lib/libkeynote/keynote.3

.\" $OpenBSD: keynote.3,v 1.54 2017/07/05 11:43:09 schwarze Exp $
.\"
.\" The author of this code is Angelos D. Keromytis (angelos@dsl.cis.upenn.edu)
.\"
.\" This code was written by Angelos D. Keromytis in Philadelphia, PA, USA,
.\" in April-May 1998
.\"
.\" Copyright (C) 1998, 1999 by Angelos D. Keromytis.
.\"
.\" Permission to use, copy, and modify this software with or without fee
.\" is hereby granted, provided that this entire notice is included in
.\" all copies of any software which is or includes a copy or
.\" modification of this software.
.\" You may use this code under the GNU public license if you so wish. Please
.\" contribute changes back to the author.
.\"
.\" THIS SOFTWARE IS BEING PROVIDED "AS IS", WITHOUT ANY EXPRESS OR
.\" IMPLIED WARRANTY. IN PARTICULAR, THE AUTHORS MAKES NO
.\" REPRESENTATION OR WARRANTY OF ANY KIND CONCERNING THE
.\" MERCHANTABILITY OF THIS SOFTWARE OR ITS FITNESS FOR ANY PARTICULAR
.\" PURPOSE.
.\"
.Dd $Mdocdate: July 5 2017 $
.Dt KN_INIT 3
.\" .TH KeyNote 3 local
.Os
.Sh NAME
.Nm kn_init ,
.Nm kn_add_assertion ,
.Nm kn_remove_assertion ,
.Nm kn_add_action ,
.Nm kn_remove_action ,
.Nm kn_add_authorizer ,
.Nm kn_remove_authorizer ,
.Nm kn_do_query ,
.Nm kn_get_failed ,
.Nm kn_cleanup_action_environment ,
.Nm kn_close ,
.Nm kn_query ,
.Nm kn_read_asserts ,
.Nm kn_keycompare ,
.Nm kn_get_authorizer ,
.Nm kn_get_licensees ,
.Nm kn_encode_base64 ,
.Nm kn_decode_base64 ,
.Nm kn_encode_hex ,
.Nm kn_decode_hex ,
.Nm kn_encode_key ,
.Nm kn_decode_key ,
.Nm kn_sign_assertion ,
.Nm kn_verify_assertion ,
.Nm kn_free_key ,
.Nm kn_get_string
.Nd a trust-management system library
.Sh SYNOPSIS
.In sys/types.h
.In regex.h
.In keynote.h
.Bd -literal
struct environment {
	char               *env_name;
	char               *env_value;
	int                 env_flags;
	regex_t             env_regex;
	struct environment *env_next;
};

struct keynote_deckey {
	int   dec_algorithm;
	void *dec_key;
};

struct keynote_binary {
	int   bn_len;
	char *bn_key;
};

struct keynote_keylist {
	int                     key_alg;
	void                   *key_key;
	char                   *key_stringkey;
	struct keynote_keylist *key_next;
};
.Ed
.Vt extern int keynote_errno;
.Ft int
.Fn kn_init "void"
.Ft int
.Fn kn_add_assertion "int sessid" "char *assertion" "int len" "int flags"
.Ft int
.Fn kn_remove_assertion "int sessid" "int assertid"
.Ft int
.Fn kn_add_action "int sessid" "char *name" "char *value" "int flags"
.Ft int
.Fn kn_remove_action "int sessid" "char *name"
.Ft int
.Fn kn_add_authorizer "int sessid" "char *principal"
.Ft int
.Fn kn_remove_authorizer "int sessid" "char *principal"
.Ft int
.Fn kn_do_query "int sessid" "char **returnvalues" "int numvalues"
.Ft int
.Fn kn_get_failed "int sessid" "int type" "int seq"
.Ft int
.Fn kn_cleanup_action_environment "int sessid"
.Ft int
.Fn kn_close "int sessid"
.Ft int
.Fo kn_query
.Fa "struct environment *env"
.Fa "char **returnvalues"
.Fa "int numvalues"
.Fa "char **trusted"
.Fa "int *trustedlen"
.Fa "int numtrusted"
.Fa "char **untrusted"
.Fa "int *untrustedlen"
.Fa "int numuntrusted"
.Fa "char **authorizers"
.Fa "int numauthorizers"
.Fc
.Ft char **
.Fn kn_read_asserts "char *array" "int arraylen" "int *numassertions"
.Ft int
.Fn kn_keycompare "void *key1" "void *key2" "int algorithm"
.Ft void *
.Fn kn_get_authorizer "int sessid" "int assertid" "int *algorithm"
.Ft struct keynote_keylist *
.Fn kn_get_licensees "int sessid" "int assertid"
.Ft int
.Fn kn_encode_base64 "unsigned char const *src" "unsigned int srclen" "char *dst" "unsigned int dstlen"
.Ft int
.Fn kn_decode_base64 "char const *src" "unsigned char *dst" "unsigned int dstlen"
.Ft int
.Fn kn_encode_hex "unsigned char *src" "char **dst" "int srclen"
.Ft int
.Fn kn_decode_hex "char *src" "char **dst"
.Ft char *
.Fn kn_encode_key "struct keynote_deckey *dc" "int iencoding" "int encoding" "int keytype"
.Ft int
.Fn kn_decode_key "struct keynote_deckey *dc" "char *key" "int keytype"
.Ft char *
.Fn kn_sign_assertion "char *assertion" "int len" "char *key" "char *algorithm" "int vflag"
.Ft int
.Fn kn_verify_assertion "char *assertion" "int len"
.Ft void
.Fn kn_free_key "struct keynote_deckey *"
.Ft char *
.Fn kn_get_string "char *"
.Fd Link options: -lkeynote -lm -lcrypto
.Sh DESCRIPTION
For more details on
.Nm keynote ,
see RFC 2704.
.Pp
.Va keynote_errno
contains an error code if some library call failed.
Failed calls return \-1 (if their return value is integer), or
.Dv NULL
(if their return value is a pointer) and set
.Va keynote_errno .
The defined error codes are:
.Bl -tag -width "ERROR_NOTFOUND" -offset indent
.It Li ERROR_MEMORY
Some memory allocation or usage error was encountered.
.It Li ERROR_SYNTAX
Some syntactic or logical error was encountered.
.It Li ERROR_NOTFOUND
One of the arguments referred to a nonexistent structure or entry.
.El
.Pp
If no errors were encountered,
.Va keynote_errno
will be set to 0.
This variable should be reset to 0 if an error was encountered,
prior to calling other library routines.
.Pp
The main interface to
.Nm
is centered around the concept of a session.
A session describes a collection of policies, assertions, action
authorizers, return values, and action attributes that the
.Nm
system uses to evaluate a query.
Information is not shared between sessions.
Policies, credentials, action authorizers, and action
attributes can be added or deleted at any point during the lifetime of
a session.
Furthermore, an application can discover which assertions failed to be
evaluated, and in what way, during a query.
.Pp
For those applications that only need to do a simple query, there
exists a single call that takes as arguments all the necessary
information and performs all the necessary steps.
This is essentially a wrapper that calls the session API functions as
necessary.
.Pp
Finally, there exist functions for doing ASCII to hexadecimal and
Base64 encoding (and vice versa), for encoding/decoding keys between
ASCII and binary formats, and for signing and verifying assertions.
.Pp
The description of all
.Nm
library functions follows.
.Pp
.Fn kn_init
creates a new
.Nm
session, and performs any necessary initializations.
On success, this function returns the new session ID, which is used by
all subsequent calls with a
.Fa sessid
argument.
On failure, it returns \-1 and sets
.Va keynote_errno
to
.Er ERROR_MEMORY .
.Pp
.Fn kn_add_assertion
adds the assertion pointed to by the array
.Fa assertion ,
of length
.Fa len
in the session identified by
.Fa sessid .
The first argument can be discarded after the call to this function.
The following flags are defined:
.Bl -tag -width ASSERT_FLAG_LOCAL -offset indent
.It ASSERT_FLAG_LOCAL
Mark this assertion as ultimately trusted.
Trusted assertions need not be signed, and the
.Fa Authorizer
and
.Fa Licensees
fields can have non-key entries.
.El
.Pp
At least one (trusted) assertion should have
.Dv POLICY
as the
.Fa Authorizer .
On success, this function will return an assertion ID which can be
used to remove the assertion from the session, by using
.Fn kn_remove_assertion .
On failure, \-1 is returned, and
.Va keynote_errno
is set to
.Er ERROR_NOTFOUND
if the session was not found,
.Er ERROR_SYNTAX
if the assertion was syntactically incorrect, or
.Er ERROR_MEMORY
if necessary memory could not be allocated.
.Pp
.Fn kn_remove_assertion
removes the assertion identified by
.Fa assertid
from the session identified by
.Fa sessid .
On success, this function returns 0.
On failure, it returns \-1 and sets
.Va keynote_errno
to
.Er ERROR_NOTFOUND .
.Pp
.Fn kn_add_action
inserts the variable
.Fa name
in the action environment of session
.Fa sessid ,
with the value
.Fa value .
The same attribute may be added more than once, but only the last
instance will be used (memory resources are consumed however).
.Pp
The
.Fa flags
specified are formed by or'ing the following values:
.Bl -tag -width ENVIRONMENT_FLAG_REGEX -offset indent
.It ENVIRONMENT_FLAG_FUNC
In this case,
.Fa value
is a pointer to a function that takes as argument a string and returns
a string.
This is used to implement callbacks for getting action attribute values.
The argument passed to such a callback function is a string identifying
the action attribute whose value is requested, and should return a pointer
to string containing that value (this pointer will not be freed by the
library), the empty string if the value was not found, or a
.Dv NULL
to indicate an error (and may set
.Va keynote_errno
appropriately).
Prior to first use (currently, at the time the attribute is added to the
session environment), such functions are called with
.Dv KEYNOTE_CALLBACK_INITIALIZE
as the argument (defined in keynote.h) so that they can perform any special
initializations.
Furthermore, when the session is deleted, all such functions will be called
with
.Dv KEYNOTE_CALLBACK_CLEANUP
to perform any special cleanup (such as free any allocated memory).
A function may be called with either of these arguments more than once,
if it has been defined as the callback function for more than one attribute.
.It ENVIRONMENT_FLAG_REGEX
In this case,
.Fa name
is a regular expression that may match more than one attribute.
In case of conflict between a regular expression and a
.Dq simple
attribute, the latter will be given priority.
In case of conflict between two regular expression attributes, the one added
later will be given priority.
A callback function should never change the current
.Nm
session, start/invoke/operate on another session, or call one of the
session-API functions.
.El
.Pp
The combination of the two flags may be used to specify callback
functions that handle large sets of attributes (even to the extent of
having one callback function handling all attribute references).
This is particularly useful when the action attribute set is particularly
large.
.Pp
On success,
.Fn kn_add_action
returns 0.
On failure, it returns \-1 and sets
.Va keynote_errno
to
.Er ERROR_NOTFOUND
if the session was not found,
.Er ERROR_SYNTAX
if the
.Fa name
was invalid (e.g., started with an underscore character) or was
.Dv NULL ,
or
.Er ERROR_MEMORY
if necessary memory could not be allocated.
.Pp
.Fn kn_remove_action
removes action attribute
.Fa name
from the environment of session
.Fa sessid .
Notice that if more than one instances of
.Fa name
exist, only the one added last will be deleted.
On success, this function returns 0.
On failure, it returns \-1 and
.Va keynote_errno
is set to
.Er ERROR_NOTFOUND
if the session or the attribute were not found, or
.Er ERROR_SYNTAX
if the name was invalid.
If the attribute value was a callback, that function will be called with
the define
.Dv KEYNOTE_CALLBACK_CLEANUP
as the argument.
.Pp
.Fn kn_add_authorizer
adds the principal pointed to by
.Fa principal
to the action authorizers list of session
.Fa sessid .
The principal is typically an ASCII-encoded key.
On success, this function will return 0.
On failure, it returns \-1 and sets
.Va keynote_errno
to
.Er ERROR_NOTFOUND
if the session was not found,
.Er ERROR_SYNTAX
if the encoding was invalid, or
.Er ERROR_MEMORY
if necessary memory could not be allocated.
.Pp
.Fn kn_remove_authorizer
removes
.Fa principal
from the action authorizer list of session
.Fa sessid .
On success, this function returns 0.
On failure, it returns \-1 and sets
.Va keynote_errno
to
.Er ERROR_NOTFOUND
if the session was not found.
.Pp
.Fn kn_do_query
evaluates the request based on the assertions, action attributes, and
action authorizers added to session
.Fa sessid .
.Fa returnvalues
is an ordered array of strings that contain the return values.
The lowest-ordered return value is contained in
.Fa returnvalues Ns Bq 0 ,
and the highest-ordered value is
.Fa returnvalues Ns Bq Fa numvalues No \- 1 .
If
.Fa returnvalues
is
.Dv NULL ,
the
.Fa returnvalues
from the previous call to
.Fn kn_do_query
will be used.
The programmer SHOULD NOT free
.Fa returnvalues
after the call to
.Fn kn_do_query
if this feature is used, as the array is not replicated internally.
On success, this function returns an index into the
.Fa returnvalues
array.
On failure, it returns \-1 and sets
.Va keynote_errno
to
.Er ERROR_NOTFOUND
if the session was not found or the authorizers list was empty,
.Er ERROR_SYNTAX
if no
.Fa returnvalues
have been specified, or
.Er ERROR_MEMORY
if necessary memory could not be allocated.
.Pp
.Fn kn_get_failed
returns the assertion ID of the
.Fa num'th
assertion (starting from zero) in session
.Fa sessid
that was somehow invalid during evaluation.
This function is typically called after
.Fn kn_do_query
is used to evaluate a request.
.Fa type
specifies the type of failure the application is interested in.
It can be set to:
.Bl -tag -width KEYNOTE_ERROR_SIGNATURE -offset indent
.It KEYNOTE_ERROR_ANY
to indicate interest in any error.
.It KEYNOTE_ERROR_SYNTAX
for syntactic or semantic errors.
.It KEYNOTE_ERROR_MEMORY
for memory-related problems.
.It KEYNOTE_ERROR_SIGNATURE
if the assertion could not be cryptographically verified.
.El
.Pp
These values are defined in keynote.h.
An application can then delete the offending assertion using
.Fn kn_remove_assertion .
For example, to remove all assertion whose signature failed, an application
could do something like:
.Bd -literal
  while ((assertid = kn_get_failed(sessid, KEYNOTE_ERROR_SIGNATURE, 0)
         != -1)
    kn_remove_assertion(sessid, assertid);
.Ed
.Pp
On success,
.Fn kn_get_failed
returns an assertion ID.
On failure, or when no assertion matching the given criteria is found,
it returns \-1 and set
.Va keynote_errno
to
.Er ERROR_NOTFOUND .
.Pp
.Fn kn_cleanup_action_environment
removes all action attributes from the action environment of session
.Fa sessid .
It returns 0 on success.
.Pp
.Fn kn_close
closes session
.Fa sessid
and frees all related resources, deleting action attributes, action
authorizers, and assertions.
On success, this function returns 0.
On failure, it returns \-1 and sets
.Va keynote_errno
to
.Er ERROR_NOTFOUND
if the session was not found.
.Pp
.Fn kn_read_asserts
parses the string
.Fa array
of length
.Fa arraylen
and returns an array of pointers to strings containing copies of
the assertions found in
.Fa array .
Both the array of pointers and the strings are allocated by
.Fn kn_read_asserts
dynamically, and thus should be freed by the programmer when they are
no longer needed.
.Fa numassertions
contains the number of assertions (and thus strings in the returned
array) found in
.Fa array .
On failure, this function returns
.Dv NULL
and sets
.Va keynote_errno
to
.Er ERROR_MEMORY
if necessary memory could not be allocated, or
.Er ERROR_SYNTAX
if
.Fa array
was
.Dv NULL .
Note that if there were no assertions found in
.Fa array ,
a valid pointer will be returned, but
.Fa numassertions
will contain the value zero on return.
The returned pointer should be freed by the programmer.
.Pp
.Fn kn_keycompare
compares
.Fa key1
and
.Fa key2
(which must be of the same
.Fa algorithm )
and returns 1 if equal and 0 otherwise.
.Pp
.Fn kn_get_authorizer
returns the authorizer key (in binary format) for assertion
.Fa assertid
in session
.Fa sessid .
It also sets the
.Fa algorithm
argument to the algorithm of the authorizer key.
On failure,
.Fn kn_get_authorizer
returns
.Dv NULL ,
and sets
.Va keynote_errno
to
.Er ERROR_NOTFOUND .
.Pp
.Fn kn_get_licensees
returns the licensee key(s) for assertion
.Fa assertid
in session
.Fa sessid .
The keys are returned in a linked list of
.Fa struct keynote_keylist
structures.
On failure,
.Fn kn_get_licensees
returns
.Dv NULL .
and sets
.Va keynote_errno
to
.Er ERROR_NOTFOUND .
.Pp
.Fn kn_query
takes as arguments a list of action attributes in
.Fa env ,
a list of return values in
.Fa returnvalues
(the number of returnvalues is indicated by
.Fa numvalues ) ,
a number
.Pf ( Fa numtrusted )
of locally-trusted assertions in
.Fa trusted
(the length of each assertion is given by the respective element of
.Fa trustedlen ) ,
a number
.Pf ( Fa numuntrusted )
of assertions that need to be cryptographically verified in
.Fa untrusted
(the length of each assertion is given by the respective element of
.Fa untrustedlen ) ,
and a number
.Pf ( Fa numauthorizers )
of action authorizers in
.Fa authorizers .
.Fa env
is a linked list of
.Fa struct environment
structures.
The
.Fa env_name ,
.Fa env_value ,
and
.Fa env_flags
fields correspond to the
.Fa name ,
.Fa value ,
and
.Fa flags
arguments to
.Fn kn_add_assertion
respectively.
.Fa env_regex
is not used.
On success, this function returns an index in
.Fa returnvalues
indicating the returned value to the query.
On failure, it returns \-1 and sets
.Va keynote_errno
to the same values as
.Fn kn_do_query ,
or to
.Er ERROR_MEMORY
if a trusted or untrusted assertion could not be added to the session due
to lack of memory resources.
Syntax errors in assertions will not be reported by
.Fn kn_query .
.Pp
.Fn kn_encode_base64
converts the data of length
.Fa srclen
contained in
.Fa src
in Base64 encoding and stores them in
.Fa dst
which is of length
.Fa dstlen .
The actual length of the encoding stored in
.Fa dst
is returned.
.Fa dst
should be long enough to also contain the trailing
string terminator.
If
.Fa dst
is not long enough to contain the encoded data, this function returns
\-1 and sets
.Va keynote_errno
to
.Er ERROR_SYNTAX .
.Pp
.Fn kn_decode_base64
decodes the Base64-encoded data stored in
.Fa src
and stores the result in
.Fa dst ,
which is of length
.Fa dstlen .
The actual length of the decoded data is returned on success.
On failure, this function returns \-1 and sets
.Va keynote_errno
to
.Er ERROR_SYNTAX ,
denoting either an invalid Base64 encoding or insufficient space in
.Fa dst .
.Pp
.Fn kn_encode_hex
encodes in ASCII-hexadecimal format the data of length
.Fa srclen
contained in
.Fa src .
This function allocates a chunk of memory to store the result, which
is returned in
.Fa dst .
Thus, this function should be used as follows:
.Bd -literal
  char *dst;

  kn_encode_hex(src, &dst, srclen);
.Ed
.Pp
The length of the allocated buffer will be (2 * srclen + 1).
On success, this function returns 0.
On failure, it returns \-1 and sets
.Va keynote_errno
to
.Er ERROR_MEMORY
if it failed to allocate enough memory,
.Er ERROR_SYNTAX
if
.Fa dst
was
.Dv NULL .
.Pp
.Fn kn_decode_hex
decodes the ASCII hex-encoded string in
.Fa src
and stores the result in a memory chunk allocated by the function.
A pointer to that memory is stored in
.Fa dst .
The length of the allocated memory will be (strlen(src) / 2).
On success, this function returns 0.
On failure, it returns \-1 and sets
.Va keynote_errno
to
.Er ERROR_MEMORY
if it could not allocate enough memory, or
.Er ERROR_SYNTAX
if
.Fa dst
was
.Dv NULL ,
or the length of
.Fa src
is not even.
.Pp
.Fn kn_encode_key
ASCII-encodes a cryptographic key.
The binary representation of the key is contained in
.Fa dc .
The field
.Fa dec_key
in that structure is a pointer to some cryptographic algorithm
dependent information describing the key.
In this implementation, this pointer should be a
.Fa DSA *
or
.Fa RSA *
for DSA or RSA keys respectively, as used in the SSL library, or a
.Fa keynote_binary *
for cryptographic keys whose algorithm
.Nm
does not know about but the application wishes to include in the
action authorizers (and thus need to be canonicalized).
The field
.Fa dec_algorithm
describes the cryptographic algorithm, and may be one of
.Dv KEYNOTE_ALGORITHM_DSA ,
.Dv KEYNOTE_ALGORITHM_RSA ,
or
.Dv KEYNOTE_ALGORITHM_BINARY
in this implementation.
.Pp
.Fa iencoding
describes how the key should be binary-encoded.
This implementation supports
.Dv INTERNAL_ENC_PKCS1
for RSA keys,
.Dv INTERNAL_ENC_ASN1
for DSA keys, and
.Dv INTERNAL_ENC_NONE
for BINARY keys.
.Fa encoding
describes what ASCII encoding should be applied to the key.
Valid values are
.Dv ENCODING_HEX
and
.Dv ENCODING_BASE64 ,
for hexadecimal and Base64 encoding respectively.
.Fa keytype
is one of
.Dv KEYNOTE_PUBLIC_KEY
or
.Dv KEYNOTE_PRIVATE_KEY
to indicate whether the key is public or private.
Private keys have the string
.Dv KEYNOTE_PRIVATE_KEY_PREFIX
(defined in keynote.h) prefixed to the algorithm name.
On success, this function returns a string containing the encoded key.
On failure, it returns
.Dv NULL
and sets
.Va keynote_errno
to
.Er ERROR_NOTFOUND
if the
.Fa dc
argument was invalid,
.Er ERROR_MEMORY
if it failed to allocate the necessary memory, or
.Er ERROR_SYNTAX
if the key to be converted was invalid.
.Pp
.Fn kn_decode_key
decodes the ASCII-encoded string contained in
.Fa key .
The result is placed in
.Fa dc ,
with
.Fa dec_algorithm
describing the algorithm (see
.Fn kn_encode_key ) ,
and
.Fa dec_key
pointing to an algorithm-dependent structure.
In this implementation, this is an SSLeay/OpenSSL-defined
.Fa DSA *
for DSA keys,
.Fa RSA *
for RSA and X.509-based keys, and a
.Fa keynote_binary *
for BINARY keys.
.Fa keytype
takes the values
.Dv KEYNOTE_PUBLIC_KEY
or
.Dv KEYNOTE_PRIVATE_KEY
to specify a public or private key, where applicable.
On success, this function returns 0.
On failure, it returns \-1 and sets
.Va keynote_errno
to
.Er ERROR_MEMORY
if necessary memory could not be allocated, or
.Er ERROR_SYNTAX
if the key or the ASCII encoding was malformed.
.Pp
.Fn kn_sign_assertion
produces the cryptographic signature for the assertion of length
.Fa len
stored in
.Fa assertion ,
using the ASCII-encoded cryptographic key contained in
.Fa key .
The type of signature to be produced is described by the string
.Fa algorithm .
Possible values for this string are
.Dv SIG_RSA_SHA1_PKCS1_HEX ,
.Dv SIG_RSA_SHA1_PKCS1_BASE64 ,
.Dv SIG_RSA_MD5_HEX
and
.Dv SIG_RSA_MD5_HEX
for RSA keys,
.Dv SIG_DSA_SHA1_HEX
and
.Dv SIG_DSA_SHA1_BASE64
for DSA keys,
.Dv SIG_X509_SHA1_HEX
and
.Dv SIG_X509_SHA1_BASE64
for X.509-based keys.
No other cryptographic signatures are currently
supported by this implementation.
If
.Fa vflag
is set to 1, then the generated signature will also be verified.
On success, this function returns a string containing the ASCII-encoded
signature, without modifying the
.Fa assertion .
On failure, it returns
.Dv NULL
and sets
.Va keynote_errno
to
.Er ERROR_NOTFOUND
if one of the arguments was
.Dv NULL ,
.Er ERROR_MEMORY
if necessary memory could not be allocated, or
.Er ERROR_SYNTAX
if the
.Fa algorithm ,
the
.Fa key ,
or the
.Fa assertion
(if signature verification was requested) was invalid.
.Pp
.Fn kn_verify_assertion
verifies the cryptographic signature on the assertion of length
.Fa len
contained in string
.Fa assertion .
On success, this function returns
.Dv SIGRESULT_TRUE
if the signature could be verified, or
.Dv SIGRESULT_FALSE
otherwise.
On failure, this function returns \-1 and sets
.Va keynote_errno
to
.Er ERROR_MEMORY
if necessary memory could not be allocated, or
.Er ERROR_SYNTAX
if the assertion contained a syntactic error, or the cryptographic
algorithm was not supported.
.Pp
.Fn kn_free_key
frees a cryptographic key.
.Pp
.Fn kn_get_string
parses the argument, treating it as a
.Xr keynote 4
(quoted) string.
This is useful for parsing key files.
On success, this function returns a pointer to the parsing result.
The result is dynamically allocated and should be freed after use.
On failure,
.Dv NULL
is returned.
.Sh FILES
.Bl -tag -width libkeynote.a -compact
.It Pa keynote.h
.It Pa libkeynote.a
.El
.Sh DIAGNOSTICS
The return values of all the functions have been given along with the
function description above.
.Sh SEE ALSO
.Xr keynote 1 ,
.Xr keynote 4 ,
.Xr keynote 5
.Rs
.%A M. Blaze
.%A J. Feigenbaum
.%A J. Lacy
.%D 1996
.%J IEEE Symposium on Security and Privacy
.%T Decentralized Trust Management
.Re
.Rs
.%A M. Blaze
.%A J. Feigenbaum
.%A M. Strauss
.%D 1998
.%J Financial Crypto Conference
.%T Compliance-Checking in the PolicyMaker Trust Management System
.Re
.Sh STANDARDS
.Rs
.%A M. Blaze
.%A J. Feigenbaum
.%A J. Ioannidis
.%A A. Keromytis
.%D September 1999
.%R RFC 2704
.%T The KeyNote Trust-Management System Version 2
.Re
.Sh AUTHORS
.An Angelos D. Keromytis Aq Mt angelos@cs.columbia.edu
.Sh WEB PAGE
.Lk http://www1.cs.columbia.edu/~angelos/keynote.html