1 Topic by jesussotofan (edited by jesussotofan 2016-11-02 04:45:07)

  • Registered: 2016-10-07
  • Posts: 20

Topic: [SOLVED] using rsa, "undefined reference to `wc_GenerateSeed'" error

Hi, I'm trying to test RSA encryption arduino.
Libs have imported correctly, but when I try to run the example I get the error:

"C: \ Users \ Eugenio \ AppData \ Local \ Temp \ ccDlIFnm.ltrans0.ltrans.o: In function` loop ':

: ( ccDlIFnm.ltrans0.o text + 0xc6c.): undefined reference to `wc_GenerateSeed '

collect2.exe: error: ld returned 1 exit status"

This is my code:

#include <wolfssl.h>
#include <wolfssl/wolfcrypt/rsa.h>

void setup(void){

  while(!Serial);
  Serial.begin(9600);
}
 
void loop(void){

RsaKey rsaPublicKey;
byte publicKeyBuffer[]  = {"MFwwDQYJKoZIhvcNAQEBBQADSwAwSAJBAL+pEyWGAfj8NRW03Ox55IXMCLwCm1EjQ0mwonOjazvAkkwLSthUPmaCq2/A01843K3zqN40dslDUwYlfAg9hC8CAwEAAQ=="}; // holds the raw data from the key, maybe from a file like RsaPublicKey.der 
word32 idx = 0;             //  where to start reading into the buffer
byte in[] = {"hola mundohola mundohola mundoho"};
byte out[128];
RNG rng;
wc_InitRng(&rng);


wc_RsaPublicKeyDecode(publicKeyBuffer, &idx, &rsaPublicKey, sizeof(publicKeyBuffer));
word32 outLen = wc_RsaPublicEncrypt(in, sizeof(in), out, sizeof(out), &rsaPublicKey, &rng);

delay(3000);
}

Can you give me a hand?

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  • Registered: 2015-10-07
  • Posts: 430

Re: [SOLVED] using rsa, "undefined reference to `wc_GenerateSeed'" error

Hi Jesussotofan,

Your platform must not have a random number seed function defined in random.c (starting at line 1133).

Either you can:
1. Locate a reference implementation in random.c and make sure you have the right define set for your hardware platform / OS.

2. Define CUSTOM_RAND_GENERATE_SEED and use your own implementation:

int rand_gen_seed(byte* output, word32 sz);
#define CUSTOM_RAND_GENERATE_SEED  rand_gen_seed

In your example above, I also recommend:
including:
#include <wolfssl/wolfcrypt/random.h>

Using WC_RNG for the rng global:
WC_RNG rng;

Let me know if you have anymore questions,

Thanks,
David Garske, wolfSSL

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  • Registered: 2016-10-07
  • Posts: 20

Re: [SOLVED] using rsa, "undefined reference to `wc_GenerateSeed'" error

I am somewhat newbie and do not know how to carry out the second solution. Regarding the first solution I think placed correctly references, this since I am able to make the call to "wc_InitRng". I have included "random.h", but the result is the same.

Can you be more specific about how to define my own "CUSTOM_RAND_GENERATE_SEED" with an example?

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  • Registered: 2015-10-07
  • Posts: 430

Re: [SOLVED] using rsa, "undefined reference to `wc_GenerateSeed'" error

Hi Jesussotofan,

I did a search for Arduino RNG and came up with this good result:
https://www.arduino.cc/en/Reference/Random

To implement option #2 you need to add the following to your settings.h or user_settins.h (if WOLFSSL_USER_SETTINGS is defined).

int rand_gen_seed(byte* output, word32 sz);
#define CUSTOM_RAND_GENERATE_SEED  rand_gen_seed

Then the function can be put into any .c file in your project (wherever it makes sense to you).

The function would look like:

int rand_gen_seed(byte* output, word32 sz)
{
    int i;
    for (i = 0; i < sz; i++ ) {
        output[i] = analogRead(0);
    }

    return 0;
}

Its important to have a good random seed, so if your micro controller has an RNG peripheral you should find example code for it and use it. The above example uses analog source 0 noise to seed the P-RNG, which is from the reference to website provided above.

Our random.c file has many references to RNG hardware implementations, so check and see if your micro-controller is already listed in there. If so you can define the value needed to enable it.

Let me know if you have any other questions.

Thanks,
David Garske, wolfSSL

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  • Registered: 2016-10-07
  • Posts: 20

Re: [SOLVED] using rsa, "undefined reference to `wc_GenerateSeed'" error

Thanks for the reply.
The problem persists, and I think is because it is still makes the call to wc_generateSeed. The problem I don't know where the call occurs because I do not do directly. Besides, I can not quite fully understand the complex structure of wolfssl.
I know it sounds silly, but could you tell me where in my code makes the call to wc_generateSeed and try to change that part of the library?

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  • Registered: 2015-10-07
  • Posts: 430

Re: [SOLVED] using rsa, "undefined reference to `wc_GenerateSeed'" error

Hi Jesussotofan,

All calls to wc_GenerateSeed are in wolfcrypt/src/random.c. There are multiple places where this function exists depending on the hardware platform. Those start at line 1133.

If you are defining CUSTOM_RAND_GENERATE_SEED then it will use the function used in that define. I'd also make sure you don't have NO_DEV_RANDOM defined.

The function wc_InitRng calls wc_GenerateSeed. Make sure the wolfcrypt/src/random.c is being included with the build. Make sure you have a wc_GenerateSeed function in your random.c or use the CUSTOM_RAND_GENERATE_SEED define to remap it to your own function.

Have you seen our Arduino example for wolfSSL?
https://github.com/wolfSSL/wolfssl/tree … DE/ARDUINO

Thanks,
David Garske, wolfSSL

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