MBEDTLS_KEY_EXCHANGE_ECDHE_ECDSA_ENABLED

Hi all,

I have a small problem with ECC. I managed to make ECC work in my platform, MBEDTLS_KEY_EXCHANGE_ECDHE_RSA_ENABLED works well, either with my server or with an external server. However, when I enable MBEDTLS_KEY_EXCHANGE_ECDHE_ECDSA_ENABLED I am able to communicate with my server, but NOT when I try to connect my application to www.google.com, I get an error -0x7780 (MBEDTLS_ERR_SSL_FATAL_ALERT_MESSAGE)

Does google support MBEDTLS_KEY_EXCHANGE_ECDHE_ECDSA_ENABLED ??

Although I am already satisfied with ECDHE_RSA, my goal is to use smaller certificate sizes, which ECDHE_ECDSA offers..

Here is my log

===>LWIP_HTTPS::  WiFi connection...[2.803,233] CONNECT:c0:56:27:b8:52:4a
[5.333,195] NOTIFY:DHCP:1
[5.380,932] NOTIFY:DHCP:8
[6.324,167] NOTIFY:DHCP:10
MYIP 172.28.49.47
 OK [HEAP]-34912.

  . RNG..  ok
  . CA root cert... ok (0 skipped)
  . tcp/www.google.se/443... ok
  . SSL/TLS ...  ok
  . SSL/TLS handshake... 2 src/ssl_tls.c: 6593 => handshake
 2 src/ssl_cli.c: 3369 client state: 0
 2 src/ssl_tls.c: 2418 => flush output
 2 src/ssl_tls.c: 2430 <= flush output
 2 src/ssl_cli.c: 3369 client state: 1
 2 src/ssl_tls.c: 2418 => flush output
 2 src/ssl_tls.c: 2430 <= flush output
 2 src/ssl_cli.c: 728 => write client hello
 3 src/ssl_cli.c: 766 client hello, max version: [3:3]
 3 src/ssl_cli.c: 775 dumping 'client hello, random bytes' (32 bytes)
 3 src/ssl_cli.c: 775 0000:  5a 02 2d 0a d3 a2 06 83 e1 2d 35 ed 0e cf 23 e3  Z.-......-5...#.
 3 src/ssl_cli.c: 775 0010:  d3 6f 1a c3 ea f7 71 a2 9e 63 1a 50 9c 02 a1 a8  .o....q..c.P....
 3 src/ssl_cli.c: 828 client hello, session id len.: 0
 3 src/ssl_cli.c: 829 dumping 'client hello, session id' (0 bytes)
 3 src/ssl_cli.c: 896 client hello, add ciphersuite: c02b
 3 src/ssl_cli.c: 929 client hello, got 2 ciphersuites
 3 src/ssl_cli.c: 960 client hello, compress len.: 1
 3 src/ssl_cli.c: 962 client hello, compress alg.: 0
 3 src/ssl_cli.c: 73 client hello, adding server name extension: localhost
 3 src/ssl_cli.c: 187 client hello, adding signature_algorithms extension
 3 src/ssl_cli.c: 272 client hello, adding supported_elliptic_curves extension
 3 src/ssl_cli.c: 337 client hello, adding supported_point_formats extension
 3 src/ssl_cli.c: 553 client hello, adding extended_master_secret extension
 3 src/ssl_cli.c: 1034 client hello, total extension length: 46
 2 src/ssl_tls.c: 2703 => write record
 3 src/ssl_tls.c: 2840 output record: msgtype = 22, version = [3:1], msglen = 95
 4 src/ssl_tls.c: 2843 dumping 'output record sent to network' (100 bytes)
 4 src/ssl_tls.c: 2843 0000:  16 03 01 00 5f 01 00 00 5b 03 03 5a 02 2d 0a d3  ...._...[..Z.-..
 4 src/ssl_tls.c: 2843 0010:  a2 06 83 e1 2d 35 ed 0e cf 23 e3 d3 6f 1a c3 ea  ....-5...#..o...
 4 src/ssl_tls.c: 2843 0020:  f7 71 a2 9e 63 1a 50 9c 02 a1 a8 00 00 04 c0 2b  .q..c.P........+
 4 src/ssl_tls.c: 2843 0030:  00 ff 01 00 00 2e 00 00 00 0e 00 0c 00 00 09 6c  ...............l
 4 src/ssl_tls.c: 2843 0040:  6f 63 61 6c 68 6f 73 74 00 0d 00 06 00 04 04 03  ocalhost........
 4 src/ssl_tls.c: 2843 0050:  03 03 00 0a 00 04 00 02 00 17 00 0b 00 02 01 00  ................
 4 src/ssl_tls.c: 2843 0060:  00 17 00 00                                      ....
 2 src/ssl_tls.c: 2418 => flush output
 2 src/ssl_tls.c: 2437 message length: 100, out_left: 100
 2 src/ssl_tls.c: 2443 ssl->f_send() returned 100 (-0xffffff9c)
 2 src/ssl_tls.c: 2462 <= flush output
 2 src/ssl_tls.c: 2852 <= write record
 2 src/ssl_cli.c: 1060 <= write client hello
 2 src/ssl_cli.c: 3369 client state: 2
 2 src/ssl_tls.c: 2418 => flush output
 2 src/ssl_tls.c: 2430 <= flush output
 2 src/ssl_cli.c: 1453 => parse server hello
 2 src/ssl_tls.c: 3723 => read record
 2 src/ssl_tls.c: 2210 => fetch input
 2 src/ssl_tls.c: 2368 in_left: 0, nb_want: 5
 2 src/ssl_tls.c: 2392 in_left: 0, nb_want: 5
 2 src/ssl_tls.c: 2393 ssl->f_recv(_timeout)() returned 5 (-0xfffffffb)
 2 src/ssl_tls.c: 2405 <= fetch input
 4 src/ssl_tls.c: 3480 dumping 'input record header' (5 bytes)
 4 src/ssl_tls.c: 3480 0000:  15 03 03 00 02                                   .....
 3 src/ssl_tls.c: 3489 input record: msgtype = 21, version = [3:3], msglen = 2
 2 src/ssl_tls.c: 2210 => fetch input
 2 src/ssl_tls.c: 2368 in_left: 5, nb_want: 7
 2 src/ssl_tls.c: 2392 in_left: 5, nb_want: 7
 2 src/ssl_tls.c: 2393 ssl->f_recv(_timeout)() returned 2 (-0xfffffffe)
 2 src/ssl_tls.c: 2405 <= fetch input
 2 src/ssl_tls.c: 4055 got an alert message, type: [2:40]
 1 src/ssl_tls.c: 4063 is a fatal alert message (msg 40)
 1 src/ssl_tls.c: 3741 mbedtls_ssl_read_record_layer() returned -30592 (-0x7780)
 1 src/ssl_cli.c: 1460 mbedtls_ssl_read_record() returned -30592 (-0x7780)
 2 src/ssl_tls.c: 6603 <= handshake
  failed  -0x7780

2 src/ssl_tls.c: 7380 => free
 2 src/ssl_tls.c: 7451 <= free

  [->]===>LWIP_HTTPS:: closing
===>LWIP_HTTPS:: exiting
^CReading trace...

HI Antonio,
I am glad you managed to make your ECC work!
According to your description, the server doesn't accept the ClientHello message your client is sending. It could be a variety of reasons, but it is most likely that it doesn't support the single cipher suite you are sending.
If you use the SSL Labs tool , you will see that the server only has certificates signed with RSA 2048 bits, and that ECDHE_ECDSA based ciphersuite is not supported by the server.
Regards,
Mbed TLS Team member
Ron

Hi Ron,

Thanks for your help. You are right, I found another webpage that I could talk to normally. However, I am still using test Certificates, and now I want to tackle verification.

Why in your applications the Certificate Verification pass, while the same code on my case fails.. I for example get this code error

  . Verifying peer X.509 certificate... failed (8)
  ! The certificate is not correctly signed by the trusted CA

Well, I am communicating with the TestServer and using exactly your certificates, only change is that the application runs on my platform.

thanks again for your help.

Hi Antonio,
The verification error flag you are encountering is returned as a generic failure of verification. There could be several reasons for it. As first step, I would compare the configuration file on your platform, and on your test application. IT could be some missing configuration on your platform.

• Do you know what is the certificate that is sent? Is it RSA or ECDSA signed?
• Could it be that your ECC implementation still has some flaws?
• Have you set the correct ca_chain using mbedtls_ssl_conf_ca_chain API?

In addition, it could be a memory issue, causing the verification to fail.
Regards,
Mbed TLS Team member
Ron

Hi Ron,

1 I am sending a ECDSA signed certificate. Before I sent an RSA signed and got same error.

2 I believe I set the * mbedtls_ssl_conf_ca_chain* correctly..

mbedtls_ssl_conf_ca_chain( &conf, &cacert, NULL );

3 memory? maybe..but not likely. I will try updating to V2.7 and see if the error persists.

Thanks anyhow.. gonna check what I can do.

Best,

HI Antonio,
Thank you for your information. Since both RSA and ECDSA certificates fail, then it is probably a matter of configuration or memory.
Since you are using the test certificates, please verify you have MBEDTLS_CERTS_C defined in your system (in addition to the RSA and ECDSA ones). In addition, you should check full logs, to understand reason for failure. Please enable debug_level to 5, for debugging.
Regards,
Mbed TLS Team member
Ron