no SSL certificate verify

[Ruan Linqi]

Hi developers:
    We made a large scale security static analysis on several open source projects, and found some mistakes in nghttp2 1.7.1. In the @example/client.c:539:
    static void fetch_uri(const struct URI *uri) {
{
   [...]
   ssl_ctx = SSL_CTX_new(SSLv23_client_method());
   if (ssl_ctx == NULL) {
     dief("SSL_CTX_new", ERR_error_string(ERR_get_error(), NULL));
   }
   init_ssl_ctx(ssl_ctx);
   ssl = SSL_new(ssl_ctx);
   if (ssl == NULL) {
     dief("SSL_new", ERR_error_string(ERR_get_error(), NULL));
   }
   /* To simplify the program, we perform SSL/TLS handshake in blocking
     I/O. */
   ssl_handshake(ssl, fd);
   [...]
}

    The function ssl_handshake(ssl, fd) achieve SSL_connect(ssl). When finish the SSL connect, you immedicately start to execute read/write operation without verify certificate,which can lead to MITM attack and cause leakage of sensitive data.We recommand you add verify operation such as SSL_CTX_set_verify or SSL_get_peer_certificate to guarantee the security.

[Nish Aravamudan (nacc)]

Has this been reported upstream to nghttp2?

[Nish Aravamudan (nacc)]

Also, 1.7.1 is only present in 16.04, there have been many updates to the package since then -- can you verify if it was fixed upstream already and at what version?

[Ruan Linqi (shoppingruan)]

The code maintainer have confirm the bug and add a large text inside the source code to implement that is insecure for production use.

[Nish Aravamudan (nacc)]

To be clear, this bug is in example code to demonstrate how one uses libnghttp2, not in any actual libnghttp2 code.

The upstream developer Tatsuhiro Tsujikawa (offlist) said:

> ​Thank you for the security analysis.
> examples/client.c is an example program to show how to use libnghttp2, and we made it intentionally simple.
> In addition, since developers often use ​self-signed certificates for developments, we omitted any verification after handshake. We never expect to see this as used in production scenario.

Ruan, I believe the upstream developer is waiting on you to respond with how you would like them to proceed: either a block comment or removal of the example code.

[Ruan Linqi (shoppingruan)]

Nowadays We find in nghttp2-client there exists other bug .
In @src/nghttp.cc:
int HttpClient::initiate_connection()

{
   [...]
   ssl = SSL_new(ssl_ctx);
    [...]
    SSL_set_fd(ssl.fd);
    SSL_set_connect_state(ssl);
   [...]

    writefn = &HttpClient::connected;

}

  The function initiate_connection achieve SSL connect. When finish
connection , you immedicately start to execute read/write operation without
verify certificate,which can lead to MITM attack and cause leakage of
sensitive data.We have built the test environment to prove such attack can
occur.We recommand you add verify operation such as SSL_CTX_set_verify or
SSL_get_peer_certificate to guarantee the security.

We have proved the MITM attack can occur.This bug report has sent to
upstream developer and we are waiting the report from them.

2017-05-17 1:48 GMT+08:00 Nish Aravamudan <email address hidden>:

> To be clear, this bug is in example code to demonstrate how one uses
> libnghttp2, not in any actual libnghttp2 code.
>
> The upstream developer Tatsuhiro Tsujikawa (offlist) said:
>
> > ​Thank you for the security analysis.
> > examples/client.c is an example program to show how to use libnghttp2,
> and we made it intentionally simple.
> > In addition, since developers often use ​self-signed certificates for
> developments, we omitted any verification after handshake. We never expect
> to see this as used in production scenario.
>
> Ruan, I believe the upstream developer is waiting on you to respond with
> how you would like them to proceed: either a block comment or removal of
> the example code.
>
> ** Changed in: nghttp2 (Ubuntu)
> Status: Confirmed => Invalid
>
> --
> You received this bug notification because you are subscribed to the bug
> report.
> https://bugs.launchpad.net/bugs/1677958
>
> Title:
> no SSL certificate verify
>
> Status in nghttp2 package in Ubuntu:
> Invalid
>
> Bug description:
> Hi developers:
> We made a large scale security static analysis on several open
> source projects, and found some mistakes in nghttp2 1.7.1. In the
> @example/client.c:539:
> static void fetch_uri(const struct URI *uri) {
> {
> [...]
> ssl_ctx = SSL_CTX_new(SSLv23_client_method());
> if (ssl_ctx == NULL) {
> dief("SSL_CTX_new", ERR_error_string(ERR_get_error(), NULL));
> }
> init_ssl_ctx(ssl_ctx);
> ssl = SSL_new(ssl_ctx);
> if (ssl == NULL) {
> dief("SSL_new", ERR_error_string(ERR_get_error(), NULL));
> }
> /* To simplify the program, we perform SSL/TLS handshake in blocking
> I/O. */
> ssl_handshake(ssl, fd);
> [...]
> }
>
> The function ssl_handshake(ssl, fd) achieve SSL_connect(ssl). When
> finish the SSL connect, you immedicately start to execute read/write
> operation without verify certificate,which can lead to MITM attack and
> cause leakage of sensitive data.We recommand you add verify operation
> such as SSL_CTX_set_verify or SSL_get_peer_certificate to guarantee
> the security.
>
> To manage notifications about this bug go to:
> https://bugs.launchpad.net/ubuntu/+source/nghttp2/+bug/
> 1677958/+subscriptions
>

[Nish Aravamudan (nacc)]

Hello Ruan,

Thank you for keeping us apprised of the situation.

I see in that function, that they do call

SSL_set_verify(ssl, SSL_VERIFY_PEER, verify_cb);

[elided from your excerpt]

but you are saying the MITM attack exists because they are not verifying the global context?

[Ruan Linqi (shoppingruan)]

This problem can be closed .Sorry for disturbing you.For some reasons ,we do analysis on Ubuntu 16.04.,where the nghttp2 version is 1.7.1, NO SSL_set_verify(ssl, SSL_VERIFY_PEER, verify_cb) exists,so we can do MITM attack.
 We find in the lastest version 1.22.0,this bug has fixed.Thank for you timely reply and patience.Also apologize for my carelessness.

[Nish Aravamudan (nacc)]

Ruan, it's ok! Thank you for your detailed analyses. It sounds like this is still a potential security issue in 16.04, at least.