NAME
libnetpgp —
digital signing and
verification, encryption and decryption
LIBRARY
Netpgp Signing, Verification, Encryption and Decryption
(libnetpgp, -lnetpgp)
SYNOPSIS
#include <netpgp.h>
The following functions relate to initialisations and finalisations:
int
netpgp_init(
netpgp_t *netpgp);
int
netpgp_end(
netpgp_t *netpgp);
The following functions are for debugging, reflection and information:
int
netpgp_set_debug(
const char *filename);
int
netpgp_get_debug(
const char *filename);
int
netpgp_get_info(
const char *type);
int
netpgp_list_packets(
netpgp_t *netpgp,
char *filename,
int armour,
char *pubringname);
The following functions are for variable management:
int
netpgp_setvar(
netpgp_t *netpgp,
const char *name,
const char
*value);
char *
netpgp_getvar(
netpgp_t *netpgp,
const char *name);
int
netpgp_incvar(
netpgp_t *netpgp,
const char *name,
const int
delta);
int
netpgp_unsetvar(
netpgp_t *netpgp,
const char *name);
The following function sets the home directory:
int
netpgp_set_homedir(
netpgp_t *netpgp,
char *homedir,
char *subdir,
const int quiet);
The following functions are used for key management:
int
netpgp_list_keys(
netpgp_t *netpgp,
const int printsigs);
int
netpgp_list_keys_json(
netpgp_t *netpgp,
char **json,
const int psigs);
int
netpgp_match_keys(
netpgp_t *netpgp,
char *name,
const char *fmt,
void *vp,
const int psigs);
int
netpgp_match_keys_json(
netpgp_t *netpgp,
char **json,
char *name,
const char *fmt,
const int psigs);
int
netpgp_match_pubkeys(
netpgp_t *netpgp,
char *name,
void *vp);
int
netpgp_find_key(
netpgp_t *netpgp,
char *userid);
char *
netpgp_get_key(
netpgp_t *netpgp,
const char *name,
const char
*fmt);
int
netpgp_export_key(
netpgp_t *netpgp,
char *userid);
int
netpgp_import_key(
netpgp_t *netpgp,
char *file);
int
netpgp_generate_key(
netpgp_t *netpgp,
char *userid,
int numbits);
int
netpgp_validate_sigs(
netpgp_t *netpgp);
int
netpgp_format_json(
void *vp,
const char *json,
const int
psigs);
The following functions are used for file management:
int
netpgp_encrypt_file(
netpgp_t *netpgp,
const char *userid,
const char
*filename,
char *out,
int
armored);
int
netpgp_decrypt_file(
netpgp_t *netpgp,
const char *filename,
char *out,
int armored);
int
netpgp_sign_file(
netpgp_t *netpgp,
const char *userid,
const char
*filename,
char *out,
int
armored,
int cleartext,
int
detached);
int
netpgp_verify_file(
netpgp_t *netpgp,
const char *in,
const char *out,
int armored);
The following functions are used for memory signing and encryption:
int
netpgp_encrypt_memory(
netpgp_t *netpgp,
const char *userid,
void *in,
const size_t insize,
char *out,
size_t outsize,
int armored);
int
netpgp_decrypt_memory(
netpgp_t *netpgp,
const void *input,
const size_t
insize,
char *out,
size_t
outsize,
const int armored);
int
netpgp_sign_memory(
netpgp_t *netpgp,
const char *userid,
char *mem,
size_t size,
char *out,
size_t outsize,
const unsigned
armored,
const unsigned cleartext);
int
netpgp_verify_memory(
netpgp_t *netpgp,
const void *in,
const size_t
insize,
void *out,
size_t
outsize,
const int armored);
DESCRIPTION
libnetpgp 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.
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.
Normal operation sees the
libnetpgp process be initialised
using the
netpgp_init() function, which will set up the
public and private keyrings, as well as set the user identity in the
userid member of the
netpgp_t
structure. These are set using the
netpgp_setvar() function.
If no public key ring file is set, initial values will be taken from those in
the
.gnupg/pubring.gpg file in the user's home directory.
Similarly, if no secret key ring file is set, initial values will be taken
from those in the
.gnupg/secring.gpg file in the user's home
directory. The user identity is obtained from the
userid
environment variable, or failing that, the
value of the “default-key” setting from
.gnupg/gpg.conf file in the user's home directory is used.
The
netpgp_init() function returns 1 on success, 0 on
failure.
To list all the keys in a keyring, the
netpgp_list_keys()
function is used. The signature subkey fields can also be displayed using this
function.
The home directory is specified as an internal variable, and its existence is
checked using the
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.
To export a key, the
netpgp_export_key() function is used.
Output is sent to the standard output.
To import a key onto the public keyring, the
netpgp_import_key() function is used. The name of the file
containing the key to be imported is provided as the filename argument.
To generate a key, the
netpgp_generate_key() function 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.
Encryption, decryption, signing and verification of files are the lifeblood of
the
libnetpgp library. To encrypt a file, the
netpgp_encrypt_file() function is used, and the
netpgp_decrypt_file() function is used to decrypt the
results of the encryption. To sign a file, the
netpgp_sign_file() function is used, and the resulting
signed file can be verified using the
netpgp_verify_file()
function.
netpgp_sign_memory() is a function which can sign an area of
memory, and
netpgp_verify_memory() verifies the digital
signature produced.
Internally, an encrypted or signed file is made up of “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
netpgp_list_packets() function.
The
netpgp_setvar() and
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
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.
In
libnetpgp 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.
Some utility functions are also provided for debugging, and for finding out
version and maintainer information from calling programs. These are the
netpgp_set_debug() and the
netpgp_get_debug() functions (for getting verbose debugging
information on a per-source file basis).
The
netpgp_get_info() function returns the version or
maintainer information depending upon the
type argument.
At the present time, two types are defined: “version” and
“maintainer”. A failure to present a known
type argument to
netpgp_get_info()
will result in the string “[unknown]” being returned.
SEE ALSO
netpgp(1),
ssl(3)
HISTORY
The
libnetpgp library first appeared in
NetBSD 6.0.
AUTHORS
Ben Laurie,
Rachel Willmer.
Alistair Crooks
<
agc@NetBSD.org> wrote
this high-level interface.
This manual page was written by
Alistair Crooks.