src/lib/libnetpgp.3

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.Dd June 17, 2010
.Dt LIBNETPGP 3
.Os
.Sh NAME
.Nm libnetpgp
.Nd digital signing and verification, encryption and decryption
.Sh LIBRARY
.Lb libnetpgp
.Sh SYNOPSIS
.In netpgp.h
.Pp
The following functions relate to initialisations and finalisations:
.Ft int
.Fo netpgp_init
.Fa "netpgp_t *netpgp"
.Fc
.Ft int
.Fo netpgp_end
.Fa "netpgp_t *netpgp"
.Fc
.Pp
The following functions are for debugging, reflection and information:
.Ft int
.Fo netpgp_set_debug
.Fa "const char *filename"
.Fc
.Ft int
.Fo netpgp_get_debug
.Fa "const char *filename"
.Fc
.Ft int
.Fo netpgp_get_info
.Fa "const char *type"
.Fc
.Ft int
.Fo netpgp_list_packets
.Fa "netpgp_t *netpgp" "char *filename" "int armour" "char *pubringname"
.Fc
.Pp
The following functions are for variable management:
.Ft int
.Fo netpgp_setvar
.Fa "netpgp_t *netpgp" "const char *name" "const char *value"
.Fc
.Ft char *
.Fo netpgp_getvar
.Fa "netpgp_t *netpgp" "const char *name"
.Fc
.Ft int
.Fo netpgp_incvar
.Fa "netpgp_t *netpgp" "const char *name" "const int delta"
.Fc
.Pp
The following function sets the home directory:
.Ft int
.Fo netpgp_set_homedir
.Fa "netpgp_t *netpgp" "char *homedir" "char *subdir" "const int quiet"
.Fc
.Pp
The following functions are used for key management:
.Ft int
.Fo netpgp_list_keys
.Fa "netpgp_t *netpgp" "const int printsigs"
.Fc
.Ft int
.Fo netpgp_match_list_keys
.Fa "netpgp_t *netpgp" "char *pattern"
.Fc
.Ft int
.Fo netpgp_find_key
.Fa "netpgp_t *netpgp" "char *userid"
.Fc
.Ft char *
.Fo netpgp_get_key
.Fa "netpgp_t *netpgp" "const char *id"
.Fc
.Ft int
.Fo netpgp_export_key
.Fa "netpgp_t *netpgp" "char *userid"
.Fc
.Ft int
.Fo netpgp_import_key
.Fa "netpgp_t *netpgp" "char *file"
.Fc
.Ft int
.Fo netpgp_generate_key
.Fa "netpgp_t *netpgp" "char *userid" "int numbits"
.Fc
.Pp
The following functions are used for file management:
.Ft int
.Fo netpgp_encrypt_file
.Fa "netpgp_t *netpgp" "char *userid" "char *filename" "char *out"
.Fa "int armored"
.Fc
.Ft int
.Fo netpgp_decrypt_file
.Fa "netpgp_t *netpgp" "char *filename" "char *out" "int armored"
.Fc
.Ft int
.Fo netpgp_sign_file
.Fa "netpgp_t *netpgp" "char *userid" "char *filename" "char *out"
.Fa "int armored" "int cleartext" "int detached"
.Fc
.Ft int
.Fo netpgp_verify_file
.Fa "netpgp_t *netpgp" "char *f" "int armored"
.Fc
.Pp
The following functions are used for memory signing and encryption:
.Ft int
.Fo netpgp_encrypt_memory
.Fa "netpgp_t *netpgp" "char *userid" "void *in" "const size_t insize"
.Fa "char *out" "size_t outsize" "int armored"
.Fc
.Ft int
.Fo netpgp_decrypt_memory
.Fa "netpgp_t *netpgp" "const void *input" "const size_t insize"
.Fa "char *out" "size_t outsize" "const int armored"
.Fc
.Ft int
.Fo netpgp_sign_memory
.Fa "netpgp_t *netpgp" "const char *userid" "char *mem"
.Fa "size_t size" "char *out" "size_t outsize"
.Fa "const unsigned armored" "const unsigned cleartext"
.Fc
.Ft int
.Fo netpgp_verify_memory
.Fa "netpgp_t *netpgp" "const void *in" "const size_t insize"
.Fa "void *out" "size_t outsize" "const int armored"
.Fc
.Sh DESCRIPTION
.Nm
is a library interface to enable digital signatures to be created and
verified, and also for files and memory to be encrypted and decrypted.
Functions are also provided for management of user keys.
.Pp
The library uses functions from the openssl library for multi-precision
integer arithmetic, and for RSA and DSA key signing and verification,
encryption and decryption.
.Pp
Normal operation sees the
.Nm
process be initialised using the
.Fn netpgp_init
function, which will set up the public and private keyrings, and set the
user identity to the
.Ar userid
argument passed stored in the
.Dv netpgp_t
structure, and set using the
.Fn netpgp_setvar
function.
If no public key ring file is set, initial values will be taken from those
in the
.Pa .gnupg/pubring.gpg
file in the user's home directory.
Similarily, if no secret key ring file is set,
initial values will be taken from those
in the
.Pa .gnupg/secring.gpg
file in the user's home directory.
The
.Fn netpgp_init
returns 1 on sucess, 0 on failure.
.Pp
To list all the keys in a keyring, the
.Fn netpgp_list_keys
function is used.
The signature subkey fields can also be displayed
using this function.
The
.Fn netpgp_match_list_keys
function is used to match (via regular expression)
a subset of the keys in the keyring.
If the expression to match is NULL,
the search will degenerate into a
listing of all keys in the keyring.
.Pp
The home directory is specified as an internal variable,
and its existence is checked using the
.Fn netpgp_set_homedir
function.
This function can operate in a verbose or quiet
manner, depending on the value of the argument provided.
If the subdirectory argument is provided, this subdirectory
is appended to the home directory in order to search for
the keyrings.
.Pp
To export a key, the
.Fn netpgp_export_key
is used.
Output is sent to the standard output.
.Pp
To import a key onto the public keyring, the
.Fn netpgp_import_key
is used.
The name of the file containing the key to be imported is provided
as the filename argument.
.Pp
To generate a key, the
.Fn netpgp_generate_key
is used.
It takes an argument of the number of bits to use in the key.
At the time that this manual page was created (April 2009),
the recommendations are that the bare minimum key size
of at least 2048 bits is used, and it would be much better
to use at least 4096 or 8192 bits.
This situation should be monitored to ensure that it does
not go out of date.
.Pp
Encryption, decryption, signing and verification of
files are the lifeblood of the
.Nm
library.
To encrypt a file, the
.Fn netpgp_encrypt_file
and the
.Fn netpgp_decrypt_file
is used to decrypt the results of the encryption.
To sign a file, the
.Fn netpgp_sign_file
is used, and the resulting signed file can be verified
using the
.Fn netpgp_verify_file
function.
.Pp
.Fn netpgp_sign_memory
is a function which can sign an area
of memory, and
.Fn netpgp_verify_memory
verifies the digital signature produced.
.Pp
Internally, an encrypted or signed file
is made up of
.Dq packets
which hold information pertaining to the signature,
encryption method, and the data which is being protected.
This information can be displayed in a verbose manner using
the
.Fn netpgp_list_packets
function.
.Pp
The
.Fn netpgp_setvar
and
.Fn netpgp_getvar
functions are used to manage the hash algorithm that
is used with RSA signatures.
These functions are general purpose functions, and
are used to set and retrieve values for internal variables.
For example, they
can be used to set and to retrieve the
value of the user id
which has been set,
the home directory from which to find the keyrings,
the verbosity settings, and many more.
The
.Fn netpgp_incvar
function is used to add a numeric increment to the
internal variable.
This incremental value can be negative.
It is primarily used to increase the verbosity settings.
.Pp
In
.Nm
files are encrypted using the public key of the userid.
The secret key is used to decrypt the results of that encryption.
Files are signed using the secret key of the userid.
The public key is used to verify that the file was signed,
who signed the file, and the date and time at which it was signed.
.Pp
Some utility functions are also provided for debugging, and for
finding out version and maintainer information from calling programs.
These are the
.Fn netpgp_set_debug
and the
.Fn netpgp_get_debug
functions (for getting verbose debugging information on a per-source
file basis).
.Pp
The
.Fn netpgp_get_info
returns the version or maintainer information depending upon the
.Ar type
argument.
At the present time, two types are defined:
.Dq version
and
.Dq maintainer .
A failure to present a known
.Ar type
argument to
.Fn netpgp_get_info
will result in the string
.Dq [unknown]
being returned.
.Sh SEE ALSO
.Xr netpgp 1 ,
.Xr ssl 3
.Sh HISTORY
The
.Nm
library first appeared in
.Nx 6.0 .
.Sh AUTHORS
.An Ben Laurie ,
.An Rachel Willmer .
.An Alistair Crooks Aq Mt agc@NetBSD.org
wrote this high-level interface.
.Pp
This manual page was written by
.An Alistair Crooks .