Add compile-time option to remove legacy CRT fields
diff --git a/include/mbedtls/config.h b/include/mbedtls/config.h
index e5d5933..4b8913b 100644
--- a/include/mbedtls/config.h
+++ b/include/mbedtls/config.h
@@ -1758,6 +1758,38 @@
#define MBEDTLS_VERSION_FEATURES
/**
+ * \def MBEDTLS_X509_ON_DEMAND_PARSING
+ *
+ * Save RAM by reducing mbedtls_x509_crt to a pointer
+ * to the raw CRT data and parsing CRTs on demand only.
+ *
+ * \warning This option changes the API by removing most of
+ * the structure fields of mbedtls_x509_crt.
+ *
+ * \warning This option and its corresponding X.509 API are currently
+ * under development and may change at any time.
+ *
+ * Regardless of whether this option is enabled or not, direct access of
+ * structure fields of `mbedtls_x509_crt` should be replaced by calls to
+ * one of the following functions:
+ * - mbedtls_x509_crt_get_frame(), to obtain a CRT frame giving
+ * access to several basic CRT fields (such as the CRT version),
+ * as well as pointers to the raw ASN.1 data of more complex fields
+ * (such as the issuer).
+ * - mbedtls_x509_crt_get_pk(), to obtain a public key context
+ * for the public key contained in the certificate.
+ * - mbedtls_x509_crt_get_issuer(), to obtain the issuer name.
+ * - mbedtls_x509_crt_get_subject(), to obtain the subject name.
+ * - mbedtls_x509_crt_get_subject_alt_names(), to obtain the
+ * alternative names from the subject alternative names extension.
+ * - mbedtls_x509_crt_get_ext_key_usage(), to obtain the state of
+ * the extended key usage extension.
+ *
+ * Uncomment this to enable on-demand CRT parsing to save RAM.
+ */
+//#define MBEDTLS_X509_ON_DEMAND_PARSING
+
+/**
* \def MBEDTLS_X509_ALLOW_EXTENSIONS_NON_V3
*
* If set, the X509 parser will not break-off when parsing an X509 certificate
diff --git a/include/mbedtls/x509_crt.h b/include/mbedtls/x509_crt.h
index 3f8350a..db99aab 100644
--- a/include/mbedtls/x509_crt.h
+++ b/include/mbedtls/x509_crt.h
@@ -122,8 +122,14 @@
typedef struct mbedtls_x509_crt
{
int own_buffer; /**< Indicates if \c raw is owned
- * by the structure or not. */
- mbedtls_x509_buf raw; /**< The raw certificate data (DER). */
+ * by the structure or not. */
+ mbedtls_x509_buf raw; /**< The raw certificate data (DER). */
+ mbedtls_x509_crt_cache *cache; /**< Internal parsing cache. */
+
+ struct mbedtls_x509_crt *next; /**< Next certificate in the CA-chain. */
+
+ /* Legacy fields */
+#if !defined(MBEDTLS_X509_ON_DEMAND_PARSING)
mbedtls_x509_buf tbs; /**< The raw certificate body (DER). The part that is To Be Signed. */
int version; /**< The X.509 version. (1=v1, 2=v2, 3=v3) */
@@ -166,10 +172,7 @@
mbedtls_md_type_t sig_md; /**< Internal representation of the MD algorithm of the signature algorithm, e.g. MBEDTLS_MD_SHA256 */
mbedtls_pk_type_t sig_pk; /**< Internal representation of the Public Key algorithm of the signature algorithm, e.g. MBEDTLS_PK_RSA */
void *sig_opts; /**< Signature options to be passed to mbedtls_pk_verify_ext(), e.g. for RSASSA-PSS */
-
- mbedtls_x509_crt_cache *cache; /**< Internal parsing cache. */
-
- struct mbedtls_x509_crt *next; /**< Next certificate in the CA-chain. */
+#endif /* !MBEDTLS_X509_ON_DEMAND_PARSING */
}
mbedtls_x509_crt;
@@ -746,7 +749,7 @@
#endif
}
-static inline int mbedtls_x509_crt_pk_acquire( mbedtls_x509_crt *crt,
+static inline int mbedtls_x509_crt_pk_acquire( mbedtls_x509_crt const *crt,
mbedtls_pk_context **pk_ptr )
{
#if defined(MBEDTLS_THREADING_C)
@@ -772,7 +775,7 @@
return( 0 );
}
-static inline void mbedtls_x509_crt_pk_release( mbedtls_x509_crt *crt,
+static inline void mbedtls_x509_crt_pk_release( mbedtls_x509_crt const *crt,
mbedtls_pk_context *pk )
{
((void) pk);
diff --git a/library/version_features.c b/library/version_features.c
index 5e9d923..e19e314 100644
--- a/library/version_features.c
+++ b/library/version_features.c
@@ -534,6 +534,9 @@
#if defined(MBEDTLS_VERSION_FEATURES)
"MBEDTLS_VERSION_FEATURES",
#endif /* MBEDTLS_VERSION_FEATURES */
+#if defined(MBEDTLS_X509_ON_DEMAND_PARSING)
+ "MBEDTLS_X509_ON_DEMAND_PARSING",
+#endif /* MBEDTLS_X509_ON_DEMAND_PARSING */
#if defined(MBEDTLS_X509_ALLOW_EXTENSIONS_NON_V3)
"MBEDTLS_X509_ALLOW_EXTENSIONS_NON_V3",
#endif /* MBEDTLS_X509_ALLOW_EXTENSIONS_NON_V3 */
diff --git a/library/x509_crt.c b/library/x509_crt.c
index 6c87959..20f0bb0 100644
--- a/library/x509_crt.c
+++ b/library/x509_crt.c
@@ -116,10 +116,19 @@
pk = mbedtls_calloc( 1, sizeof( mbedtls_pk_context ) );
if( pk == NULL )
return( MBEDTLS_ERR_X509_ALLOC_FAILED );
- *pk = crt->pk;
-
cache->pk = pk;
+
+#if !defined(MBEDTLS_X509_ON_DEMAND_PARSING)
+ *pk = crt->pk;
return( 0 );
+#else
+ {
+ mbedtls_x509_buf_raw pk_raw = cache->pk_raw;
+ return( mbedtls_pk_parse_subpubkey( &pk_raw.p,
+ pk_raw.p + pk_raw.len,
+ pk ) );
+ }
+#endif /* MBEDTLS_X509_ON_DEMAND_PARSING */
}
static void x509_crt_cache_init( mbedtls_x509_crt_cache *cache )
@@ -133,9 +142,15 @@
static void x509_crt_cache_clear_pk( mbedtls_x509_crt_cache *cache )
{
+#if !defined(MBEDTLS_X509_ON_DEMAND_PARSING)
/* The cache holds a shallow copy of the PK context
* in the legacy struct, so don't free PK context. */
mbedtls_free( cache->pk );
+#else
+ mbedtls_pk_free( cache->pk );
+ mbedtls_free( cache->pk );
+#endif /* MBEDTLS_X509_ON_DEMAND_PARSING */
+
cache->pk = NULL;
}
@@ -1182,6 +1197,7 @@
return( 0 );
}
+#if !defined(MBEDTLS_X509_ON_DEMAND_PARSING)
static int x509_crt_pk_from_frame( mbedtls_x509_crt_frame *frame,
mbedtls_pk_context *pk )
{
@@ -1189,6 +1205,7 @@
unsigned char *end = p + frame->pubkey_raw.len;
return( mbedtls_pk_parse_subpubkey( &p, end, pk ) );
}
+#endif /* !MBEDTLS_X509_ON_DEMAND_PARSING */
/*
* Parse and fill a single X.509 certificate in DER format
@@ -1248,6 +1265,7 @@
cache->pk_raw = frame->pubkey_raw;
+#if !defined(MBEDTLS_X509_ON_DEMAND_PARSING)
/* Copy frame to legacy CRT structure -- that's inefficient, but if
* memory matters, the new CRT structure should be used anyway. */
crt->tbs.p = frame->tbs.p;
@@ -1336,7 +1354,7 @@
ret = x509_crt_ext_key_usage_from_frame( frame, &crt->ext_key_usage );
if( ret != 0 )
goto exit;
-
+#endif /* !MBEDTLS_X509_ON_DEMAND_PARSING */
/* The cache just references the PK structure from the legacy
* implementation, so set up the latter first before setting up
@@ -3330,6 +3348,8 @@
{
x509_crt_cache_free( cert_cur->cache );
mbedtls_free( cert_cur->cache );
+
+#if !defined(MBEDTLS_X509_ON_DEMAND_PARSING)
mbedtls_pk_free( &cert_cur->pk );
#if defined(MBEDTLS_X509_RSASSA_PSS_SUPPORT)
@@ -3340,6 +3360,7 @@
x509_free_name( cert_cur->subject.next );
x509_free_sequence( cert_cur->ext_key_usage.next );
x509_free_sequence( cert_cur->subject_alt_names.next );
+#endif /* !MBEDTLS_X509_ON_DEMAND_PARSING */
if( cert_cur->raw.p != NULL && cert_cur->own_buffer )
{