sorted/postgres: create databases on boot

Previously, `create table ...` sql migrations were being made without the
database existing. This resulted in a panic and error like:

pq: database "pk_3a94488d_blobpacked" does not exist

There seems to be an upstream issue with our postgres library in which
`CREATE DATABASE ...` queries are not prepared so we have to build the
sql manually. For now I've added a regex to make sure we don't allow
anything too crazy in.

Fixes #1022

Change-Id: I0da16759e9219347bb11713b92337021546f9d57

pkg/sorted/postgres/postgreskv.go

@@ -20,6 +20,7 @@ package postgres // import "perkeep.org/pkg/sorted/postgres"
 
 import (
 	"database/sql"
+	"errors"
 	"fmt"
 	"regexp"
 
@@ -36,20 +37,39 @@ func init() {
 }
 
 func newKeyValueFromJSONConfig(cfg jsonconfig.Obj) (sorted.KeyValue, error) {
-	conninfo := fmt.Sprintf("user=%s dbname=%s host=%s password=%s sslmode=%s",
-		cfg.RequiredString("user"),
-		cfg.RequiredString("database"),
-		cfg.OptionalString("host", "localhost"),
-		cfg.OptionalString("password", ""),
-		cfg.OptionalString("sslmode", "require"),
+	var (
+		user     = cfg.RequiredString("user")
+		database = cfg.RequiredString("database")
+		host     = cfg.OptionalString("host", "localhost")
+		password = cfg.OptionalString("password", "")
+		sslmode  = cfg.OptionalString("sslmode", "require")
 	)
 	if err := cfg.Validate(); err != nil {
 		return nil, err
 	}
+
+	// connect without a database, it may not exist yet
+	conninfo := fmt.Sprintf("user=%s host=%s sslmode=%s", user, host, sslmode)
+	if password != "" {
+		conninfo += fmt.Sprintf(" password=%s", password)
+	}
 	db, err := sql.Open("postgres", conninfo)
 	if err != nil {
 		return nil, err
 	}
+	err = createDB(db, database)
+	db.Close() // ignoring error, if createDB failed db.Close() will likely also fail
+	if err != nil {
+		return nil, err
+	}
+
+	// reconnect after database is created
+	conninfo += fmt.Sprintf(" dbname=%s", database)
+	db, err = sql.Open("postgres", conninfo)
+	if err != nil {
+		return nil, err
+	}
+
 	for _, tableSql := range SQLCreateTables() {
 		if _, err := db.Exec(tableSql); err != nil {
 			return nil, fmt.Errorf("error creating table with %q: %v", tableSql, err)
@@ -141,3 +161,34 @@ func (kv *keyValue) SchemaVersion() (version int, err error) {
 	err = kv.db.QueryRow("SELECT value FROM meta WHERE metakey='version'").Scan(&version)
 	return
 }
+
+var validDatabaseRegex = regexp.MustCompile(`^[a-zA-Z0-9\-_]+$`)
+
+func validDatabaseName(database string) bool {
+	return validDatabaseRegex.MatchString(database)
+}
+
+func createDB(db *sql.DB, database string) error {
+	if database == "" {
+		return errors.New("database name can't be empty")
+	}
+
+	rows, err := db.Query(`SELECT 1 FROM pg_database WHERE datname = $1`, database)
+	if err != nil {
+		return err
+	}
+	defer rows.Close()
+	if rows.Next() {
+		return nil // database is already created
+	}
+
+	// Verify database only has runes we expect
+	if !validDatabaseName(database) {
+		return fmt.Errorf("Invalid postgres database name: %q", database)
+	}
+	_, err = db.Exec(fmt.Sprintf("CREATE DATABASE %s", database))
+	if err != nil {
+		return err
+	}
+	return err
+}

pkg/sorted/postgres/postgreskv_test.go

@@ -45,3 +45,21 @@ func TestPostgreSQLKV(t *testing.T) {
 	}
 	kvtest.TestSorted(t, kv)
 }
+
+func TestPostgresDBNaming(t *testing.T) {
+	cases := []struct {
+		name  string
+		valid bool
+	}{
+		{"perkeep", true},
+		{"perkeep_2", true},
+		{"perkeep-2", true},
+		{"'; drop tables;", false}, // validDatabaseName doesn't actually check for sql injection
+	}
+	for i := range cases {
+		res := validDatabaseName(cases[i].name)
+		if res != cases[i].valid {
+			t.Errorf("%q got %v expected %v", cases[i].name, res, cases[i].valid)
+		}
+	}
+}