Merge pull request #22 from avast/fix-null-strdup

fix: Check for NULLs in certificate_copy strdup

src/certificate.c

@@ -379,15 +379,15 @@ Certificate* certificate_copy(Certificate* cert)
  return NULL;
 
  result->version = cert->version;
- result->issuer = strdup(cert->issuer);
- result->subject = strdup(cert->subject);
- result->serial = strdup(cert->serial);
+ result->issuer = cert->issuer ? strdup(cert->issuer) : NULL;
+ result->subject = cert->subject ? strdup(cert->subject) : NULL;
+ result->serial = cert->serial ? strdup(cert->serial) : NULL;
  result->not_after = cert->not_after;
  result->not_before = cert->not_before;
- result->sig_alg = strdup(cert->sig_alg);
- result->sig_alg_oid = strdup(cert->sig_alg_oid);
- result->key_alg = strdup(cert->key_alg);
- result->key = strdup(cert->key);
+ result->sig_alg = cert->sig_alg ? strdup(cert->sig_alg) : NULL;
+ result->sig_alg_oid = cert->sig_alg_oid ? strdup(cert->sig_alg_oid) : NULL;
+ result->key_alg = cert->key_alg ? strdup(cert->key_alg) : NULL;
+ result->key = cert->key ? strdup(cert->key) : NULL;
  byte_array_init(&result->sha1, cert->sha1.data, cert->sha1.len);
  byte_array_init(&result->sha256, cert->sha256.data, cert->sha256.len);
  attributes_copy(&result->issuer_attrs, &cert->issuer_attrs);