Re: SSH tunnel key exchange methods

On Wed, Dec 2, 2015 at 3:20 PM, Dave Page <dpage(at)pgadmin(dot)org> wrote:

> Hi
>
> On Wed, Dec 2, 2015 at 9:19 AM, Akshay Joshi <
> akshay(dot)joshi(at)enterprisedb(dot)com> wrote:
>
>> Hi Dave
>>
>> I have updated the *libssh2* library with the latest available code on
>> their git repository. The new code used "diffie-hellman-group-exchange-sha256" algorithm for
>> key exchange and they also fixed some memory leak. I have verified it by
>> putting the breakpoint in the libssh2 code, so when we called "
>> libssh2_session_init()" it will automatically call "static int diffie_
>> hellman_sha256(...)" function, but I don't know exactly how to identify
>> the key exchange method (sha1 or sha256) used by the latest libssh2 library.
>>
>> I have tested the pgadmin3 after updating the libssh2 library on CentOS
>> 6.5 (64 bit) and it works fine. I have also modified the code to add
>> human readable error message returned by the library. Attached is the
>> patch file. Can you please review it and if it looks good can you please
>> commit the code.
>>
>
> I'm seeing the following build error on OS X 10.7:
>
> depbase=`echo libssh2/agent.o | sed 's|[^/]*$|.deps/&|;s|\.o$||'`;\
> ccache gcc -Qunused-arguments -DHAVE_CONFIG_H -I. -I..
> -I../pgadmin/include/libssh2 -I../pgadmin/include
> -I../pgadmin/include/libssh2 -I/usr/local/pgsql-9.5/include
> -I/usr/local/pgsql-9.5/include/server -I/usr/local/pgsql-9.5/include
> -DPG_SSL -DHAVE_CONNINFO_PARSE
> -I/usr/local/lib/wx/include/mac-unicode-release-static-2.8
> -I/usr/local/include/wx-2.8 -D_FILE_OFFSET_BITS=64 -D_LARGE_FILES
> -D__WXMAC__ -DEMBED_XRC -arch i386 -I/usr/include/libxml2
> -I/opt/local/include/libxml2 -DHAVE_OPENSSL_CRYPTO -O2 -MT libssh2/agent.o
> -MD -MP -MF $depbase.Tpo -c -o libssh2/agent.o libssh2/agent.c &&\
> mv -f $depbase.Tpo $depbase.Po
> In file included from ../pgadmin/include/libssh2/libssh2_priv.h:136,
> from libssh2/agent.c:41:
> ../pgadmin/include/libssh2/crypto.h:53: error: expected ‘)’ before ‘*’
> token
> ../pgadmin/include/libssh2/crypto.h:69: error: expected ‘)’ before ‘*’
> token
> ../pgadmin/include/libssh2/crypto.h:73: error: expected ‘)’ before ‘*’
> token
> ../pgadmin/include/libssh2/crypto.h:78: error: expected declaration
> specifiers or ‘...’ before ‘libssh2_rsa_ctx’
> ../pgadmin/include/libssh2/crypto.h:83: error: expected ‘)’ before ‘*’
> token
> ../pgadmin/include/libssh2/crypto.h:115: error: expected ‘)’ before ‘*’
> token
> ../pgadmin/include/libssh2/crypto.h:120: error: expected ‘)’ before ‘*’
> token
> In file included from libssh2/agent.c:41:
> ../pgadmin/include/libssh2/libssh2_priv.h:240: error:
> ‘SHA256_DIGEST_LENGTH’ undeclared here (not in a function)
> ../pgadmin/include/libssh2/libssh2_priv.h:245: error: expected
> specifier-qualifier-list before ‘_libssh2_bn_ctx’
> ../pgadmin/include/libssh2/libssh2_priv.h:267: error: expected
> specifier-qualifier-list before ‘_libssh2_bn’
> ../pgadmin/include/libssh2/libssh2_priv.h:604: error: ‘SHA_DIGEST_LENGTH’
> undeclared here (not in a function)
> ../pgadmin/include/libssh2/libssh2_priv.h:899: error: expected
> specifier-qualifier-list before ‘_libssh2_cipher_type’
> libssh2/agent.c: In function ‘agent_connect_unix’:
> libssh2/agent.c:150: warning: assignment makes pointer from integer
> without a cast
> make[3]: *** [libssh2/agent.o] Error 1
> make[2]: *** [all] Error 2
> make[1]: *** [all-recursive] Error 1
> make: *** [all] Error 2
>

I have modified the configure.ac.in and added "-DLIBSSH2_OPENSSL" to
solve the above. You need to run the configure command again.

>
>
>
>>
>> Sven, how you have identified the key exchange algorithm used by libssh2,
>> is there any way to identify using fingerprint or key??
>>
>> On Mon, Nov 30, 2015 at 6:38 PM, Dave Page <dpage(at)pgadmin(dot)org> wrote:
>>
>>> Ok, thanks Akshay.
>>>
>>> --
>>> Dave Page
>>> Blog: http://pgsnake.blogspot.com
>>> Twitter: @pgsnake
>>>
>>> EnterpriseDB UK:http://www.enterprisedb.com
>>> The Enterprise PostgreSQL Company
>>>
>>> On 30 Nov 2015, at 12:57, Akshay Joshi <akshay(dot)joshi(at)enterprisedb(dot)com>
>>> wrote:
>>>
>>> Hi Dave
>>>
>>> On Mon, Nov 30, 2015 at 10:41 AM, Akshay Joshi <akshay.joshi@
>>> enterprisedb.com> wrote:
>>>
>>>> Hi Dave
>>>>
>>>> On Fri, Nov 27, 2015 at 3:01 PM, Dave Page <dpage(at)pgadmin(dot)org> wrote:
>>>>
>>>>> On Fri, Nov 27, 2015 at 9:23 AM, Sven <svoop_6cedifwf9e(at)delirium(dot)ch>
>>>>> wrote:
>>>>> >> The key exchange methods offered when opening an SSH tunnel are all
>>>>> >> SHA1 and therefore too weak:
>>>>> >>
>>>>> >> [sshd] fatal: Unable to negotiate with xxx.xxx.xxx.xxx: no matching
>>>>> >> key exchange method found. Their offer:
>>>>> >> diffie-hellman-group14-sha1,diffie-hellman-group-exchange-sha1,
>>>>> >> diffie-hellman-group1-sha1 [preauth]
>>>>> >
>>>>> > Any news on this? If there's no easy way to add safer kexes, I
>>>>> suggest
>>>>> > you disable the SSH feature altogether. SHA1 is dead and IMO nobody
>>>>> > should trust a connection established with SHA1 kexes in order to
>>>>> talk
>>>>> > to databases.
>>>>>
>>>>> Akshay, you know that code best of all. How do we enable safer kexes?
>>>>>
>>>>
>>>> Today I'll look into it on priority and update accordingly.
>>>>
>>>
>>> I have found that "diffie-hellman-group-exchange-sha256" support
>>> has been added to the libssh2 code on September 24, it's not released yet.
>>> Please check https://github.com/libssh2/libssh2/pull/48 . Today I have
>>> tried to update the libssh2, but facing some compilation issues which needs
>>> to be fixed. I am working on it and then check do we need to change our
>>> logic or libssh2 will automatically used "diffie-hellman
>>> -group-exchange-sha256".
>>>
>>>
>>>>
>>>>> --
>>>>> Dave Page
>>>>> Blog: http://pgsnake.blogspot.com
>>>>> Twitter: @pgsnake
>>>>>
>>>>> EnterpriseDB UK: http://www.enterprisedb.com
>>>>> The Enterprise PostgreSQL Company
>>>>>
>>>>
>>>>
>>>>
>>>> --
>>>> *Akshay Joshi*
>>>> *Principal Software Engineer *
>>>>
>>>>
>>>>
>>>> *Phone: +91 20-3058-9517 <%2B91%2020-3058-9517>Mobile: +91 976-788-8246*
>>>>
>>>
>>>
>>>
>>> --
>>> *Akshay Joshi*
>>> *Principal Software Engineer *
>>>
>>>
>>>
>>> *Phone: +91 20-3058-9517 <%2B91%2020-3058-9517>Mobile: +91 976-788-8246*
>>>
>>>
>>
>>
>> --
>> *Akshay Joshi*
>> *Principal Software Engineer *
>>
>>
>>
>> *Phone: +91 20-3058-9517 <%2B91%2020-3058-9517>Mobile: +91 976-788-8246*
>>
>
>
>
> --
> Dave Page
> Blog: http://pgsnake.blogspot.com
> Twitter: @pgsnake
>
> EnterpriseDB UK: http://www.enterprisedb.com
> The Enterprise PostgreSQL Company
>

--
*Akshay Joshi*
*Principal Software Engineer *

*Phone: +91 20-3058-9517Mobile: +91 976-788-8246*