Merge branch 'null-entropy' into development

include/mbedtls/check_config.h

@@ -130,6 +130,16 @@
 #error "MBEDTLS_ENTROPY_FORCE_SHA256 defined, but not all prerequisites"
 #endif
 
+#if defined(MBEDTLS_TEST_NULL_ENTROPY) && \
+    ( !defined(MBEDTLS_ENTROPY_C) || !defined(MBEDTLS_NO_DEFAULT_ENTROPY_SOURCES) )
+#error "MBEDTLS_TEST_NULL_ENTROPY defined, but not all prerequisites"
+#endif
+#if defined(MBEDTLS_TEST_NULL_ENTROPY) && \
+     ( defined(MBEDTLS_ENTROPY_NV_SEED) || defined(MBEDTLS_ENTROPY_HARDWARE_ALT) || \
+    defined(MBEDTLS_HAVEGE_C) )
+#error "MBEDTLS_TEST_NULL_ENTROPY defined, but entropy sources too"
+#endif
+
 #if defined(MBEDTLS_GCM_C) && (                                        \
         !defined(MBEDTLS_AES_C) && !defined(MBEDTLS_CAMELLIA_C) )
 #error "MBEDTLS_GCM_C defined, but not all prerequisites"

include/mbedtls/config.h

@@ -279,6 +279,23 @@
 //#define MBEDTLS_AES_ENCRYPT_ALT
 //#define MBEDTLS_AES_DECRYPT_ALT
 
+/**
+ * \def MBEDTLS_TEST_NULL_ENTROPY
+ *
+ * Enables testing and use of mbed TLS without any configured entropy sources.
+ * This permits use of the library on platforms before an entropy source has
+ * been integrated (see for example the MBEDTLS_ENTROPY_HARDWARE_ALT or the
+ * MBEDTLS_ENTROPY_NV_SEED switches).
+ *
+ * WARNING! This switch MUST be disabled in production builds, and is suitable
+ * only for development.
+ * Enabling the switch negates any security provided by the library.
+ *
+ * Requires MBEDTLS_ENTROPY_C, MBEDTLS_NO_DEFAULT_ENTROPY_SOURCES
+ *
+ */
+//#define MBEDTLS_TEST_NULL_ENTROPY
+
 /**
  * \def MBEDTLS_ENTROPY_HARDWARE_ALT
  *

include/mbedtls/entropy_poll.h

@@ -43,6 +43,14 @@ extern "C" {
 #define MBEDTLS_ENTROPY_MIN_HARDCLOCK     4     /**< Minimum for mbedtls_timing_hardclock()        */
 #define MBEDTLS_ENTROPY_MIN_HARDWARE     32     /**< Minimum for the hardware source */
 
+/**
+ * \brief           Entropy poll callback that provides 0 entropy.
+ */
+#if defined(MBEDTLS_TEST_NULL_ENTROPY)
+    int mbedtls_null_entropy_poll( void *data,
+                                unsigned char *output, size_t len, size_t *olen );
+#endif
+
 #if !defined(MBEDTLS_NO_PLATFORM_ENTROPY)
 /**
  * \brief           Platform-specific entropy poll callback

library/entropy.c

@@ -27,6 +27,12 @@
 
 #if defined(MBEDTLS_ENTROPY_C)
 
+#if defined(MBEDTLS_TEST_NULL_ENTROPY)
+#warning "**** WARNING!  MBEDTLS_TEST_NULL_ENTROPY defined! ****"
+#warning "**** THIS BUILD HAS NO DEFINED ENTROPY SOURCES    ****"
+#warning "**** NOT SUITABLE FOR PRODUCTION                  ****"
+#endif
+
 #include "mbedtls/entropy.h"
 #include "mbedtls/entropy_poll.h"
 
@@ -73,6 +79,11 @@ void mbedtls_entropy_init( mbedtls_entropy_context *ctx )
     mbedtls_havege_init( &ctx->havege_data );
 #endif
 
+#if defined(MBEDTLS_TEST_NULL_ENTROPY)
+    mbedtls_entropy_add_source( ctx, mbedtls_null_entropy_poll, NULL,
+                                1, MBEDTLS_ENTROPY_SOURCE_STRONG );
+#endif
+
 #if !defined(MBEDTLS_NO_DEFAULT_ENTROPY_SOURCES)
 #if !defined(MBEDTLS_NO_PLATFORM_ENTROPY)
     mbedtls_entropy_add_source( ctx, mbedtls_platform_entropy_poll, NULL,

library/entropy_poll.c

@@ -191,6 +191,23 @@ int mbedtls_platform_entropy_poll( void *data,
 #endif /* _WIN32 && !EFIX64 && !EFI32 */
 #endif /* !MBEDTLS_NO_PLATFORM_ENTROPY */
 
+#if defined(MBEDTLS_TEST_NULL_ENTROPY)
+int mbedtls_null_entropy_poll( void *data,
+                    unsigned char *output, size_t len, size_t *olen )
+{
+    ((void) data);
+    ((void) output);
+    *olen = 0;
+
+    if( len < sizeof(unsigned char) )
+        return( 0 );
+
+    *olen = sizeof(unsigned char);
+
+    return( 0 );
+}
+#endif
+
 #if defined(MBEDTLS_TIMING_C)
 int mbedtls_hardclock_poll( void *data,
                     unsigned char *output, size_t len, size_t *olen )

library/version_features.c

@@ -159,6 +159,12 @@ static const char *features[] = {
 #if defined(MBEDTLS_AES_DECRYPT_ALT)
     "MBEDTLS_AES_DECRYPT_ALT",
 #endif /* MBEDTLS_AES_DECRYPT_ALT */
+#if defined(MBEDTLS_TEST_NULL_ENTROPY)
+    "MBEDTLS_TEST_NULL_ENTROPY",
+#endif /* MBEDTLS_TEST_NULL_ENTROPY */
+#if defined(MBEDTLS_ENTROPY_NV_SEED)
+    "MBEDTLS_ENTROPY_NV_SEED",
+#endif /* MBEDTLS_ENTROPY_NV_SEED */
 #if defined(MBEDTLS_ENTROPY_HARDWARE_ALT)
     "MBEDTLS_ENTROPY_HARDWARE_ALT",
 #endif /* MBEDTLS_ENTROPY_HARDWARE_ALT */

scripts/config.pl

@@ -18,6 +18,7 @@
 #
 # Things that shouldn't be enabled with "full".
 #
+#   MBEDTLS_TEST_NULL_ENTROPY
 #   MBEDTLS_DEPRECATED_REMOVED
 #   MBEDTLS_HAVE_SSE2
 #   MBEDTLS_PLATFORM_NO_STD_FUNCTIONS
@@ -69,6 +70,7 @@ Options
 EOU
 
 my @excluded = qw(
+MBEDTLS_TEST_NULL_ENTROPY
 MBEDTLS_DEPRECATED_REMOVED
 MBEDTLS_HAVE_SSE2
 MBEDTLS_PLATFORM_NO_STD_FUNCTIONS

tests/scripts/all.sh

@@ -265,6 +265,22 @@ scripts/config.pl unset MBEDTLS_NET_C # getaddrinfo() undeclared, etc.
 scripts/config.pl set MBEDTLS_NO_PLATFORM_ENTROPY # uses syscall() on GNU/Linux
 CC=gcc CFLAGS='-Werror -O0 -std=c99 -pedantic' make lib
 
+msg "build: default config with  MBEDTLS_TEST_NULL_ENTROPY (ASan build)"
+cleanup
+cp "$CONFIG_H" "$CONFIG_BAK"
+scripts/config.pl set MBEDTLS_TEST_NULL_ENTROPY
+scripts/config.pl set MBEDTLS_NO_DEFAULT_ENTROPY_SOURCES
+scripts/config.pl set MBEDTLS_ENTROPY_C
+scripts/config.pl unset MBEDTLS_ENTROPY_NV_SEED
+scripts/config.pl unset MBEDTLS_ENTROPY_HARDWARE_ALT
+scripts/config.pl unset MBEDTLS_HAVEGE_C
+CC=gcc cmake -D CMAKE_C_FLAGS:String="-fsanitize=address -fno-common -O3" .
+make
+
+msg "test: MBEDTLS_TEST_NULL_ENTROPY - main suites and selftest (ASan build)"
+make test
+programs/test/selftest
+
 if uname -a | grep -F Linux >/dev/null; then
 msg "build/test: make shared" # ~ 40s
 cleanup