Fix out-of-bounds heap write in string encoder

.github/workflows/ci.yml

@@ -30,30 +30,20 @@ jobs:
       run: |
         make REBAR=${{matrix.rebar}} check
 
-  # Keep this no more than 2 releases away from EQC-mini beam files. Currently
-  # they are on OTP 25 so we can use erlang up to version 27 technically.
-  #
-  eqc-mini-25:
-    name: eqc-mini-25
-    runs-on: ubuntu-latest
-    container:
-      image: erlang:25
-    steps:
-      - uses: actions/checkout@v6
-      - name: rebar3 make check-with-eqc
-        run: |
-          make REBAR=rebar3 check-with-eqc
-
-  eqc-mini-27:
-    name: eqc-mini-27
+  prop-tests:
+    name: proper-${{matrix.otp_version}}
     runs-on: ubuntu-latest
+    strategy:
+      fail-fast: false
+      matrix:
+        otp_version: [27, 28]
     container:
-      image: erlang:27
+      image: erlang:${{matrix.otp_version}}
     steps:
       - uses: actions/checkout@v6
-      - name: rebar3 make check-with-eqc
+      - name: rebar3 make check-with-proper
         run: |
-          make REBAR=rebar3 check-with-eqc
+          make REBAR=rebar3 check-with-proper
 
   lcov-coverage:
     name: lcov-coverage

.gitignore

@@ -15,13 +15,10 @@ erln8.config
 hexer.config
 rebar.lock
 TEST-*.xml
-/eqc/
 /bench/
 coverage.info
 coverage-jiffy.info
 coverage-html/
-.eqc-info
-current_counterexample.eqc
 *.gcda
 *.gcno
 .cache

Makefile

@@ -9,7 +9,6 @@ clean:
 	rm -rf logs
 	rm -rf .eunit
 	rm -f test/*.beam
-	rm -rf eqc
 	rm -rf _build
 	rm -f c_src/*.gcno c_src/*.gcda c_src/ryu/*.gcno c_src/ryu/*.gcda
 	rm -f coverage.info coverage-jiffy.info
@@ -30,10 +29,8 @@ eunit:
 
 check: build eunit
 
-check-with-eqc: install_eqc build eunit
-
-install_eqc:
-	./test/install_eqc_mini.sh
+check-with-proper:
+	$(REBAR) as proper eunit
 
 # macos:
 #   brew install lcov on macos
@@ -42,7 +39,7 @@ install_eqc:
 #
 coverage:
 	$(MAKE) clean
-	CFLAGS="--coverage -O0" CXXFLAGS="--coverage -O0" LDFLAGS="--coverage" $(MAKE) check-with-eqc
+	CFLAGS="--coverage -O0" CXXFLAGS="--coverage -O0" LDFLAGS="--coverage" $(MAKE) check-with-proper
 	@lcov --capture --directory c_src -o coverage.info --ignore-errors inconsistent,unsupported
 	@lcov --extract coverage.info '*/c_src/*' --exclude '*/ryu/*' -o coverage-jiffy.info --ignore-errors inconsistent,unsupported
 	@genhtml coverage-jiffy.info -o coverage-html --title "jiffy lcov report"
@@ -56,4 +53,4 @@ release:
 	erlc -o test/ $<
 
 
-.PHONY: all clean distclean depends build etap eunit check coverage
+.PHONY: all clean distclean depends build etap eunit check check-with-proper coverage

c_src/encoder.c

@@ -276,8 +276,16 @@ enc_ensure(Encoder* e, size_t req)
             return 0;
         }
 
+        // If we have_buffer we don't want to short-cut return unless that
+        // buffer size is big enough. If it isn't, release it and allocate a
+        // newer one of the right size. Otherwise we could return a small
+        // buffer then risk a memory overrwrite on a memcpy.
         if(e->have_buffer) {
-            return 1;
+            if(req < (e->buffer.size - e->i)) {
+                return 1;
+            }
+            enif_release_binary(&e->buffer);
+            e->have_buffer = 0;
         }
     }
 

rebar.config

@@ -17,3 +17,12 @@
 {eunit_opts, [
     verbose
 ]}.
+
+% Use in CI only. It's totaly optional
+%
+{profiles, [
+    {proper, [
+        {deps, [{proper, "1.5.0"}]},
+        {erl_opts, [{d, 'WITH_PROPER'}]}
+    ]}
+]}.

rebar.config.script

@@ -2,31 +2,6 @@
 % See the LICENSE file for more information.
 %
 
-% Only run the EQC checks when EQC is present.
-%
-% We have a helper tests/install_eqc_mini.sh script to install it ./eqc, so we
-% look for it there first, and add that to the code path. Users may have also
-% installed it directly into their OTP distribution, which should be fine,
-% code:which(eqc) should find that as well.
-%
-LocalEQC = filename:join([filename:dirname(SCRIPT), "eqc", "ebin"]),
-case filelib:is_dir(LocalEQC) of
-    true -> code:add_patha(LocalEQC);
-    false -> ok
-end,
-HaveEQC = code:which(eqc) =/= non_existing,
-ErlOpts = if not HaveEQC -> []; true ->
-    [{d, 'HAVE_EQC'}]
-end,
-
-Config1 = case lists:keyfind(erl_opts, 1, CONFIG) of
-    {erl_opts, Opts} ->
-        NewOpts = {erl_opts, Opts ++ ErlOpts},
-        lists:keyreplace(erl_opts, 1, CONFIG, NewOpts);
-    false ->
-        CONFIG ++ [{erl_opts, ErlOpts}]
-end,
-
 IsRebar2 = case lists:keyfind(rebar, 1, application:loaded_applications()) of
     {rebar, _Desc, Vsn} ->
         case string:split(Vsn, ".") of
@@ -39,9 +14,9 @@ end,
 
 case IsRebar2 of
     true ->
-        Config1;
+        CONFIG;
     false ->
-        Config1 ++ [
+        CONFIG ++ [
             {plugins, [{pc, "~> 1.15"}]},
             case os:type() of
                 {win32, _} -> {artifacts, ["priv/jiffy.dll"]};