Improve robustness and help lint.

* cipher/rsa.c (rsa_encrypt): Check for !DATA.
* cipher/md.c (search_oid): Check early for !OID.
(md_copy): Use gpg_err_code_from_syserror.  Replace chains of if(!err)
tests.
* cipher/cipher.c (search_oid): Check early for !OID.
* src/misc.c (do_printhex): Allow for BUFFER==NULL even with LENGTH>0.
* mpi/mpicoder.c (onecompl): Allow for A==NULL to help static
analyzers.
--

The change for md_copy is to help static analyzers which have no idea
that gpg_err_code_from_syserror will never return 0.  A gcc attribute
returns_nonzero would be a nice to have.

Some changes are due to the fact the macros like mpi_is_immutable
gracefully handle a NULL arg but a static analyzer the considers that
the function allows for a NULL arg.

Signed-off-by: Werner Koch <wk@gnupg.org>

1 files changed, 4 insertions, 2 deletions

diff --git a/cipher/cipher.c b/cipher/cipher.c
index bdcbfbd7..2b7bf210 100644
--- a/cipher/cipher.c
+++ b/cipher/cipher.c
@@ -175,8 +175,10 @@ search_oid (const char *oid, gcry_cipher_oid_spec_t *oid_spec)
   gcry_cipher_spec_t *spec;
   int i;
 
-  if (oid && ((! strncmp (oid, "oid.", 4))
-	      || (! strncmp (oid, "OID.", 4))))
+  if (!oid)
+    return NULL;
+
+  if (!strncmp (oid, "oid.", 4) || !strncmp (oid, "OID.", 4))
     oid += 4;
 
   spec = spec_from_oid (oid);