provider: Fix segfault with 'openssl list -signature-algorithms -verbose'

Command 'openssl list -signature-algorithms -verbose' calls OpenSSL function
EVP_SIGNATURE_settable_ctx_params() which in turn calls the provider's
settable_ctx_params() function, but with NULL for the operation
context. This causes segfaults in IBMCAs settable_ctx_params() functions,
as they assume that the operation context is not NULL.

While at it, make sure that the settable/gettable_ctx_md_params() functions
do not crash if called with a NULL context.

Signed-off-by: Ingo Franzki <ifranzki@linux.ibm.com>

Author: ifranzki

src/provider/ec_signature.c

@@ -823,7 +823,7 @@ static const OSSL_PARAM *ibmca_signature_ec_settable_ctx_params(
 
     ibmca_debug_ctx(provctx, "ctx: %p", ctx);
 
-    if (ctx->ec.signature.set_md_allowed)
+    if (ctx == NULL || ctx->ec.signature.set_md_allowed)
         params = ibmca_signature_ec_settable_params;
     else
         params = ibmca_signature_ec_settable_params_no_digest;

src/provider/p_context.c

@@ -392,9 +392,10 @@ const OSSL_PARAM *ibmca_gettable_ctx_md_params(const struct ibmca_op_ctx *ctx,
     ibmca_debug_op_ctx(ctx, "ctx: %p", ctx);
 
     if (md == NULL) {
-        put_error_op_ctx(ctx, IBMCA_ERR_INVALID_PARAM,
-                         "Digest sign/verify context not initialized");
-        return 0;
+        if (ctx != NULL)
+            put_error_op_ctx(ctx, IBMCA_ERR_INVALID_PARAM,
+                             "Digest sign/verify context not initialized");
+        return NULL;
     }
 
     params = EVP_MD_gettable_ctx_params(md);
@@ -413,9 +414,10 @@ const OSSL_PARAM *ibmca_settable_ctx_md_params(const struct ibmca_op_ctx *ctx,
     ibmca_debug_op_ctx(ctx, "ctx: %p", ctx);
 
     if (md == NULL) {
-        put_error_op_ctx(ctx, IBMCA_ERR_INVALID_PARAM,
-                         "Digest sign/verify context not initialized");
-        return 0;
+        if (ctx != NULL)
+            put_error_op_ctx(ctx, IBMCA_ERR_INVALID_PARAM,
+                            "Digest sign/verify context not initialized");
+        return NULL;
     }
 
     params = EVP_MD_settable_ctx_params(md);

src/provider/rsa_signature.c

@@ -1814,7 +1814,7 @@ static const OSSL_PARAM *ibmca_signature_rsa_settable_ctx_params(
 
     ibmca_debug_ctx(provctx, "ctx: %p", ctx);
 
-    if (ctx->rsa.signature.set_md_allowed)
+    if (ctx == NULL || ctx->rsa.signature.set_md_allowed)
         params = ibmca_signature_rsa_settable_params;
     else
         params = ibmca_signature_rsa_settable_params_no_digest;