From: Matt Caswell <matt@openssl.org>
Date: Fri, 10 Mar 2017 10:51:35 +0000 (+0000)
Subject: Fix out-of-memory condition in conf
X-Git-Tag: OpenSSL_1_1_1-pre1~2065
X-Git-Url: https://git.openssl.org/gitweb/?p=openssl.git;a=commitdiff_plain;h=8a585601fea1091022034dd14b961c1ecd5916c3

Fix out-of-memory condition in conf

conf has the ability to expand variables in config files. Repeatedly doing
this can lead to an exponential increase in the amount of memory required.
This places a limit on the length of a value that can result from an
expansion.

Credit to OSS-Fuzz for finding this problem.

Reviewed-by: Rich Salz <rsalz@openssl.org>
Reviewed-by: Richard Levitte <levitte@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/2894)
---

diff --git a/crypto/conf/conf_def.c b/crypto/conf/conf_def.c
index 8861b3a5a0..a7b11d1598 100644
--- a/crypto/conf/conf_def.c
+++ b/crypto/conf/conf_def.c
@@ -20,6 +20,12 @@
 #include <openssl/buffer.h>
 #include <openssl/err.h>
 
+/*
+ * The maximum length we can grow a value to after variable expansion. 64k
+ * should be more than enough for all reasonable uses.
+ */
+#define MAX_CONF_VALUE_LENGTH       65536
+
 static char *eat_ws(CONF *conf, char *p);
 static char *eat_alpha_numeric(CONF *conf, char *p);
 static void clear_comments(CONF *conf, char *p);
@@ -457,6 +463,8 @@ static int str_copy(CONF *conf, char *section, char **pto, char *from)
         } else if (IS_EOF(conf, *from))
             break;
         else if (*from == '$') {
+            size_t newsize;
+
             /* try to expand it */
             rrp = NULL;
             s = &(from[1]);
@@ -511,8 +519,12 @@ static int str_copy(CONF *conf, char *section, char **pto, char *from)
                 CONFerr(CONF_F_STR_COPY, CONF_R_VARIABLE_HAS_NO_VALUE);
                 goto err;
             }
-            if (!BUF_MEM_grow_clean(buf,
-                        (strlen(p) + buf->length - (e - from)))) {
+            newsize = strlen(p) + buf->length - (e - from);
+            if (newsize > MAX_CONF_VALUE_LENGTH) {
+                CONFerr(CONF_F_STR_COPY, CONF_R_VARIABLE_EXPANSION_TOO_LONG);
+                goto err;
+            }
+            if (!BUF_MEM_grow_clean(buf, newsize)) {
                 CONFerr(CONF_F_STR_COPY, ERR_R_MALLOC_FAILURE);
                 goto err;
             }
diff --git a/crypto/conf/conf_err.c b/crypto/conf/conf_err.c
index b583c057cd..0863bc4d36 100644
--- a/crypto/conf/conf_err.c
+++ b/crypto/conf/conf_err.c
@@ -1,6 +1,6 @@
 /*
  * Generated by util/mkerr.pl DO NOT EDIT
- * Copyright 1995-2016 The OpenSSL Project Authors. All Rights Reserved.
+ * Copyright 1995-2017 The OpenSSL Project Authors. All Rights Reserved.
  *
  * Licensed under the OpenSSL license (the "License").  You may not use
  * this file except in compliance with the License.  You can obtain a copy
@@ -60,6 +60,8 @@ static ERR_STRING_DATA CONF_str_reasons[] = {
     {ERR_REASON(CONF_R_UNABLE_TO_CREATE_NEW_SECTION),
      "unable to create new section"},
     {ERR_REASON(CONF_R_UNKNOWN_MODULE_NAME), "unknown module name"},
+    {ERR_REASON(CONF_R_VARIABLE_EXPANSION_TOO_LONG),
+     "variable expansion too long"},
     {ERR_REASON(CONF_R_VARIABLE_HAS_NO_VALUE), "variable has no value"},
     {0, NULL}
 };
diff --git a/doc/man5/config.pod b/doc/man5/config.pod
index 24ebafb533..ba9a8ab174 100644
--- a/doc/man5/config.pod
+++ b/doc/man5/config.pod
@@ -44,7 +44,8 @@ or B<${section::name}>. By using the form B<$ENV::name> environment
 variables can be substituted. It is also possible to assign values to
 environment variables by using the name B<ENV::name>, this will work
 if the program looks up environment variables using the B<CONF> library
-instead of calling getenv() directly.
+instead of calling getenv() directly. The value string must not exceed 64k in
+length after variable expansion. Otherwise an error will occur.
 
 It is possible to escape certain characters by using any kind of quote
 or the B<\> character. By making the last character of a line a B<\>
diff --git a/fuzz/corpora/conf/0d7ad6e04c0235cdc590756ceec867a05cff5823 b/fuzz/corpora/conf/0d7ad6e04c0235cdc590756ceec867a05cff5823
new file mode 100644
index 0000000000..b0ed1912b2
--- /dev/null
+++ b/fuzz/corpora/conf/0d7ad6e04c0235cdc590756ceec867a05cff5823
@@ -0,0 +1,41 @@
+=;2I8
+=$$$$$$󠁉
+=$$$$$$$
+=$$$
+=$$$󠁷
+=$$$
+=$$$
+=$$$
+=
+=$$$
+=$$$
+=$$$󠁷
+=$$$
+=$$$
+=$$$
+=$$$
+=$$$$$$$
+=$$$
+=$$$
+=$$$
+=$$$
+=$$$
+=$$$
+=$$$$$$$
+=$$$
+=$$$
+=$$$
+=$$$
+=$$$
+=$
+=$$$
+=$$$$$$$
+=$$$
+=$󠁝$$
+=$$$
+=$$$
+=$$$
+=$$$
+=$$$
+=$$$
+=$$$$$
\ No newline at end of file
diff --git a/include/openssl/conf.h b/include/openssl/conf.h
index 462e3c9d39..980a51b157 100644
--- a/include/openssl/conf.h
+++ b/include/openssl/conf.h
@@ -208,6 +208,7 @@ int ERR_load_CONF_strings(void);
 # define CONF_R_NO_VALUE                                  108
 # define CONF_R_UNABLE_TO_CREATE_NEW_SECTION              103
 # define CONF_R_UNKNOWN_MODULE_NAME                       113
+# define CONF_R_VARIABLE_EXPANSION_TOO_LONG               116
 # define CONF_R_VARIABLE_HAS_NO_VALUE                     104
 
 # ifdef  __cplusplus