From 3efe53562fea2f4d71f0f620e10f4b5319b99fcb Mon Sep 17 00:00:00 2001
From: teor <teor@riseup.net>
Date: Mon, 18 May 2020 21:50:35 +1000
Subject: [PATCH] rust/protover: Fix protocol version support error handling

Make Rust protocol version support checks consistent with the
undocumented error behaviour of the corresponding C code.

Fixes bug 34251; bugfix on 0.3.3.5-rc.
---
 changes/bug34251         |  4 ++++
 src/core/or/protover.c   |  9 +++++++++
 src/rust/protover/ffi.rs | 10 +++++-----
 3 files changed, 18 insertions(+), 5 deletions(-)
 create mode 100644 changes/bug34251

diff --git a/changes/bug34251 b/changes/bug34251
new file mode 100644
index 0000000000..bbf0535256
--- /dev/null
+++ b/changes/bug34251
@@ -0,0 +1,4 @@
+  o Minor bugfixes (rust, protocol versions):
+    - Make Rust protocol version support checks consistent with the
+      undocumented error behaviour of the corresponding C code.
+      Fixes bug 34251; bugfix on 0.3.3.5-rc.
diff --git a/src/core/or/protover.c b/src/core/or/protover.c
index 43fb67772f..c6b0243693 100644
--- a/src/core/or/protover.c
+++ b/src/core/or/protover.c
@@ -326,6 +326,9 @@ protover_is_supported_here(protocol_type_t pr, uint32_t ver)
 /**
  * Return true iff "list" encodes a protocol list that includes support for
  * the indicated protocol and version.
+ *
+ * If the protocol list is unparseable, treat it as if it defines no
+ * protocols, and return 0.
  */
 int
 protocol_list_supports_protocol(const char *list, protocol_type_t tp,
@@ -348,6 +351,9 @@ protocol_list_supports_protocol(const char *list, protocol_type_t tp,
 /**
  * Return true iff "list" encodes a protocol list that includes support for
  * the indicated protocol and version, or some later version.
+ *
+ * If the protocol list is unparseable, treat it as if it defines no
+ * protocols, and return 0.
  */
 int
 protocol_list_supports_protocol_or_later(const char *list,
@@ -740,6 +746,9 @@ protover_compute_vote(const smartlist_t *list_of_proto_strings,
  * one that we support, and false otherwise.  If <b>missing_out</b> is
  * provided, set it to the list of protocols we do not support.
  *
+ * If the protocol version string is unparseable, treat it as if it defines no
+ * protocols, and return 1.
+ *
  * NOTE: This is quadratic, but we don't do it much: only a few times per
  * consensus. Checking signatures should be way more expensive than this
  * ever would be.
diff --git a/src/rust/protover/ffi.rs b/src/rust/protover/ffi.rs
index 14170d0353..2bf8d3a987 100644
--- a/src/rust/protover/ffi.rs
+++ b/src/rust/protover/ffi.rs
@@ -84,7 +84,7 @@ pub extern "C" fn protocol_list_supports_protocol(
     version: uint32_t,
 ) -> c_int {
     if c_protocol_list.is_null() {
-        return 1;
+        return 0;
     }
 
     // Require an unsafe block to read the version from a C string. The pointer
@@ -93,7 +93,7 @@ pub extern "C" fn protocol_list_supports_protocol(
 
     let protocol_list = match c_str.to_str() {
         Ok(n) => n,
-        Err(_) => return 1,
+        Err(_) => return 0,
     };
     let proto_entry: UnvalidatedProtoEntry = match protocol_list.parse() {
         Ok(n) => n,
@@ -140,7 +140,7 @@ pub extern "C" fn protocol_list_supports_protocol_or_later(
     version: uint32_t,
 ) -> c_int {
     if c_protocol_list.is_null() {
-        return 1;
+        return 0;
     }
 
     // Require an unsafe block to read the version from a C string. The pointer
@@ -149,7 +149,7 @@ pub extern "C" fn protocol_list_supports_protocol_or_later(
 
     let protocol_list = match c_str.to_str() {
         Ok(n) => n,
-        Err(_) => return 1,
+        Err(_) => return 0,
     };
 
     let protocol = match translate_to_rust(c_protocol) {
@@ -159,7 +159,7 @@ pub extern "C" fn protocol_list_supports_protocol_or_later(
 
     let proto_entry: UnvalidatedProtoEntry = match protocol_list.parse() {
         Ok(n) => n,
-        Err(_) => return 1,
+        Err(_) => return 0,
     };
 
     if proto_entry.supports_protocol_or_later(&protocol.into(), &version) {