FauxFauxGH-79: backport supposed fix for CVE-2013-4852

"Add an assortment of extra safety checks." Direct cherry-pick of svn://svn.tartarus.org/sgt/putty@9896
soarqin · Aug 5, 2013 · 76ba385 · 76ba385
1 parent 1513cc4
commit 76ba385
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Showing 3 changed files with 6 additions and 2 deletions.
diff --git a/import.c b/import.c
@@ -290,7 +290,7 @@ static int ssh2_read_mpint(void *data, int len, struct mpint_pos *ret)
     if (len < 4)
         goto error;
     bytes = GET_32BIT(d);
-    if (len < 4+bytes)
+    if (bytes < 0 || len-4 < bytes)
         goto error;
 
     ret->start = d + 4;

diff --git a/sshdss.c b/sshdss.c
@@ -43,6 +43,8 @@ static void getstring(char **data, int *datalen, char **p, int *length)
     if (*datalen < 4)
 	return;
     *length = GET_32BIT(*data);
+    if (*length < 0)
+        return;
     *datalen -= 4;
     *data += 4;
     if (*datalen < *length)
@@ -98,7 +100,7 @@ static void *dss_newkey(char *data, int len)
     }
 #endif
 
-    if (!p || memcmp(p, "ssh-dss", 7)) {
+    if (!p || slen != 7 || memcmp(p, "ssh-dss", 7)) {
 	sfree(dss);
 	return NULL;
     }

diff --git a/sshrsa.c b/sshrsa.c
@@ -526,6 +526,8 @@ static void getstring(char **data, int *datalen, char **p, int *length)
     if (*datalen < 4)
 	return;
     *length = GET_32BIT(*data);
+    if (*length < 0)
+        return;
     *datalen -= 4;
     *data += 4;
     if (*datalen < *length)