On Thu, Jan 15, 2004, Matt Margush wrote:
> Hi,
>
> I searched the mailing list archives but couldn't find this question.
> When I run the following code, I get an "EXC_BAD_ACCESS" signal at line
> 29. If I reverse the order (encode the private key first, then the
> public key), then the error happens on the call to encode the public
> key. So it seems like encoding one key might do something to the DSA
> structure that makes it impossible to encode the other key... or (more
> likely), something is wrong with my code here (which I hope is the case
> because it will be easier to fix.) I am using version 0.9.7.
>
> Thanks,
>
> Matt
>
>
> #include <stdio.h>
> #include <openssl/dsa.h>
>
> int main (int argc, const char * argv[]) {
> DSA *dsa = DSA_generate_parameters(1024, NULL, 0, NULL, NULL, NULL,
> NULL);
> DSA_generate_key(dsa);
>
> {
> unsigned char *buffer;
> unsigned char *p = buffer;
> int length;
>
> length = i2d_DSAPublicKey(dsa, NULL);
> if (length > -1) {
> buffer = OPENSSL_malloc(length);
> i2d_DSAPublicKey(dsa, &p);
> OPENSSL_free(buffer);
> }
> }
>
> {
> unsigned char *buffer;
> unsigned char *p = buffer;
> int length;
>
> length = i2d_DSAPrivateKey(dsa, NULL);
> if (length > -1) {
> buffer = OPENSSL_malloc(length);
> i2d_DSAPrivateKey(dsa, &p); /* THIS IS LINE 29 */
> OPENSSL_free(buffer);
> }
> }
>
> DSA_free(dsa);
>
> return 0;
> }
>
As someone has pointed out you need to set p to the buffer after you've set it
to a valid block of memory.
For 0.9.7 or later you can simplify this to:
buffer = NULL;
length = i2d_DSAPrivateKey(dsa, &buffer);
which will allocate and encode in one operation and it will *not* increment
buffer so you don't even need a temporary variable. Just don't try that on
0.9.6 or earlier because it will crash.
See:
http://www.openssl.org/docs/crypto/d2i_X509.html
Steve.
--
Dr Stephen N. Henson. Email, S/MIME and PGP keys: see homepage
OpenSSL project core developer and freelance consultant.
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