hs-v3: Fix implicit ssize_t to size_t conversion

Found by Coverity.

Fixes #31682

Signed-off-by: David Goulet <dgoulet@torproject.org>

1 files changed, 21 insertions, 5 deletions

diff --git a/src/feature/hs/hs_cell.c b/src/feature/hs/hs_cell.c
index 547dda3e16..3147b898bc 100644
--- a/src/feature/hs/hs_cell.c
+++ b/src/feature/hs/hs_cell.c
@@ -495,11 +495,12 @@ build_establish_intro_dos_param(trn_cell_extension_dos_t *dos_ext,
 
 /* Build the DoS defense cell extension and put it in the given extensions
  * object. This can't fail. */
-static void
+static int
 build_establish_intro_dos_extension(const hs_service_config_t *service_config,
                                     trn_cell_extension_t *extensions)
 {
-  ssize_t ret, dos_ext_encoded_len;
+  ssize_t ret;
+  size_t dos_ext_encoded_len;
   uint8_t *field_array;
   trn_cell_extension_field_t *field;
   trn_cell_extension_dos_t *dos_ext;
@@ -526,7 +527,11 @@ build_establish_intro_dos_extension(const hs_service_config_t *service_config,
                                   service_config->intro_dos_burst_per_sec);
 
   /* Set the field with the encoded DoS extension. */
-  dos_ext_encoded_len = trn_cell_extension_dos_encoded_len(dos_ext);
+  ret = trn_cell_extension_dos_encoded_len(dos_ext);
+  if (BUG(ret <= 0)) {
+    return -1;
+  }
+  dos_ext_encoded_len = ret;
   /* Set length field and the field array size length. */
   trn_cell_extension_field_set_field_len(field, dos_ext_encoded_len);
   trn_cell_extension_field_setlen_field(field, dos_ext_encoded_len);
@@ -534,7 +539,10 @@ build_establish_intro_dos_extension(const hs_service_config_t *service_config,
   field_array = trn_cell_extension_field_getarray_field(field);
   ret = trn_cell_extension_dos_encode(field_array,
                  trn_cell_extension_field_getlen_field(field), dos_ext);
-  tor_assert(ret == dos_ext_encoded_len);
+  if (BUG(ret <= 0)) {
+    return -1;
+  }
+  tor_assert(ret == (ssize_t) dos_ext_encoded_len);
 
   /* Finally, encode field into the cell extension. */
   trn_cell_extension_add_fields(extensions, field);
@@ -546,6 +554,8 @@ build_establish_intro_dos_extension(const hs_service_config_t *service_config,
 
   /* Cleanup. DoS extension has been encoded at this point. */
   trn_cell_extension_dos_free(dos_ext);
+
+  return 0;
 }
 
 /* ========== */
@@ -558,6 +568,7 @@ STATIC trn_cell_extension_t *
 build_establish_intro_extensions(const hs_service_config_t *service_config,
                                  const hs_service_intro_point_t *ip)
 {
+  int ret;
   trn_cell_extension_t *extensions;
 
   tor_assert(service_config);
@@ -571,9 +582,14 @@ build_establish_intro_extensions(const hs_service_config_t *service_config,
   if (service_config->has_dos_defense_enabled &&
       ip->support_intro2_dos_defense) {
     /* This function takes care to increment the number of extensions. */
-    build_establish_intro_dos_extension(service_config, extensions);
+    ret = build_establish_intro_dos_extension(service_config, extensions);
+    if (ret < 0) {
+      /* Return no extensions on error. */
+      goto end;
+    }
   }
 
+ end:
   return extensions;
 }