From 3be59f968362b9405d81ec39388d9ed41ea3dc02 Mon Sep 17 00:00:00 2001
From: "Serge A. Zaitsev" <zaitsev.serge@gmail.com>
Date: Wed, 7 Jun 2017 17:36:37 +0200
Subject: [PATCH] fixed buffer overflow issues (#4), some formatting changes
 with newer clang-format

---
 tcl.c            | 37 ++++++++++++++++++++++++++-----------
 tcl_test.c       |  3 +++
 tcl_test_flow.h  |  1 +
 tcl_test_lexer.h |  4 ++--
 4 files changed, 32 insertions(+), 13 deletions(-)

diff --git a/tcl.c b/tcl.c
index 5028000..29dfc87 100644
--- a/tcl.c
+++ b/tcl.c
@@ -9,6 +9,8 @@
 #define DBG(...)
 #endif
 
+#define MAX_VAR_LENGTH 256
+
 struct tcl;
 int tcl_eval(struct tcl *tcl, const char *s, size_t len);
 
@@ -35,6 +37,8 @@ int tcl_next(const char *s, size_t n, const char **from, const char **to,
   char open;
   char close;
 
+  DBG("tcl_next(%.*s)+%d+%d|%d\n", n, s, *from - s, *to - s, *q);
+
   /* Skip leading spaces if not quoted */
   for (; !*q && n > 0 && tcl_is_space(*s); s++, n--)
     ;
@@ -101,9 +105,9 @@ struct tcl_parser {
 #define tcl_each(s, len, skiperr)                                              \
   for (struct tcl_parser p = {NULL, NULL, s, s + len, 0, TERROR};              \
        p.start < p.end &&                                                      \
-           (((p.token = tcl_next(p.start, p.end - p.start, &p.from, &p.to,     \
-                                 &p.q)) != TERROR) ||                          \
-            skiperr);                                                          \
+       (((p.token = tcl_next(p.start, p.end - p.start, &p.from, &p.to,         \
+                             &p.q)) != TERROR) ||                              \
+        skiperr);                                                              \
        p.start = p.to)
 
 /* ------------------------------------------------------- */
@@ -292,11 +296,19 @@ int tcl_subst(struct tcl *tcl, const char *s, size_t len) {
     return tcl_result(tcl, FNORMAL, tcl_alloc("", 0));
   }
   if (s[0] == '{') {
-    return tcl_result(tcl, FNORMAL, tcl_alloc(s + 1, len - 2));
+    if (len > 1) {
+      return tcl_result(tcl, FNORMAL, tcl_alloc(s + 1, len - 2));
+    } else {
+      return tcl_result(tcl, FERROR, tcl_alloc("", 0));
+    }
   } else if (s[0] == '$') {
-    char buf[256] = "set ";
-    strncat(buf, s+1, len-1);
-    return tcl_eval(tcl, buf, strlen(buf) + 1);
+    if (len < MAX_VAR_LENGTH) {
+      char buf[5 + MAX_VAR_LENGTH] = "set ";
+      strncat(buf, s + 1, len - 1);
+      return tcl_eval(tcl, buf, strlen(buf) + 1);
+    } else {
+      return tcl_result(tcl, FERROR, tcl_alloc("", 0));
+    }
   } else if (s[0] == '[') {
     tcl_value_t *expr = tcl_alloc(s + 1, len - 2);
     int r = tcl_eval(tcl, tcl_string(expr), tcl_length(expr) + 1);
@@ -312,7 +324,7 @@ int tcl_eval(struct tcl *tcl, const char *s, size_t len) {
   tcl_value_t *list = tcl_list_alloc();
   tcl_value_t *cur = NULL;
   tcl_each(s, len, 1) {
-    /*DBG("tcl_next %d %.*s\n", p.token, (int)(p.to - p.from), p.from);*/
+    DBG("tcl_next %d %.*s\n", p.token, (int)(p.to - p.from), p.from);
     switch (p.token) {
     case TERROR:
       DBG("eval: FERROR, lexer error\n");
@@ -546,12 +558,14 @@ static int tcl_cmd_math(struct tcl *tcl, tcl_value_t *args, void *arg) {
   char *p = buf + sizeof(buf) - 1;
   char neg = (c < 0);
   *p-- = 0;
-  if (neg) c = -c;
+  if (neg)
+    c = -c;
   do {
     *p-- = '0' + (c % 10);
     c = c / 10;
   } while (c > 0);
-  if (neg) *p-- = '-';
+  if (neg)
+    *p-- = '-';
   p++;
 
   tcl_free(opval);
@@ -623,6 +637,7 @@ int main() {
       if (p.token == TERROR && (p.to - buf) != i) {
         memset(buf, 0, buflen);
         i = 0;
+        break;
       } else if (p.token == TCMD && *(p.from) != '\0') {
         int r = tcl_eval(&tcl, buf, strlen(buf));
         if (r != FERROR) {
@@ -639,7 +654,7 @@ int main() {
     }
   }
 
-  if(i) {
+  if (i) {
     printf("incomplete input\n");
     return -1;
   }
diff --git a/tcl_test.c b/tcl_test.c
index fcd5a4e..371d6d4 100644
--- a/tcl_test.c
+++ b/tcl_test.c
@@ -11,8 +11,11 @@ int status = 0;
   } while (0)
 
 #include "tcl_test_lexer.h"
+
 #include "tcl_test_subst.h"
+
 #include "tcl_test_flow.h"
+
 #include "tcl_test_math.h"
 
 int main() {
diff --git a/tcl_test_flow.h b/tcl_test_flow.h
index c8f5332..4d82025 100644
--- a/tcl_test_flow.h
+++ b/tcl_test_flow.h
@@ -53,6 +53,7 @@ static void test_flow() {
                    "continue;}; puts \"I can compute that $a[]x$a = [square "
                    "$a]\" ; set a [+ $a 1]}",
              "0");
+
   tcl_destroy(&tcl);
 }
 
diff --git a/tcl_test_lexer.h b/tcl_test_lexer.h
index 3931360..610976c 100644
--- a/tcl_test_lexer.h
+++ b/tcl_test_lexer.h
@@ -1,9 +1,9 @@
 #ifndef TCL_TEST_LEXER_H
 #define TCL_TEST_LEXER_H
 
-#include <string.h>
-#include <stdarg.h>
 #include <assert.h>
+#include <stdarg.h>
+#include <string.h>
 
 static void va_check_tokens(const char *s, size_t len, int count, va_list ap) {
   int j = 0;