openssl/doc/crypto/X509_verify_cert.pod
Viktor Dukhovni 5fba3912cc Clarify negative return from X509_verify_cert()
Reviewed-by: Richard Levitte <levitte@openssl.org>
2016-05-18 15:15:24 -04:00

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=pod
=head1 NAME
X509_verify_cert - discover and verify X509 certificate chain
=head1 SYNOPSIS
#include <openssl/x509.h>
int X509_verify_cert(X509_STORE_CTX *ctx);
=head1 DESCRIPTION
The X509_verify_cert() function attempts to discover and validate a
certificate chain based on parameters in B<ctx>. A complete description of
the process is contained in the L<verify(1)> manual page.
=head1 RETURN VALUES
If a complete chain can be built and validated this function returns 1,
otherwise it return zero, in exceptional circumstances it can also
return a negative code.
If the function fails additional error information can be obtained by
examining B<ctx> using, for example X509_STORE_CTX_get_error().
=head1 NOTES
Applications rarely call this function directly but it is used by
OpenSSL internally for certificate validation, in both the S/MIME and
SSL/TLS code.
A negative return value from X509_verify_cert() can occur if it is invoked
incurrectly, such as with no certificate set in B<ctx>, or when it is called
twice in succession without reinitialising B<ctx> for the second call.
A negative return value can also happen due to internal resource problems or if
a retry operation is requested during internal lookups (which never happens
with standard lookup methods).
Applications must check for <= 0 return value on error.
=head1 BUGS
This function uses the header B<x509.h> as opposed to most chain verification
functions which use B<x509_vfy.h>.
=head1 SEE ALSO
L<X509_STORE_CTX_get_error(3)>
=cut