1.\" $NetBSD: libnetpgpverify.3,v 1.6 2014/02/17 07:23:18 agc Exp $
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3.\" Copyright (c) 2012 Alistair Crooks <agc@NetBSD.org>
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26.Dd February 16, 2014
27.Dt LIBNETPGPVERIFY 3
28.Os
29.Sh NAME
30.Nm libnetpgpverify
31.Nd library to verify digital signatures
32.Sh LIBRARY
33.Lb libnetpgpverify
34.Sh SYNOPSIS
35.In netpgp/verify.h
36.Ft int
37.Fo pgpv_read_pubring
38.Fa "pgpv_t *pgp" "const void *keyring" "ssize_t size"
39.Fc
40.Ft size_t
41.Fo pgpv_verify
42.Fa "pgpv_cursor_t *cursor" "pgpv_t *pgp" "const void *ptr" "ssize_t size"
43.Fc
44.Ft size_t
45.Fo pgpv_get_verified
46.Fa "pgpv_cursor_t *cursor" "size_t cookie" "char **ret"
47.Fc
48.Ft size_t
49.Fo pgpv_get_entry
50.Fa "pgpv_t *pgp" "unsigned ent" "char **ret"
51.Fc
52.Ft int
53.Fo pgpv_close
54.Fa "pgpv_t *pgp"
55.Fc
56.Sh DESCRIPTION
57.Nm
58is a small library which will verify a digital signature on a text or
59binary document.
60It has been kept deliberately small and only uses compression libraries
61to function.
62.Pp
63PGP messages, including key rings, are made up of PGP packets, defined
64in RFC 4880.
65To match a digital signature, the public key of the signer must be
66located in a public key ring.
67This library has enough functionality to parse a pubkey keyring,
68using
69.Fn pgpv_read_pubring
70to read the public keys of trusted identities,
71and to read files or memory which has already been signed.
72The
73.Fn pgpv_verify
74function is used to verify the signature, either on data, or on memory.
75To signal to
76.Fn pgpv_verify
77to read a file and verify it, the
78.Dv size
79argument should be set to
80.Dv -1
81whilst a positive size signals that the pointer value should be that
82of signed memory.
83.Fn pgpv_verify
84returns a cookie if the ignature was verified, or 0 if it did not.
85This cookie can subsequently be used to retrieve the data which
86was verified.
87.Pp
88If the signature does match, then the file or memory can be considered as being
89verified as being unmodified and unchanged, integrally sound.
90.Pp
91Signatures have validity dates on them, and it is possible for a signature to
92have expired when it is being checked.
93If for any reason the signature does not match, then the reason for not
94verifying the signature will be stored in the
95.Dv why
96buffer in the
97.Dv pgpv_cursor_t
98structure.
99.Pp
100Occasionally, the memory or contents of the file which matched the signature
101will be needed, rather than a boolean value of whether it was verified.
102To do this, the
103.Fn pgpv_get_verified
104function is used.
105Arguments to
106.Fn pgpv_get_verified
107are the cookie returned from the verification, and a buffer
108allocated for the returned data and its size.
109If an error occurs, or the signature is not verified, a zero value is returned
110for the size.
111.Nm
112stores the starts of the data of all verified matches, and so the entry
113number argument is the index of the occurrence of verification.
114The first match will have an entry number of 0, the second 1, and so on.
115.Pp
116The
117.Fn pgpv_close
118function is used to clean up after all matching and verification has taken place.
119It frees and de-allocates all resources used in the verification of the signature.
120.Pp
121The program used for signing may encode into base64 encoding, and it may also
122use embedded compression to make the output smaller than it would otherwise be.
123This is handled automatically by
124.Nm .
125.Sh SEE ALSO
126.Xr bn 3 ,
127.\" .Xr bzlib2 3 ,
128.Xr zlib 3
129.Sh STANDARDS
130.Rs
131.%A J. Callas
132.%A L. Donnerhacke
133.%A H. Finney
134.%A D. Shaw
135.%A R. Thayer
136.%D November 2007
137.%R RFC 4880
138.%T OpenPGP Message Format
139.Re
140.Sh HISTORY
141The
142.Nm
143library first appeared in
144.Nx 7.0 .
145.Sh AUTHORS
146.An Alistair Crooks Aq Mt agc@NetBSD.org
147