mbed-os-examples / Mbed OS mbed-os-example-tls-tls-client

Hello world example of a TLS client: fetch an HTTPS page. The canonical source for this example lives at https://github.com/ARMmbed/mbed-os-example-tls

HTTPS File Download Example for TLS Client on mbed OS

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

Getting started

Building with mbed CLI

If you'd like to use mbed CLI to build this, then you should set up your environment if you have not done so already. For instructions, refer to the main readme. The instructions here relate to using the developer.mbed.org Online Compiler

Import the program in to the Online Compiler, select your board from the drop down in the top right hand corner and then compile the application. Once it has built, you can drag and drop the binary onto your device.

Required hardware

This example also requires an Ethernet cable an connection to the internet additional to the hardware requirements in the main readme.

Monitoring the application

NOTE: Make sure that the Ethernet cable is plugged in correctly before running the application.

The output in the terminal window should be similar to this:

terminal output

Using Ethernet LWIP
Client IP Address is 10.2.203.43
Connecting with developer.mbed.org
Starting the TLS handshake...
TLS connection to developer.mbed.org established
Server certificate:
    cert. version     : 3
    serial number     : 11:21:B8:47:9B:21:6C:B1:C6:AF:BC:5D:0C:19:52:DC:D7:C3
    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        : 2016-03-03 12:26:08
    expires on        : 2017-04-05 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 439 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: Wed, 20 Jul 2016 10:00:35 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, 20 Jul 2016 20:00:35 GMT
X-Upstream-L3: 172.17.0.3:80
X-Upstream-L2: developer-sjc-indigo-1-nginx
Strict-Transport-Security: max-age=31536000; includeSubdomains

Hello world!

Debugging the TLS connection

To print out more debug information about the TLS connection, edit the file `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.

The TLS connection can fail with an error similar to:

error message

    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

This 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 possible reason for this error is 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, so use at your own risk or for debugging only!

Diff: README.md

Revision:
42:5236ebc3d12a
Parent:
22:3fbb4afb6a43
Child:
47:c84bc63913c6
--- a/README.md	Wed Aug 30 17:00:21 2017 +0100
+++ b/README.md	Wed Sep 20 12:17:15 2017 +0100
@@ -1,12 +1,12 @@
 # HTTPS File Download Example for TLS Client on mbed OS
 
-This application downloads a file from an HTTPS server (developer.mbed.org) and looks for a specific string in that file.
+This application downloads a file from an HTTPS server (os.mbed.com) and looks for a specific string in that file.
 
 ## Getting started
 
 Set up your environment if you have not done so already. For instructions, refer to the [main readme](../README.md).
 
-You can also compile this example with the [mbed Online Compiler](https://developer.mbed.org/compiler/) by using [this project](https://developer.mbed.org/teams/mbed-os-examples/code/mbed-os-example-tls-tls-client).
+You can also compile this example with the [mbed Online Compiler](https://os.mbed.com/compiler/) by using [this project](https://os.mbed.com/teams/mbed-os-examples/code/mbed-os-example-tls-tls-client).
 
 ## Required hardware
 
@@ -14,7 +14,7 @@
 
 The networking stack used in this example requires TLS functionality to be enabled on mbed TLS. On devices where hardware entropy is not present, TLS is disabled by default. This would result in compile time or linking failures.
 
-To learn why entropy is required, read the [TLS Porting guide](https://docs.mbed.com/docs/mbed-os-handbook/en/5.2/advanced/tls_porting/).
+To learn why entropy is required, read the [TLS Porting guide](https://docs.mbed.com/docs/mbed-os-handbook/en/latest/advanced/tls_porting/).
 
 ## Monitoring the application
 
@@ -24,17 +24,17 @@
 
 ```
 Using Ethernet LWIP
-Client IP Address is 10.2.203.43
-Connecting with developer.mbed.org
+Client IP Address is 172.16.8.12
+Connecting with os.mbed.com
 Starting the TLS handshake...
-TLS connection to developer.mbed.org established
+TLS connection to os.mbed.com established
 Server certificate:
     cert. version     : 3
-    serial number     : 11:21:B8:47:9B:21:6C:B1:C6:AF:BC:5D:0C:19:52:DC:D7:C3
+    serial number     : 65:7B:6D:8D:15:A5:B6:86:87:6B:5E:BC
     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        : 2016-03-03 12:26:08
-    expires on        : 2017-04-05 10:31:02
+    issued  on        : 2017-04-03 13:54:02
+    expires on        : 2018-05-06 10:31:02
     signed using      : RSA with SHA-256
     RSA key size      : 2048 bits
     basic constraints : CA=false
@@ -43,23 +43,22 @@
     ext key usage     : TLS Web Server Authentication, TLS Web Client Authentication
 Certificate verification passed
 
-HTTPS: Received 439 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: Wed, 20 Jul 2016 10:00:35 GMT
+Server: nginx/1.11.12
+Date: Mon, 18 Sep 2017 12:54:59 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, 20 Jul 2016 20:00:35 GMT
-X-Upstream-L3: 172.17.0.3:80
-X-Upstream-L2: developer-sjc-indigo-1-nginx
+Expires: Mon, 18 Sep 2017 22:54:59 GMT
+X-Upstream-L3: 172.17.0.4:80
+X-Upstream-L2: developer-sjc-cyan-1-nginx
 Strict-Transport-Security: max-age=31536000; includeSubdomains
 
 Hello world!
@@ -81,9 +80,9 @@
 The TLS connection can fail 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
+    Failed to fetch /media/uploads/mbed_official/hello.txt from os.mbed.com:443
 
-This 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).
+This 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 `os.mbed.com` switches to a new CA when updating its certificate).
 
 Another possible reason for this error is 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.