tcplay.3

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.Dd January 20, 2014
.Dt TCPLAY 3
.Os
.Sh NAME
.Nm tc_api_init ,
.Nm tc_api_uninit ,
.Nm tc_api_has ,
.Nm tc_api_cipher_iterate ,
.Nm tc_api_prf_iterate ,
.Nm tc_api_task_init ,
.Nm tc_api_task_uninit ,
.Nm tc_api_task_set ,
.Nm tc_api_task_do ,
.Nm tc_api_task_info_get ,
.Nm tc_api_task_get_error
.Nd TrueCrypt volume management
.Sh LIBRARY
.Lb libtcplay
.Sh SYNOPSIS
.In tcplay_api.h
.Ft typedef int
.Fn (*tc_api_cipher_iterator_fn) "void *priv" "const char *name" "int key_length_in_bits" "int ciphers_in_chain"
.Ft typedef int
.Fn (*tc_api_prf_iterator_fn) "void *priv" "const char *name"
.Ft typedef int
.Fn (*tc_api_state_change_fn) "void *priv" "const char *state" "int enter_state"
.Ft int
.Fn tc_api_init "int verbose"
.Ft int
.Fn tc_api_uninit "void"
.Ft int
.Fn tc_api_has "const char *feature"
.Ft int
.Fn tc_api_cipher_iterate "tc_api_cipher_iterator_fn fn" "void *priv"
.Ft int
.Fn tc_api_prf_iterate "tc_api_prf_iterator_fn fn" "void *priv"
.Ft tc_api_task
.Fn tc_api_task_init "const char *op"
.Ft int
.Fn tc_api_task_uninit "tc_api_task task"
.Ft int
.Fn tc_api_task_set "tc_api_task task" "const char *key" "..."
.Ft int
.Fn tc_api_task_do "tc_api_task task"
.Ft int
.Fn tc_api_task_info_get "tc_api_task task" "const char *key" "..."
.Ft const char *
.Fn tc_api_task_get_error "tc_api_task task"
.Sh DESCRIPTION
The
.Nm tcplay
library provides an interface to create, query, map and manage
TrueCrypt-compatible volumes.
.Pp
The
.Fn tc_api_init
function initializes the library internals and prepares it for use via
the API.
This function has to be called before using any other API function.
If the
.Fa verbose
argument is non-zero, then the library will output information such as
errors via stdout and stderr.
.Pp
The
.Fn tc_api_uninit
function clears up all internal secure memory, such as memory used for
decrypted headers, passphrases, keyfiles, etc.
.Pp
The
.Fn tc_api_has
function checks whether the loaded tcplay library has the feature
specified by the
.Fa feature
argument.
The current version of the
.Nm tcplay
library supports the following features:
.Bl -column "some_long_feature" "Description"
.It Sy Feature         Ta Sy Description
.It Li trim            Ta    Allows enabling discards/TRIM when mapping a volume
.El
.Pp
The
.Fn tc_api_cipher_iterate
function passes every available cipher chain to the callback provided in the
.Fa fn
argument.
The
.Fa priv
argument is passed on every call of the callback function.
The name of the cipher chain is passed to the callback function in the
.Fa name
argument.
Similarly,
the
.Fa ciphers_in_chain
argument holds the number of ciphers in the current chain,
and
.Fa key_length_in_bits
holds the total key length for the cipher chain,
in bits.
.Pp
The
.Fn tc_api_prf_iterate
function passes every available cipher chain to the callback provided in the
.Fa fn
argument.
The
.Fa priv
argument is passed on every call of the callback function.
The name of the PKBDF2 PRF algorithm is passed to the callback function in the
.Fa name
argument.
.Pp
The
.Fn tc_api_task_init
function initializes and returns a
.Ft tc_api_task
opaque pointer that can be used to run
.Nm tcplay
commands.
Each task can be used only for a single
.Fn tc_api_task_do
call,
and must be deallocated using
.Fn tc_api_task_uninit .
The
.Fa op
argument can be one of the following:
.Bl -tag -width indent
.It Sy create
Create a new encrypted TrueCrypt volume.
.It Sy map
Map an existing TrueCrypt volume.
.It Sy info
Request information about an encrypted TrueCrypt volume.
.It Sy info_mapped
Request information about a mapped TrueCrypt volume.
.It Sy unmap
Unmap a mapped TrueCrypt volume.
.It Sy modify
Modify the TrueCrypt volume by changing the passphrase, keyfiles, PRF algorithm,
restoring from a backup header, restoring from a header file or saving to a header file.
.It Sy restore
Modify the TrueCrypt volume as
.Sy modify
does, but without changing the passphrase, keyfiles or PRF algorithm.
.El
.Pp
The
.Fn tc_api_task_set
function allows settting a number of different options for the current task.
The following table shows which keys are available on calls to
.Fn tc_api_task_set
for each of the operations.
The letter
.Sy M
indicates the setting is mandatory,
whilst
.Sy *
indicates the setting is optional.
.Bl -column "hidden_header_from_filexxx" "createxxx" "infoxxx" "mapxxx" "unmapxxx" "info_mappedxxx" "modifyxxx" "restorexxx"
.It Sy Key                      Ta Sy create Ta Sy info Ta Sy map Ta Sy unmap Ta Sy info_mapped Ta Sy modify Ta Sy restore
.It Li dev                      Ta    "M"    Ta    "M"  Ta    "M" Ta    "*"   Ta                Ta    "M"    Ta    "M"
.It Li map_name                 Ta           Ta         Ta    "M" Ta    "M"   Ta    "M"         Ta           Ta    ""
.It Li interactive              Ta    "*"    Ta    "*"  Ta    "*" Ta          Ta                Ta    "*"    Ta    "*"
.It Li retries                  Ta    "*"    Ta    "*"  Ta    "*" Ta          Ta                Ta    "*"    Ta    "*"
.It Li timeout                  Ta    "*"    Ta    "*"  Ta    "*" Ta          Ta                Ta           Ta    ""
.It Li state_change_fn          Ta    "*"    Ta         Ta        Ta          Ta                Ta    "*"    Ta    "*"
.It Li weak_keys_and_salt       Ta    "*"    Ta         Ta        Ta          Ta                Ta    "*"    Ta    "*"
.It Li secure_erase             Ta    "*"    Ta         Ta        Ta          Ta                Ta           Ta    ""
.It Li hidden_size_bytes        Ta    "*"    Ta         Ta        Ta          Ta                Ta           Ta    ""
.It Li prf_algo                 Ta    "*"    Ta         Ta        Ta          Ta                Ta           Ta    ""
.It Li h_prf_algo               Ta    "*"    Ta         Ta        Ta          Ta                Ta           Ta    ""
.It Li cipher_chain             Ta    "*"    Ta         Ta        Ta          Ta                Ta           Ta    ""
.It Li h_cipher_chain           Ta    "*"    Ta         Ta        Ta          Ta                Ta           Ta    ""
.It Li protect_hidden           Ta           Ta    "*"  Ta    "*" Ta          Ta                Ta           Ta    ""
.It Li fde                      Ta           Ta    "*"  Ta    "*" Ta          Ta                Ta           Ta    ""
.It Li sys                      Ta           Ta    "*"  Ta    "*" Ta          Ta                Ta    "?"    Ta    "?"
.It Li use_backup_header        Ta           Ta    "*"  Ta    "*" Ta          Ta                Ta    "*"    Ta    "*"
.It Li header_from_file         Ta           Ta    "*"  Ta    "*" Ta          Ta                Ta    "*"    Ta    "*"
.It Li hidden_header_from_file  Ta           Ta    "*"  Ta    "*" Ta          Ta                Ta    "*"    Ta    "*"
.It Li allow_trim               Ta           Ta         Ta    "*" Ta          Ta                Ta           Ta    ""
.It Li save_header_to_file      Ta           Ta         Ta        Ta          Ta                Ta    "*"    Ta    ""
.It Li passphrase               Ta    "*"    Ta    "*"  Ta    "*" Ta          Ta                Ta    "*"    Ta    "*"
.It Li h_passphrase             Ta    "*"    Ta    "*"  Ta    "*" Ta          Ta                Ta    "*"    Ta    "*"
.It Li keyfiles                 Ta    "*"    Ta    "*"  Ta    "*" Ta          Ta                Ta    "*"    Ta    "*"
.It Li h_keyfiles               Ta    "*"    Ta    "*"  Ta    "*" Ta          Ta                Ta    "*"    Ta    "*"
.It Li new_passphrase           Ta           Ta         Ta        Ta          Ta                Ta    "*"    Ta    ""
.It Li new_keyfiles             Ta           Ta         Ta        Ta          Ta                Ta    "*"    Ta    ""
.It Li new_prf_algo             Ta           Ta         Ta        Ta          Ta                Ta    "*"    Ta    ""
.It Li read_only                Ta           Ta         Ta    "*" Ta          Ta                Ta    "*"    Ta    ""

.El
The varargs accepted by the
.Fn tc_api_task_set
function depend on the key being set.
.Bl -tag -width indent
.It dev
The vararg is of type
.Ft const char * .
It sets the device that contains the TrueCrypt volume to operate on.
.It map_name
The vararg is of type
.Ft const char * .
It set the name of the mapped volume.
.It interactive
The vararg is of type
.Ft int .
It determines whether the user will be prompted for a passphrase or whether
the settings are taken from the arguments set using
.Fn tc_api_task_set .
.It retries
The vararg is of type
.Ft int .
It determines the number of passphrase retries if
.Fa interactive
is set.
.It weak_keys_and_salt
The vararg is of type
.Ft int .
It determines whether to use a weak source of entropy for key material and/or
the salt.
.It secure_erase
The vararg is of type
.Ft int .
It determines whether a secure erase is performed as part of the volume creation.
.It read_only
The vararg is of type
.Ft int .
It determines whether a mapper should be created in read only mode or not.
.It hidden_size_bytes
The vararg is of type
.Ft int64_t .
If set to
.Fa 0
it implies no hidden volume will be created.
A positive value implies a hidden volume of the specified size in bytes is created.
.It prf_algo
The vararg is of type
.Ft const char *
and must be a valid PBKDF2 PRF algorithm.
It determines which PBKDF2 PRF algorithm is used for the outer volume.
.It h_prf_algo
The vararg is of type
.Ft const char *
and must be a valid PBKDF2 PRF algorithm.
It determines which PBKDF2 PRF algorithm is used for the hidden volume.
.It cipher_chain
The vararg is of type
.Ft const char *
and must be a valid
.Nm tcplay
cipher chain.
It determines which cipher chain is used to encrypt the outer volume.
.It h_cipher_chain
The vararg is of type
.Ft const char *
and must be a valid
.Nm tcplay
cipher chain.
It determines which cipher chain is used to encrypt the hidden volume.
.It protect_hidden
The vararg is of type
.Ft int .
It determines whether the size of the outer volume should be adjusted to protect
any hidden volume.
Using this mode requires both outer and hidden passphrases and keyfiles.
.It sys
The vararg is of type
.Ft const char * .
It determines whether the volume is a system encrypted volume,
and if so, which disk is the system disk and hence contains the header.
If set to
.Dv NULL
the volume will implicitly be treated as a non-system encrypted volume.
.It fde
The vararg is of type
.Ft int .
It determines whether the disk uses full disk encryption or not.
If specified, the device pointed to by the
.Fa dev
setting should be a whole disk device, not any partition.
The device will be mapped or queried as a whole.
To access individual partitions, a utility such as
.Xr kpartx 8
should be used, which will create additional individual mappings
for each partition in the decrypted mapped volume.
For more details on full disk encryption, see
.Xr tcplay 8 .
.It use_backup_header
The vararg is of type
.Ft int .
It determines whether the backup header should be used instead of the regular
header to access the volume.
.It header_from_file
The vararg is of type
.Ft const char * .
If not
.Dv NULL
it forces
.Nm tcplay
to use the header in the specified file instead of the regular outer volume header.
.It hidden_header_from_file
The vararg is of type
.Ft const char * .
If not
.Dv NULL
it forces
.Nm tcplay
to use the header in the specified file instead of the regular hidden volume header.
.It allow_trim
The vararg is of type
.Ft int .
It specifies whether the mapped volume should allow discards (TRIM).
.It save_header_to_file
The vararg is of type
.Ft const char * .
If not
.Dv NULL
it forces
.Nm tcplay
to write the (modified) header to the specified file instead of replacing the volume
headers.
.It passphrase
The vararg is of type
.Ft const char * .
It sets the passphrase that
.Nm tcplay
uses to access the volume.
.It h_passphrase
The vararg is of type
.Ft const char * .
It sets the passphrase that
.Nm tcplay
uses to unlock the hidden volume header.
This option is only used if a hidden volume is being created or the
.Fa protect_hidden
setting is set.
Otherwise
.Nm tcplay
will first use the regular passphrase to try to unlock the outer volume and then
try to unlock the hidden volume header with the same passphrase without ever
using
.Fa h_passphrase .
.It keyfiles
The vararg is of type
.Ft const char * .
If not
.Dv NULL
the given keyfile will be added to the keyfile pool.
Multiple calls to set this option with a non-
.Dv NULL
argument result add additional keyfiles.
If
.Dv NULL
all keyfiles are cleared.
.It h_keyfiles
The vararg is of type
.Ft const char * .
If not
.Dv NULL
the given keyfile will be added to the keyfile pool.
Multiple calls to set this option with a non-
.Dv NULL
argument result add additional keyfiles.
If
.Dv NULL
all keyfiles are cleared.
This option is only used if a hidden volume is being created or the
.Fa protect_hidden
setting is set.
Otherwise
.Nm tcplay
will first use the regular keyfiles to try to unlock the outer volume and then
try to unlock the hidden volume header with the same keyfiles without ever
using
.Fa h_keyfiles .
.It new_passphrase
The vararg is of type
.Fa const char * .
It specifies the new passphrase to use when modifying the volume header.
.It new_keyfiles
The vararg is of type
.Fa const char * .
If not
.Dv NULL
the given keyfile will be added to the new keyfile pool.
Multiple calls to set this option with a non-
.Dv NULL
argument result add additional keyfiles.
If
.Dv NULL
all new keyfiles are cleared.
When the volume header is modified,
it will be reencrypted using the new keyfiles.
.It new_prf_algo
The vararg is of type
.Ft const char *
and must be a valid PBKDF2 PRF algorithm.
It determines which PBKDF2 PRF algorithm is used when reencrypting the (modified)
volume header.
.It state_change_fn
The first vararg is of type
.Fa tc_api_state_change_fn
and the second vararg is of type
.Fa void * .
It allows the consumer to provide a callback function which will be called when
starting and stopping a time-intensive sub-operation such as collecting entropy
or erasing a volume.
The second vararg is passed as the
.Fa priv
argument to the callback.
The
.Fa enter_state
argument to the callback determines whether
.Nm tcplay
is starting or stopping the time-intensive sub-task specified in the
.Fa state
argument.
.El
.Pp
The
.Fn tc_api_task_do
function runs the task specified in the
.Fa task
argument.
Before running the task,
.Fn tc_api_task_do
performs a simple sanity check of the arguments set previously using
.Fn tc_api_task_set
before performing the actual operation.
After a call to
.Fn tc_api_task_do
for the
.Sy info
or
.Sy info_mapped
operations,
the queried information is available to be accessed using
.Fn tc_api_task_info_get .
.Pp
The
.Fn tc_api_task_info_get
function can be used to query the result of a
.Sy info
or
.Sy info_mapped
operation.
The
.Fa task
argument is the task used in a previous
.Fn tc_api_task_do
call.
The
.Fa key
argument can be one of the following:
.Bl -column "some_long_feature" "very_long_type" "Description"
.It Sy Key             Ta Sy type       Ta Sy Description
.It Li device          Ta Ft char *     Ta Corresponding device node
.It Li cipher          Ta Ft char *     Ta Used cipher chain
.It Li prf             Ta Ft char *     Ta Used PBKDF2 PRF algorithm
.It Li key_bits        Ta Ft int *      Ta Number of key bits
.It Li size            Ta Ft int64_t *  Ta Volume size in bytes
.It Li iv_offset       Ta Ft int64_t *  Ta IV Offset of volume in bytes
.It Li block_offset    Ta Ft int64_t *  Ta Block Offset of volume in bytes
.El
.Pp
The second vararg argument must be of the type specified in the above table.
The first vararg argument is always the size of the storage provided
in the second argument.
For a
.Ft char *
argument, the size corresponds to the size of the buffer at the provided
location and must be of type
.Ft size_t .
For an
.Ft int *
or
.Ft int64_t *
argument, it should be the size of the underlying type.
.Pp
The
.Fn tc_api_task_get_error
function can be used to get a detailed error message after a failed
.Fa tc_api_task_do
call.
The
.Fa task
argument is the task used in a previous
.Fn tc_api_task_do
call.
.Sh NOTES
TrueCrypt limits passphrases to 64 characters (including the terminating
null character).
To be compatible with it,
.Nm tcplay
does the same.
All passphrases (exlcuding keyfiles) are trimmed to 64 characters.
Similarly, keyfiles are limited to a size of 1 MB, but up to 256
keyfiles can be used.
.Sh RETURN VALUES
All functions except
.Fn tc_api_task_init
and
.Fn tc_api_task_get_error
return either
.Dv TC_OK
to indicate that the operation completed successfully, or
.Dv TC_ERR_UNIMPL
to indicate that the operation is not implemented
, or
.Dv TC_ERR
to indicate that any other error occured.
.Pp
The
.Fn tc_api_task_get_error
function always return a valid, but possibly empty (or irrelevant,
if not called after an error occurred) string.
.Pp
The
.Fn tc_api_task_init
function returns
.Dv NULL
if an error occurred and an opaque
.Ft tc_api_task
otherwise.
.Sh COMPATIBILITY
The
.Nm tcplay
library offers full compatibility with TrueCrypt volumes including
hidden
volumes, system encryption (map-only), keyfiles and cipher cascading.
.Sh SEE ALSO
.Xr tcplay 8 ,
.Xr kpartx 8
.Sh HISTORY
The
.Nm tcplay
library appeared in
.Dx 2.11 .
.Sh AUTHORS
.An Alex Hornung