CDRIVER-4231: New random generation of OID values (#931)

* New random generation of OID values [Fixes CDRIVER-4231]

* Restore hashing of machine attributes, plus an atomic init-counter,
  plus the process ID.
* Instead of MD5 hashing, use SipHash.
* No more magic numbers, make bson-context -Wconversion clean, comment what's happening in the random init.
* Remove old deprecated docs and no-op tests.
* Host name mocking is gone

Author: vector-of-bool

src/libbson/CMakeLists.txt

@@ -70,13 +70,6 @@ else ()
    set (BSON_HAVE_GMTIME_R 1)
 endif ()
 
-CHECK_SYMBOL_EXISTS (arc4random_buf stdlib.h BSON_HAVE_ARC4RANDOM_BUF)
-if (NOT BSON_HAVE_ARC4RANDOM_BUF)
-   set (BSON_HAVE_ARC4RANDOM_BUF 0)
-else ()
-   set (BSON_HAVE_ARC4RANDOM_BUF 1)
-endif ()
-
 CHECK_FUNCTION_EXISTS (rand_r BSON_HAVE_RAND_R)
 if (NOT BSON_HAVE_RAND_R)
    set (BSON_HAVE_RAND_R 0)
@@ -109,7 +102,6 @@ CHECK_INCLUDE_FILE (stdbool.h BSON_HAVE_STDBOOL_H)
 if (MSVC)
    set (BSON_HAVE_CLOCK_GETTIME 0)
    set (BSON_HAVE_STRNLEN 0)
-   set (BSON_HAVE_SYSCALL_TID 0)
 else ()
    check_symbol_exists (clock_gettime time.h BSON_HAVE_CLOCK_GETTIME)
    if (NOT BSON_HAVE_CLOCK_GETTIME)
@@ -119,11 +111,6 @@ else ()
    if (NOT BSON_HAVE_STRNLEN)
       set (BSON_HAVE_STRNLEN 0)
    endif ()
-   CHECK_SYMBOL_EXISTS (SYS_gettid sys/syscall.h BSON_HAVE_SYSCALL_TID)
-   check_symbol_exists (syscall unistd.h _TMP_HAVE_SYSCALL)
-   if (NOT BSON_HAVE_SYSCALL_TID OR NOT _TMP_HAVE_SYSCALL OR APPLE OR ANDROID)
-      set (BSON_HAVE_SYSCALL_TID 0)
-   endif ()
 endif ()
 
 if (BSON_BIG_ENDIAN)

src/libbson/doc/bson_context_new.rst

@@ -18,11 +18,14 @@ Parameters
 
 The following ``flags`` may be used:
 * ``BSON_CONTEXT_NONE`` meaning creating ObjectIDs with this context is not a thread-safe operation.
-* ``BSON_CONTEXT_THREAD_SAFE`` meaning creating ObjectIDs with this context is a thread-safe operation.
 * ``BSON_CONTEXT_DISABLE_PID_CACHE`` meaning creating ObjectIDs will also check if the process has
 changed by calling ``getpid()`` on every ObjectID generation.
 
-To use multiple flags, xor them together.
+The following flags are deprecated and have no effect:
+
+- ``BSON_CONTEXT_DISABLE_HOST_CACHE``
+- ``BSON_CONTEXT_THREAD_SAFE``
+- ``BSON_CONTEXT_USE_TASK_ID``
 
 Description
 -----------

src/libbson/doc/bson_context_t.rst

@@ -14,12 +14,7 @@ Synopsis
 
   typedef enum {
     BSON_CONTEXT_NONE = 0,
-    BSON_CONTEXT_THREAD_SAFE = (1 << 0),
-    BSON_CONTEXT_DISABLE_HOST_CACHE = (1 << 1),
     BSON_CONTEXT_DISABLE_PID_CACHE = (1 << 2),
-  #ifdef BSON_HAVE_SYSCALL_TID
-    BSON_CONTEXT_USE_TASK_ID = (1 << 3),
-  #endif
   } bson_context_flags_t;
 
   typedef struct _bson_context_t bson_context_t;
@@ -69,7 +64,7 @@ Example
      bson_oid_init (&oid, NULL);
 
      /* specify a local context for additional control */
-     ctx = bson_context_new (BSON_CONTEXT_THREAD_SAFE);
+     ctx = bson_context_new (BSON_CONTEXT_NONE);
      bson_oid_init (&oid, ctx);
 
      bson_context_destroy (ctx);

src/libbson/src/bson/bson-config.h.in

@@ -105,24 +105,6 @@
 #endif
 
 
-/*
- * Define to 1 if you have SYS_gettid syscall
- */
-#define BSON_HAVE_SYSCALL_TID @BSON_HAVE_SYSCALL_TID@
-#if BSON_HAVE_SYSCALL_TID != 1
-# undef BSON_HAVE_SYSCALL_TID
-#endif
-
-
-/*
- * Define to 1 if you have arc4random_buf available on your platform.
- */
-#define BSON_HAVE_ARC4RANDOM_BUF @BSON_HAVE_ARC4RANDOM_BUF@
-#if BSON_HAVE_ARC4RANDOM_BUF != 1
-# undef BSON_HAVE_ARC4RANDOM_BUF
-#endif
-
-
 /*
  * Define to 1 if you have rand_r available on your platform.
  */

src/libbson/src/bson/bson-context-private.h

@@ -28,24 +28,55 @@
 BSON_BEGIN_DECLS
 
 
+enum {
+   BSON_OID_RANDOMESS_OFFSET = 4,
+   BSON_OID_RANDOMNESS_SIZE = 5,
+   BSON_OID_SEQ32_OFFSET = 9,
+   BSON_OID_SEQ32_SIZE = 3,
+   BSON_OID_SEQ64_OFFSET = 4,
+   BSON_OID_SEQ64_SIZE = 8
+};
+
 struct _bson_context_t {
    /* flags are defined in bson_context_flags_t */
    int flags;
-   int32_t seq32;
-   int64_t seq64;
-   uint8_t rand[5];
-   uint16_t pid;
-
-   void (*oid_set_seq32) (bson_context_t *context, bson_oid_t *oid);
-   void (*oid_set_seq64) (bson_context_t *context, bson_oid_t *oid);
-
-   /* this function pointer allows us to mock gethostname for testing. */
-   void (*gethostname) (char *out);
+   uint32_t seq32;
+   uint64_t seq64;
+   uint8_t randomness[BSON_OID_RANDOMNESS_SIZE];
+   uint64_t pid;
 };
 
+/**
+ * @brief Insert the context's randomness data into the given OID
+ *
+ * @param context A context for some random data
+ * @param oid The OID to update.
+ */
 void
 _bson_context_set_oid_rand (bson_context_t *context, bson_oid_t *oid);
 
+/**
+ * @brief Insert the context's sequence counter into the given OID. Increments
+ * the context's sequence counter.
+ *
+ * @param context The context with the counter to get+update
+ * @param oid The OID to modify
+ */
+void
+_bson_context_set_oid_seq32 (bson_context_t *context, bson_oid_t *oid);
+
+/**
+ * @brief Write a 64-bit counter from the given context into the OID. Increments
+ * the context's sequence counter.
+ *
+ * @param context The context with the counter to get+update
+ * @param oid The OID to modify
+ *
+ * @note Only used by the deprecated @ref bson_oid_init_sequence
+ */
+void
+_bson_context_set_oid_seq64 (bson_context_t *context, bson_oid_t *oid);
+
 
 BSON_END_DECLS