JSON Body Processor

apache2/Makefile.am

@@ -8,7 +8,7 @@ pkglib_LTLIBRARIES = mod_security2.la
 mod_security2_la_SOURCES = mod_security2.c \
                            apache2_config.c apache2_io.c apache2_util.c \
                            re.c re_operators.c re_actions.c re_tfns.c \
-                           re_variables.c msc_logging.c msc_xml.c \
+                           re_variables.c msc_logging.c msc_xml.c msc_json.c \
                            msc_multipart.c modsecurity.c msc_parsers.c \
                            msc_util.c msc_pcre.c persist_dbm.c msc_reqbody.c \
                            msc_geo.c msc_gsb.c msc_crypt.c msc_tree.c msc_unicode.c acmp.c msc_lua.c msc_release.c

apache2/modsecurity.c

@@ -19,6 +19,7 @@
 #include "modsecurity.h"
 #include "msc_parsers.h"
 #include "msc_util.h"
+#include "msc_json.h"
 #include "msc_xml.h"
 #include "apr_version.h"
 
@@ -255,6 +256,9 @@ static apr_status_t modsecurity_tx_cleanup(void *data) {
     /* XML processor cleanup. */
     if (msr->xml != NULL) xml_cleanup(msr);
 
+    /* JSON processor cleanup. */
+    if (msr->json != NULL) json_cleanup(msr);
+
     // TODO: Why do we ignore return code here?
     modsecurity_request_body_clear(msr, &my_error_msg);
     if (my_error_msg != NULL) {

apache2/modsecurity.h

@@ -38,6 +38,7 @@ typedef struct msc_parm msc_parm;
 #include "msc_multipart.h"
 #include "msc_pcre.h"
 #include "msc_util.h"
+#include "msc_json.h"
 #include "msc_xml.h"
 #include "msc_geo.h"
 #include "msc_gsb.h"
@@ -358,6 +359,7 @@ struct modsec_rec {
     multipart_data      *mpd;                        /* MULTIPART processor data structure */
 
     xml_data            *xml;                        /* XML processor data structure       */
+    json_data           *json;                       /* JSON processor data structure      */
 
     /* audit logging */
     char                *new_auditlog_boundary;

apache2/modules.mk

@@ -1,10 +1,10 @@
 MOD_SECURITY2 = mod_security2 apache2_config apache2_io apache2_util \
-    re re_operators re_actions re_tfns re_variables \
+    re re_operators re_actions re_tfns re_variables msc_json \
     msc_logging msc_xml msc_multipart modsecurity msc_parsers msc_util msc_pcre \
     persist_dbm msc_reqbody pdf_protect msc_geo msc_gsb msc_crypt msc_tree msc_unicode acmp msc_lua
 
 H = re.h modsecurity.h msc_logging.h msc_multipart.h msc_parsers.h \
-    msc_pcre.h msc_util.h msc_xml.h persist_dbm.h apache2.h pdf_protect.h \
+    msc_pcre.h msc_util.h msc_xml.h persist_dbm.h apache2.h pdf_protect.h msc_json.h \
     msc_geo.h msc_gsb.h msc_crypt.h msc_tree.h msc_unicode.h acmp.h utf8tables.h msc_lua.h
 
 ${MOD_SECURITY2:=.slo}: ${H}

apache2/msc_json.c

@@ -0,0 +1,313 @@
+/*
+ * ModSecurity for Apache 2.x, http://www.modsecurity.org/
+ * Copyright (c) 2004-2011 Trustwave Holdings, Inc. (http://www.trustwave.com/)
+ *
+ * You may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * If any of the files related to licensing are missing or if you have any
+ * other questions related to licensing please contact Trustwave Holdings, Inc.
+ * directly using the email address security@modsecurity.org.
+ */
+
+#include "msc_json.h"
+
+int json_add_argument(modsec_rec *msr, const char *value, unsigned length)
+{
+    msc_arg *arg;
+
+    /**
+     * If we do not have a prefix, we cannot create a variable name
+     * to reference this argument; for now we simply ignore these
+     */
+    if (!msr->json->current_key) {
+        msr_log(msr, 3, "Cannot add scalar value without an associated key");
+        return 1;
+    }
+
+    arg = (msc_arg *) apr_pcalloc(msr->mp, sizeof(msc_arg));
+
+    /**
+     * Argument name is 'prefix + current_key'
+     */
+    if (msr->json->prefix) {
+        arg->name = apr_psprintf(msr->mp, "%s.%s", msr->json->prefix,
+            msr->json->current_key);
+    }
+    else {
+        arg->name = apr_psprintf(msr->mp, "%s", msr->json->current_key);
+    }
+    arg->name_len = strlen(arg->name);
+
+    /**
+     * Argument value is copied from the provided string
+     */
+    arg->value = apr_pstrmemdup(msr->mp, value, length);
+    arg->value_len = length;
+
+    if (msr->txcfg->debuglog_level >= 9) {
+        msr_log(msr, 9, "Adding JSON argument '%s' with value '%s'",
+            arg->name, arg->value);
+    }
+
+    apr_table_addn(msr->arguments,
+        log_escape_nq_ex(msr->mp, arg->name, arg->name_len), (void *) arg);
+
+    return 1;
+}
+
+/**
+ * yajl callback functions
+ * For more information on the function signatures and order, check
+ * http://lloyd.github.com/yajl/yajl-1.0.12/structyajl__callbacks.html
+ */
+
+/**
+ * Callback for hash key values; we use those to define the variable names
+ * under ARGS. Whenever we reach a new key, we update the current key value.
+ */
+static int yajl_map_key(void *ctx, const unsigned char *key, unsigned int length)
+{
+    modsec_rec *msr = (modsec_rec *) ctx;
+    unsigned char *safe_key;
+
+    /**
+     * yajl does not provide use with null-terminated strings, but
+     * rather expects us to copy the data from the key up to the
+     * length informed; we create a standalone null-termined copy
+     * in safe_key
+     */
+    safe_key = apr_pstrndup(msr->mp, key, length);
+
+    if (msr->txcfg->debuglog_level >= 9) {
+        msr_log(msr, 9, "New JSON hash key '%s'", safe_key);
+    }
+
+    /**
+     * TODO: How do we free the previously string value stored here?
+     */
+    msr->json->current_key = safe_key;
+
+    return 1;
+}
+
+/**
+ * Callback for null values
+ *
+ * TODO: Is there a way to define true null parameter values instead of
+ * empty values?
+ */
+static int yajl_null(void *ctx)
+{
+    modsec_rec *msr = (modsec_rec *) ctx;
+
+    return json_add_argument(msr, "", 0);
+}
+
+/**
+ * Callback for boolean values
+ */
+static int yajl_boolean(void *ctx, int value)
+{
+    modsec_rec *msr = (modsec_rec *) ctx;
+
+    if (value) {
+        return json_add_argument(msr, "true", strlen("true"));
+    }
+    else {
+        return json_add_argument(msr, "false", strlen("false"));
+    }
+}
+
+/**
+ * Callback for string values
+ */
+static int yajl_string(void *ctx, const unsigned char *value, unsigned int length)
+{
+    modsec_rec *msr = (modsec_rec *) ctx;
+
+    return json_add_argument(msr, value, length);
+}
+
+/**
+ * Callback for numbers; YAJL can use separate callbacks for integers/longs and
+ * float/double values, but since we are not interested in using the numeric
+ * values here, we use a generic handler which uses numeric strings
+ */
+static int yajl_number(void *ctx, const unsigned char *value, unsigned int length)
+{
+    modsec_rec *msr = (modsec_rec *) ctx;
+
+    return json_add_argument(msr, value, length);
+}
+
+/**
+ * Callback for a new hash, which indicates a new subtree, labeled as the current
+ * argument name, is being created
+ */
+static int yajl_start_map(void *ctx)
+{
+    modsec_rec *msr = (modsec_rec *) ctx;
+
+    /**
+     * If we do not have a current_key, this is a top-level hash, so we do not
+     * need to do anything
+     */
+    if (!msr->json->current_key) return 1;
+
+    /**
+     * Check if we are already inside a hash context, and append or create the
+     * current key name accordingly
+     */
+    if (msr->json->prefix) {
+        msr->json->prefix = apr_psprintf(msr->mp, "%s.%s", msr->json->prefix,
+            msr->json->current_key);
+    }
+    else {
+        msr->json->prefix = apr_pstrdup(msr->mp, msr->json->current_key);
+    }
+
+    if (msr->txcfg->debuglog_level >= 9) {
+        msr_log(msr, 9, "New JSON hash context (prefix '%s')", msr->json->prefix);
+    }
+
+    return 1;
+}
+
+/**
+ * Callback for end hash, meaning the current subtree is being closed, and that
+ * we should go back to the parent variable label
+ */
+static int yajl_end_map(void *ctx)
+{
+    modsec_rec *msr = (modsec_rec *) ctx;
+    unsigned char *separator;
+
+    /**
+     * If we have no prefix, then this is the end of a top-level hash and
+     * we don't do anything
+     */
+    if (msr->json->prefix == NULL) return 1;
+
+    /**
+     * Current prefix might or not include a separator character; top-level
+     * hash keys do not have separators in the variable name
+     */
+    separator = strrchr(msr->json->prefix, '.');
+
+    if (separator) {
+        msr->json->prefix = apr_pstrmemdup(msr->mp, msr->json->prefix,
+            separator - msr->json->prefix);
+        msr->json->current_key = apr_psprintf(msr->mp, "%s", separator + 1);
+    }
+    else {
+        /**
+         * TODO: Check if it is safe to do this kind of pointer tricks
+         */
+        msr->json->current_key = msr->json->prefix;
+        msr->json->prefix = (unsigned char *) NULL;
+    }
+
+    return 1;
+}
+
+/**
+ * Initialise JSON parser.
+ */
+int json_init(modsec_rec *msr, char **error_msg) {
+    /**
+     * yajl configuration and callbacks
+     */
+    static yajl_parser_config config = { 0, 1 };
+    static yajl_callbacks callbacks = {
+        yajl_null,
+        yajl_boolean,
+        NULL /* yajl_integer     */,
+        NULL /* yajl_double      */,
+        yajl_number,
+        yajl_string,
+        yajl_start_map,
+        yajl_map_key,
+        yajl_end_map,
+        NULL /* yajl_start_array */,
+        NULL /* yajl_end_array   */
+    };
+
+    if (error_msg == NULL) return -1;
+    *error_msg = NULL;
+
+    msr_log(msr, 4, "JSON parser initialization");
+    msr->json = apr_pcalloc(msr->mp, sizeof(json_data));
+    if (msr->json == NULL) return -1;
+
+    /**
+     * Prefix and current key are initially empty
+     */
+    msr->json->prefix = (unsigned char *) NULL;
+    msr->json->current_key = (unsigned char *) NULL;
+
+    /**
+     * yajl initialization
+     *
+     * yajl_parser_config definition:
+     * http://lloyd.github.com/yajl/yajl-1.0.12/structyajl__parser__config.html
+     *
+     * TODO: make UTF8 validation optional, as it depends on Content-Encoding
+     */
+    if (msr->txcfg->debuglog_level >= 9) {
+        msr_log(msr, 9, "yajl JSON parsing callback initialization");
+    }
+    msr->json->handle = yajl_alloc(&callbacks, &config, NULL, msr);
+
+    return 1;
+}
+
+/**
+ * Feed one chunk of data to the JSON parser.
+ */
+int json_process_chunk(modsec_rec *msr, const char *buf, unsigned int size, char **error_msg) {
+    if (error_msg == NULL) return -1;
+    *error_msg = NULL;
+
+    /* Feed our parser and catch any errors */
+    msr->json->status = yajl_parse(msr->json->handle, buf, size);
+    if (msr->json->status != yajl_status_ok &&
+            msr->json->status != yajl_status_insufficient_data) {
+        /* We need to free the yajl error message later, how to do this? */
+        *error_msg = yajl_get_error(msr->json->handle, 0, buf, size);
+    }
+
+    return 1;
+}
+
+/**
+ * Finalise JSON parsing.
+ */
+int json_complete(modsec_rec *msr, char **error_msg) {
+    char *json_data = (char *) NULL;
+
+    if (error_msg == NULL) return -1;
+    *error_msg = NULL;
+
+    /* Wrap up the parsing process */
+    msr->json->status = yajl_parse_complete(msr->json->handle);
+    if (msr->json->status != yajl_status_ok &&
+            msr->json->status != yajl_status_insufficient_data) {
+        /* We need to free the yajl error message later, how to do this? */
+        *error_msg = yajl_get_error(msr->json->handle, 0, NULL, 0);
+    }
+
+    return 1;
+}
+
+/**
+ * Frees the resources used for XML parsing.
+ */
+apr_status_t json_cleanup(modsec_rec *msr) {
+    msr_log(msr, 4, "JSON: Cleaning up JSON results");
+
+    return 1;
+}
+