NAME
keynote — a trust-management system library
SYNOPSIS
#include <sys/types.h>
#include <regex.h>
#include <keynote.h>
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;
};
int keynote_errno ;
int
kn_init(void);
int
kn_add_assertion(int sessid, char *assertion, int len, int flags);
int
kn_remove_assertion(int sessid, int assertid);
int
kn_add_action(int sessid, char *name, char *value, int flags);
int
kn_remove_action(int sessid, char *name);
int
kn_add_authorizer(int sessid, char *principal);
int
kn_remove_authorizer(int sessid, char *principal);
int
kn_do_query(int sessid, char **returnvalues, int numvalues);
int
kn_get_failed(int sessid, int type, int seq);
int
kn_cleanup_action_environment(int sessid);
int
kn_close(int sessid);
int
kn_query(struct environment *env, char **returnvalues, int numvalues, char **trusted, int *trustedlen, int numtrusted, char **untrusted, int *untrustedlen, int numuntrusted, char **authorizers, int numauthauthorizers);
char **
kn_read_asserts(char *array, int arraylen, int *numassertions);
int
kn_keycompare(void *key1, void *key2, int algorithm);
void *
kn_get_authorizer(int sessid, int assertid, int *algorithm);
struct keynote_keylist *
kn_get_licensees(int sessid, int assertid);
int
kn_encode_base64(unsigned char const *src, unsigned int srclen, char *dst, unsigned int dstlen);
int
kn_decode_base64(char const *src, unsigned char *dst, unsigned int dstlen);
int
kn_encode_hex(unsigned char *src, char **dst, int srclen);
int
kn_decode_hex(char *src, char **dst);
char *
kn_encode_key(struct keynote_deckey *dc, int iencoding, int encoding, int keytype);
int
kn_decode_key(struct keynote_deckey *dc, char *key, int keytype);
char *
kn_sign_assertion(char *assertion, int len, char *key, char *algorithm, int vflag);
int
kn_verify_assertion(char *assertion, int len);
void
kn_free_key(struct keynote_deckey *);
char *
kn_get_string(char *);
Link options: -lkeynote -lm -lcrypto
DESCRIPTION
For more details on KeyNote, see RFC 2704.
keynote_errno contains an error code if some library call failed. Failed calls return −1 (if their return value is integer), or NULL (if their return value is a pointer) and set keynote_errno. The defined error codes are:
ERROR_MEMORY
Some memory allocation or usage error was encountered.
ERROR_SYNTAX
Some syntactic or logical error was encountered.
ERROR_NOTFOUND
One of the arguments referred to a nonexistent structure or entry.
If no errors were encountered, 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.
The main interface to KeyNote 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 KeyNote 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.
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.
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.
The description of all KeyNote library functions follows.
kn_init() creates a new KeyNote session, and performs any necessary initializations. On success, this function returns the new session ID, which is used by all subsequent calls with a sessid argument. On failure, it returns −1 and sets keynote_errno to ERROR_MEMORY.
kn_add_assertion() adds the assertion pointed to by the array assertion, of length len in the session identified by sessid. The first argument can be discarded after the call to this function. The following flags are defined:
ASSERT_FLAG_LOCAL
Mark this assertion as ultimately trusted. Trusted assertions need not be signed, and the Authorizer and Licensees fields can have non-key entries.
At least one (trusted) assertion should have POLICY as the Authorizer. On success, this function will return an assertion ID which can be used to remove the assertion from the session, by using kn_remove_assertion(3). On failure, −1 is returned, and keynote_errno is set to ERROR_NOTFOUND if the session was not found, ERROR_SYNTAX if the assertion was syntactically incorrect, or ERROR_MEMORY if necessary memory could not be allocated.
kn_remove_assertion() removes the assertion identified by assertid from the session identified by sessid. On success, this function returns 0. On failure, it returns −1 and sets keynote_errno to ERROR_NOTFOUND.
kn_add_action() inserts the variable name in the action environment of session sessid, with the value value. The same attribute may be added more than once, but only the last instance will be used (memory resources are consumed however).
The flags specified are formed by or’ing the following values:
ENVIRONMENT_FLAG_FUNC
In this case, 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 NULL to indicate an error (and may set keynote_errno appropriately). Prior to first use (currently, at the time the attribute is added to the session environment), such functions are called with 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 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.
ENVIRONMENT_FLAG_REGEX
In this case, name is a regular expression that may match more than one attribute. In case of conflict between a regular expression and a ’’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 KeyNote session, start/invoke/operate on another session, or call one of the session-API functions.
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.
On success, keynote_add_action(3) returns 0. On failure, it returns −1 and sets keynote_errno to ERROR_NOTFOUND if the session was not found, ERROR_SYNTAX if the name was invalid (e.g., started with an underscore character) or was NULL, or ERROR_MEMORY if necessary memory could not be allocated.
kn_remove_action() removes action attribute name from the environment of session sessid. Notice that if more than one instances of name exist, only the one added last will be deleted. On success, this function returns 0. On failure, it returns −1 and keynote_errno is set to ERROR_NOTFOUND if the session or the attribute were not found, or ERROR_SYNTAX if the name was invalid. If the attribute value was a callback, that function will be called with the define KEYNOTE_CALLBACK_CLEANUP as the argument.
kn_add_authorizer() adds the principal pointed to by principal to the action authorizers list of session sessid. The principal is typically an ASCII-encoded key. On success, this function will return 0. On failure, it returns −1 and sets keynote_errno to ERROR_NOTFOUND if the session was not found, ERROR_SYNTAX if the encoding was invalid, or ERROR_MEMORY if necessary memory could not be allocated.
kn_remove_authorizer() removes principal from the action authorizer list of session sessid. On success, this function returns 0. On failure, it returns −1 and sets keynote_errno to ERROR_NOTFOUND if the session was not found.
kn_do_query() evaluates the request based on the assertions, action attributes, and action authorizers added to session sessid. returnvalues is an ordered array of strings that contain the return values. The lowest-ordered return value is contained in returnvalues[0], and the highest-ordered value is returnvalues[numvalues - 1]. If returnvalues is NULL, the returnvalues from the previous call to kn_do_query(3) will be used. The programmer SHOULD NOT free returnvalues after the call to kn_do_query(3) if this feature is used, as the array is not replicated internally. On success, this function returns an index into the returnvalues array. On failure, it returns −1 and sets keynote_errno to ERROR_NOTFOUND if the session was not found or the authorizers list was empty, ERROR_SYNTAX if no returnvalues have been specified, or ERROR_MEMORY if necessary memory could not be allocated.
kn_get_failed() returns the assertion ID of the num’th assertion (starting from zero) in session sessid that was somehow invalid during evaluation. This function is typically called after kn_do_query(3) is used to evaluate a request. type specifies the type of failure the application is interested in. It can be set to:
KEYNOTE_ERROR_ANY
to indicate interest in any error.
KEYNOTE_ERROR_SYNTAX
for syntactic or semantic errors.
KEYNOTE_ERROR_MEMORY
for memory-related problems.
KEYNOTE_ERROR_SIGNATURE
if the assertion could not be cryptographically verified.
These values are defined in keynote.h. An application can then delete the offending assertion using kn_remove_assertion(3). For example, to remove all assertion whose signature failed, an application could do something like:
while ((assertid
= kn_get_failed(sessid, KEYNOTE_ERROR_SIGNATURE, 0)
!= -1)
kn_remove_assertion(sessid, assertid);
On success, kn_get_failed(3) returns an assertion ID. On failure, or when no assertion matching the given criteria is found, it returns −1 and set keynote_errno to ERROR_NOTFOUND.
kn_cleanup_action_environment() removes all action attributes from the action environment of session sessid. It returns 0 on success.
kn_close() closes session 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 keynote_errno to ERROR_NOTFOUND if the session was not found.
kn_read_asserts() parses the string array of length arraylen and returns an array of pointers to strings containing copies of the assertions found in array. Both the array of pointers and the strings are allocated by kn_read_asserts() dynamically, and thus should be freed by the programmer when they are no longer needed. numassertions contains the number of assertions (and thus strings in the returned array) found in array. On failure, this function returns NULL and sets keynote_errno to ERROR_MEMORY if necessary memory could not be allocated, or ERROR_SYNTAX if array was NULL. Note that if there were no assertions found in array, a valid pointer will be returned, but numassertions will contain the value zero on return. The returned pointer should be freed by the programmer.
kn_keycompare() compares key1 and key2 (which must be of the same algorithm) and returns 1 if equal and 0 otherwise.
kn_get_authorizer() returns the authorizer key (in binary format) for assertion assertid in session sessid. It also sets the algorithm argument to the algorithm of the authorizer key. On failure, kn_get_authorizer() returns NULL, and sets keynote_errno to ERROR_NOTFOUND.
kn_get_licensees() returns the licensee key(s) for assertion assertid in session sessid. The keys are returned in a linked list of struct keynote_keylist structures. On failure, kn_get_licensees() returns NULL. and sets keynote_errno to ERROR_NOTFOUND.
kn_query() takes as arguments a list of action attributes in env, a list of return values in returnvalues (the number of returnvalues in indicated by numvalues), a number (numtrusted) of locally-trusted assertions in trusted (the length of each assertion is given by the respective element of trustedlen), a number (numuntrusted) of assertions that need to be cryptographically verified in untrusted (the length of each assertion is given by the respective element of untrustedlen), and a number (numauthorizers) of action authorizers in authorizers. env is a linked list of struct environment structures. The env_name, env_value, and env_flags fields correspond to the name, value, and flags arguments to kn_add_assertion(3) respectively. env_regex is not used. On success, this function returns an index in returnvalues indicating the returned value to the query. On failure, it returns −1 and sets keynote_errno to the same values as kn_do_query(3), or to 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 kn_query().
kn_encode_base64() converts the data of length srclen contained in src in Base64 encoding and stores them in dst which is of length dstlen. The actual length of the encoding stored in dst is returned. dst should be long enough to also contain the trailing string terminator. If srclen is not a multiple of 4, or dst is not long enough to contain the encoded data, this function returns −1 and sets keynote_errno to ERROR_SYNTAX.
kn_decode_base64() decodes the Base64-encoded data stored in src and stores the result in dst, which is of length dstlen. The actual length of the decoded data is returned on success. On failure, this function returns −1 and sets keynote_errno to ERROR_SYNTAX, denoting either an invalid Base64 encoding or insufficient space in dst.
kn_encode_hex() encodes in ASCII-hexadecimal format the data of length srclen contained in src. This function allocates a chunk of memory to store the result, which is returned in dst. Thus, this function should be used as follows:
char *dst;
kn_encode_hex(src, &dst, srclen);
The length of the allocated buffer will be (2 * srclen + 1). On success, this function returns 0. On failure, it returns −1 and sets keynote_errno to ERROR_MEMORY if it failed to allocate enough memory, ERROR_SYNTAX if dst was NULL.
kn_decode_hex() decodes the ASCII hex-encoded string in src and stores the result in a memory chunk allocated by the function. A pointer to that memory is stored in 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 keynote_errno to ERROR_MEMORY if it could not allocate enough memory, or ERROR_SYNTAX if dst was NULL, or the length of src is not even.
kn_encode_key() ASCII-encodes a cryptographic key. The binary representation of the key is contained in dc. The field 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 DSA * or RSA * for DSA or RSA keys respectively, as used in the SSL library, or a keynote_binary * for cryptographic keys whose algorithm KeyNote does not know about but the application wishes to include in the action authorizers (and thus need to be canonicalized). The field dec_algorithm describes the cryptographic algorithm, and may be one of KEYNOTE_ALGORITHM_DSA, KEYNOTE_ALGORITHM_RSA, or KEYNOTE_ALGORITHM_BINARY in this implementation.
iencoding describes how the key should be binary-encoded. This implementation supports INTERNAL_ENC_PKCS1 for RSA keys, INTERNAL_ENC_ASN1 for DSA keys, and INTERNAL_ENC_NONE for BINARY keys. encoding describes what ASCII encoding should be applied to the key. Valid values are ENCODING_HEX and ENCODING_BASE64, for hexadecimal and Base64 encoding respectively. keytype is one of KEYNOTE_PUBLIC_KEY or KEYNOTE_PRIVATE_KEY to indicate whether the key is public or private. Private keys have the string 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 NULL and sets keynote_errno to ERROR_NOTFOUND if the dc argument was invalid, ERROR_MEMORY if it failed to allocate the necessary memory, or ERROR_SYNTAX if the key to be converted was invalid.
kn_decode_key() decodes the ASCII-encoded string contained in key. The result is placed in dc, with dec_algorithm describing the algorithm (see kn_encode_key(3)), and dec_key pointing to an algorithm-dependent structure. In this implementation, this is an SSLeay/OpenSSL-defined DSA * for DSA keys, RSA * for RSA and X509-based keys, and a keynote_binary * for BINARY keys. keytype takes the values KEYNOTE_PUBLIC_KEY or 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 keynote_errno to ERROR_MEMORY if necessary memory could not be allocated, or ERROR_SYNTAX if the key or the ASCII encoding was malformed.
kn_sign_assertion() produces the cryptographic signature for the assertion of length len stored in assertion, using the ASCII-encoded cryptographic key contained in key. The type of signature to be produced is described by the string algorithm. Possible values for this string are SIG_RSA_SHA1_HEX SIG_RSA_SHA1_BASE64, SIG_RSA_MD5_HEX, and SIG_RSA_MD5_HEX for RSA keys, SIG_DSA_SHA1_HEX and SIG_DSA_SHA1_BASE64 for DSA keys, SIG_X509_SHA1_HEX, and SIG_X509_SHA1_BASE64 for X509-based keys. No other cryptographic signatures are currently supported by this implementation. If 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 assertion. On failure, it returns NULL and sets keynote_errno to ERROR_NOTFOUND if one of the arguments was NULL, ERROR_MEMORY if necessary memory could not be allocated, or ERROR_SYNTAX if the algorithm, the key, or the assertion (if signature verification was requested) was invalid.
kn_verify_assertion() verifies the cryptographic signature on the assertion of length len contained in string assertion. On success, this function returns SIGRESULT_TRUE if the signature could be verified, or SIGRESULT_FALSE otherwise. On failure, this function returns −1 and sets keynote_errno to ERROR_MEMORY if necessary memory could not be allocated, or ERROR_SYNTAX if the assertion contained a syntactic error, or the cryptographic algorithm was not supported.
kn_free_key() frees a cryptographic key.
kn_get_string() parses the argument, treating it as a keynote(4) (quoted) string. This is useful for parsing key files.
FILES
keynote.h
libkeynote.a
SEE ALSO
keynote(1), keynote(4), keynote(5)
’’The KeyNote Trust-Management System, Version 2’’
M. Blaze, J. Feigenbaum, A. D. Keromytis, Internet Drafts, RFC 2704.
’’Decentralized Trust Management’’
M. Blaze, J. Feigenbaum, J. Lacy, 1996 IEEE Conference on Privacy and Security
’’Compliance-Checking in the PolicyMaker Trust Management System’’
M. Blaze, J. Feigenbaum, M. Strauss, 1998 Financial Crypto Conference
Web Page
http://www.cis.upenn.edu/~keynote
AUTHOR
Angelos D. Keromytis (angelos [AT] dsl.edu)
DIAGNOSTICS
The return values of all the functions have been given along with the function description above.
BUGS
None that we know of. If you find any, please report them to
BSD April 29, 1999 BSD