*: add ability to define custom pg_hba.conf entries

Add a new cluster spec option called `pgHBA` where users can define a
custom list of pg_hba.conf entries.

These entries will be added to the pg_hba.conf after all the
stolon managed entries so we'll guarantee local connections from the
keeper and replication connection between pg instances.

These entries aren't validated by stolon so if any of them is wrong the
postgres instance will fail to start of return a warning on reload.

If no custom pg_hba.conf entries are provided then we'll use the current
behavior of accepting all hosts for all dbs and users with md5
authentincation:

```
host all all 0.0.0.0/0 md5
host all all ::0/0 md5
```

cmd/keeper/keeper.go

@@ -21,6 +21,7 @@ import (
 	"os"
 	"os/signal"
 	"path/filepath"
+	"reflect"
 	"strconv"
 	"strings"
 	"sync"
@@ -658,8 +659,7 @@ func (p *PostgresKeeper) Start() {
 
 	// TODO(sgotti) reconfigure the various configurations options
 	// (RequestTimeout) after a changed cluster config
-	pgParameters := make(common.Parameters)
-	pgm := postgresql.NewManager(p.pgBinPath, p.dataDir, pgParameters, p.getLocalConnParams(), p.getLocalReplConnParams(), p.pgSUUsername, p.pgSUPassword, p.pgReplUsername, p.pgReplPassword, p.requestTimeout)
+	pgm := postgresql.NewManager(p.pgBinPath, p.dataDir, p.getLocalConnParams(), p.getLocalReplConnParams(), p.pgSUUsername, p.pgSUPassword, p.pgReplUsername, p.pgReplPassword, p.requestTimeout)
 	p.pgm = pgm
 
 	p.pgm.Stop(true)
@@ -885,7 +885,8 @@ func (p *PostgresKeeper) postgresKeeperSM(pctx context.Context) {
 
 	followersUIDs := db.Spec.Followers
 
-	prevPGParameters := pgm.GetParameters()
+	pgm.SetHba(db.Spec.PGHBA)
+
 	var pgParameters common.Parameters
 
 	dbls := p.dbLocalState
@@ -1465,7 +1466,7 @@ func (p *PostgresKeeper) postgresKeeperSM(pctx context.Context) {
 	pgParameters = p.createPGParameters(db)
 
 	// Log synchronous replication changes
-	prevSyncStandbyNames := prevPGParameters["synchronous_standby_names"]
+	prevSyncStandbyNames := pgm.CurParameters()["synchronous_standby_names"]
 	syncStandbyNames := pgParameters["synchronous_standby_names"]
 	if db.Spec.SynchronousReplication {
 		if prevSyncStandbyNames != syncStandbyNames {
@@ -1477,17 +1478,32 @@ func (p *PostgresKeeper) postgresKeeperSM(pctx context.Context) {
 		}
 	}
 
-	if !pgParameters.Equals(prevPGParameters) {
+	needsReload := false
+
+	if !pgParameters.Equals(pgm.CurParameters()) {
 		log.Infow("postgres parameters changed, reloading postgres instance")
 		pgm.SetParameters(pgParameters)
-		if err := pgm.Reload(); err != nil {
-			log.Errorw("failed to reload postgres instance", err)
-		}
+		needsReload = true
 	} else {
 		// for tests
 		log.Infow("postgres parameters not changed")
 	}
 
+	if !reflect.DeepEqual(db.Spec.PGHBA, pgm.CurHba()) {
+		log.Infow("postgres hba entries changed, reloading postgres instance")
+		pgm.SetHba(db.Spec.PGHBA)
+		needsReload = true
+	} else {
+		// for tests
+		log.Infow("postgres hba entries not changed")
+	}
+
+	if needsReload {
+		if err := pgm.Reload(); err != nil {
+			log.Errorw("failed to reload postgres instance", err)
+		}
+	}
+
 	// If we are here, then all went well and we can update the db generation and save it locally
 	p.localStateMutex.Lock()
 	dbls.Generation = db.Generation

cmd/sentinel/sentinel.go

@@ -368,6 +368,7 @@ func (s *Sentinel) setDBSpecFromClusterSpec(cd *cluster.ClusterData) {
 		db.Spec.SynchronousReplication = s.syncRepl(clusterSpec)
 		db.Spec.UsePgrewind = *clusterSpec.UsePgrewind
 		db.Spec.PGParameters = clusterSpec.PGParameters
+		db.Spec.PGHBA = clusterSpec.PGHBA
 		if db.Spec.FollowConfig != nil && db.Spec.FollowConfig.Type == cluster.FollowTypeExternal {
 			db.Spec.FollowConfig.StandbySettings = clusterSpec.StandbySettings
 		}

cmd/stolonctl/update.go

@@ -117,7 +117,6 @@ func update(cmd *cobra.Command, args []string) {
 			if err != nil {
 				die("failed to patch cluster spec: %v", err)
 			}
-
 		} else {
 			if err := json.Unmarshal(data, &newcs); err != nil {
 				die("failed to unmarshal cluster spec: %v", err)

doc/README.md

@@ -7,6 +7,7 @@ We suggest that you first read the [Stolon Architecture and Requirements](archit
 * [Cluster Specification](cluster_spec.md)
 * [Cluster Initialization](initialization.md)
 * [Setting instance parameters](postgres_parameters.md)
+* [Custom pg_hba.conf entries](custom_pg_hba_entries.md)
 * [Stolon Client](stolonctl.md)
 * Backup/Restore
   * [Point In Time Recovery](pitr.md)

doc/custom_pg_hba_entries.md

@@ -0,0 +1,14 @@
+## Setting custom pg_hba.conf entries
+
+Stolon manages the pg_hba.conf file entries. The first rules are generated by stolon to permit local keeper connections and remote replication connections since these are needed to ensure the correct operation of the cluster.
+
+Users can specify custom pg_hba.conf entries setting the [cluster_specification](cluster_spec.md) `pgHBA` option. It must be a list of string containing additional pg_hba.conf entries. They will be added to the pg_hba.conf generated by stolon.
+
+**NOTE**: these lines aren't validated so if some of them are wrong postgres will refuse to start or, on reload, will log a warning and ignore the updated pg_hba.conf file. Stolon will just check that the string doesn't contain newlines characters.
+
+By default, if no custom pg_hba entries are defined (clusterpsec pgHBA option is null, not an empty list), to keep backward compatibility, stolon will add two rules to permit tcp (both ipv4 and ipv6) connections from every host to all dbs and usernames with md5 password authentication:
+
+```
+host all all 0.0.0.0/0 md5
+host all all ::0/0 md5
+```

pkg/cluster/cluster.go

@@ -16,15 +16,14 @@ package cluster
 
 import (
 	"encoding/json"
+	"fmt"
 	"reflect"
+	"sort"
 	"strings"
 	"time"
 
 	"github.com/sorintlab/stolon/common"
 
-	"fmt"
-	"sort"
-
 	"github.com/mitchellh/copystructure"
 )
 
@@ -243,6 +242,9 @@ type ClusterSpec struct {
 	StandbySettings *StandbySettings `json:"standbySettings,omitempty"`
 	// Map of postgres parameters
 	PGParameters PGParameters `json:"pgParameters,omitempty"`
+	// Additional pg_hba.conf entries
+	// we don't set omitempty since we want to distinguish between null or empty slice
+	PGHBA []string `json:"pgHBA"`
 }
 
 type ClusterStatus struct {
@@ -392,6 +394,13 @@ func (os *ClusterSpec) Validate() error {
 	if s.InitMode == nil {
 		return fmt.Errorf("initMode undefined")
 	}
+	// The unique validation we're doing on pgHBA entries is that they don't contain a newline character
+	for _, e := range s.PGHBA {
+		if strings.Contains(e, "\n") {
+			return fmt.Errorf("pgHBA entries cannot contain newline characters")
+		}
+	}
+
 	switch *s.InitMode {
 	case ClusterInitModeNew:
 		if *s.Role == ClusterRoleStandby {
@@ -526,6 +535,9 @@ type DBSpec struct {
 	PITRConfig *PITRConfig `json:"pitrConfig,omitempty"`
 	// Map of postgres parameters
 	PGParameters PGParameters `json:"pgParameters,omitempty"`
+	// Additional pg_hba.conf entries
+	// We don't set omitempty since we want to distinguish between null or empty slice
+	PGHBA []string `json:"pgHBA"`
 	// DB Role (master or standby)
 	Role common.Role `json:"role,omitempty"`
 	// FollowConfig when Role is "standby"

pkg/postgresql/postgresql.go

@@ -31,6 +31,7 @@ import (
 	slog "github.com/sorintlab/stolon/pkg/log"
 
 	_ "github.com/lib/pq"
+	"github.com/mitchellh/copystructure"
 	"golang.org/x/net/context"
 )
 
@@ -45,6 +46,9 @@ type Manager struct {
 	pgBinPath       string
 	dataDir         string
 	parameters      common.Parameters
+	hba             []string
+	curParameters   common.Parameters
+	curHba          []string
 	localConnParams ConnParams
 	replConnParams  ConnParams
 	suUsername      string
@@ -72,11 +76,12 @@ type InitConfig struct {
 	DataChecksums bool
 }
 
-func NewManager(pgBinPath string, dataDir string, parameters common.Parameters, localConnParams, replConnParams ConnParams, suUsername, suPassword, replUsername, replPassword string, requestTimeout time.Duration) *Manager {
+func NewManager(pgBinPath string, dataDir string, localConnParams, replConnParams ConnParams, suUsername, suPassword, replUsername, replPassword string, requestTimeout time.Duration) *Manager {
 	return &Manager{
 		pgBinPath:       pgBinPath,
 		dataDir:         filepath.Join(dataDir, "postgres"),
-		parameters:      parameters,
+		parameters:      make(common.Parameters),
+		curParameters:   make(common.Parameters),
 		replConnParams:  replConnParams,
 		localConnParams: localConnParams,
 		suUsername:      suUsername,
@@ -91,8 +96,32 @@ func (p *Manager) SetParameters(parameters common.Parameters) {
 	p.parameters = parameters
 }
 
-func (p *Manager) GetParameters() common.Parameters {
-	return p.parameters
+func (p *Manager) CurParameters() common.Parameters {
+	return p.curParameters
+}
+
+func (p *Manager) SetHba(hba []string) {
+	p.hba = hba
+}
+
+func (p *Manager) CurHba() []string {
+	return p.curHba
+}
+
+func (p *Manager) UpdateCurParameters() {
+	n, err := copystructure.Copy(p.parameters)
+	if err != nil {
+		panic(err)
+	}
+	p.curParameters = n.(common.Parameters)
+}
+
+func (p *Manager) UpdateCurHba() {
+	n, err := copystructure.Copy(p.hba)
+	if err != nil {
+		panic(err)
+	}
+	p.curHba = n.([]string)
 }
 
 func (p *Manager) Init(initConfig *InitConfig) error {
@@ -221,6 +250,9 @@ func (p *Manager) start(args ...string) error {
 		return fmt.Errorf("error: %v", err)
 	}
 
+	p.UpdateCurParameters()
+	p.UpdateCurHba()
+
 	// pg_ctl with -w will exit after the timeout and return 0 also if the
 	// instance isn't accepting connection because already in recovery (usually
 	// waiting for wals during a pitr or a pg_rewind)
@@ -280,6 +312,10 @@ func (p *Manager) Reload() error {
 	if err := cmd.Run(); err != nil {
 		return fmt.Errorf("error: %v", err)
 	}
+
+	p.UpdateCurParameters()
+	p.UpdateCurHba()
+
 	return nil
 }
 
@@ -608,10 +644,16 @@ func (p *Manager) writePgHba() error {
 	f.WriteString(fmt.Sprintf("host replication %s %s md5\n", p.replUsername, "0.0.0.0/0"))
 	f.WriteString(fmt.Sprintf("host replication %s %s md5\n", p.replUsername, "::0/0"))
 
-	// By default accept connections for all databases and users with md5 auth
-	// TODO(sgotti) Do not set this but let the user provide its pg_hba.conf file/entries
-	f.WriteString("host all all 0.0.0.0/0 md5\n")
-	f.WriteString("host all all ::0/0 md5\n")
+	if p.hba != nil {
+		for _, e := range p.hba {
+			f.WriteString(e + "\n")
+		}
+	} else {
+		// By default, if no custom pg_hba entries are provided, accept
+		// connections for all databases and users with md5 auth
+		f.WriteString("host all all 0.0.0.0/0 md5\n")
+		f.WriteString("host all all ::0/0 md5\n")
+	}
 
 	if err = os.Rename(f.Name(), filepath.Join(p.dataDir, "pg_hba.conf")); err != nil {
 		os.Remove(f.Name())