Adds support to JSON request body parser

src/request_body_processor/json.cc

@@ -0,0 +1,275 @@
+/*
+ * ModSecurity, http://www.modsecurity.org/
+ * Copyright (c) 2015 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 "request_body_processor/json.h"
+
+#include <list>
+#include <iostream>
+#include <string>
+
+
+namespace modsecurity {
+namespace RequestBodyProcessor {
+
+/**
+ * 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.
+ */
+int JSON::yajl_map_key(void *ctx, const unsigned char *key, size_t length) {
+    JSON *tthis = reinterpret_cast<JSON *>(ctx);
+    std::string safe_key;
+
+    /**
+     * yajl does not provide us 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.assign((const char *)key, length);
+
+    tthis->debug(9, "New JSON hash key '" + safe_key + "'");
+
+    /**
+     * TODO: How do we free the previously string value stored here?
+     */
+    tthis->m_data.current_key = safe_key;
+
+    return 1;
+}
+
+/**
+ * Callback for null values
+ *
+ */
+int JSON::yajl_null(void *ctx) {
+    JSON *tthis = reinterpret_cast<JSON *>(ctx);
+
+    return tthis->addArgument("");
+}
+
+/**
+ * Callback for boolean values
+ */
+int JSON::yajl_boolean(void *ctx, int value) {
+    JSON *tthis =  reinterpret_cast<JSON *>(ctx);
+
+    if (value) {
+        return tthis->addArgument("true");
+    }
+
+    return tthis->addArgument("false");
+}
+
+/**
+ * Callback for string values
+ */
+int JSON::yajl_string(void *ctx, const unsigned char *value, size_t length) {
+    JSON *tthis = reinterpret_cast<JSON *>(ctx);
+    std::string v = std::string((const char*)value, length);
+
+    return tthis->addArgument(v);
+}
+
+/**
+ * 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
+ */
+int JSON::yajl_number(void *ctx, const char *value, size_t length) {
+    JSON *tthis = reinterpret_cast<JSON *>(ctx);
+    std::string v = std::string((const char*)value, length);
+
+    return tthis->addArgument(v);
+}
+
+/**
+ * Callback for a new hash, which indicates a new subtree, labeled as the
+ * current argument name, is being created
+ */
+int JSON::yajl_start_map(void *ctx) {
+    JSON *tthis = reinterpret_cast<JSON *>(ctx);
+
+    /**
+     * If we do not have a current_key, this is a top-level hash, so we do not
+     * need to do anything
+     */
+    if (tthis->m_data.current_key.empty() == true) {
+        return true;
+    }
+
+    /**
+     * Check if we are already inside a hash context, and append or create the
+     * current key name accordingly
+     */
+    if (tthis->m_data.prefix.empty() == false) {
+        tthis->m_data.prefix.append("." + tthis->m_data.current_key);
+    } else {
+        tthis->m_data.prefix.assign(tthis->m_data.current_key);
+    }
+
+    tthis->debug(9, "New JSON hash context (prefix '" + \
+        tthis->m_data.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
+ */
+int JSON::yajl_end_map(void *ctx) {
+    JSON *tthis = reinterpret_cast<JSON *>(ctx);
+    size_t sep_pos = std::string::npos;
+
+    /**
+     * If we have no prefix, then this is the end of a top-level hash and
+     * we don't do anything
+     */
+    if (tthis->m_data.prefix.empty() == true) {
+        return true;
+    }
+
+    /**
+     * Current prefix might or not include a separator character; top-level
+     * hash keys do not have separators in the variable name
+     */
+    sep_pos = tthis->m_data.prefix.find(".");
+
+    if (sep_pos != std::string::npos) {
+        std::string tmp = tthis->m_data.prefix;
+        tthis->m_data.prefix.assign(tmp, 0, sep_pos);
+        tthis->m_data.current_key.assign(tmp, sep_pos + 1,
+            tmp.length() - sep_pos - 1);
+    } else {
+        tthis->m_data.current_key.assign(tthis->m_data.prefix);
+        tthis->m_data.prefix = "";
+    }
+
+    return 1;
+}
+
+
+int JSON::addArgument(const std::string& value) {
+    /**
+     * If we do not have a prefix, we cannot create a variable name
+     * to reference this argument; for now we simply ignore these
+     */
+    if (m_data.current_key.empty()) {
+        debug(3, "Cannot add scalar value without an associated key");
+        return 1;
+    }
+
+    if (m_data.prefix.empty()) {
+        m_transaction->addArgument("JSON", m_data.current_key, value);
+    } else {
+        m_transaction->addArgument("JSON", m_data.prefix + "." + \
+            m_data.current_key, value);
+    }
+
+    return 1;
+}
+
+
+bool JSON::init() {
+    return true;
+}
+
+
+bool JSON::processChunk(const char *buf, unsigned int size, std::string *err) {
+    /* Feed our parser and catch any errors */
+    m_data.status = yajl_parse(m_data.handle,
+        (const unsigned char *)buf, size);
+    if (m_data.status != yajl_status_ok) {
+        const unsigned char *e = yajl_get_error(m_data.handle, 0,
+            (const unsigned char *)buf, size);
+        /* We need to free the yajl error message later, how to do this? */
+        err->assign((const char *)e);
+        return false;
+    }
+
+    return true;
+}
+
+
+bool JSON::complete(std::string *err) {
+    /* Wrap up the parsing process */
+    m_data.status = yajl_complete_parse(m_data.handle);
+    if (m_data.status  != yajl_status_ok) {
+        const unsigned char *e = yajl_get_error(m_data.handle, 0, NULL, 0);
+        /* We need to free the yajl error message later, how to do this? */
+        err->assign((const char *)e);
+        return false;
+    }
+
+    return true;
+}
+
+
+JSON::JSON(Transaction *transaction) : m_transaction(transaction) {
+    /**
+     * yajl configuration and callbacks
+     */
+    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  */
+    };
+
+
+    debug(4, "JSON parser initialization");
+
+    /**
+     * Prefix and current key are initially empty
+     */
+    m_data.prefix = "";
+    m_data.current_key = "";
+
+    /**
+     * yajl initialization
+     *
+     * yajl_parser_config definition:
+     * http://lloyd.github.io/yajl/yajl-2.0.1/yajl__parse_8h.html#aec816c5518264d2ac41c05469a0f986c
+     *
+     * TODO: make UTF8 validation optional, as it depends on Content-Encoding
+     */
+    debug(9, "yajl JSON parsing callback initialization");
+    m_data.handle = yajl_alloc(&callbacks, NULL, this);
+
+    yajl_config(m_data.handle, yajl_allow_partial_values, 0);
+}
+
+
+JSON::~JSON() {
+    debug(4, "JSON: Cleaning up JSON results");
+    yajl_free(m_data.handle);
+}
+
+
+}  // namespace RequestBodyProcessor
+}  // namespace modsecurity

src/request_body_processor/json.h

@@ -0,0 +1,84 @@
+/*
+ * ModSecurity, http://www.modsecurity.org/
+ * Copyright (c) 2015 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 <yajl/yajl_parse.h>
+
+#include <string>
+#include <iostream>
+
+#include "modsecurity/transaction.h"
+#include "modsecurity/rules.h"
+
+#ifndef SRC_REQUEST_BODY_PROCESSOR_JSON_H_
+#define SRC_REQUEST_BODY_PROCESSOR_JSON_H_
+
+
+namespace modsecurity {
+namespace RequestBodyProcessor {
+
+
+struct json_data {
+    /* yajl configuration and parser state */
+    yajl_handle handle;
+    yajl_status status;
+
+    /* prefix is used to create data hierarchy (i.e., 'parent.child.value') */
+    std::string prefix;
+    std::string current_key;
+};
+
+typedef struct json_data json_data;
+
+
+class JSON {
+ public:
+    explicit JSON(Transaction *transaction);
+    ~JSON();
+
+    bool init();
+    bool processChunk(const char *buf, unsigned int size, std::string *err);
+    bool complete(std::string *err);
+
+    int addArgument(const std::string& value);
+
+    static int yajl_end_map(void *ctx);
+    static int yajl_start_map(void *ctx);
+    static int yajl_number(void *ctx, const char *value, size_t length);
+    static int yajl_string(void *ctx, const unsigned char *value,
+        size_t length);
+    static int yajl_boolean(void *ctx, int value);
+    static int yajl_null(void *ctx);
+    static int yajl_map_key(void *ctx, const unsigned char *key,
+        size_t length);
+
+#ifndef NO_LOGS
+    void debug(int a, std::string str) {
+        m_transaction->debug(a, str);
+    }
+#endif
+    json_data m_data;
+
+ private:
+    Transaction *m_transaction;
+    std::string m_header;
+};
+
+
+}  // namespace RequestBodyProcessor
+}  // namespace modsecurity
+
+
+#endif  // SRC_REQUEST_BODY_PROCESSOR_JSON_H_