From 7c476394e799f39f749d7a7a50f62e5d3ec8db61 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Petr=20P=C3=ADsa=C5=99?= <ppisar@redhat.com>
Date: Mon, 19 May 2025 13:49:32 +0200
Subject: [PATCH] Fix size_t overflow in Malloc() argument in ReadParams()
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There were still two issues after commit
b0eabcaf4d4f371514891a52115c746815c2ff15 (Update fcgiapp.c, Fixing an
integer overflow (CVE-2025-23016)):

* Signed int overflow in "nameLen + valueLen + 2" expression.

* Sizes of size_t and int types are in general unrelated.

This fix resolves both of the issues.

Related to CVE-2025-23016.
Resolve #67.
<https://github.com/FastCGI-Archives/fcgi2/pull/77>

Signed-off-by: Petr Písař <ppisar@redhat.com>
---
 libfcgi/fcgiapp.c | 13 ++++++++++---
 1 file changed, 10 insertions(+), 3 deletions(-)

diff --git a/fcgiapp.c b/fcgiapp.c
index 99c3630..0cd3dd1 100644
--- a/fcgiapp.c
+++ b/fcgiapp.c
@@ -18,6 +18,7 @@
 #include <memory.h>     /* for memchr() */
 #include <stdarg.h>
 #include <stdio.h>
+#include <stdint.h>
 #include <stdlib.h>
 #include <string.h>
 #include <sys/types.h>
@@ -1160,6 +1161,7 @@ char *FCGX_GetParam(const char *name, FCGX_ParamArray envp)
 static int ReadParams(Params *paramsPtr, FCGX_Stream *stream)
 {
     int nameLen, valueLen;
+    size_t totalLen;
     unsigned char lenBuff[3];
     char *nameValue;
 
@@ -1175,7 +1177,7 @@ static int ReadParams(Params *paramsPtr, FCGX_Stream *stream)
 	    }
             nameLen = ((nameLen & 0x7f) << 24) + (lenBuff[0] << 16)
                     + (lenBuff[1] << 8) + lenBuff[2];
-	    if (nameLen >= INT_MAX) {
+	    if (nameLen >= INT_MAX || nameLen >= SIZE_MAX) {
                 SetError(stream, FCGX_PARAMS_ERROR);
                 return -1;
 	    }
@@ -1191,16 +1193,21 @@ static int ReadParams(Params *paramsPtr, FCGX_Stream *stream)
 	    }
             valueLen = ((valueLen & 0x7f) << 24) + (lenBuff[0] << 16)
                     + (lenBuff[1] << 8) + lenBuff[2];
-	    if (valueLen >= INT_MAX) {
+	    if (valueLen >= INT_MAX || valueLen >= SIZE_MAX) {
                 SetError(stream, FCGX_PARAMS_ERROR);
                 return -1;
 	    }
         }
+        totalLen = (size_t)nameLen + (size_t)valueLen + 2u;
+        if (totalLen < (size_t)nameLen || totalLen < (size_t)valueLen) {
+            SetError(stream, FCGX_PARAMS_ERROR);
+            return -1;
+        }
         /*
          * nameLen and valueLen are now valid; read the name and value
          * from stream and construct a standard environment entry.
          */
-        nameValue = (char *)Malloc(nameLen + valueLen + 2);
+        nameValue = (char *)Malloc(totalLen);
         if(FCGX_GetStr(nameValue, nameLen, stream) != nameLen) {
             SetError(stream, FCGX_PARAMS_ERROR);
             free(nameValue);
-- 
2.49.0