LIBNETPGPVERIFY(3) FreeBSD Library Functions Manual LIBNETPGPVERIFY(3)
NAME
libnetpgpverify - library to verify digital signatures
LIBRARY
Netpgp Verification (libnetpgpverify, -lnetpgpverify)
SYNOPSIS
#include <netpgp/verify.h>
int
pgpv_new(void);
int
pgpv_new_cursor(void);
int
pgpv_read_pubring(pgpv_t *pgp, const void *keyring, ssize_t size);
int
pgpv_read_ssh_pubkeys(pgpv_t *pgp, const void *keyring, ssize_t size);
size_t
pgpv_verify(pgpv_cursor_t *cursor, pgpv_t *pgp, const void *ptr,
ssize_t size);
size_t
pgpv_get_verified(pgpv_cursor_t *cursor, size_t cookie, char **ret);
size_t
pgpv_get_cursor_element(pgpv_cursor_t *cursor, size_t element);
size_t
pgpv_dump(pgpv_t *pgp, char **data);
size_t
pgpv_get_entry(pgpv_t *pgp, unsigned ent, char **ret,
const char *modifiers);
int64_t
pgpv_get_cursor_num(pgpv_t *pgp, const char *field);
char *
pgpv_get_cursor_str(pgpv_t *pgp, const char *field);
int
pgpv_close(pgpv_t *pgp);
DESCRIPTION
libnetpgpverify is a small library which will verify a digital signature
on a text or binary document. It has been kept deliberately small and
only uses compression libraries to function.
PGP messages, including key rings, are made up of PGP packets, defined in
RFC 4880. To match a digital signature, the public key of the signer
must be located in a public key ring. This library has enough
functionality to parse a pubkey keyring, using pgpv_read_pubring() to
read the public keys of trusted identities, and to read files or memory
which has already been signed. SSH public keys can also be used for
signature verification by using the pgpv_read_ssh_pubkeys() function.
Please note that the creation date of the signature key will show up as
January 1st 1970, due to the fact that the creation date of the key is
not encoded anywhere for an ssh key, whilst it is an inherent part of the
PGP fingerprint. In order that the correct fingerprint is used, the key
creation date is forced to 0.
The pgpv_verify() function is used to verify the signature, either on
data, or on memory. To signal to pgpv_verify() to read a file and verify
it, the size argument should be set to -1 whilst a positive size signals
that the pointer value should be that of signed memory. pgpv_verify()
returns a cookie if the ignature was verified, or 0 if it did not. This
cookie can subsequently be used to retrieve the data which was verified.
If the signature does match, then the file or memory can be considered as
being verified as being unmodified and unchanged, integrally sound.
Signatures have validity dates on them, and it is possible for a
signature to have expired when it is being checked. If for any reason
the signature does not match, then the reason for not verifying the
signature will be stored in the why buffer in the pgpv_cursor_t
structure.
Occasionally, the memory or contents of the file which matched the
signature will be needed, rather than a boolean value of whether it was
verified. To do this, the pgpv_get_verified() function is used.
Arguments to pgpv_get_verified() are the cookie returned from the
verification, and a buffer allocated for the returned data and its size.
If an error occurs, or the signature is not verified, a zero value is
returned for the size. libnetpgpverify stores the starts of the data of
all verified matches, and so the entry number argument is the index of
the occurrence of verification. The first match will have an entry
number of 0, the second 1, and so on.
The pgpv_close() function is used to clean up after all matching and
verification has taken place. It frees and de-allocates all resources
used in the verification of the signature.
The program used for signing may encode into base64 encoding, and it may
also use embedded compression to make the output smaller than it would
otherwise be. This is handled automatically by libnetpgpverify
SEE ALSO
bn(3), zlib(3)
STANDARDS
The libnetpgpverify utility is designed to conform to IETF RFC 4880.
HISTORY
The libnetpgpverify library first appeared in NetBSD 7.0.
AUTHORS
Alistair Crooks <
[email protected]>
FreeBSD 14.1-RELEASE-p8 June 26, 2016 FreeBSD 14.1-RELEASE-p8