File: pg_snakeoil.c

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pg-snakeoil 1.1-1
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/*-------------------------------------------------------------------------
 *
 * pg_snakeoil.c
 * 		ClamAV antivirus integration, can check given data with ClamAV
 *
 * Copyright (c) 2018, Alexander Sosna <alexander.sosna@credativ.de>
 *
 *-------------------------------------------------------------------------
 */

#include "postgres.h"

#include <ctype.h>

#include "utils/builtins.h"
#if PG_VERSION_NUM >= 100000
#include "utils/varlena.h"
#endif
#include "miscadmin.h"

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <clamav.h>

/*
 * Set SNAKEOIL_DEBUG to 1 to enable additional debug output
 * This can produce overhead, only enable when needed
 */
#define SNAKEOIL_DEBUG 0

/* ClamAV defines */
#define NO_SIGNATURE_CHANGE 0
#define SIGNATURE_CHANGE 1


PG_MODULE_MAGIC;

void reload_engine(void);
bool update_signatures(void);
void _PG_init(void);
void _PG_fini(void);
struct scan_result scan_data(const char *data, size_t data_size);
Datum pg_snakeoil_find_virus(PG_FUNCTION_ARGS);
Datum pg_snakeoil_virus_name(PG_FUNCTION_ARGS);


/*
 * Holds the data of a virus scan
 */
struct scan_result
{
	int return_code;
	const char *virus_name;
	long unsigned int scanned;
};

/*
 * Global variable to access the ClamAV engine
 */
struct cl_engine *engine;
const char *signatureDir;
struct cl_stat signatureStat;

void _PG_init()
{
	/*
	 * Get different randomness for each process, recommended by ClamAV
	 */
	srand(getpid());

	reload_engine();
}

void _PG_fini()
{
	cl_engine_free(engine);
}

/*
 * Initialize the engine for further use, this takes some time!
 */
void reload_engine()
{
	unsigned int signatureNum;
	int rv;
	rv = cl_init(CL_INIT_DEFAULT);

	if (CL_SUCCESS != rv)
	{
		elog(ERROR, "can't initialize libclamav: %s", cl_strerror(rv));
	}

	engine = cl_engine_new();
	signatureDir = cl_retdbdir();
	signatureNum = 0;
	elog(DEBUG1, "use default signature dir '%s'", signatureDir);

	/*
	 * Get the current state of the signatures
	 */
	memset(&signatureStat, 0, sizeof(struct cl_stat));
	cl_statinidir(signatureDir, &signatureStat);

	rv = cl_load(signatureDir, engine, &signatureNum, CL_DB_STDOPT);
	if (CL_SUCCESS != rv)
	{
		elog(ERROR, "failure loading ClamAV databases: %s", cl_strerror(rv));
	}

	elog(DEBUG1, "(cl_engine_compile)");
	rv = cl_engine_compile(engine);
	if (CL_SUCCESS != rv)
	{
		elog(ERROR, "cannot create ClamAV engine: %s", cl_strerror(rv));
		cl_engine_free(engine);
	}

	/*
	 * Only log start info if loaded via shared_preload_libraries,
	 * othervise we could spam the log.
	 */
	if (process_shared_preload_libraries_in_progress)
		elog(LOG, "ClamAV engine started with signatureNum %d from %s",
			signatureNum, signatureDir);
}

bool update_signatures()
{
	/*
	 * If signatures have changed, reload the engine
	 */
	if(cl_statchkdir(&signatureStat) == SIGNATURE_CHANGE) {
		elog(DEBUG1, "newer ClamAV signatures found");
		reload_engine();
		return true;
	}

	return false;
}

struct scan_result scan_data(const char *data, size_t data_size)
{
	struct scan_result result = {0, "", 0};
	cl_fmap_t *map;

	/*
	 * Open a map for scanning custom data, where the data is already in memory,
	 * either in the form of a buffer, a memory mapped file, etc.
	 * Note that the memory [start, start+len) must be the _entire_ file,
	 * you can't give it parts of a file and expect detection to work.
	 */
	map = cl_fmap_open_memory(data, data_size);

	#ifdef SNAKEOIL_DEBUG
		elog(DEBUG4, "data_size: %lu", data_size);
		elog(DEBUG4, "data: %s", pnstrdup(data, data_size));
	#endif

	/*
	 * Scan data
	 */

#if defined(CL_SCAN_STDOPT) /* test for incompatible API change in 0.101 */
	/* version 0.100 */
	result.return_code = cl_scanmap_callback(map, &result.virus_name, &result.scanned, engine, CL_SCAN_STDOPT, NULL);
#else
	/* version 0.101 */
	{
	     static struct cl_scan_options cl_scan_options = {
		  .parse = CL_SCAN_PARSE_ARCHIVE | CL_SCAN_PARSE_ELF
		  | CL_SCAN_PARSE_PDF | CL_SCAN_PARSE_SWF | CL_SCAN_PARSE_HWP3
		  | CL_SCAN_PARSE_XMLDOCS | CL_SCAN_PARSE_MAIL
		  | CL_SCAN_PARSE_OLE2 | CL_SCAN_PARSE_HTML | CL_SCAN_PARSE_PE
	};

	result.return_code =
	     cl_scanmap_callback(map,
				 NULL,
				 &result.virus_name,
				 &result.scanned,
				 engine,
				 &cl_scan_options,
				 NULL);
	}
#endif
	elog(DEBUG2, "cl_scanmap_callback returned: %d virusname: %s", result.return_code, result.virus_name);

	/*
	 * Releases resources associated with the map, you should release any resources
	 * you hold only after (handles, maps) calling this function
	 */
	cl_fmap_close(map);

	return result;
}

PG_FUNCTION_INFO_V1(so_update_signatures);
Datum
so_update_signatures(PG_FUNCTION_ARGS)
{
	PG_RETURN_BOOL(update_signatures());
}

PG_FUNCTION_INFO_V1(so_is_infected);
Datum
so_is_infected(PG_FUNCTION_ARGS)
{
	bytea	   *input = PG_GETARG_BYTEA_P(0);

	const char *data;
	size_t data_size;
	struct scan_result result;

	/*
	 * Extract a pointer to the actual character data
	 */
	data = VARDATA_ANY(input);
	data_size = VARSIZE_ANY_EXHDR(input);

	result = scan_data(data, data_size);

	if (result.return_code == 0)
	{
		PG_RETURN_BOOL(false);
	} else
	{
		elog(DEBUG1, "Virus found: %s", result.virus_name);
		PG_RETURN_BOOL(true);
	}
}

PG_FUNCTION_INFO_V1(so_virus_name);
Datum
so_virus_name(PG_FUNCTION_ARGS)
{
	bytea 	   *input = PG_GETARG_BYTEA_P(0);

	const char *data;
	size_t data_size;
	struct scan_result result;

	/*
	 * Extract a pointer to the actual character data
	 */
	data = VARDATA_ANY(input);
	data_size = VARSIZE_ANY_EXHDR(input);

	result = scan_data(data, data_size);

	if (result.return_code == 0)
	{
		PG_RETURN_NULL();
	} else
	{
		PG_RETURN_TEXT_P(cstring_to_text(result.virus_name));
	}
}