auth: fix NULL pointer access when trying to delete CryptoAESKeyHandl…

…er instance

the caller needs to check the nullity of the parameter before calling
PK11_FreeSymKey or PK11_FreeSlot, otherwise if CryptoAESKeyHandler::init
failed, we will hit a segfault as follows:
  #0  0x00007f76844f5a95 in PK11_FreeSymKey () from /lib64/libnss3.so
  ceph#1  0x00007f76586b6e49 in CryptoAESKeyHandler::~CryptoAESKeyHandler() () from /lib64/librados.so.2
  ceph#2  0x00007f76586b5eea in CryptoAES::get_key_handler(ceph::buffer::ptr const&, std::string&) () from /lib64/librados.so.2
  ceph#3  0x00007f76586b4b9c in CryptoKey::_set_secret(int, ceph::buffer::ptr const&) () from /lib64/librados.so.2
  ceph#4  0x00007f76586b4e95 in CryptoKey::decode(ceph::buffer::list::iterator&) () from /lib64/librados.so.2
  ceph#5  0x00007f76586b7ee6 in KeyRing::set_modifier(char const*, char const*, EntityName&, std::map<std::string, ceph::buffer::list, std::less<std::string>, std::allocator<std::pair<std::string const, ceph::buffer::list> > >&) () from /lib64/librados.so.2
  ceph#6  0x00007f76586b8882 in KeyRing::decode_plaintext(ceph::buffer::list::iterator&) () from /lib64/librados.so.2
  ceph#7  0x00007f76586b9803 in KeyRing::decode(ceph::buffer::list::iterator&) () from /lib64/librados.so.2
  ceph#8  0x00007f76586b9a1f in KeyRing::load(CephContext*, std::string const&) () from /lib64/librados.so.2
  ceph#9  0x00007f76586ba04b in KeyRing::from_ceph_context(CephContext*) () from /lib64/librados.so.2
  ceph#10 0x00007f765852d0cd in MonClient::init() () from /lib64/librados.so.2
  ceph#11 0x00007f76583c15f5 in librados::RadosClient::connect() () from /lib64/librados.so.2
  ceph#12 0x00007f765838cb1c in rados_connect () from /lib64/librados.so.2
  ...

Signed-off-by: runsisi <runsisi@zte.com.cn>

src/auth/Crypto.cc

@@ -269,8 +269,10 @@ class CryptoAESKeyHandler : public CryptoKeyHandler {
       param(NULL) {}
   ~CryptoAESKeyHandler() {
     SECITEM_FreeItem(param, PR_TRUE);
-    PK11_FreeSymKey(key);
-    PK11_FreeSlot(slot);
+    if (key)
+      PK11_FreeSymKey(key);
+    if (slot)
+      PK11_FreeSlot(slot);
   }
 
   int init(const bufferptr& s, ostringstream& err) {