[Qemu-devel] [PATCH 1/2] libcacard: fix soft=... parsing in vcard_emul_options

[Christophe Fergeau]

The previous parser had copy and paste errors when computing
vname_length and type_params_length, "name" was used instead
of respectively vname and type_params. This led to length that could
be bigger than the input string, and to access out of the array
bounds when trying to copy these strings. valgrind rightfully
complained about this. It also didn't handle empty fields correctly,
and there were some args = strip(args++); which also didn't do what
was expected.

Since the token parsing is always the same, I factored all the
repetitive code in a NEXT_TOKEN macro.

Signed-off-by: Christophe Fergeau <address@hidden>
---
 libcacard/vcard_emul_nss.c |   90 +++++++++++++++++++-------------------------
 1 files changed, 39 insertions(+), 51 deletions(-)

diff --git a/libcacard/vcard_emul_nss.c b/libcacard/vcard_emul_nss.c
index f3db657..2a20bd6 100644
--- a/libcacard/vcard_emul_nss.c
+++ b/libcacard/vcard_emul_nss.c
@@ -975,13 +975,31 @@ find_blank(const char *str)
 static VCardEmulOptions options;
 #define READER_STEP 4
 
+/* Expects "args" to be at the beginning of a token (ie right after the ','
+ * ending the previous token), and puts the next token start in "token",
+ * and its length in "token_length". "token" will not be nul-terminated.
+ * After calling the macro, "args" will be advanced to the beginning of
+ * the next token.
+ * This macro may call continue or break.
+ */
+#define NEXT_TOKEN(token) \
+            (token) = args; \
+            args = strpbrk(args, ",)"); \
+            if (*args == 0) { \
+                break; \
+            } \
+            if (*args == ')') { \
+                args++; \
+                continue; \
+            } \
+            (token##_length) = args - (token); \
+            args = strip(args+1);
+
 VCardEmulOptions *
 vcard_emul_options(const char *args)
 {
     int reader_count = 0;
     VCardEmulOptions *opts;
-    char type_str[100];
-    int type_len;
 
     /* Allow the future use of allocating the options structure on the fly */
     memcpy(&options, &default_options, sizeof(options));
@@ -996,63 +1014,32 @@ vcard_emul_options(const char *args)
          *       cert_2,cert_3...) */
         if (strncmp(args, "soft=", 5) == 0) {
             const char *name;
+            size_t name_length;
             const char *vname;
+            size_t vname_length;
             const char *type_params;
+            size_t type_params_length;
+            char type_str[100];
             VCardEmulType type;
-            int name_length, vname_length, type_params_length, count, i;
+            int count, i;
             VirtualReaderOptions *vreaderOpt = NULL;
 
             args = strip(args + 5);
             if (*args != '(') {
                 continue;
             }
-            name = args;
-            args = strpbrk(args + 1, ",)");
-            if (*args == 0) {
-                break;
-            }
-            if (*args == ')') {
-                args++;
-                continue;
-            }
-            args = strip(args+1);
-            name_length = args - name - 2;
-            vname = args;
-            args = strpbrk(args + 1, ",)");
-            if (*args == 0) {
-                break;
-            }
-            if (*args == ')') {
-                args++;
-                continue;
-            }
-            vname_length = args - name - 2;
             args = strip(args+1);
-            type_len = strpbrk(args, ",)") - args;
-            assert(sizeof(type_str) > type_len);
-            strncpy(type_str, args, type_len);
-            type_str[type_len] = 0;
+
+            NEXT_TOKEN(name)
+            NEXT_TOKEN(vname)
+            NEXT_TOKEN(type_params)
+            type_params_length = MIN(type_params_length, sizeof(type_str)-1);
+            strncpy(type_str, type_params, type_params_length);
+            type_str[type_params_length] = 0;
             type = vcard_emul_type_from_string(type_str);
-            args = strpbrk(args, ",)");
-            if (*args == 0) {
-                break;
-            }
-            if (*args == ')') {
-                args++;
-                continue;
-            }
-            args = strip(args++);
-            type_params = args;
-            args = strpbrk(args + 1, ",)");
-            if (*args == 0) {
-                break;
-            }
-            if (*args == ')') {
-                args++;
-                continue;
-            }
-            type_params_length = args - name;
-            args = strip(args++);
+
+            NEXT_TOKEN(type_params)
+
             if (*args == 0) {
                 break;
             }
@@ -1072,13 +1059,14 @@ vcard_emul_options(const char *args)
             vreaderOpt->card_type = type;
             vreaderOpt->type_params =
                 copy_string(type_params, type_params_length);
-            count = count_tokens(args, ',', ')');
+            count = count_tokens(args, ',', ')') + 1;
             vreaderOpt->cert_count = count;
             vreaderOpt->cert_name = (char **)qemu_malloc(count*sizeof(char *));
             for (i = 0; i < count; i++) {
-                const char *cert = args + 1;
-                args = strpbrk(args + 1, ",)");
+                const char *cert = args;
+                args = strpbrk(args, ",)");
                 vreaderOpt->cert_name[i] = copy_string(cert, args - cert);
+                args = strip(args+1);
             }
             if (*args == ')') {
                 args++;
-- 
1.7.5.4