X509_check_purpose - Check the purpose of a certificate
#include <openssl/x509v3.h>
int X509_check_purpose(X509 *x, int id, int ca);
This function checks if certificate
x was created with the purpose
represented by
id. If
ca is nonzero, then certificate
x
is checked to determine if it's a possible CA with various levels of certainty
possibly returned. The certificate
x must be a complete certificate
otherwise the function returns an error.
Below are the potential ID's that can be checked:
# define X509_PURPOSE_SSL_CLIENT 1
# define X509_PURPOSE_SSL_SERVER 2
# define X509_PURPOSE_NS_SSL_SERVER 3
# define X509_PURPOSE_SMIME_SIGN 4
# define X509_PURPOSE_SMIME_ENCRYPT 5
# define X509_PURPOSE_CRL_SIGN 6
# define X509_PURPOSE_ANY 7
# define X509_PURPOSE_OCSP_HELPER 8
# define X509_PURPOSE_TIMESTAMP_SIGN 9
The checks performed take into account the X.509 extensions keyUsage,
extendedKeyUsage, and basicConstraints.
For non-CA checks
- -1 an error condition has occurred
- 1 if the certificate was created to perform the purpose
represented by id
- 0 if the certificate was not created to perform the
purpose represented by id
For CA checks the below integers could be returned with the following meanings:
- -1 an error condition has occurred
- 0 not a CA or does not have the purpose represented by
id
- 1 is a CA.
- 2 Only possible in old versions of openSSL when
basicConstraints are absent. New versions will not return this value. May be
a CA
- 3 basicConstraints absent but self signed V1.
- 4 basicConstraints absent but keyUsage present and
keyCertSign asserted.
- 5 legacy Netscape specific CA Flags present
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