pam

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Published: Nov 30, 2023 License: BSD-2-Clause Imports: 6 Imported by: 0

README

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Go PAM

This is a Go wrapper for the PAM application API.

Testing

To run the full suite, the tests must be run as the root user. To setup your system for testing, create a user named "test" with the password "secret". For example:

$ sudo useradd test \
    -d /tmp/test \
    -p '$1$Qd8H95T5$RYSZQeoFbEB.gS19zS99A0' \
    -s /bin/false

Then execute the tests:

$ sudo GOPATH=$GOPATH $(which go) test -v

Documentation

Overview

Package pam provides a wrapper for the PAM application API.

Example

This example uses the default PAM service to authenticate any users. This should cause PAM to ask its conversation handler for a username and password in sequence.

t, err := pam.StartFunc("passwd", "", func(s pam.Style, msg string) (string, error) {
	switch s {
	case pam.PromptEchoOff:
		fmt.Print(msg)
		pw, err := term.ReadPassword(int(os.Stdin.Fd()))
		if err != nil {
			return "", err
		}
		fmt.Println()
		return string(pw), nil
	case pam.PromptEchoOn:
		fmt.Print(msg)
		s := bufio.NewScanner(os.Stdin)
		s.Scan()
		return s.Text(), nil
	case pam.ErrorMsg:
		fmt.Fprintf(os.Stderr, "%s\n", msg)
		return "", nil
	case pam.TextInfo:
		fmt.Println(msg)
		return "", nil
	default:
		return "", errors.New("unrecognized message style")
	}
})
if err != nil {
	fmt.Fprintf(os.Stderr, "start: %v\n", err)
	os.Exit(1)
}
defer func() {
	err := t.End()
	if err != nil {
		fmt.Fprintf(os.Stderr, "end: %v\n", err)
		os.Exit(1)
	}
}()
err = t.Authenticate(0)
if err != nil {
	fmt.Fprintf(os.Stderr, "authenticate: %v\n", err)
	os.Exit(1)
}
fmt.Println("authentication succeeded!")
Output:

Index

Examples

Constants

This section is empty.

Variables

This section is empty.

Functions

func CheckPamHasBinaryProtocol

func CheckPamHasBinaryProtocol() bool

CheckPamHasBinaryProtocol return if pam on system supports PAM_BINARY_PROMPT

func CheckPamHasStartConfdir

func CheckPamHasStartConfdir() bool

CheckPamHasStartConfdir return if pam on system supports pam_system_confdir

Types

type BinaryConversationHandler

type BinaryConversationHandler interface {
	ConversationHandler
	// RespondPAMBinary receives a pointer to the binary message. It's up to
	// the receiver to parse it according to the protocol specifications.
	// The function can return a byte array that will passed as pointer back
	// to the module.
	RespondPAMBinary(BinaryPointer) ([]byte, error)
}

BinaryConversationHandler is an interface for objects that can be used as conversation callbacks during PAM authentication if binary protocol is going to be supported.

type BinaryPointer

type BinaryPointer unsafe.Pointer

BinaryPointer exposes the type used for the data in a binary conversation it represents a pointer to data that is produced by the module and that must be parsed depending on the protocol in use

type ConversationFunc

type ConversationFunc func(Style, string) (string, error)

ConversationFunc is an adapter to allow the use of ordinary functions as conversation callbacks.

func (ConversationFunc) RespondPAM

func (f ConversationFunc) RespondPAM(s Style, msg string) (string, error)

RespondPAM is a conversation callback adapter.

type ConversationHandler

type ConversationHandler interface {
	// RespondPAM receives a message style and a message string. If the
	// message Style is PromptEchoOff or PromptEchoOn then the function
	// should return a response string.
	RespondPAM(Style, string) (string, error)
}

ConversationHandler is an interface for objects that can be used as conversation callbacks during PAM authentication.

type Error

type Error int

Error is the Type for PAM Return types

const (
	// OpenErr indicates a dlopen() failure when dynamically loading a
	// service module.
	ErrOpen Error = C.PAM_OPEN_ERR
	// ErrSymbol indicates a symbol not found.
	ErrSymbol Error = C.PAM_SYMBOL_ERR
	// ErrService indicates a error in service module.
	ErrService Error = C.PAM_SERVICE_ERR
	// ErrSystem indicates a system error.
	ErrSystem Error = C.PAM_SYSTEM_ERR
	// ErrBuf indicates a memory buffer error.
	ErrBuf Error = C.PAM_BUF_ERR
	// ErrPermDenied indicates a permission denied.
	ErrPermDenied Error = C.PAM_PERM_DENIED
	// ErrAuth indicates a authentication failure.
	ErrAuth Error = C.PAM_AUTH_ERR
	// ErrCredInsufficient indicates a can not access authentication data due to
	// insufficient credentials.
	ErrCredInsufficient Error = C.PAM_CRED_INSUFFICIENT
	// ErrAuthinfoUnavail indicates that the underlying authentication service
	// can not retrieve authentication information.
	ErrAuthinfoUnavail Error = C.PAM_AUTHINFO_UNAVAIL
	// ErrUserUnknown indicates a user not known to the underlying authentication
	// module.
	ErrUserUnknown Error = C.PAM_USER_UNKNOWN
	// ErrMaxtries indicates that an authentication service has maintained a retry
	// count which has been reached. No further retries should be attempted.
	ErrMaxtries Error = C.PAM_MAXTRIES
	// ErrNewAuthtokReqd indicates a new authentication token required. This is
	// normally returned if the machine security policies require that the
	// password should be changed because the password is nil or it has aged.
	ErrNewAuthtokReqd Error = C.PAM_NEW_AUTHTOK_REQD
	// ErrAcctExpired indicates that an user account has expired.
	ErrAcctExpired Error = C.PAM_ACCT_EXPIRED
	// ErrSession indicates a can not make/remove an entry for the
	// specified session.
	ErrSession Error = C.PAM_SESSION_ERR
	// ErrCredUnavail indicates that an underlying authentication service can not
	// retrieve user credentials.
	ErrCredUnavail Error = C.PAM_CRED_UNAVAIL
	// ErrCredExpired indicates that an user credentials expired.
	ErrCredExpired Error = C.PAM_CRED_EXPIRED
	// ErrCred indicates a failure setting user credentials.
	ErrCred Error = C.PAM_CRED_ERR
	// ErrNoModuleData indicates a no module specific data is present.
	ErrNoModuleData Error = C.PAM_NO_MODULE_DATA
	// ErrConv indicates a conversation error.
	ErrConv Error = C.PAM_CONV_ERR
	// ErrAuthtokErr indicates an authentication token manipulation error.
	ErrAuthtok Error = C.PAM_AUTHTOK_ERR
	// ErrAuthtokRecoveryErr indicates an authentication information cannot
	// be recovered.
	ErrAuthtokRecovery Error = C.PAM_AUTHTOK_RECOVERY_ERR
	// ErrAuthtokLockBusy indicates am authentication token lock busy.
	ErrAuthtokLockBusy Error = C.PAM_AUTHTOK_LOCK_BUSY
	// ErrAuthtokDisableAging indicates an authentication token aging disabled.
	ErrAuthtokDisableAging Error = C.PAM_AUTHTOK_DISABLE_AGING
	// ErrTryAgain indicates a preliminary check by password service.
	ErrTryAgain Error = C.PAM_TRY_AGAIN
	// ErrIgnore indicates to ignore underlying account module regardless of
	// whether the control flag is required, optional, or sufficient.
	ErrIgnore Error = C.PAM_IGNORE
	// ErrAbort indicates a critical error (module fail now request).
	ErrAbort Error = C.PAM_ABORT
	// ErrAuthtokExpired indicates an user's authentication token has expired.
	ErrAuthtokExpired Error = C.PAM_AUTHTOK_EXPIRED
	// ErrModuleUnknown indicates a module is not known.
	ErrModuleUnknown Error = C.PAM_MODULE_UNKNOWN
	// ErrBadItem indicates a bad item passed to pam_*_item().
	ErrBadItem Error = C.PAM_BAD_ITEM
	// ErrConvAgain indicates a conversation function is event driven and data
	// is not available yet.
	ErrConvAgain Error = C.PAM_CONV_AGAIN
	// ErrIncomplete indicates to please call this function again to complete
	// authentication stack. Before calling again, verify that conversation
	// is completed.
	ErrIncomplete Error = C.PAM_INCOMPLETE
)

Pam Return types

func (Error) Error

func (status Error) Error() string

Error returns the error message for the given status.

type Flags

type Flags int

Flags are inputs to various PAM functions than be combined with a bitwise or. Refer to the official PAM documentation for which flags are accepted by which functions.

const (
	// Silent indicates that no messages should be emitted.
	Silent Flags = C.PAM_SILENT
	// DisallowNullAuthtok indicates that authorization should fail
	// if the user does not have a registered authentication token.
	DisallowNullAuthtok Flags = C.PAM_DISALLOW_NULL_AUTHTOK
	// EstablishCred indicates that credentials should be established
	// for the user.
	EstablishCred Flags = C.PAM_ESTABLISH_CRED
	// DeleteCred indicates that credentials should be deleted.
	DeleteCred Flags = C.PAM_DELETE_CRED
	// ReinitializeCred indicates that credentials should be fully
	// reinitialized.
	ReinitializeCred Flags = C.PAM_REINITIALIZE_CRED
	// RefreshCred indicates that the lifetime of existing credentials
	// should be extended.
	RefreshCred Flags = C.PAM_REFRESH_CRED
	// ChangeExpiredAuthtok indicates that the authentication token
	// should be changed if it has expired.
	ChangeExpiredAuthtok Flags = C.PAM_CHANGE_EXPIRED_AUTHTOK
)

PAM Flag types.

type Item

type Item int

Item is a an PAM information type.

const (
	// Service is the name which identifies the PAM stack.
	Service Item = C.PAM_SERVICE
	// User identifies the username identity used by a service.
	User Item = C.PAM_USER
	// Tty is the terminal name.
	Tty Item = C.PAM_TTY
	// Rhost is the requesting host name.
	Rhost Item = C.PAM_RHOST
	// Authtok is the currently active authentication token.
	Authtok Item = C.PAM_AUTHTOK
	// Oldauthtok is the old authentication token.
	Oldauthtok Item = C.PAM_OLDAUTHTOK
	// Ruser is the requesting user name.
	Ruser Item = C.PAM_RUSER
	// UserPrompt is the string use to prompt for a username.
	UserPrompt Item = C.PAM_USER_PROMPT
	// FailDelay is the app supplied function to override failure delays.
	FailDelay Item = C.PAM_FAIL_DELAY
	// Xdisplay is the X display name
	Xdisplay Item = C.PAM_XDISPLAY
	// Xauthdata is the X server authentication data.
	Xauthdata Item = C.PAM_XAUTHDATA
	// AuthtokType is the type for pam_get_authtok
	AuthtokType Item = C.PAM_AUTHTOK_TYPE
)

PAM Item types.

type Style

type Style int

Style is the type of message that the conversation handler should display.

const (
	// PromptEchoOff indicates the conversation handler should obtain a
	// string without echoing any text.
	PromptEchoOff Style = C.PAM_PROMPT_ECHO_OFF
	// PromptEchoOn indicates the conversation handler should obtain a
	// string while echoing text.
	PromptEchoOn Style = C.PAM_PROMPT_ECHO_ON
	// ErrorMsg indicates the conversation handler should display an
	// error message.
	ErrorMsg Style = C.PAM_ERROR_MSG
	// TextInfo indicates the conversation handler should display some
	// text.
	TextInfo Style = C.PAM_TEXT_INFO
	// BinaryPrompt indicates the conversation handler that should implement
	// the private binary protocol
	BinaryPrompt Style = C.PAM_BINARY_PROMPT
)

Coversation handler style types.

type Transaction

type Transaction struct {
	// contains filtered or unexported fields
}

Transaction is the application's handle for a PAM transaction.

func Start

func Start(service, user string, handler ConversationHandler) (*Transaction, error)

Start initiates a new PAM transaction. Service is treated identically to how pam_start treats it internally.

All application calls to PAM begin with Start*. The returned transaction provides an interface to the remainder of the API.

It's responsibility of the Transaction owner to release all the resources allocated underneath by PAM by calling End() once done.

It's not advised to End the transaction using a runtime.SetFinalizer unless you're absolutely sure that your stack is multi-thread friendly (normally it is not!) and using a LockOSThread/UnlockOSThread pair.

func StartConfDir

func StartConfDir(service, user string, handler ConversationHandler, confDir string) (*Transaction, error)

StartConfDir initiates a new PAM transaction. Service is treated identically to how pam_start treats it internally. confdir allows to define where all pam services are defined. This is used to provide custom paths for tests.

All application calls to PAM begin with Start*. The returned transaction provides an interface to the remainder of the API.

It's responsibility of the Transaction owner to release all the resources allocated underneath by PAM by calling End() once done.

It's not advised to End the transaction using a runtime.SetFinalizer unless you're absolutely sure that your stack is multi-thread friendly (normally it is not!) and using a LockOSThread/UnlockOSThread pair.

func StartFunc

func StartFunc(service, user string, handler func(Style, string) (string, error)) (*Transaction, error)

StartFunc registers the handler func as a conversation handler and starts the transaction (see Start() documentation).

func (*Transaction) AcctMgmt

func (t *Transaction) AcctMgmt(f Flags) error

AcctMgmt is used to determine if the user's account is valid.

Valid flags: Silent, DisallowNullAuthtok

func (*Transaction) Authenticate

func (t *Transaction) Authenticate(f Flags) error

Authenticate is used to authenticate the user.

Valid flags: Silent, DisallowNullAuthtok

func (*Transaction) ChangeAuthTok

func (t *Transaction) ChangeAuthTok(f Flags) error

ChangeAuthTok is used to change the authentication token.

Valid flags: Silent, ChangeExpiredAuthtok

func (*Transaction) CloseSession

func (t *Transaction) CloseSession(f Flags) error

CloseSession closes a previously opened session.

Valid flags: Silent

func (*Transaction) End

func (t *Transaction) End() error

End cleans up the PAM handle and deletes the callback function. It must be called when done with the transaction.

func (*Transaction) GetEnv

func (t *Transaction) GetEnv(name string) string

GetEnv is used to retrieve a PAM environment variable.

func (*Transaction) GetEnvList

func (t *Transaction) GetEnvList() (map[string]string, error)

GetEnvList returns a copy of the PAM environment as a map.

func (*Transaction) GetItem

func (t *Transaction) GetItem(i Item) (string, error)

GetItem retrieves a PAM information item.

func (*Transaction) OpenSession

func (t *Transaction) OpenSession(f Flags) error

OpenSession sets up a user session for an authenticated user.

Valid flags: Slient

func (*Transaction) PutEnv

func (t *Transaction) PutEnv(nameval string) error

PutEnv adds or changes the value of PAM environment variables.

NAME=value will set a variable to a value. NAME= will set a variable to an empty value. NAME (without an "=") will delete a variable.

func (*Transaction) SetCred

func (t *Transaction) SetCred(f Flags) error

SetCred is used to establish, maintain and delete the credentials of a user.

Valid flags: EstablishCred, DeleteCred, ReinitializeCred, RefreshCred

func (*Transaction) SetItem

func (t *Transaction) SetItem(i Item, item string) error

SetItem sets a PAM information item.

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