build/frdm-k64f-gcc/test/mbedtls-test-example-tls-client.bin` to your mbed board and wait until the LED next to the USB port stops blinking.

	7. Start the serial terminal emulator and connect to the virtual serial port presented by FRDM-K64F.

	Use the following settings:

	* 115200 baud (not 9600).
	* 8N1.
	* No flow control.

	8. Press the Reset button on the board.

	9. The output in the terminal window should look similar to this:

	```
	{{timeout;120}}
	{{host_test_name;default}}
	{{description;mbed TLS example HTTPS client}}
	{{test_id;MBEDTLS_EX_HTTPS_CLIENT}}
	{{start}}

	Client IP Address is 192.168.0.2
	Starting DNS lookup for developer.mbed.org
	DNS Response Received:
	developer.mbed.org: 217.140.101.30
	Connecting to 217.140.101.30:443
	Connected to 217.140.101.30:443
	Starting the TLS handshake...
	TLS connection to developer.mbed.org established
	Server certificate:
	cert. version : 3
	serial number : 11:21:4E:4B:13:27:F0:89:21:FB:70:EC:3B:B5:73:5C:FF:B9
	issuer name : C=BE, O=GlobalSign nv-sa, CN=GlobalSign Organization Validation CA - SHA256 - G2
	subject name : C=GB, ST=Cambridgeshire, L=Cambridge, O=ARM Ltd, CN=*.mbed.com
	issued on : 2015-03-05 10:31:02
	expires on : 2016-03-05 10:31:02
	signed using : RSA with SHA-256
	RSA key size : 2048 bits
	basic constraints : CA=false
	subject alt name : .mbed.com, .mbed.org, mbed.org, mbed.com
	key usage : Digital Signature, Key Encipherment
	ext key usage : TLS Web Server Authentication, TLS Web Client Authentication
	Certificate verification passed

	HTTPS: Received 473 chars from server
	HTTPS: Received 200 OK status ... [OK]
	HTTPS: Received 'Hello world!' status ... [OK]
	HTTPS: Received message:

	HTTP/1.1 200 OK
	Server: nginx/1.7.10
	Date: Tue, 18 Aug 2015 18:34:04 GMT
	Content-Type: text/plain
	Content-Length: 14
	Connection: keep-alive
	Last-Modified: Fri, 27 Jul 2012 13:30:34 GMT
	Accept-Ranges: bytes
	Cache-Control: max-age=36000
	Expires: Wed, 19 Aug 2015 04:34:04 GMT
	X-Upstream-L3: 172.17.42.1:8080
	X-Upstream-L2: developer-sjc-indigo-2-nginx
	X-Upstream-L1-next-hop: 217.140.101.86:8001
	X-Upstream-L1: developer-sjc-indigo-border-nginx

	Hello world!
	{{success}}
	{{end}}
	```

	## Debugging the TLS connection

	If you are experiencing problems with this example, you should first rule out network issues by making sure the [simple HTTP file downloader example](https://github.com/ARMmbed/mbed-example-network-private/tree/master/test/helloworld-tcpclient) for the TCP module works as expected. If not, please follow the debug instructions for the HTTP file example before proceeding with the instructions below.

	To print out more debug information about the TLS connection, edit the file `source/main.cpp` and change the definition of `DEBUG_LEVEL` (near the top of the file) from 0 to a positive number:

	* Level 1 only prints non-zero return codes from SSL functions and information about the full certificate chain being verified.

	* Level 2 prints more information about internal state updates.

	* Level 3 is intermediate.

	* Level 4 (the maximum) includes full binary dumps of the packets.


	If the TLS connection is failing with an error similar to:

	```
	mbedtls_ssl_write() failed: -0x2700 (-9984): X509 - Certificate verification failed, e.g. CRL, CA or signature check failed
	Failed to fetch /media/uploads/mbed_official/hello.txt from developer.mbed.org:443
	```

	it probably means you need to update the contents of the `SSL_CA_PEM` constant (this can happen if you modify `HTTPS_SERVER_NAME`, or when `developer.mbed.org` switches to a new CA when updating its certificate).

	Another reason for this error may be a proxy providing a different certificate. Proxies can be used in some network configurations or for performing man-in-the-middle attacks. If you choose to ignore this error and proceed with the connection anyway, you can change the definition of `UNSAFE` near the top of the file from 0 to 1. Warning: this removes all security against a possible active attacker, therefore use at your own risk, or for debugging only!