MQTT TLS on Google cloud - invalid JWT generated

Hi S,

Have you try modifying  the Base64urlEncoder() in Base64Decode.c to strip the padding, "="? Would it pass checking jwt.io?

The hash/signature would definitely be different without '=', As the Header/payload is available, the receiver could have use it to verify the signature,   

Hi S,

Have you try modifying  the Base64urlEncoder() in Base64Decode.c to strip the padding, "="? Would it pass checking jwt.io?

The hash/signature would definitely be different without '=', As the Header/payload is available, the receiver could have use it to verify the signature,   

Hi,

Yes I've tried but still doesn't pass the jwt.io check. Is there a valid Base64url encoder library that actually works with Google IoT Core?

Also, it has something to do with the pkcs1 padding in the jwt_create() ?

Thanks

Hi Rusty,

I change (in Base64Decode.c)

base64digits[] = "ABC...789+/"; 

to

base64digits[] = "ABC...789-_";

last 2, '+', '/' change to '-', '_' 

and in Base64urlEncoder() 

'=' change to '\0'  to omit the last 1 or 2 padding. (2 instances of this)

        *out++ = (inlen < 2) ? '\0'  /*'='*/   : base64digits[(in[1] << 2) & 0x3c];
        *out++ = '\0';   //'=';

Now the jwt.io verifies the JWT submitted has correct signature. 

No changes to pkcs1 padding.

Can you check if you can reach google server after these changes?

Hi Yep,

I made the changes you suggested, but still I can not generate a valid JWT, here some extract from my logs and the base64 library I'm using.

Any suggestions on how to get it working much appreciated.

----LOG----

[hsp_wble.c:0690] - PPP init SUCCESS
[hsp_wble.c:0692] - Wifi station link UP and PPP mode active
[hsp_wble.c:0707] - Initialised NX common
[hsp_wble.c:0826] - WBLE module init_connection
[hsp_wble.c:0859] - Initialised IP
[hsp_wble.c:0885] - Initialised PPP
[hsp_wble.c:0908] - Initialised DNS
[new_thread0_entry.c:0260] - START TIME/DATE >> Sep 2, 2021 12:32:54.841 UTC <<
[new_thread0_entry.c:0321] - mqtt.2030.ltsapis.goog is at 173.194.76.206:8883
[new_thread0_entry.c:0344] - Secure TLS session created!
[new_thread0_entry.c:0375] - JWT token created successfully eyJhbGciOiJSUzI1NiIsInR5cCI6IkpXVCJ9.eyJhdWQiOiJoNG5oNDQtMSIsImV4cCI6MTYzMDU4NjI3NCwiaWF0IjoxNjMwNTg1OTc0fQ.ce4xJaVwO0HV4ybdnC8-vKTCUrHRroiYY_9R8egWW_izKQPGlUOxv6Ku2-ZLsquh7EJFcARPkg4EkewKymbQDCrBdBYND8Kyd6_NPF_A7nqPRcTwwUTHLOa9xzZxAI_xJpgpicAhGlM7kJCHDeerwSTNu6HWsi1E2uCjwM8NxuyWnsut9Lg12EXcBb8FJ2bF_km8QO6BGqHnlCbQf3byQ58IJ6LIaIy8buCgtu7GHc1FSVbmUHk263QwuFD99yGrh1k-91DkIf5QHUZHnGyn-r7bERQkYev8ef9m_gKiFDUz6sNZ3R1ibW62S6ufTrJGfgs6bQHCkI_n3JxcpCunaw

[new_thread0_entry.c:0384] - MQTT Client login set successful
[new_thread0_entry.c:0397] - nxd_mqtt_client_secure_connect error 0x10005

---Base64Decode.c

#include <stdio.h>
#include <string.h>
#include <stdint.h>
#include <assert.h>
#include "base64.h"

void Base64urlEncoder(unsigned char *out, const unsigned char *in, int inlen);

//Base64 char table - used internally for encoding
static const unsigned char base64digits[] =
"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-_";

unsigned int base64_int(unsigned int ch)
{

/* ASCII to base64_int
65-90 Upper Case >> 0-25
97-122 Lower Case >> 26-51
48-57 Numbers >> 52-61
43 Plus (+) >> 62
47 Slash (/) >> 63
61 Equal (=) >> 64~
*/
if (ch==43)
return 62;
if (ch==47)
return 63;
if (ch==61)
return 64;
if ((ch>47) && (ch<58))
return ch + 4;
if ((ch>64) && (ch<91))
return ch - 'A';
if ((ch>96) && (ch<123))
return (ch - 'a') + 26;
return 0;
}

unsigned int base64_decode(const unsigned char* in, unsigned int in_len, unsigned int* out)
{

unsigned int i=0, j=0, k=0, s[4] = {0};

for (i=0;i<in_len;i++)
{
s[j++]=base64_int(*(in+i));
if (j==4)
{
out[k+0] = ((s[0]&255)<<2)+((s[1]&0x30)>>4);
if (s[2]!=64)
{
out[k+1] = ((s[1]&0x0F)<<4)+((s[2]&0x3C)>>2);
if ((s[3]!=64))
{
out[k+2] = ((s[2]&0x03)<<6)+(s[3]); k+=3;
}
else
{
k+=2;
}
}
else
{
k+=1;
}
j=0;
}
}

return k;
}

unsigned int base64d_size(unsigned int in_size)
{

return ((3*in_size)/4);
}

///////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
//
// Function : Base64urlEncoder
// Purpose : Converts a given string into a base64 encoded buffer.
// Last updated : 01/09/200515/05/2005
// Notes :
//////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////

void Base64urlEncoder(unsigned char *out, const unsigned char *in, int inlen)
/* [OUT] out A pointer to a char to hold the converted string
[IN] in String to convert
[IN] inlen Length of the string to be converted
*/
{
for (; inlen >= 3; inlen -= 3)
{
*out++ = base64digits[in[0] >> 2];
*out++ = base64digits[((in[0] << 4) & 0x30) | (in[1] >> 4)];
*out++ = base64digits[((in[1] << 2) & 0x3c) | (in[2] >> 6)];
*out++ = base64digits[in[2] & 0x3f];
in += 3;
}

if (inlen > 0)
{
unsigned char fragment;

*out++ = base64digits[in[0] >> 2];
fragment = (in[0] << 4) & 0x30;

if (inlen > 1)
fragment |= in[1] >> 4;

*out++ = base64digits[fragment];
*out++ = (inlen < 2) ? '\0' : base64digits[(in[1] << 2) & 0x3c];
*out++ = '\0';
}

*out = '\0';
}

Correction: 

The JWT is actually now verified as correct, using jwt.io and the device / private key.

At this point what could be the cause?

Timestamp is calculated correctly? (gives me epochs that when converted are in UTC+0)

I've tried JWT expiration to 1 hour, 2 hours, but seems not to make a difference.

Again, all the certificate work with a python mqtt project, and I can connect securely to the same broker "mqtt.2030.ltsapis.goog", on port 8883.

Is there a way to see why this is failing, other that the generic error 0x10005 from nxd_mqtt_client_secure_connect()?

Debugging to lower level I get that NX is not connected, even though I have an IP layer opened and working.

///> In nx_secure_tls_session_start.c
///> function _nx_secure_tls_handshake_process Fails with 56 (0x38) error
///> (NX_NOT_CONNECTED 0x38)

Thanks

my configuration: all IP instances are shared, TLS common is shared between MQTT and TLS Session:

Hi,

Could you get a wireshark logs? Hope to understand why server terminates this tcp connection.

Just to double check, is the size of your certificate correct?  You mention you convert this certificate into byte array. Could you do a memory dump of this and check if it's correct?

Hi Yep, 

Yes I've done a capture of my wifi network from my PC while application running, the DHCP address assigned to my uBlox NINA is 192.168.1.12, something is going on but I'm not sure at what to look at.

Following are my google certificate in PEM format (that I use from Python with no problems) and the corresponding byte array used in my FW. Size seems the same. 

CA_cert.zip

Should I use a different certificate or check if is loaded correctly into netx secure?

Can I send the capture file in private to you? 

Also, would it be possible to create a TLS session project (client) and use the same certificate just to see if it's loaded and checked correctly? I tried also an openssl s_client -connect with this certificate and broker endpoint and status returns 0 from openssl (verified, OK).

 Thanks,

S

edit: Looking here:AE-CLOUD2. Google cloud. Could not create tls session. - Synergy - Forum - Renesas Synergy Platform - RenesasRulz

I have confirmed that I can connect to Azure and Amazon using the 2.1.0 SECT binary, but I cannot connect to Google. There has been a change in the Google certificate chain, that requires a different intermediate CA certificate to be used for Google. This would require a new SECT binary firmware.

This answer maybe is a clue? Not sure how I load a certificate and an intermediate certificate, as a chain?

Hi Rusty,

The CA_cert_der[] is an ECC cert.  Can you check if ECC is added to nx_crypto_tls_ciphers_synergys7. 

Could you find/use RSA cert instead? You have install a root/intermediate cert as trusted cert.

Other intermediate certs in the chain will be downloaded as needed to verify the server cert.

Hi,

Yes all the suites are enabled, including ECC. 

Do I need to specify that is an ECC cert in tls init?

That certificate has been given by google, not sure If/how I can find an RSA version of it

Do you call nx_secure_tls_ecc_initialize() in the mqtt tls setup function?

extern const USHORT     nx_crypto_ecc_supported_groups_synergys7[];
extern const USHORT     nx_crypto_ecc_supported_groups_synergys7_size;
extern const NX_CRYPTO_METHOD *     nx_crypto_ecc_curves_synergys7[];

 nx_secure_tls_ecc_initialize(p_tls_session,
                                          nx_crypto_ecc_supported_groups_synergys7,
                                          nx_crypto_ecc_supported_groups_synergys7_size,
                                          nx_crypto_ecc_curves_synergys7);

in the mqtt tls setup function?

Hi Jeremy,

No, I call x509 for both CA_cert and device cert. should I substitute the ca_cert one?

Or add nx_secure_tls_ecc_initialize() at the beginning/end of the mqtt_tls_setup?

Here's my mqtt tls setup function:

static UINT NX_MQTT_tls_setup(NXD_MQTT_CLIENT *p_client, NX_SECURE_TLS_SESSION *p_tls_session,
NX_SECURE_X509_CERT *p_cert, NX_SECURE_X509_CERT *p_trusted_cert)
{
UINT status = NX_SUCCESS;
UINT index = 0;

SSP_PARAMETER_NOT_USED (p_client);

/* Need to allocate space for the certificate coming in from the remote host. */
memset(&remote_cert_buffer, 0, sizeof(remote_cert_buffer));
memset(&remote_certificate, 0, sizeof(remote_certificate));

status = nx_secure_tls_remote_certificate_allocate(p_tls_session, &remote_certificate,
remote_cert_buffer, sizeof(remote_cert_buffer));
if (NX_SUCCESS != status)
{
HSP_APP_LOG(HSP_LOG_LEVEL_DEBUG,"Unabe to allocate memory for the certificate buffer %d", status);
return status;
}

memset(remote_int_ca_cert_buffer, 0, sizeof(remote_int_ca_cert_buffer));
memset(remote_intermediate_ca, 0, sizeof(remote_intermediate_ca));
for (index = 0; index < ARRAY_SIZE(remote_intermediate_ca); index++)
{
status = nx_secure_tls_remote_certificate_allocate(p_tls_session, &(remote_intermediate_ca[index]),
&(remote_int_ca_cert_buffer[index * CERTIFICATE_BUFFER_SIZE]),
CERTIFICATE_BUFFER_SIZE);
if (NX_SUCCESS != status)
{
HSP_APP_LOG(HSP_LOG_LEVEL_DEBUG,"Unable to allocate memory for interemediate CA certificate %d", status);
return status;
}
}

/* Add a CA Certificate to our trusted store for verifying incoming server certificates. */
status = nx_secure_x509_certificate_initialize(p_trusted_cert,
(UCHAR *) CA_cert_der, (USHORT) CA_CERT_DER_LEN,
NX_NULL, 0, NULL, 0,
NX_SECURE_X509_KEY_TYPE_RSA_PKCS1_DER);
if (NX_SUCCESS != status)
{
HSP_APP_LOG(HSP_LOG_LEVEL_DEBUG,"Unable to initialize CA certificate %d", status);
return status;
}

status = nx_secure_tls_trusted_certificate_add(p_tls_session, p_trusted_cert);
if (NX_SUCCESS != status)
{
HSP_APP_LOG(HSP_LOG_LEVEL_DEBUG,"Unable to add CA certificate to trusted store, %d", status);
return status;
}

if (dev_cert != NULL)
{
/* Add the local certificate for client authentication. */
status = nx_secure_x509_certificate_initialize(p_cert, (UCHAR *) dev_cert, (USHORT) DEV_CERT_LEN,
NX_NULL, 0, rsa_private_pkcs1, RSA_PRIVATE_LEN,
NX_SECURE_X509_KEY_TYPE_RSA_PKCS1_DER);
if (NX_SUCCESS != status)
{
HSP_APP_LOG(HSP_LOG_LEVEL_DEBUG,"Unable to initialize device certificate, %d",status);
return status;
}
status = nx_secure_tls_local_certificate_add(p_tls_session, p_cert);
if (NX_SUCCESS != status)
{
HSP_APP_LOG(HSP_LOG_LEVEL_DEBUG,"Unable to add device certificate to trusted store, %d",status);
return status;
}
}

/* Add a timestamp function for time checking and timestamps in the TLS handshake. */
nx_secure_tls_session_time_function_set(p_tls_session, get_time);

return status;
}

Thanks a lot