Implement static dispatch with SINGLE_PK_TYPE

For optional functions, we introduce an extra macro to tell if the function is
omitted. As the C preprocessor doesn't directly support comparing strings,
testing if the _FUNC macro is defined to NULL isn't obvious. One could
probably play tricks to avoid the need for _OMIT macros, but the small amount
of (entirely local) duplication here is probably a lesser evil than extra
preprocessor complexity.

include/mbedtls/pk_internal.h

@@ -41,6 +41,9 @@
  * Each PK type that can be used with MBEDTLS_PK_SINGLE_TYPE needs to have
  * the following MBEDTLS_PK_INFO_{FIELD} definitions, plus a dummy one for the
  * base name. For now, only ECKEY with MBEDTLS_USE_TINYCRYPT is defined.
+ *
+ * For optional functions that are omitted, we need both the _FUNC field
+ * defined to NULL, and an extra macro _OMIT defined to 1.
  */
 
 #if defined(MBEDTLS_USE_TINYCRYPT)
@@ -54,11 +57,14 @@
 #define MBEDTLS_PK_INFO_ECKEY_VERIFY_FUNC       uecc_eckey_verify_wrap
 #define MBEDTLS_PK_INFO_ECKEY_SIGN_FUNC         uecc_eckey_sign_wrap
 #define MBEDTLS_PK_INFO_ECKEY_DECRYPT_FUNC      NULL
+#define MBEDTLS_PK_INFO_ECKEY_DECRYPT_OMIT      1
 #define MBEDTLS_PK_INFO_ECKEY_ENCRYPT_FUNC      NULL
+#define MBEDTLS_PK_INFO_ECKEY_ENCRYPT_OMIT      1
 #define MBEDTLS_PK_INFO_ECKEY_CHECK_PAIR_FUNC   uecc_eckey_check_pair
 #define MBEDTLS_PK_INFO_ECKEY_CTX_ALLOC_FUNC    uecc_eckey_alloc_wrap
 #define MBEDTLS_PK_INFO_ECKEY_CTX_FREE_FUNC     uecc_eckey_free_wrap
 #define MBEDTLS_PK_INFO_ECKEY_DEBUG_FUNC        NULL
+#define MBEDTLS_PK_INFO_ECKEY_DEBUG_OMIT        1
 #endif /* MBEDTLS_USE_TINYCRYPT */
 
 /*
@@ -69,13 +75,19 @@
 #define MBEDTLS_PK_INFO_GET_BITLEN_T( PK )      PK ## _GET_BITLEN
 #define MBEDTLS_PK_INFO_CAN_DO_T( PK )          PK ## _CAN_DO
 #define MBEDTLS_PK_INFO_VERIFY_FUNC_T( PK )     PK ## _VERIFY_FUNC
+#define MBEDTLS_PK_INFO_VERIFY_OMIT_T( PK )     PK ## _VERIFY_OMIT
 #define MBEDTLS_PK_INFO_SIGN_FUNC_T( PK )       PK ## _SIGN_FUNC
+#define MBEDTLS_PK_INFO_SIGN_OMIT_T( PK )       PK ## _SIGN_OMIT
 #define MBEDTLS_PK_INFO_DECRYPT_FUNC_T( PK )    PK ## _DECRYPT_FUNC
+#define MBEDTLS_PK_INFO_DECRYPT_OMIT_T( PK )    PK ## _DECRYPT_OMIT
 #define MBEDTLS_PK_INFO_ENCRYPT_FUNC_T( PK )    PK ## _ENCRYPT_FUNC
+#define MBEDTLS_PK_INFO_ENCRYPT_OMIT_T( PK )    PK ## _ENCRYPT_OMIT
 #define MBEDTLS_PK_INFO_CHECK_PAIR_FUNC_T( PK ) PK ## _CHECK_PAIR_FUNC
+#define MBEDTLS_PK_INFO_CHECK_PAIR_OMIT_T( PK ) PK ## _CHECK_PAIR_OMIT
 #define MBEDTLS_PK_INFO_CTX_ALLOC_FUNC_T( PK )  PK ## _CTX_ALLOC_FUNC
 #define MBEDTLS_PK_INFO_CTX_FREE_FUNC_T( PK )   PK ## _CTX_FREE_FUNC
 #define MBEDTLS_PK_INFO_DEBUG_FUNC_T( PK )      PK ## _DEBUG_FUNC
+#define MBEDTLS_PK_INFO_DEBUG_OMIT_T( PK )      PK ## _DEBUG_OMIT
 
 /* Wrappers around MBEDTLS_PK_INFO_{FIELD}_T() which makes sure that
  * the argument is macro-expanded before concatenated with the
@@ -87,13 +99,19 @@
 #define MBEDTLS_PK_INFO_GET_BITLEN( PK )      MBEDTLS_PK_INFO_GET_BITLEN_T( PK )
 #define MBEDTLS_PK_INFO_CAN_DO( PK )          MBEDTLS_PK_INFO_CAN_DO_T( PK )
 #define MBEDTLS_PK_INFO_VERIFY_FUNC( PK )     MBEDTLS_PK_INFO_VERIFY_FUNC_T( PK )
+#define MBEDTLS_PK_INFO_VERIFY_OMIT( PK )     MBEDTLS_PK_INFO_VERIFY_OMIT_T( PK )
 #define MBEDTLS_PK_INFO_SIGN_FUNC( PK )       MBEDTLS_PK_INFO_SIGN_FUNC_T( PK )
+#define MBEDTLS_PK_INFO_SIGN_OMIT( PK )       MBEDTLS_PK_INFO_SIGN_OMIT_T( PK )
 #define MBEDTLS_PK_INFO_DECRYPT_FUNC( PK )    MBEDTLS_PK_INFO_DECRYPT_FUNC_T( PK )
+#define MBEDTLS_PK_INFO_DECRYPT_OMIT( PK )    MBEDTLS_PK_INFO_DECRYPT_OMIT_T( PK )
 #define MBEDTLS_PK_INFO_ENCRYPT_FUNC( PK )    MBEDTLS_PK_INFO_ENCRYPT_FUNC_T( PK )
+#define MBEDTLS_PK_INFO_ENCRYPT_OMIT( PK )    MBEDTLS_PK_INFO_ENCRYPT_OMIT_T( PK )
 #define MBEDTLS_PK_INFO_CHECK_PAIR_FUNC( PK ) MBEDTLS_PK_INFO_CHECK_PAIR_FUNC_T( PK )
+#define MBEDTLS_PK_INFO_CHECK_PAIR_OMIT( PK ) MBEDTLS_PK_INFO_CHECK_PAIR_OMIT_T( PK )
 #define MBEDTLS_PK_INFO_CTX_ALLOC_FUNC( PK )  MBEDTLS_PK_INFO_CTX_ALLOC_FUNC_T( PK )
 #define MBEDTLS_PK_INFO_CTX_FREE_FUNC( PK )   MBEDTLS_PK_INFO_CTX_FREE_FUNC_T( PK )
 #define MBEDTLS_PK_INFO_DEBUG_FUNC( PK )      MBEDTLS_PK_INFO_DEBUG_FUNC_T( PK )
+#define MBEDTLS_PK_INFO_DEBUG_OMIT( PK )      MBEDTLS_PK_INFO_DEBUG_OMIT_T( PK )
 
 struct mbedtls_pk_info_t
 {

library/pk.c

@@ -1001,8 +1001,9 @@ const mbedtls_pk_info_t mbedtls_rsa_alt_info = {
 #endif /* MBEDTLS_PK_RSA_ALT_SUPPORT */
 
 /*
- * Access to members of the pk_info structure. These are meant to be replaced
+ * Access to members of the pk_info structure. When a single PK type is
- * by zero-runtime-cost accessors when a single PK type is hardcoded.
+ * hardcoded, these should have zero runtime cost; otherwise, the usual
+ * dynamic dispatch based on pk_info is used.
  *
  * For function members, don't make a getter, but a function that directly
  * calls the method, so that we can entirely get rid of function pointers
@@ -1012,6 +1013,171 @@ const mbedtls_pk_info_t mbedtls_rsa_alt_info = {
  * MBEDTLS_ECP_RESTARTABLE for now, as the main target for hardcoded is builds
  * with MBEDTLS_USE_TINYCRYPT, which don't have MBEDTLS_ECP_RESTARTABLE.
  */
+#if defined(MBEDTLS_PK_SINGLE_TYPE)
+
+MBEDTLS_ALWAYS_INLINE static inline mbedtls_pk_type_t pk_info_type(
+    const mbedtls_pk_info_t *info )
+{
+    (void) info;
+    return( MBEDTLS_PK_INFO_TYPE( MBEDTLS_PK_SINGLE_TYPE ) );
+}
+
+MBEDTLS_ALWAYS_INLINE static inline const char * pk_info_name(
+    const mbedtls_pk_info_t *info )
+{
+    (void) info;
+    return( MBEDTLS_PK_INFO_NAME( MBEDTLS_PK_SINGLE_TYPE ) );
+}
+
+MBEDTLS_ALWAYS_INLINE static inline size_t pk_info_get_bitlen(
+    const mbedtls_pk_info_t *info, const void *ctx )
+{
+    (void) info;
+    return( MBEDTLS_PK_INFO_GET_BITLEN( MBEDTLS_PK_SINGLE_TYPE )( ctx ) );
+}
+
+MBEDTLS_ALWAYS_INLINE static inline int pk_info_can_do(
+    const mbedtls_pk_info_t *info, mbedtls_pk_type_t type )
+{
+    (void) info;
+    return( MBEDTLS_PK_INFO_CAN_DO( MBEDTLS_PK_SINGLE_TYPE )( type ) );
+}
+
+MBEDTLS_ALWAYS_INLINE static inline int pk_info_verify_func(
+    const mbedtls_pk_info_t *info, void *ctx, mbedtls_md_type_t md_alg,
+    const unsigned char *hash, size_t hash_len,
+    const unsigned char *sig, size_t sig_len )
+{
+    (void) info;
+#if MBEDTLS_PK_INFO_VERIFY_OMIT( MBEDTLS_PK_SINGLE_TYPE )
+    (void) ctx;
+    (void) md_alg;
+    (void) hash;
+    (void) hash_len;
+    (void) sig;
+    (void) sig_len;
+    return( MBEDTLS_ERR_PK_TYPE_MISMATCH );
+#else
+    return( MBEDTLS_PK_INFO_VERIFY_FUNC( MBEDTLS_PK_SINGLE_TYPE )(
+                ctx, md_alg, hash, hash_len, sig, sig_len ) );
+#endif
+}
+
+MBEDTLS_ALWAYS_INLINE static inline int pk_info_sign_func(
+    const mbedtls_pk_info_t *info, void *ctx, mbedtls_md_type_t md_alg,
+    const unsigned char *hash, size_t hash_len,
+    unsigned char *sig, size_t *sig_len,
+    int (*f_rng)(void *, unsigned char *, size_t),
+    void *p_rng )
+{
+    (void) info;
+#if MBEDTLS_PK_INFO_SIGN_OMIT( MBEDTLS_PK_SINGLE_TYPE )
+    (void) ctx;
+    (void) md_alg;
+    (void) hash;
+    (void) hash_len;
+    (void) sig;
+    (void) sig_len;
+    (void) f_rng;
+    (void) p_rng;
+    return( MBEDTLS_ERR_PK_TYPE_MISMATCH );
+#else
+    return( MBEDTLS_PK_INFO_SIGN_FUNC( MBEDTLS_PK_SINGLE_TYPE )(
+                ctx, md_alg, hash, hash_len, sig, sig_len, f_rng, p_rng ) );
+#endif
+}
+
+MBEDTLS_ALWAYS_INLINE static inline int pk_info_decrypt_func(
+    const mbedtls_pk_info_t *info, void *ctx,
+    const unsigned char *input, size_t ilen,
+    unsigned char *output, size_t *olen, size_t osize,
+    int (*f_rng)(void *, unsigned char *, size_t),
+    void *p_rng )
+{
+    (void) info;
+#if MBEDTLS_PK_INFO_DECRYPT_OMIT( MBEDTLS_PK_SINGLE_TYPE )
+    (void) ctx;
+    (void) input;
+    (void) ilen;
+    (void) output;
+    (void) olen;
+    (void) osize;
+    (void) f_rng;
+    (void) p_rng;
+    return( MBEDTLS_ERR_PK_TYPE_MISMATCH );
+#else
+    return( MBEDTLS_PK_INFO_DECRYPT_FUNC( MBEDTLS_PK_SINGLE_TYPE )(
+                ctx, input, ilen, output, olen, osize, f_rng, p_rng ) );
+#endif
+}
+
+MBEDTLS_ALWAYS_INLINE static inline int pk_info_encrypt_func(
+    const mbedtls_pk_info_t *info, void *ctx,
+    const unsigned char *input, size_t ilen,
+    unsigned char *output, size_t *olen, size_t osize,
+    int (*f_rng)(void *, unsigned char *, size_t),
+    void *p_rng )
+{
+    (void) info;
+#if MBEDTLS_PK_INFO_ENCRYPT_OMIT( MBEDTLS_PK_SINGLE_TYPE )
+    (void) ctx;
+    (void) input;
+    (void) ilen;
+    (void) output;
+    (void) olen;
+    (void) osize;
+    (void) f_rng;
+    (void) p_rng;
+    return( MBEDTLS_ERR_PK_TYPE_MISMATCH );
+#else
+    return( MBEDTLS_PK_INFO_ENCRYPT_FUNC( MBEDTLS_PK_SINGLE_TYPE )(
+                ctx, input, ilen, output, olen, osize, f_rng, p_rng ) );
+#endif
+}
+
+MBEDTLS_ALWAYS_INLINE static inline int pk_info_check_pair_func(
+    const mbedtls_pk_info_t *info, const void *pub, const void *prv )
+{
+    (void) info;
+#if MBEDTLS_PK_INFO_CHECK_PAIR_OMIT( MBEDTLS_PK_SINGLE_TYPE )
+    (void) pub;
+    (void) prv;
+    return( MBEDTLS_ERR_PK_BAD_INPUT_DATA );
+#else
+    return( MBEDTLS_PK_INFO_CHECK_PAIR_FUNC( MBEDTLS_PK_SINGLE_TYPE )(
+                pub, prv ) );
+#endif
+}
+
+MBEDTLS_ALWAYS_INLINE static inline void *pk_info_ctx_alloc_func(
+    const mbedtls_pk_info_t *info )
+{
+    (void) info;
+    return( MBEDTLS_PK_INFO_CTX_ALLOC_FUNC( MBEDTLS_PK_SINGLE_TYPE )( ) );
+}
+
+MBEDTLS_ALWAYS_INLINE static inline void pk_info_ctx_free_func(
+    const mbedtls_pk_info_t *info, void *ctx )
+{
+    (void) info;
+    MBEDTLS_PK_INFO_CTX_FREE_FUNC( MBEDTLS_PK_SINGLE_TYPE )( ctx );
+}
+
+MBEDTLS_ALWAYS_INLINE static inline int pk_info_debug_func(
+    const mbedtls_pk_info_t *info,
+    const void *ctx, mbedtls_pk_debug_item *items )
+{
+    (void) info;
+#if MBEDTLS_PK_INFO_DEBUG_OMIT( MBEDTLS_PK_SINGLE_TYPE )
+    (void) ctx;
+    (void) items;
+    return( MBEDTLS_ERR_PK_TYPE_MISMATCH );
+#else
+    return( MBEDTLS_PK_INFO_DEBUG_FUNC( MBEDTLS_PK_SINGLE_TYPE )( ctx, items ) );
+#endif
+}
+
+#else /* MBEDTLS_PK_SINGLE_TYPE */
 
 MBEDTLS_ALWAYS_INLINE static inline mbedtls_pk_type_t pk_info_type(
     const mbedtls_pk_info_t *info )
@@ -1122,6 +1288,8 @@ MBEDTLS_ALWAYS_INLINE static inline int pk_info_debug_func(
     return( 0 );
 }
 
+#endif /* MBEDTLS_PK_SINGLE_TYPE */
+
 /*
  * Initialise a mbedtls_pk_context
  */