mbed-os-examples
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:
- 66:ce8709d9912c
- Parent:
- 54:042e70e75517
--- a/README.md Wed May 02 06:30:32 2018 +0100 +++ b/README.md Fri May 04 12:30:06 2018 +0100 @@ -25,47 +25,46 @@ ``` Starting mbed-os-example-tls/tls-client -Using Mbed OS 5.X.Y -[EasyConnect] Connected to Network successfully -[EasyConnect] MAC address ae:41:46:27:31:e7 -[EasyConnect] IP address 192.168.64.255 -Connecting with os.mbed.com +Using Mbed OS 5.6.3 +[EasyConnect] IPv4 mode +Successfully connected to os.mbed.com at port 443 Starting the TLS handshake... -TLS connection to os.mbed.com established +Successfully completed the TLS handshake Server certificate: - cert. version : 3 - 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 : 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 - 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 + cert. version : 3 + 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 : 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 + 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 200 OK status ... [OK] -HTTPS: Received 'Hello world!' status ... [OK] -HTTPS: Received message: - +Established TLS connection to os.mbed.com +HTTP: Received 365 chars from server +HTTP: Received '200 OK' status ... OK +HTTP: Received message: HTTP/1.1 200 OK -Server: nginx/1.11.12 -Date: Mon, 18 Sep 2017 12:54:59 GMT +Server: nginx/1.11.10 +Date: Wed, 08 Nov 2017 09:07:59 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: Mon, 18 Sep 2017 22:54:59 GMT -X-Upstream-L3: 172.17.0.4:80 -X-Upstream-L2: developer-sjc-cyan-1-nginx +Expires: Wed, 08 Nov 2017 19:07:59 GMT Strict-Transport-Security: max-age=31536000; includeSubdomains Hello world! + + +DONE ``` ## Debugging the TLS connection