CVE-2021-32792 (published 2021-07-26T17:15Z)

mod_auth_openidc is an authentication/authorization module for the Apache 2.x HTTP server that functions as an OpenID Connect Relying Party, authenticating users against an OpenID Connect Provider. In mod_auth_openidc before version 2.4.9, there is an XSS vulnerability in when using `OIDCPreservePost On`.

Severity: MEDIUM
CVSS v2 base score: 4.3 (AV:N/AC:M/Au:N/C:N/I:P/A:N)
CVSS v3 base score: 6.1, MEDIUM (CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N)

Weakness information:
cwe_id: CWE-79
cwe_name: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
description: The product does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users.
extended_description: 
            Cross-site scripting (XSS) vulnerabilities occur when:
            
               Untrusted data enters a web application, typically from a web request.
               The web application dynamically generates a web page that contains this untrusted data.
               During page generation, the application does not prevent the data from containing content that is executable by a web browser, such as JavaScript, HTML tags, HTML attributes, mouse events, Flash, ActiveX, etc.
               A victim visits the generated web page through a web browser, which contains malicious script that was injected using the untrusted data.
               Since the script comes from a web page that was sent by the web server, the victim's web browser executes the malicious script in the context of the web server's domain.
               This effectively violates the intention of the web browser's same-origin policy, which states that scripts in one domain should not be able to access resources or run code in a different domain.
            
            There are three main kinds of XSS:
            
               
                  Type 1: Reflected XSS (or Non-Persistent) - 
         			The server reads data directly from the HTTP request and reflects it back in the HTTP response. Reflected XSS exploits occur when an attacker causes a victim to supply dangerous content to a vulnerable web application, which is then reflected back to the victim and executed by the web browser. The most common mechanism for delivering malicious content is to include it as a parameter in a URL that is posted publicly or e-mailed directly to the victim. URLs constructed in this manner constitute the core of many phishing schemes, whereby an attacker convinces a victim to visit a URL that refers to a vulnerable site. After the site reflects the attacker's content back to the victim, the content is executed by the victim's browser.
               
                  Type 2: Stored XSS (or Persistent) - 
               The application stores dangerous data in a database, message forum, visitor log, or other trusted data store. At a later time, the dangerous data is subsequently read back into the application and included in dynamic content. From an attacker's perspective, the optimal place to inject malicious content is in an area that is displayed to either many users or particularly interesting users. Interesting users typically have elevated privileges in the application or interact with sensitive data that is valuable to the attacker. If one of these users executes malicious content, the attacker may be able to perform privileged operations on behalf of the user or gain access to sensitive data belonging to the user. For example, the attacker might inject XSS into a log message, which might not be handled properly when an administrator views the logs.
            
               
                  Type 0: DOM-Based XSS - 
               In DOM-based XSS, the client performs the injection of XSS into the page; in the other types, the server performs the injection. DOM-based XSS generally involves server-controlled, trusted script that is sent to the client, such as Javascript that performs sanity checks on a form before the user submits it. If the server-supplied script processes user-supplied data and then injects it back into the web page (such as with dynamic HTML), then DOM-based XSS is possible.
            
            
            Once the malicious script is injected, the attacker can perform a variety of malicious activities. The attacker could transfer private information, such as cookies that may include session information, from the victim's machine to the attacker. The attacker could send malicious requests to a web site on behalf of the victim, which could be especially dangerous to the site if the victim has administrator privileges to manage that site. Phishing attacks could be used to emulate trusted web sites and trick the victim into entering a password, allowing the attacker to compromise the victim's account on that web site. Finally, the script could exploit a vulnerability in the web browser itself possibly taking over the victim's machine, sometimes referred to as "drive-by hacking."
            In many cases, the attack can be launched without the victim even being aware of it. Even with careful users, attackers frequently use a variety of methods to encode the malicious portion of the attack, such as URL encoding or Unicode, so the request looks less suspicious.
         
         

Fix information:
repo_url: https://github.com/zmartzone/mod_auth_openidc
commit_details: repo_url: https://github.com/zmartzone/mod_auth_openidc
author: AIMOTO NORIHITO
author_date: 2021-06-28 13:05:52+09:00
msg: Add a function to escape Javascript characters
repository: repo_url: https://github.com/zmartzone/mod_auth_openidc
repo_name: OpenIDC/mod_auth_openidc
description: OpenID Certified™ OpenID Connect Relying Party implementation for Apache HTTP Server 2.x
repo_language: C
owner: zmartzone
file_changes: filename: mod_auth_openidc.c
change_type: ModificationType.MODIFY
diff: @@ -468,7 +468,7 @@ apr_byte_t oidc_post_preserve_javascript(request_rec *r, const char *location,
 					"    </script>\n", jmethod, json,
 					location ?
 							apr_psprintf(r->pool, "window.location='%s';\n",
-									location) :
+									oidc_util_javascript_escape(r->pool, location)) :
 									"");
 	if (location == NULL) {
 		if (javascript_method)
@@ -516,7 +516,7 @@ static int oidc_request_post_preserved_restore(request_rec *r,
 					"        document.forms[0].action = \"%s\";\n"
 					"        document.forms[0].submit();\n"
 					"      }\n"
-					"    </script>\n", method, original_url);
+					"    </script>\n", method, oidc_util_javascript_escape(r->pool, original_url));
 
 	const char *body = "    <p>Restoring...</p>\n"
 			"    <form method=\"post\"></form>\n";
@@ -1553,7 +1553,7 @@ static int oidc_session_redirect_parent_window_to_logout(request_rec *r,
 	char *java_script = apr_psprintf(r->pool,
 			"    <script type=\"text/javascript\">\n"
 			"      window.top.location.href = '%s?session=logout';\n"
-			"    </script>\n", oidc_get_redirect_uri(r, c));
+			"    </script>\n", oidc_util_javascript_escape(r->pool, oidc_get_redirect_uri(r, c)));
 
 	return oidc_util_html_send(r, "Redirecting...", java_script, NULL, NULL,
 			OK);

programming_language: C
filename: mod_auth_openidc.h
change_type: ModificationType.MODIFY
diff: @@ -776,6 +776,7 @@ apr_byte_t oidc_json_object_get_string(apr_pool_t *pool, json_t *json, const cha
 apr_byte_t oidc_json_object_get_int(apr_pool_t *pool, json_t *json, const char *name, int *value, const int default_value);
 apr_byte_t oidc_json_object_get_bool(apr_pool_t *pool, json_t *json, const char *name, int *value, const int default_value);
 char *oidc_util_html_escape(apr_pool_t *pool, const char *input);
+char *oidc_util_javascript_escape(apr_pool_t *pool, const char *input);
 void oidc_util_table_add_query_encoded_params(apr_pool_t *pool, apr_table_t *table, const char *params);
 apr_hash_t * oidc_util_merge_key_sets(apr_pool_t *pool, apr_hash_t *k1, const apr_array_header_t *k2);
 apr_hash_t * oidc_util_merge_key_sets_hash(apr_pool_t *pool, apr_hash_t *k1, apr_hash_t *k2);

programming_language: C
filename: util.c
change_type: ModificationType.MODIFY
diff: @@ -366,6 +366,87 @@ char* oidc_util_html_escape(apr_pool_t *pool, const char *s) {
 	return apr_pstrdup(pool, r);
 }
 
+/*
+ * JavaScript escape a string
+ */
+char* oidc_util_javascript_escape(apr_pool_t *pool, const char *s) {
+    const char *cp;
+    char *output;
+    size_t outputlen;
+    int i;
+
+    if (s == NULL) {
+        return NULL;
+    }
+
+    outputlen = 0;
+    for (cp = s; *cp; cp++) {
+        switch (*cp) {
+        case '\'':
+        case '"':
+        case '\\':
+        case '/':
+        case 0x0D:
+        case 0x0A:
+            outputlen += 2;
+            break;
+        case '<':
+        case '>':
+            outputlen += 4;
+            break;
+        default:
+            outputlen += 1;
+            break;
+        }
+    }
+
+    i = 0;
+    output = apr_palloc(pool, outputlen + 1);
+    for (cp = s; *cp; cp++) {
+        switch (*cp) {
+        case '\'':
+            (void)strcpy(&output[i], "\\'");
+            i += 2;
+            break;
+        case '"':
+            (void)strcpy(&output[i], "\\\"");
+            i += 2;
+            break;
+        case '\\':
+            (void)strcpy(&output[i], "\\\\");
+            i += 2;
+            break;
+        case '/':
+            (void)strcpy(&output[i], "\\/");
+            i += 2;
+            break;
+        case 0x0D:
+            (void)strcpy(&output[i], "\\r");
+            i += 2;
+            break;
+        case 0x0A:
+            (void)strcpy(&output[i], "\\n");
+            i += 2;
+            break;
+        case '<':
+            (void)strcpy(&output[i], "\\x3c");
+            i += 4;
+            break;
+        case '>':
+            (void)strcpy(&output[i], "\\x3e");
+            i += 4;
+            break;
+        default:
+            output[i] = *cp;
+            i += 1;
+            break;
+        }
+    }
+    output[i] = '\0';
+    return output;
+}
+
+
 /*
  * get the URL scheme that is currently being accessed
  */

programming_language: C
repo_url: https://github.com/zmartzone/mod_auth_openidc
commit_details: repo_url: https://github.com/zmartzone/mod_auth_openidc
author: Hans Zandbelt
author_date: 2021-06-25 11:42:57+02:00
msg: avoid XSS vulnerability when using OIDCPreservePost On

and supplying URLs that contain single quotes; thanks @oss-aimoto

Signed-off-by: Hans Zandbelt <hans.zandbelt@zmartzone.eu>
repository: repo_url: https://github.com/zmartzone/mod_auth_openidc
repo_name: OpenIDC/mod_auth_openidc
description: OpenID Certified™ OpenID Connect Relying Party implementation for Apache HTTP Server 2.x
repo_language: C
owner: zmartzone
file_changes: filename: ChangeLog
change_type: ModificationType.MODIFY
diff: @@ -1,3 +1,7 @@
+06/25/2021
+- avoid XSS vulnerability when using OIDCPreservePost On and supplying URLs that contain single quotes
+  thanks @oss-aimoto
+
 06/21/2021
 - strip A256GCM JWT header from encrypted JWTS used for state cookies, cache encryption and by-value session cookies
   resulting in smaller cookies and reduced cache content size

programming_language: Markdown
filename: mod_auth_openidc.c
change_type: ModificationType.MODIFY
diff: @@ -513,7 +513,7 @@ static int oidc_request_post_preserved_restore(request_rec *r,
 					"          input.type = \"hidden\";\n"
 					"          document.forms[0].appendChild(input);\n"
 					"        }\n"
-					"        document.forms[0].action = '%s';\n"
+					"        document.forms[0].action = \"%s\";\n"
 					"        document.forms[0].submit();\n"
 					"      }\n"
 					"    </script>\n", method, original_url);

programming_language: C