OSSL_PARAM: Add string pointer getters

When some function receives an OSSL_PARAM array to pilfer for data,
and there is a string of some sort, and all the code needs is to get
the pointer to the data, rather than a copy, there is currently no
other way than to use |param->data| directly.  This is of course a
valid method, but lacks any safety check (is |param->data_type|
correct, for example?).

OSSL_PARAM_get_utf8_string_ptr() and OSSL_PARAM_get_octet_string_ptr()
helps the programmer with such things, by setting the argument pointer
to |param->data|.
Additionally, the handle the data types OSSL_PARAM_UTF8_PTR and
OSSL_PARAM_OCTET_PTR as well.

Reviewed-by: Shane Lontis <shane.lontis@oracle.com>
(Merged from https://github.com/openssl/openssl/pull/12512)

crypto/params.c

@@ -969,3 +969,29 @@ OSSL_PARAM OSSL_PARAM_construct_end(void)
 
     return end;
 }
+
+static int get_string_ptr_internal(const OSSL_PARAM *p, const void **val,
+                                   size_t *used_len, unsigned int type)
+{
+    if (val == NULL || p == NULL || p->data_type != type)
+        return 0;
+    if (used_len != NULL)
+        *used_len = p->data_size;
+    *val = p->data;
+    return 1;
+}
+
+int OSSL_PARAM_get_utf8_string_ptr(const OSSL_PARAM *p, const char **val)
+{
+    return OSSL_PARAM_get_utf8_ptr(p, val)
+        || get_string_ptr_internal(p, (const void **)val, NULL,
+                                   OSSL_PARAM_UTF8_STRING);
+}
+
+int OSSL_PARAM_get_octet_string_ptr(const OSSL_PARAM *p, const void **val,
+                                    size_t *used_len)
+{
+    return OSSL_PARAM_get_octet_ptr(p, val, used_len)
+        || get_string_ptr_internal(p, val, used_len, OSSL_PARAM_OCTET_STRING);
+}
+

doc/man3/OSSL_PARAM_int.pod

@@ -24,6 +24,7 @@ OSSL_PARAM_get_time_t, OSSL_PARAM_get_uint, OSSL_PARAM_get_uint32,
 OSSL_PARAM_get_uint64, OSSL_PARAM_get_ulong, OSSL_PARAM_get_BN,
 OSSL_PARAM_get_utf8_string, OSSL_PARAM_get_octet_string,
 OSSL_PARAM_get_utf8_ptr, OSSL_PARAM_get_octet_ptr,
+OSSL_PARAM_get_utf8_string_ptr, OSSL_PARAM_get_octet_string_ptr,
 OSSL_PARAM_set_double, OSSL_PARAM_set_int, OSSL_PARAM_set_int32,
 OSSL_PARAM_set_int64, OSSL_PARAM_set_long, OSSL_PARAM_set_size_t,
 OSSL_PARAM_set_time_t, OSSL_PARAM_set_uint, OSSL_PARAM_set_uint32,
@@ -96,6 +97,10 @@ OSSL_PARAM_UNMODIFIED, OSSL_PARAM_modified, OSSL_PARAM_set_all_unmodified
  int OSSL_PARAM_set_octet_ptr(OSSL_PARAM *p, const void *val,
                               size_t used_len);
 
+ int OSSL_PARAM_get_utf8_string_ptr(const OSSL_PARAM *p, const char **val);
+ int OSSL_PARAM_get_octet_string_ptr(const OSSL_PARAM *p, const void **val,
+                                     size_t *used_len);
+
  int OSSL_PARAM_modified(const OSSL_PARAM *param);
  void OSSL_PARAM_set_all_unmodified(OSSL_PARAM *params);
 
@@ -264,6 +269,17 @@ OSSL_PARAM_set_octet_ptr() sets the OCTET string pointer in the parameter
 referenced by B<p> to the values B<val>.
 The length of the OCTET string is provided by B<used_len>.
 
+OSSL_PARAM_get_utf8_string_ptr() retrieves the pointer to a UTF8 string from
+the parameter pointed to by B<p>, and stores that pointer in B<*val>.
+This is different from OSSL_PARAM_get_utf8_string(), which copies the
+string.
+
+OSSL_PARAM_get_octet_string_ptr() retrieves the pointer to a octet string
+from the parameter pointed to by B<p>, and stores that pointer in B<*val>,
+along with the string's length in B<*used_len>.
+This is different from OSSL_PARAM_get_octet_string(), which copies the
+string.
+
 The OSSL_PARAM_UNMODIFIED macro is used to detect if a parameter was set.  On
 creation, via either the macros or construct calls, the I<return_size> field
 is set to this.  If the parameter is set using the calls defined herein, the

include/openssl/params.h

@@ -142,6 +142,10 @@ int OSSL_PARAM_get_octet_ptr(const OSSL_PARAM *p, const void **val,
 int OSSL_PARAM_set_octet_ptr(OSSL_PARAM *p, const void *val,
                              size_t used_len);
 
+int OSSL_PARAM_get_utf8_string_ptr(const OSSL_PARAM *p, const char **val);
+int OSSL_PARAM_get_octet_string_ptr(const OSSL_PARAM *p, const void **val,
+                                    size_t *used_len);
+
 int OSSL_PARAM_modified(const OSSL_PARAM *p);
 void OSSL_PARAM_set_all_unmodified(OSSL_PARAM *p);
 

util/libcrypto.num

@@ -5281,3 +5281,5 @@ OSSL_STORE_LOADER_number                ?	3_0_0	EXIST::FUNCTION:
 OSSL_STORE_LOADER_is_a                  ?	3_0_0	EXIST::FUNCTION:
 OSSL_STORE_LOADER_do_all_provided       ?	3_0_0	EXIST::FUNCTION:
 OSSL_STORE_LOADER_names_do_all          ?	3_0_0	EXIST::FUNCTION:
+OSSL_PARAM_get_utf8_string_ptr          ?	3_0_0	EXIST::FUNCTION:
+OSSL_PARAM_get_octet_string_ptr         ?	3_0_0	EXIST::FUNCTION: