Factor out get_wwwroot_parent and test it.

.gitignore

@@ -9,4 +9,5 @@ devel/test.out.stdout
 devel/test.out.stderr
 devel/test_make_safe_uri
 devel/test_password_equal
+devel/test_get_wwwroot_parent
 devel/tmp.httpd.tests

darkhttpd.c

@@ -2916,6 +2916,38 @@ static void pidfile_create(void) {
 }
 /* [<-] end of pidfile helpers. */
 
+/* In the --single-file case, wwwroot is a path to a file.
+ * Return the parent dir of the wwwroot and mutate the wwwroot
+ * to just the filename. Caller must free the return value. */
+char* get_wwwroot_parent() {
+    off_t ofs;
+    size_t len = strlen(wwwroot) + 1;
+    if (len == 1) return xstrdup(".");
+    char *path = xstrdup(wwwroot);
+    for (ofs = strlen(wwwroot);
+            (ofs >= 0) && (wwwroot[ofs] != '/');
+            ofs--)
+        ;
+    /* wwwroot file is not in current directory */
+    if (ofs >= 0) {
+        path[ofs + 1] = '\0';
+        memmove(wwwroot, &wwwroot[ofs], len - ofs);
+    } else {
+        path[0] = '.';
+        path[1] = '\0';
+    }
+    return path;
+}
+
+static void xchroot(const char *path) {
+    if (chdir(path) == -1)
+        err(1, "chdir(%s)", path);
+    if (chroot(path) == -1)
+        err(1, "chroot(%s)", path);
+    printf("chrooted to `%s'\n", path);
+}
+
+/* chroot() into wwwroot. */
 static void change_root(void) {
     #ifdef HAVE_NON_ROOT_CHROOT
     /* We run this even as root, which should never be a bad thing. */
@@ -2927,33 +2959,11 @@ static void change_root(void) {
 
     tzset(); /* read /etc/localtime before we chroot */
     if (want_single_file) {
-        off_t ofs;
-        size_t len = strlen(wwwroot) + 1;
-        char *path = xstrdup(wwwroot);
-        for (ofs = strlen(wwwroot);
-             (ofs >= 0) && (wwwroot[ofs] != '/');
-             ofs--)
-            ;
-        /* wwwroot file is not in current directory */
-        if (ofs >= 0) {
-            path[ofs + 1] = '\0';
-            if (chdir(path) == -1)
-                err(1, "chdir(%s)", path);
-            memmove(wwwroot, &wwwroot[ofs], len - ofs);
-        } else {
-            path[0] = '.';
-            path[1] = '\0';
-        }
-        if (chroot(path) == -1)
-            err(1, "chroot(%s)", path);
-        printf("chrooted to `%s'\n", path);
+        char *path = get_wwwroot_parent();
+        xchroot(path);
         free(path);
     } else {
-        if (chdir(wwwroot) == -1)
-            err(1, "chdir(%s)", wwwroot);
-        if (chroot(wwwroot) == -1)
-            err(1, "chroot(%s)", wwwroot);
-        printf("chrooted to `%s'\n", wwwroot);
+        xchroot(wwwroot);
         wwwroot[0] = '\0'; /* empty string */
     }
 }

devel/Makefile

@@ -9,6 +9,12 @@ clean:
 		test.pyc \
 		test_make_safe_uri \
 		test_password_equal \
-		a.out darkhttpd.gcda darkhttpd.gcno \
-		fuzz_darkhttpd.o fuzz_llvm_make_safe_uri fuzz_socket
+		test_get_wwwroot_parent \
+		a.out \
+		darkhttpd.gcda \
+		darkhttpd.gcno \
+		fuzz_darkhttpd.o \
+		fuzz_llvm_make_safe_uri \
+		fuzz_socket \
+		fuzz_get_wwwroot_parent
 	rm -rf tmp.fuzz tmp.httpd.tests

devel/fuzz_get_wwwroot_parent.c

@@ -0,0 +1,20 @@
+#define main darkhttpd_main
+#include "../darkhttpd.c"
+#undef main
+
+char* sdup(const uint8_t *data, size_t size) {
+  char *buf = malloc(size + 1);
+  memcpy(buf, data, size);
+  buf[size] = 0;
+  return buf;
+}
+
+int LLVMFuzzerTestOneInput(const uint8_t *data, size_t size) {
+  wwwroot = sdup(data, size);
+  char *path = get_wwwroot_parent();
+  free(path);
+  free(wwwroot);
+  return 0;
+}
+
+/* vim:set ts=2 sw=2 sts=2 expandtab tw=78: */

devel/fuzz_get_wwwroot_parent.sh

@@ -0,0 +1,6 @@
+#!/bin/bash -e
+set -x
+clang -g -O -fsanitize=fuzzer,address \
+  fuzz_get_wwwroot_parent.c -o fuzz_get_wwwroot_parent
+mkdir -p fuzz_get_wwwroot_parent_testcases
+./fuzz_get_wwwroot_parent -only_ascii=1 $* fuzz_get_wwwroot_parent_testcases/

devel/run-tests

@@ -196,6 +196,14 @@ if ./test_password_equal | egrep '^FAIL:'; then
   exit 1
 fi
 
+echo "===> test_get_wwwroot_parent"
+$CC -g -O2 -fsanitize=address -fsanitize=undefined \
+  test_get_wwwroot_parent.c -o test_get_wwwroot_parent | exit 1
+if ./test_get_wwwroot_parent | egrep '^FAIL:'; then
+  echo test_get_wwwroot_parent failed >&2
+  exit 1
+fi
+
 # Check that the code builds with various defines.
 echo "===> building without -DDEBUG"
 $CC -O2 -Wall ../darkhttpd.c || exit 1
@@ -239,7 +247,7 @@ $CC -g -O2 -fprofile-arcs -ftest-coverage -fsanitize=address \
   exit 1
 }
 echo "===> generating report"
-gcov darkhttpd
+gcov a-darkhttpd
 chmod 755 $DIR/forbidden
 chmod 755 $DIR/unreadable
 rm -rf $DIR

devel/test_get_wwwroot_parent.c

@@ -0,0 +1,29 @@
+#define main _main_disabled_
+#include "../darkhttpd.c"
+#undef main
+
+static void test(const char* input_wwwroot, const char* expected_path,
+                 const char* expected_wwwroot) {
+  wwwroot = xstrdup(input_wwwroot);
+  char* path = get_wwwroot_parent();
+  int pass = (strcmp(path, expected_path) == 0) &&
+             (strcmp(wwwroot, expected_wwwroot) == 0);
+  printf("%s: \"%s\" -> \"%s\" : \"%s\"", pass ? "PASS" : "FAIL", input_wwwroot,
+         path, wwwroot);
+  if (!pass) {
+    printf(" (expected \"%s\" : \"%s\")", expected_path, expected_wwwroot);
+  }
+  printf("\n");
+  free(path);
+  free(wwwroot);
+}
+
+int main(void) {
+  test("", ".", "");
+  test(".", ".", ".");
+  test("dir/file", "dir/", "/file");
+  test("./a/b/c", "./a/b/", "/c");
+  return 0;
+}
+
+/* vim:set tabstop=4 shiftwidth=4 expandtab tw=78: */