realtime: Fix LIKE escaping in SQL backends

The realtime framework allows for components to look up values using a
LIKE clause with similar syntax to SQL's. pbx_realtime uses this
functionality to search for pattern matching extensions that start with
an underscore (_).

When passing an underscore to SQL's LIKE clause, it will be interpreted
as a wildcard matching a single character and therefore needs to be
escaped. It is (for better or for worse) the responsibility of the
component that is querying realtime to escape it with a backslash before
passing it in. Some RDBMs support escape characters by default, but the
SQL92 standard explicitly says that there are no escape characters
unless they are specified with an ESCAPE clause, e.g.

	SELECT * FROM table WHERE column LIKE '\_%' ESCAPE '\'

This patch instructs 3 backends - res_config_mysql, res_config_pgsql,
and res_config_sqlite3 - to use the ESCAPE clause where appropriate.

Looking through documentation and source tarballs, I was able to
determine that the ESCAPE clause is supported in:

MySQL 5.0.15   (released 2005-10-22 - earliest version available from
                archives)
PostgreSQL 7.1 (released 2001-04-13)
SQLite 3.1.0   (released 2005-01-21)

The versions of the relevant libraries that we depend on to access MySQL
and PostgreSQL will not work on versions that old, and I've added an
explicit check in res_config_sqlite3 to only use the ESCAPE clause when
we have a sufficiently new version of SQLite3.

res_config_odbc already handles the escape characters appropriately, so
no changes were required there.

ASTERISK-15858 #close
Reported by: Humberto Figuera

ASTERISK-26057 #close
Reported by: Stepan

Change-Id: I93117fbb874189ae819f4a31222df7c82cd20efa

3 files changed, 118 insertions, 24 deletions

diff --git a/addons/res_config_mysql.c b/addons/res_config_mysql.c
index 1041c1120..b9ca81f36 100644
--- a/addons/res_config_mysql.c
+++ b/addons/res_config_mysql.c
@@ -305,6 +305,11 @@ static char *decode_chunk(char *chunk)
 	return orig;
 }
 
+#define IS_SQL_LIKE_CLAUSE(x) ((x) && ast_ends_with(x, " LIKE"))
+
+/* MySQL requires us to escape the escape... yo dawg */
+static char *ESCAPE_CLAUSE = " ESCAPE '\\\\'";
+
 static struct ast_variable *realtime_mysql(const char *database, const char *table, const struct ast_variable *rt_fields)
 {
 	struct mysql_conn *dbh;
@@ -317,6 +322,7 @@ static struct ast_variable *realtime_mysql(const char *database, const char *tab
 	char *stringp;
 	char *chunk;
 	char *op;
+	char *escape = "";
 	const struct ast_variable *field = rt_fields;
 	struct ast_variable *var=NULL, *prev=NULL;
 
@@ -347,20 +353,29 @@ static struct ast_variable *realtime_mysql(const char *database, const char *tab
 	/* Create the first part of the query using the first parameter/value pairs we just extracted
 	   If there is only 1 set, then we have our query. Otherwise, loop thru the list and concat */
 
-	if (!strchr(field->name, ' ')) 
-		op = " ="; 
-	else 
+	if (!strchr(field->name, ' ')) {
+		op = " =";
+	} else {
 		op = "";
+		if (IS_SQL_LIKE_CLAUSE(field->name)) {
+			escape = ESCAPE_CLAUSE;
+		}
+	}
 
 	ESCAPE_STRING(buf, field->value);
-	ast_str_set(&sql, 0, "SELECT * FROM %s WHERE %s%s '%s'", table, field->name, op, ast_str_buffer(buf));
+	ast_str_set(&sql, 0, "SELECT * FROM %s WHERE %s%s '%s'%s", table, field->name, op, ast_str_buffer(buf), escape);
 	while ((field = field->next)) {
-		if (!strchr(field->name, ' ')) 
-			op = " ="; 
-		else
+		escape = "";
+		if (!strchr(field->name, ' ')) {
+			op = " =";
+		} else {
 			op = "";
+			if (IS_SQL_LIKE_CLAUSE(field->name)) {
+				escape = ESCAPE_CLAUSE;
+			}
+		}
 		ESCAPE_STRING(buf, field->value);
-		ast_str_append(&sql, 0, " AND %s%s '%s'", field->name, op, ast_str_buffer(buf));
+		ast_str_append(&sql, 0, " AND %s%s '%s'%s", field->name, op, ast_str_buffer(buf), escape);
 	}
 
 	ast_debug(1, "MySQL RealTime: Retrieve SQL: %s\n", ast_str_buffer(sql));
@@ -418,6 +433,7 @@ static struct ast_config *realtime_multi_mysql(const char *database, const char
 	char *stringp;
 	char *chunk;
 	char *op;
+	char *escape = "";
 	const struct ast_variable *field = rt_fields;
 	struct ast_variable *var = NULL;
 	struct ast_config *cfg = NULL;
@@ -464,17 +480,29 @@ static struct ast_config *realtime_multi_mysql(const char *database, const char
 	/* Create the first part of the query using the first parameter/value pairs we just extracted
 	   If there is only 1 set, then we have our query. Otherwise, loop thru the list and concat */
 
-	if (!strchr(field->name, ' '))
+	if (!strchr(field->name, ' ')) {
 		op = " =";
-	else
+	} else {
 		op = "";
+		if (IS_SQL_LIKE_CLAUSE(field->name)) {
+			escape = ESCAPE_CLAUSE;
+		}
+	}
 
 	ESCAPE_STRING(buf, field->value);
-	ast_str_set(&sql, 0, "SELECT * FROM %s WHERE %s%s '%s'", table, field->name, op, ast_str_buffer(buf));
+	ast_str_set(&sql, 0, "SELECT * FROM %s WHERE %s%s '%s'%s", table, field->name, op, ast_str_buffer(buf), escape);
 	while ((field = field->next)) {
-		if (!strchr(field->name, ' ')) op = " ="; else op = "";
+		escape = "";
+		if (!strchr(field->name, ' ')) {
+			op = " =";
+		} else {
+			op = "";
+			if (IS_SQL_LIKE_CLAUSE(field->name)) {
+				escape = ESCAPE_CLAUSE;
+			}
+		}
 		ESCAPE_STRING(buf, field->value);
-		ast_str_append(&sql, 0, " AND %s%s '%s'", field->name, op, ast_str_buffer(buf));
+		ast_str_append(&sql, 0, " AND %s%s '%s'%s", field->name, op, ast_str_buffer(buf), escape);
 	}
 
 	if (initfield) {
diff --git a/res/res_config_pgsql.c b/res/res_config_pgsql.c
index 52c8ede74..58c34d082 100644
--- a/res/res_config_pgsql.c
+++ b/res/res_config_pgsql.c
@@ -417,6 +417,9 @@ static struct columns *find_column(struct tables *t, const char *colname)
 	return NULL;
 }
 
+#define IS_SQL_LIKE_CLAUSE(x) ((x) && ast_ends_with(x, " LIKE"))
+static char *ESCAPE_CLAUSE = " ESCAPE '\\'";
+
 static struct ast_variable *realtime_pgsql(const char *database, const char *tablename, const struct ast_variable *fields)
 {
 	RAII_VAR(PGresult *, result, NULL, PQclear);
@@ -426,6 +429,7 @@ static struct ast_variable *realtime_pgsql(const char *database, const char *tab
 	char *stringp;
 	char *chunk;
 	char *op;
+	char *escape = "";
 	const struct ast_variable *field = fields;
 	struct ast_variable *var = NULL, *prev = NULL;
 
@@ -453,7 +457,14 @@ static struct ast_variable *realtime_pgsql(const char *database, const char *tab
 
 	/* Create the first part of the query using the first parameter/value pairs we just extracted
 	   If there is only 1 set, then we have our query. Otherwise, loop thru the list and concat */
-	op = strchr(field->name, ' ') ? "" : " =";
+	if (!strchr(field->name, ' ')) {
+		op = " =";
+	} else {
+		op = "";
+		if (IS_SQL_LIKE_CLAUSE(field->name)) {
+			escape = ESCAPE_CLAUSE;
+		}
+	}
 
 	ESCAPE_STRING(escapebuf, field->value);
 	if (pgresult) {
@@ -461,12 +472,17 @@ static struct ast_variable *realtime_pgsql(const char *database, const char *tab
 		return NULL;
 	}
 
-	ast_str_set(&sql, 0, "SELECT * FROM %s WHERE %s%s '%s'", tablename, field->name, op, ast_str_buffer(escapebuf));
+	ast_str_set(&sql, 0, "SELECT * FROM %s WHERE %s%s '%s'%s", tablename, field->name, op, ast_str_buffer(escapebuf), escape);
 	while ((field = field->next)) {
-		if (!strchr(field->name, ' '))
+		escape = "";
+		if (!strchr(field->name, ' ')) {
 			op = " =";
-		else
+		} else {
 			op = "";
+			if (IS_SQL_LIKE_CLAUSE(field->name)) {
+				escape = ESCAPE_CLAUSE;
+			}
+		}
 
 		ESCAPE_STRING(escapebuf, field->value);
 		if (pgresult) {
@@ -474,7 +490,7 @@ static struct ast_variable *realtime_pgsql(const char *database, const char *tab
 			return NULL;
 		}
 
-		ast_str_append(&sql, 0, " AND %s%s '%s'", field->name, op, ast_str_buffer(escapebuf));
+		ast_str_append(&sql, 0, " AND %s%s '%s'%s", field->name, op, ast_str_buffer(escapebuf), escape);
 	}
 
 	/* We now have our complete statement; Lets connect to the server and execute it. */
@@ -540,6 +556,7 @@ static struct ast_config *realtime_multi_pgsql(const char *database, const char
 	char *stringp;
 	char *chunk;
 	char *op;
+	char *escape = "";
 	struct ast_variable *var = NULL;
 	struct ast_config *cfg = NULL;
 	struct ast_category *cat = NULL;
@@ -578,10 +595,15 @@ static struct ast_config *realtime_multi_pgsql(const char *database, const char
 	/* Create the first part of the query using the first parameter/value pairs we just extracted
 	   If there is only 1 set, then we have our query. Otherwise, loop thru the list and concat */
 
-	if (!strchr(field->name, ' '))
+	if (!strchr(field->name, ' ')) {
 		op = " =";
-	else
+		escape = "";
+	} else {
 		op = "";
+		if (IS_SQL_LIKE_CLAUSE(field->name)) {
+			escape = ESCAPE_CLAUSE;
+		}
+	}
 
 	ESCAPE_STRING(escapebuf, field->value);
 	if (pgresult) {
@@ -590,12 +612,18 @@ static struct ast_config *realtime_multi_pgsql(const char *database, const char
 		return NULL;
 	}
 
-	ast_str_set(&sql, 0, "SELECT * FROM %s WHERE %s%s '%s'", table, field->name, op, ast_str_buffer(escapebuf));
+	ast_str_set(&sql, 0, "SELECT * FROM %s WHERE %s%s '%s'%s", table, field->name, op, ast_str_buffer(escapebuf), escape);
 	while ((field = field->next)) {
-		if (!strchr(field->name, ' '))
+		escape = "";
+		if (!strchr(field->name, ' ')) {
 			op = " =";
-		else
+			escape = "";
+		} else {
 			op = "";
+			if (IS_SQL_LIKE_CLAUSE(field->name)) {
+				escape = ESCAPE_CLAUSE;
+			}
+		}
 
 		ESCAPE_STRING(escapebuf, field->value);
 		if (pgresult) {
@@ -604,7 +632,7 @@ static struct ast_config *realtime_multi_pgsql(const char *database, const char
 			return NULL;
 		}
 
-		ast_str_append(&sql, 0, " AND %s%s '%s'", field->name, op, ast_str_buffer(escapebuf));
+		ast_str_append(&sql, 0, " AND %s%s '%s'%s", field->name, op, ast_str_buffer(escapebuf), escape);
 	}
 
 	if (initfield) {
diff --git a/res/res_config_sqlite3.c b/res/res_config_sqlite3.c
index 4c4b82051..ee723d3e3 100644
--- a/res/res_config_sqlite3.c
+++ b/res/res_config_sqlite3.c
@@ -60,6 +60,8 @@ ASTERISK_FILE_VERSION(__FILE__, "$Revision$")
 /*** DOCUMENTATION
  ***/
 
+static int has_explicit_like_escaping;
+
 static struct ast_config *realtime_sqlite3_load(const char *database, const char *table, const char *configfile, struct ast_config *config, struct ast_flags flags, const char *suggested_include_file, const char *who_asked);
 static struct ast_variable *realtime_sqlite3(const char *database, const char *table, const struct ast_variable *fields);
 static struct ast_config *realtime_sqlite3_multi(const char *database, const char *table, const struct ast_variable *fields);
@@ -660,6 +662,8 @@ static struct ast_config *realtime_sqlite3_load(const char *database, const char
 	return config;
 }
 
+#define IS_SQL_LIKE_CLAUSE(x) ((x) && ast_ends_with(x, " LIKE"))
+
 /*! \brief Helper function for single and multi-row realtime load functions */
 static int realtime_sqlite3_helper(const char *database, const char *table, const struct ast_variable *fields, int is_multi, void *arg)
 {
@@ -685,6 +689,15 @@ static int realtime_sqlite3_helper(const char *database, const char *table, cons
 			ast_str_append(&sql, 0, " AND %s %s", sqlite3_escape_column_op(field->name),
 					sqlite3_escape_value(field->value));
 		}
+
+		if (has_explicit_like_escaping && IS_SQL_LIKE_CLAUSE(field->name)) {
+			/*
+			 * The realtime framework is going to pre-escape these
+			 * for us with a backslash. We just need to make sure
+			 * to tell SQLite about it
+			 */
+			ast_str_append(&sql, 0, " ESCAPE '\\'");
+		}
 	}
 
 	if (!is_multi) {
@@ -1184,6 +1197,29 @@ static int unload_module(void)
 	return 0;
 }
 
+static void discover_sqlite3_caps(void)
+{
+	/*
+	 * So we cheat a little bit here. SQLite3 added support for the
+	 * 'ESCAPE' keyword in 3.1.0. They added SQLITE_VERSION_NUMBER
+	 * in 3.1.2. So if we run into 3.1.0 or 3.1.1 in the wild, we
+	 * just treat it like < 3.1.0.
+	 *
+	 * For reference: 3.1.0, 3.1.1, and 3.1.2 were all released
+	 * within 30 days of each other in Jan/Feb 2005, so I don't
+	 * imagine we'll be finding something pre-3.1.2 that often in
+	 * practice.
+	 */
+#if defined(SQLITE_VERSION_NUMBER)
+	has_explicit_like_escaping = 1;
+#else
+	has_explicit_like_escaping = 0;
+#endif
+
+	ast_debug(3, "SQLite3 has 'LIKE ... ESCAPE ...' support? %s\n",
+			has_explicit_like_escaping ? "Yes" : "No");
+}
+
 /*!
  * \brief Load the module
  *
@@ -1196,6 +1232,8 @@ static int unload_module(void)
  */
 static int load_module(void)
 {
+	discover_sqlite3_caps();
+
 	if (!((databases = ao2_container_alloc(DB_BUCKETS, db_hash_fn, db_cmp_fn)))) {
 		return AST_MODULE_LOAD_FAILURE;
 	}