Document additions for X509 chain verification from HEAD

=head1 SYNOPSIS

 #include <openssl/DSA.h>

 #include <openssl/dsa.h>

 int DSA_get_ex_new_index(long argl, void *argp,

		CRYPTO_EX_new *new_func,

=pod

=head1 NAME

X509_STORE_CTX_get_error, X509_STORE_CTX_set_error, X509_STORE_CTX_get_error_depth, X509_STORE_CTX_get_current_cert, X509_STORE_CTX_get1_chain, X509_verify_cert_error_string - get or set certificate verification status information

=head1 SYNOPSIS

 #include <openssl/x509.h>

 #include <openssl/x509_vfy.h>

 int	X509_STORE_CTX_get_error(X509_STORE_CTX *ctx);

 void	X509_STORE_CTX_set_error(X509_STORE_CTX *ctx,int s);

 int	X509_STORE_CTX_get_error_depth(X509_STORE_CTX *ctx);

 X509 *	X509_STORE_CTX_get_current_cert(X509_STORE_CTX *ctx);

 STACK_OF(X509) *X509_STORE_CTX_get1_chain(X509_STORE_CTX *ctx);

 const char *X509_verify_cert_error_string(long n);

=head1 DESCRIPTION

These functions are typically called after X509_verify_cert() has indicated

an error or in a verification callback to determine the nature of an error.

X509_STORE_CTX_get_error() returns the error code of B<ctx>, see

the B<ERROR CODES> section for a full description of all error codes.

X509_STORE_CTX_set_error() sets the error code of B<ctx> to B<s>. For example

it might be used in a verification callback to set an error based on additional

checks.

X509_STORE_CTX_get_error_depth() returns the B<depth> of the error. This is a

non-negative integer representing where in the certificate chain the error

occurred. If it is zero it occured in the end entity certificate, one if

it is the certificate which signed the end entity certificate and so on.

X509_STORE_CTX_get_current_cert() returns the certificate in B<ctx> which

caused the error or B<NULL> if no certificate is relevant.

X509_STORE_CTX_get1_chain() returns a complete validate chain if a previous

call to X509_verify_cert() is successful. If the call to X509_verify_cert()

is B<not> successful the returned chain may be incomplete or invalid. The

returned chain persists after the B<ctx> structure is freed, when it is

no longer needed it should be free up using:

  sk_X509_pop_free(chain, X509_free);

X509_verify_cert_error_string() returns a human readable error string for

verification error B<n>.

=head1 RETURN VALUES

X509_STORE_CTX_get_error() returns B<X509_V_OK> or an error code.

X509_STORE_CTX_get_error_depth() returns a non-negative error depth.

X509_STORE_CTX_get_current_cert() returns the cerificate which caused the

error or B<NULL> if no certificate is relevant to the error.

X509_verify_cert_error_string() returns a human readable error string for

verification error B<n>.

=head1 ERROR CODES

A list of error codes and messages is shown below.  Some of the

error codes are defined but currently never returned: these are described as

"unused".

=over 4

=item B<X509_V_OK: ok>

the operation was successful.

=item B<X509_V_ERR_UNABLE_TO_GET_ISSUER_CERT: unable to get issuer certificate>

the issuer certificate could not be found: this occurs if the issuer certificate

of an untrusted certificate cannot be found.

=item B<X509_V_ERR_UNABLE_TO_GET_CRL: unable to get certificate CRL>

the CRL of a certificate could not be found.

=item B<X509_V_ERR_UNABLE_TO_DECRYPT_CERT_SIGNATURE: unable to decrypt certificate's signature>

the certificate signature could not be decrypted. This means that the actual

signature value could not be determined rather than it not matching the

expected value, this is only meaningful for RSA keys.

=item B<X509_V_ERR_UNABLE_TO_DECRYPT_CRL_SIGNATURE: unable to decrypt CRL's signature>

the CRL signature could not be decrypted: this means that the actual signature

value could not be determined rather than it not matching the expected value.

Unused.

=item B<X509_V_ERR_UNABLE_TO_DECODE_ISSUER_PUBLIC_KEY: unable to decode issuer public key>

the public key in the certificate SubjectPublicKeyInfo could not be read.

=item B<X509_V_ERR_CERT_SIGNATURE_FAILURE: certificate signature failure>

the signature of the certificate is invalid.

=item B<X509_V_ERR_CRL_SIGNATURE_FAILURE: CRL signature failure>

the signature of the certificate is invalid.

=item B<X509_V_ERR_CERT_NOT_YET_VALID: certificate is not yet valid>

the certificate is not yet valid: the notBefore date is after the current time.

=item B<X509_V_ERR_CERT_HAS_EXPIRED: certificate has expired>

the certificate has expired: that is the notAfter date is before the current time.

=item B<X509_V_ERR_CRL_NOT_YET_VALID: CRL is not yet valid>

the CRL is not yet valid.

=item B<X509_V_ERR_CRL_HAS_EXPIRED: CRL has expired>

the CRL has expired.

=item B<X509_V_ERR_ERROR_IN_CERT_NOT_BEFORE_FIELD: format error in certificate's notBefore field>

the certificate notBefore field contains an invalid time.

=item B<X509_V_ERR_ERROR_IN_CERT_NOT_AFTER_FIELD: format error in certificate's notAfter field>

the certificate notAfter field contains an invalid time.

=item B<X509_V_ERR_ERROR_IN_CRL_LAST_UPDATE_FIELD: format error in CRL's lastUpdate field>

the CRL lastUpdate field contains an invalid time.

=item B<X509_V_ERR_ERROR_IN_CRL_NEXT_UPDATE_FIELD: format error in CRL's nextUpdate field>

the CRL nextUpdate field contains an invalid time.

=item B<X509_V_ERR_OUT_OF_MEM: out of memory>

an error occurred trying to allocate memory. This should never happen.

=item B<X509_V_ERR_DEPTH_ZERO_SELF_SIGNED_CERT: self signed certificate>

the passed certificate is self signed and the same certificate cannot be found

in the list of trusted certificates.

=item B<X509_V_ERR_SELF_SIGNED_CERT_IN_CHAIN: self signed certificate in certificate chain>

the certificate chain could be built up using the untrusted certificates but

the root could not be found locally.

=item B<X509_V_ERR_UNABLE_TO_GET_ISSUER_CERT_LOCALLY: unable to get local issuer certificate>

the issuer certificate of a locally looked up certificate could not be found.

This normally means the list of trusted certificates is not complete.

=item B<X509_V_ERR_UNABLE_TO_VERIFY_LEAF_SIGNATURE: unable to verify the first certificate>

no signatures could be verified because the chain contains only one certificate

and it is not self signed.

=item B<X509_V_ERR_CERT_CHAIN_TOO_LONG: certificate chain too long>

the certificate chain length is greater than the supplied maximum depth. Unused.

=item B<X509_V_ERR_CERT_REVOKED: certificate revoked>

the certificate has been revoked.

=item B<X509_V_ERR_INVALID_CA: invalid CA certificate>

a CA certificate is invalid. Either it is not a CA or its extensions are not

consistent with the supplied purpose.

=item B<X509_V_ERR_PATH_LENGTH_EXCEEDED: path length constraint exceeded>

the basicConstraints pathlength parameter has been exceeded.

=item B<X509_V_ERR_INVALID_PURPOSE: unsupported certificate purpose>

the supplied certificate cannot be used for the specified purpose.

=item B<X509_V_ERR_CERT_UNTRUSTED: certificate not trusted>

the root CA is not marked as trusted for the specified purpose.

=item B<X509_V_ERR_CERT_REJECTED: certificate rejected>

the root CA is marked to reject the specified purpose.

=item B<X509_V_ERR_SUBJECT_ISSUER_MISMATCH: subject issuer mismatch>

the current candidate issuer certificate was rejected because its subject name

did not match the issuer name of the current certificate. This is only set

if issuer check debugging is enabled it is used for status notification and

is B<not> in itself an error.

=item B<X509_V_ERR_AKID_SKID_MISMATCH: authority and subject key identifier mismatch>

the current candidate issuer certificate was rejected because its subject key

identifier was present and did not match the authority key identifier current

certificate. This is only set if issuer check debugging is enabled it is used

for status notification and is B<not> in itself an error.

=item B<X509_V_ERR_AKID_ISSUER_SERIAL_MISMATCH: authority and issuer serial number mismatch>

the current candidate issuer certificate was rejected because its issuer name

and serial number was present and did not match the authority key identifier of

the current certificate. This is only set if issuer check debugging is enabled

it is used for status notification and is B<not> in itself an error.

=item B<X509_V_ERR_KEYUSAGE_NO_CERTSIGN:key usage does not include certificate signing>

the current candidate issuer certificate was rejected because its keyUsage

extension does not permit certificate signing. This is only set if issuer check

debugging is enabled it is used for status notification and is B<not> in itself

an error.

=item B<X509_V_ERR_INVALID_EXTENSION: invalid or inconsistent certificate extension>

A certificate extension had an invalid value (for example an incorrect

encoding) or some value inconsistent with other extensions.

=item B<X509_V_ERR_INVALID_POLICY_EXTENSION: invalid or inconsistent certificate policy extension>

A certificate policies extension had an invalid value (for example an incorrect

encoding) or some value inconsistent with other extensions. This error only

occurs if policy processing is enabled.

=item B<X509_V_ERR_NO_EXPLICIT_POLICY: no explicit policy>

The verification flags were set to require and explicit policy but none was

present.

=item B<X509_V_ERR_DIFFERENT_CRL_SCOPE: Different CRL scope>

The only CRLs that could be found did not match the scope of the certificate.

=item B<X509_V_ERR_UNSUPPORTED_EXTENSION_FEATURE: Unsupported extension feature>

Some feature of a certificate extension is not supported. Unused.

=item B<X509_V_ERR_PERMITTED_VIOLATION: permitted subtree violation>

A name constraint violation occured in the permitted subtrees.

=item B<X509_V_ERR_EXCLUDED_VIOLATION: excluded subtree violation>

A name constraint violation occured in the excluded subtrees.

=item B<X509_V_ERR_SUBTREE_MINMAX: name constraints minimum and maximum not supported>

A certificate name constraints extension included a minimum or maximum field:

this is not supported.

=item B<X509_V_ERR_UNSUPPORTED_CONSTRAINT_TYPE: unsupported name constraint type>

An unsupported name constraint type was encountered. OpenSSL currently only

supports directory name, DNS name, email and URI types.

=item B<X509_V_ERR_UNSUPPORTED_CONSTRAINT_SYNTAX: unsupported or invalid name constraint syntax>

The format of the name constraint is not recognised: for example an email

address format of a form not mentioned in RFC3280. This could be caused by

a garbage extension or some new feature not currently supported.

=item B<X509_V_ERR_CRL_PATH_VALIDATION_ERROR: CRL path validation error>

An error occured when attempting to verify the CRL path. This error can only

happen if extended CRL checking is enabled.

=item B<X509_V_ERR_APPLICATION_VERIFICATION: application verification failure>

an application specific error. This will never be returned unless explicitly

set by an application.

=head1 NOTES

The above functions should be used instead of directly referencing the fields

in the B<X509_VERIFY_CTX> structure.

In versions of OpenSSL before 1.0 the current certificate returned by

X509_STORE_CTX_get_current_cert() was never B<NULL>. Applications should

check the return value before printing out any debugging information relating

to the current certificate.

If an unrecognised error code is passed to X509_verify_cert_error_string() the

numerical value of the unknown code is returned in a static buffer. This is not

thread safe but will never happen unless an invalid code is passed.

=head1 SEE ALSO

L<X509_verify_cert(3)|X509_verify_cert(3)>

=head1 HISTORY

TBA

=cut

=pod

=head1 NAME

X509_STORE_CTX_get_ex_new_index, X509_STORE_CTX_set_ex_data, X509_STORE_CTX_get_ex_data - add application specific data to X509_STORE_CTX structures

=head1 SYNOPSIS

 #include <openssl/x509_vfy.h>

 int X509_STORE_CTX_get_ex_new_index(long argl, void *argp,

		CRYPTO_EX_new *new_func,

		CRYPTO_EX_dup *dup_func,

		CRYPTO_EX_free *free_func);

 int X509_STORE_CTX_set_ex_data(X509_STORE_CTX *d, int idx, void *arg);

 char *X509_STORE_CTX_get_ex_data(X509_STORE_CTX *d, int idx);

=head1 DESCRIPTION

These functions handle application specific data in X509_STORE_CTX structures.

Their usage is identical to that of RSA_get_ex_new_index(), RSA_set_ex_data()

and RSA_get_ex_data() as described in L<RSA_get_ex_new_index(3)>.

=head1 NOTES

This mechanism is used internally by the B<ssl> library to store the B<SSL>

structure associated with a verification operation in an B<X509_STORE_CTX>

structure. 

=head1 SEE ALSO

L<RSA_get_ex_new_index(3)|RSA_get_ex_new_index(3)>

=head1 HISTORY

X509_STORE_CTX_get_ex_new_index(), X509_STORE_CTX_set_ex_data() and

X509_STORE_CTX_get_ex_data() are available since OpenSSL 0.9.5.

=cut

=pod

=head1 NAME

X509_STORE_CTX_new, X509_STORE_CTX_cleanup, X509_STORE_CTX_free, X509_STORE_CTX_init, X509_STORE_CTX_trusted_stack, X509_STORE_CTX_set_cert, X509_STORE_CTX_set_chain, X509_STORE_CTX_set0_crls, X509_STORE_CTX_get0_param, X509_STORE_CTX_set0_param, X509_STORE_CTX_set_default - X509_STORE_CTX initialisation

=head1 SYNOPSIS

 #include <openssl/x509_vfy.h>

 X509_STORE_CTX *X509_STORE_CTX_new(void);

 void X509_STORE_CTX_cleanup(X509_STORE_CTX *ctx);

 void X509_STORE_CTX_free(X509_STORE_CTX *ctx);

 int X509_STORE_CTX_init(X509_STORE_CTX *ctx, X509_STORE *store,

			 X509 *x509, STACK_OF(X509) *chain);

 void X509_STORE_CTX_trusted_stack(X509_STORE_CTX *ctx, STACK_OF(X509) *sk);

 void	X509_STORE_CTX_set_cert(X509_STORE_CTX *ctx,X509 *x);

 void	X509_STORE_CTX_set_chain(X509_STORE_CTX *ctx,STACK_OF(X509) *sk);

 void	X509_STORE_CTX_set0_crls(X509_STORE_CTX *ctx, STACK_OF(X509_CRL) *sk);

 X509_VERIFY_PARAM *X509_STORE_CTX_get0_param(X509_STORE_CTX *ctx);

 void X509_STORE_CTX_set0_param(X509_STORE_CTX *ctx, X509_VERIFY_PARAM *param);

 int X509_STORE_CTX_set_default(X509_STORE_CTX *ctx, const char *name);

=head1 DESCRIPTION

These functions initialise an B<X509_STORE_CTX> structure for subsequent use

by X509_verify_cert().

X509_STORE_CTX_new() returns a newly initialised B<X509_STORE_CTX> structure.

X509_STORE_CTX_cleanup() internally cleans up an B<X509_STORE_CTX> structure.

The context can then be reused with an new call to X509_STORE_CTX_init().

X509_STORE_CTX_free() completely frees up B<ctx>. After this call B<ctx>

is no longer valid.

X509_STORE_CTX_init() sets up B<ctx> for a subsequent verification operation.

The trusted certificate store is set to B<store>, the end entity certificate

to be verified is set to B<x509> and a set of additional certificates (which

will be untrusted but may be used to build the chain) in B<chain>. Any or

all of the B<store>, B<x509> and B<chain> parameters can be B<NULL>.

X509_STORE_CTX_trusted_stack() sets the set of trusted certificates of B<ctx>

to B<sk>. This is an alternative way of specifying trusted certificates 

instead of using an B<X509_STORE>.

X509_STORE_CTX_set_cert() sets the certificate to be vertified in B<ctx> to

B<x>.

X509_STORE_CTX_set_chain() sets the additional certificate chain used by B<ctx>

to B<sk>.

X509_STORE_CTX_set0_crls() sets a set of CRLs to use to aid certificate

verification to B<sk>. These CRLs will only be used if CRL verification is

enabled in the associated B<X509_VERIFY_PARAM> structure. This might be

used where additional "useful" CRLs are supplied as part of a protocol,

for example in a PKCS#7 structure.

X509_VERIFY_PARAM *X509_STORE_CTX_get0_param() retrieves an intenal pointer

to the verification parameters associated with B<ctx>.

X509_STORE_CTX_set0_param() sets the intenal verification parameter pointer

to B<param>. After this call B<param> should not be used.

X509_STORE_CTX_set_default() looks up and sets the default verification

method to B<name>. This uses the function X509_VERIFY_PARAM_lookup() to

find an appropriate set of parameters from B<name>.

=head1 NOTES

The certificates and CRLs in a store are used internally and should B<not>

be freed up until after the associated B<X509_STORE_CTX> is freed. Legacy

applications might implicitly use an B<X509_STORE_CTX> like this:

  X509_STORE_CTX ctx;

  X509_STORE_CTX_init(&ctx, store, cert, chain);

this is B<not> recommended in new applications they should instead do:

  X509_STORE_CTX *ctx;

  ctx = X509_STORE_CTX_new();

  if (ctx == NULL)

	/* Bad error */

  X509_STORE_CTX_init(ctx, store, cert, chain);

=head1 BUGS

The certificates and CRLs in a context are used internally and should B<not>

be freed up until after the associated B<X509_STORE_CTX> is freed. Copies

should be made or reference counts increased instead.

=head1 RETURN VALUES

X509_STORE_CTX_new() returns an newly allocates context or B<NULL> is an

error occurred.

X509_STORE_CTX_init() returns 1 for success or 0 if an error occurred.

X509_STORE_CTX_get0_param() returns a pointer to an B<X509_VERIFY_PARAM>

structure or B<NULL> if an error occurred.

X509_STORE_CTX_cleanup(), X509_STORE_CTX_free(), X509_STORE_CTX_trusted_stack(),

X509_STORE_CTX_set_cert(), X509_STORE_CTX_set_chain(),

X509_STORE_CTX_set0_crls() and X509_STORE_CTX_set0_param() do not return

values.

X509_STORE_CTX_set_default() returns 1 for success or 0 if an error occurred.

=head1 SEE ALSO

L<X509_verify_cert(3)|X509_verify_cert(3)>

L<X509_VERIFY_PARAM_set_flags(3)|X509_VERIFY_PARAM_set_flags(3)>

=head1 HISTORY

X509_STORE_CTX_set0_crls() was first added to OpenSSL 1.0.0

=cut

=pod

=head1 NAME

X509_STORE_CTX_set_verify_cb - set verification callback

=head1 SYNOPSIS

 #include <openssl/x509_vfy.h>

 void X509_STORE_CTX_set_verify_cb(X509_STORE_CTX *ctx,

				int (*verify_cb)(int ok, X509_STORE_CTX *ctx));

=head1 DESCRIPTION

X509_STORE_CTX_set_verify_cb() sets the verification callback of B<ctx> to

B<verify_cb> overwriting any existing callback.

The verification callback can be used to customise the operation of certificate

verification, either by overriding error conditions or logging errors for

debugging purposes.

However a verification callback is B<not> essential and the default operation

is often sufficient.

The B<ok> parameter to the callback indicates the value the callback should

return to retain the default behaviour. If it is zero then and error condition

is indicated. If it is 1 then no error occurred. If the flag

B<X509_V_FLAG_NOTIFY_POLICY> is set then B<ok> is set to 2 to indicate the

policy checking is complete.

The B<ctx> parameter to the callback is the B<X509_STORE_CTX> structure that

is performing the verification operation. A callback can examine this

structure and receive additional information about the error, for example

by calling X509_STORE_CTX_get_current_cert(). Additional application data can

be passed to the callback via the B<ex_data> mechanism.

=head1 WARNING

In general a verification callback should B<NOT> unconditionally return 1 in

all circumstances because this will allow verification to succeed no matter

what the error. This effectively removes all security from the application

because B<any> certificate (including untrusted generated ones) will be

accepted.

=head1 NOTES

The verification callback can be set and inherited from the parent structure

performing the operation. In some cases (such as S/MIME verification) the

B<X509_STORE_CTX> structure is created and destroyed internally and the

only way to set a custom verification callback is by inheriting it from the

associated B<X509_STORE>.

=head1 RETURN VALUES

X509_STORE_CTX_set_verify_cb() does not return a value.

=head1 EXAMPLES

Default callback operation:

 int verify_callback(int ok, X509_STORE_CTX *ctx)

	{

	return ok;

	}

Simple example, suppose a certificate in the chain is expired and we wish

to continue after this error:

 int verify_callback(int ok, X509_STORE_CTX *ctx)

	{

	/* Tolerate certificate expiration */

	if (X509_STORE_CTX_get_error(ctx) == X509_V_ERR_CERT_HAS_EXPIRED)

			return 1;

	/* Otherwise don't override */

	return ok;

	}

More complex example, we don't wish to continue after B<any> certificate has

expired just one specific case:

 int verify_callback(int ok, X509_STORE_CTX *ctx)

	{

	int err = X509_STORE_CTX_get_error(ctx);

	X509 *err_cert = X509_STORE_CTX_get_current_cert(ctx);

	if (err == X509_V_ERR_CERT_HAS_EXPIRED)

		{

		if (check_is_acceptable_expired_cert(err_cert)

			return 1;

		}

	return ok;

	}

Full featured logging callback. In this case the B<bio_err> is assumed to be

a global logging B<BIO>, an alternative would to store a BIO in B<ctx> using

B<ex_data>.

 int verify_callback(int ok, X509_STORE_CTX *ctx)

	{

	X509 *err_cert;

	int err,depth;

	err_cert = X509_STORE_CTX_get_current_cert(ctx);

	err =	X509_STORE_CTX_get_error(ctx);

	depth =	X509_STORE_CTX_get_error_depth(ctx);

	BIO_printf(bio_err,"depth=%d ",depth);

	if (err_cert)

		{

		X509_NAME_print_ex(bio_err, X509_get_subject_name(err_cert),

					0, XN_FLAG_ONELINE);

		BIO_puts(bio_err, "\n");

		}

	else

		BIO_puts(bio_err, "<no cert>\n");

	if (!ok)

		BIO_printf(bio_err,"verify error:num=%d:%s\n",err,

			X509_verify_cert_error_string(err));

	switch (err)

		{

	case X509_V_ERR_UNABLE_TO_GET_ISSUER_CERT:

		BIO_puts(bio_err,"issuer= ");

		X509_NAME_print_ex(bio_err, X509_get_issuer_name(err_cert),

					0, XN_FLAG_ONELINE);

		BIO_puts(bio_err, "\n");

		break;

	case X509_V_ERR_CERT_NOT_YET_VALID:

	case X509_V_ERR_ERROR_IN_CERT_NOT_BEFORE_FIELD:

		BIO_printf(bio_err,"notBefore=");

		ASN1_TIME_print(bio_err,X509_get_notBefore(err_cert));

		BIO_printf(bio_err,"\n");

		break;

	case X509_V_ERR_CERT_HAS_EXPIRED:

	case X509_V_ERR_ERROR_IN_CERT_NOT_AFTER_FIELD:

		BIO_printf(bio_err,"notAfter=");

		ASN1_TIME_print(bio_err,X509_get_notAfter(err_cert));

		BIO_printf(bio_err,"\n");

		break;

	case X509_V_ERR_NO_EXPLICIT_POLICY:

		policies_print(bio_err, ctx);

		break;

		}

	if (err == X509_V_OK && ok == 2)

		/* print out policies */

	BIO_printf(bio_err,"verify return:%d\n",ok);

	return(ok);

	}

=head1 SEE ALSO

L<X509_STORE_CTX_get_error(3)|X509_STORE_CTX_get_error(3)>

L<X509_STORE_set_verify_cb_func(3)|X509_STORE_set_verify_cb_func(3)>

L<X509_STORE_CTX_get_ex_new_index(3)|X509_STORE_CTX_get_ex_new_index(3)>

=head1 HISTORY

X509_STORE_CTX_set_verify_cb() is available in all versions of SSLeay and

OpenSSL.

=cut