redact passwords in parse config errors

Redact passwords when printing the parseConfigError in a best effort manner.
This prevents people from leaking the password into logs, if they just print the error in logs.

errors.go

@@ -4,6 +4,8 @@ import (
 	"context"
 	"fmt"
 	"net"
+	"net/url"
+	"regexp"
 	"strings"
 
 	errors "golang.org/x/xerrors"
@@ -98,10 +100,11 @@ type parseConfigError struct {
 }
 
 func (e *parseConfigError) Error() string {
+	connString := redactPW(e.connString)
 	if e.err == nil {
-		return fmt.Sprintf("cannot parse `%s`: %s", e.connString, e.msg)
+		return fmt.Sprintf("cannot parse `%s`: %s", connString, e.msg)
 	}
-	return fmt.Sprintf("cannot parse `%s`: %s (%s)", e.connString, e.msg, e.err.Error())
+	return fmt.Sprintf("cannot parse `%s`: %s (%s)", connString, e.msg, e.err.Error())
 }
 
 func (e *parseConfigError) Unwrap() error {
@@ -164,3 +167,26 @@ func (e *writeError) SafeToRetry() bool {
 func (e *writeError) Unwrap() error {
 	return e.err
 }
+
+func redactPW(connString string) string {
+	if strings.HasPrefix(connString, "postgres://") || strings.HasPrefix(connString, "postgresql://") {
+		if u, err := url.Parse(connString); err == nil {
+			return redactURL(u)
+		}
+	}
+	quotedDSN := regexp.MustCompile(`password='[^']*'`)
+	connString = quotedDSN.ReplaceAllLiteralString(connString, "password=xxxxx")
+	plainDSN := regexp.MustCompile(`password=[^ ]*`)
+	connString = plainDSN.ReplaceAllLiteralString(connString, "password=xxxxx")
+	return connString
+}
+
+func redactURL(u *url.URL) string {
+	if u == nil {
+		return ""
+	}
+	if _, pwSet := u.User.Password(); pwSet {
+		u.User = url.UserPassword(u.User.Username(), "xxxxx")
+	}
+	return u.String()
+}

errors_test.go

@@ -0,0 +1,44 @@
+package pgconn_test
+
+import (
+	"testing"
+
+	"github.com/jackc/pgconn"
+	"github.com/stretchr/testify/assert"
+)
+
+func TestConfigError(t *testing.T) {
+	tests := []struct {
+		name        string
+		err         error
+		expectedMsg string
+	}{
+		{
+			name:        "url with password",
+			err:         pgconn.NewParseConfigError("postgresql://foo:password@host", "msg", nil),
+			expectedMsg: "cannot parse `postgresql://foo:xxxxx@host`: msg",
+		},
+		{
+			name:        "dsn with password unquoted",
+			err:         pgconn.NewParseConfigError("host=host password=password user=user", "msg", nil),
+			expectedMsg: "cannot parse `host=host password=xxxxx user=user`: msg",
+		},
+		{
+			name:        "dsn with password quoted",
+			err:         pgconn.NewParseConfigError("host=host password='pass word' user=user", "msg", nil),
+			expectedMsg: "cannot parse `host=host password=xxxxx user=user`: msg",
+		},
+		{
+			name:        "weird url",
+			err:         pgconn.NewParseConfigError("postgresql://foo::pasword@host:1:", "msg", nil),
+			expectedMsg: "cannot parse `postgresql://foo:xxxxx@host:1:`: msg",
+		},
+	}
+	for _, tt := range tests {
+		tt := tt
+		t.Run(tt.name, func(t *testing.T) {
+			t.Parallel()
+			assert.EqualError(t, tt.err, tt.expectedMsg)
+		})
+	}
+}

export_test.go

@@ -0,0 +1,11 @@
+// File export_test exports some methods for better testing.
+
+package pgconn
+
+func NewParseConfigError(conn, msg string, err error) error {
+	return &parseConfigError{
+		connString: conn,
+		msg:        msg,
+		err:        err,
+	}
+}