1 files changed, 244 insertions, 0 deletions
diff --git a/src/lib/tls/nss_countbytes.c b/src/lib/tls/nss_countbytes.c
new file mode 100644
index 0000000000..c727684529
--- /dev/null
+++ b/src/lib/tls/nss_countbytes.c
@@ -0,0 +1,244 @@
+/* Copyright 2018, The Tor Project Inc. */
+/* See LICENSE for licensing information */
+
+/**
+ * \file nss_countbytes.c
+ * \brief A PRFileDesc layer to let us count the number of bytes
+ *        bytes actually written on a PRFileDesc.
+ **/
+
+#include "orconfig.h"
+
+#include "lib/log/util_bug.h"
+#include "lib/malloc/malloc.h"
+#include "lib/tls/nss_countbytes.h"
+
+#include <stdlib.h>
+#include <string.h>
+
+#include <prio.h>
+
+/** Boolean: have we initialized this module */
+static bool countbytes_initialized = false;
+
+/** Integer to identity this layer. */
+static PRDescIdentity countbytes_layer_id = PR_INVALID_IO_LAYER;
+
+/** Table of methods for this layer.*/
+static PRIOMethods countbytes_methods;
+
+/** Default close function provided by NSPR.  We use this to help
+ *  implement our own close function.*/
+static PRStatus(*default_close_fn)(PRFileDesc *fd);
+
+static PRStatus countbytes_close_fn(PRFileDesc *fd);
+static PRInt32 countbytes_read_fn(PRFileDesc *fd, void *buf, PRInt32 amount);
+static PRInt32 countbytes_write_fn(PRFileDesc *fd, const void *buf,
+                                   PRInt32 amount);
+static PRInt32 countbytes_writev_fn(PRFileDesc *fd, const PRIOVec *iov,
+                                    PRInt32 size, PRIntervalTime timeout);
+static PRInt32 countbytes_send_fn(PRFileDesc *fd, const void *buf,
+                                  PRInt32 amount, PRIntn flags,
+                                  PRIntervalTime timeout);
+static PRInt32 countbytes_recv_fn(PRFileDesc *fd, void *buf, PRInt32 amount,
+                                  PRIntn flags, PRIntervalTime timeout);
+
+/** Private fields for the byte-counter layer.  We cast this to and from
+ * PRFilePrivate*, which is supposed to be allowed. */
+typedef struct tor_nss_bytecounts_t {
+  uint64_t n_read;
+  uint64_t n_written;
+} tor_nss_bytecounts_t;
+
+/**
+ * Initialize this module, if it is not already initialized.
+ **/
+void
+tor_nss_countbytes_init(void)
+{
+  if (countbytes_initialized)
+    return;
+
+  countbytes_layer_id = PR_GetUniqueIdentity("Tor byte-counting layer");
+  tor_assert(countbytes_layer_id != PR_INVALID_IO_LAYER);
+
+  memcpy(&countbytes_methods, PR_GetDefaultIOMethods(), sizeof(PRIOMethods));
+
+  default_close_fn = countbytes_methods.close;
+  countbytes_methods.close = countbytes_close_fn;
+  countbytes_methods.read = countbytes_read_fn;
+  countbytes_methods.write = countbytes_write_fn;
+  countbytes_methods.writev = countbytes_writev_fn;
+  countbytes_methods.send = countbytes_send_fn;
+  countbytes_methods.recv = countbytes_recv_fn;
+  /* NOTE: We aren't wrapping recvfrom, sendto, or sendfile, since I think
+   * NSS won't be using them for TLS connections. */
+
+  countbytes_initialized = true;
+}
+
+/**
+ * Return the tor_nss_bytecounts_t object for a given IO layer. Asserts that
+ * the IO layer is in fact a layer created by this module.
+ */
+static tor_nss_bytecounts_t *
+get_counts(PRFileDesc *fd)
+{
+  tor_assert(fd->identity == countbytes_layer_id);
+  return (tor_nss_bytecounts_t*) fd->secret;
+}
+
+/** Helper: increment the read-count of an fd by n. */
+#define INC_READ(fd, n) STMT_BEGIN                      \
+    get_counts(fd)->n_read += (n);                      \
+  STMT_END
+
+/** Helper: increment the write-count of an fd by n. */
+#define INC_WRITTEN(fd, n) STMT_BEGIN                      \
+    get_counts(fd)->n_written += (n);                      \
+  STMT_END
+
+/** Implementation for PR_Close: frees the 'secret' field, then passes control
+ * to the default close function */
+static PRStatus
+countbytes_close_fn(PRFileDesc *fd)
+{
+  tor_assert(fd);
+
+  tor_nss_bytecounts_t *counts = (tor_nss_bytecounts_t *)fd->secret;
+  tor_free(counts);
+  fd->secret = NULL;
+
+  return default_close_fn(fd);
+}
+
+/** Implementation for PR_Read: Calls the lower-level read function,
+ * and records what it said. */
+static PRInt32
+countbytes_read_fn(PRFileDesc *fd, void *buf, PRInt32 amount)
+{
+  tor_assert(fd);
+  tor_assert(fd->lower);
+
+  PRInt32 result = (fd->lower->methods->read)(fd->lower, buf, amount);
+  if (result > 0)
+    INC_READ(fd, result);
+  return result;
+}
+/** Implementation for PR_Write: Calls the lower-level write function,
+ * and records what it said. */
+static PRInt32
+countbytes_write_fn(PRFileDesc *fd, const void *buf, PRInt32 amount)
+{
+  tor_assert(fd);
+  tor_assert(fd->lower);
+
+  PRInt32 result = (fd->lower->methods->write)(fd->lower, buf, amount);
+  if (result > 0)
+    INC_WRITTEN(fd, result);
+  return result;
+}
+/** Implementation for PR_Writev: Calls the lower-level writev function,
+ * and records what it said. */
+static PRInt32
+countbytes_writev_fn(PRFileDesc *fd, const PRIOVec *iov,
+                     PRInt32 size, PRIntervalTime timeout)
+{
+  tor_assert(fd);
+  tor_assert(fd->lower);
+
+  PRInt32 result = (fd->lower->methods->writev)(fd->lower, iov, size, timeout);
+  if (result > 0)
+    INC_WRITTEN(fd, result);
+  return result;
+}
+/** Implementation for PR_Send: Calls the lower-level send function,
+ * and records what it said. */
+static PRInt32
+countbytes_send_fn(PRFileDesc *fd, const void *buf,
+                   PRInt32 amount, PRIntn flags, PRIntervalTime timeout)
+{
+  tor_assert(fd);
+  tor_assert(fd->lower);
+
+  PRInt32 result = (fd->lower->methods->send)(fd->lower, buf, amount, flags,
+                                              timeout);
+  if (result > 0)
+    INC_WRITTEN(fd, result);
+  return result;
+}
+/** Implementation for PR_Recv: Calls the lower-level recv function,
+ * and records what it said. */
+static PRInt32
+countbytes_recv_fn(PRFileDesc *fd, void *buf, PRInt32 amount,
+                                  PRIntn flags, PRIntervalTime timeout)
+{
+  tor_assert(fd);
+  tor_assert(fd->lower);
+
+  PRInt32 result = (fd->lower->methods->recv)(fd->lower, buf, amount, flags,
+                                              timeout);
+  if (result > 0)
+    INC_READ(fd, result);
+  return result;
+}
+
+/**
+ * Wrap a PRFileDesc from NSPR with a new PRFileDesc that will count the
+ * total number of bytes read and written.  Return the new PRFileDesc.
+ *
+ * This function takes ownership of its input.
+ */
+PRFileDesc *
+tor_wrap_prfiledesc_with_byte_counter(PRFileDesc *stack)
+{
+  if (BUG(! countbytes_initialized)) {
+    tor_nss_countbytes_init();
+  }
+
+  tor_nss_bytecounts_t *bytecounts = tor_malloc_zero(sizeof(*bytecounts));
+
+  PRFileDesc *newfd = PR_CreateIOLayerStub(countbytes_layer_id,
+                                           &countbytes_methods);
+  tor_assert(newfd);
+  newfd->secret = (PRFilePrivate *)bytecounts;
+
+  /* This does some complicated messing around with the headers of these
+     objects; see the NSPR documentation for more. The upshot is that
+     after PushIOLayer, "stack" will be the head of the stack.
+  */
+  PRStatus status = PR_PushIOLayer(stack, PR_TOP_IO_LAYER, newfd);
+  tor_assert(status == PR_SUCCESS);
+
+  return stack;
+}
+
+/**
+ * Given a PRFileDesc returned by tor_wrap_prfiledesc_with_byte_counter(),
+ * or another PRFileDesc wrapping that PRFileDesc, set the provided
+ * pointers to the number of bytes read and written on the descriptor since
+ * it was created.
+ *
+ * Return 0 on success, -1 on failure.
+ */
+int
+tor_get_prfiledesc_byte_counts(PRFileDesc *fd,
+                               uint64_t *n_read_out,
+                               uint64_t *n_written_out)
+{
+  if (BUG(! countbytes_initialized)) {
+    tor_nss_countbytes_init();
+  }
+
+  tor_assert(fd);
+  PRFileDesc *bclayer = PR_GetIdentitiesLayer(fd, countbytes_layer_id);
+  if (BUG(bclayer == NULL))
+    return -1;
+
+  tor_nss_bytecounts_t *counts = get_counts(bclayer);
+
+  *n_read_out = counts->n_read;
+  *n_written_out = counts->n_written;
+
+  return 0;
+}