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therefore won't be available. \*(C` and \*(C' expand to `' in nroff,
nothing in troff, for use with C<>.
.tr \(*W- . ds -- \(*W- . ds PI pi . if (\n(.H=4u)&(1m=24u) .ds -- \(*W\h'-12u'\(*W\h'-12u'-\" diablo 10 pitch . if (\n(.H=4u)&(1m=20u) .ds -- \(*W\h'-12u'\(*W\h'-8u'-\" diablo 12 pitch . ds L" "" . ds R" "" . ds C` "" . ds C' "" 'br\} . ds -- \|\(em\| . ds PI \(*p . ds L" `` . ds R" '' . ds C` . ds C' 'br\}
Escape single quotes in literal strings from groff's Unicode transform.
If the F register is >0, we'll generate index entries on stderr for
titles (.TH), headers (.SH), subsections (.SS), items (.Ip), and index
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Accent mark definitions (@(#)ms.acc 1.5 88/02/08 SMI; from UCB 4.2).
Fear. Run. Save yourself. No user-serviceable parts.
. \" fudge factors for nroff and troff . ds #H 0 . ds #V .8m . ds #F .3m . ds #[ \f1 . ds #] .\} . ds #H ((1u-(\\\\n(.fu%2u))*.13m) . ds #V .6m . ds #F 0 . ds #[ \& . ds #] \& .\} . \" simple accents for nroff and troff . ds ' \& . ds ` \& . ds ^ \& . ds , \& . ds ~ ~ . ds / .\} . ds ' \\k:\h'-(\\n(.wu*8/10-\*(#H)'\'\h"|\\n:u" . ds ` \\k:\h'-(\\n(.wu*8/10-\*(#H)'\`\h'|\\n:u' . ds ^ \\k:\h'-(\\n(.wu*10/11-\*(#H)'^\h'|\\n:u' . ds , \\k:\h'-(\\n(.wu*8/10)',\h'|\\n:u' . ds ~ \\k:\h'-(\\n(.wu-\*(#H-.1m)'~\h'|\\n:u' . ds / \\k:\h'-(\\n(.wu*8/10-\*(#H)'\z\(sl\h'|\\n:u' .\} . \" troff and (daisy-wheel) nroff accents . \" corrections for vroff . \" for low resolution devices (crt and lpr) \{\ . ds : e . ds 8 ss . ds o a . ds d- d\h'-1'\(ga . ds D- D\h'-1'\(hy . ds th \o'bp' . ds Th \o'LP' . ds ae ae . ds Ae AE .\} ========================================================================
Title "X509_STORE_CTX_set_verify_cb 3"
way too many mistakes in technical documents.
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 not essential and the default operation is often sufficient.
The 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 \fBX509_V_FLAG_NOTIFY_POLICY is set then ok is set to 2 to indicate the policy checking is complete.
The ctx parameter to the callback is the 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 ex_data mechanism.
.Vb 4 int verify_callback(int ok, X509_STORE_CTX *ctx) { return ok; } .Ve
Simple example, suppose a certificate in the chain is expired and we wish to continue after this error:
.Vb 8 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\*(Aqt override */ return ok; } .Ve
More complex example, we don't wish to continue after any certificate has expired just one specific case:
.Vb 11 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; } .Ve
Full featured logging callback. In this case the bio_err is assumed to be a global logging \s-1BIO\s0, an alternative would to store a \s-1BIO\s0 in ctx using \fBex_data.
.Vb 4 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, "\en"); } else BIO_puts(bio_err, "<no cert>\en"); if (!ok) BIO_printf(bio_err,"verify error:num=%d:%s\en",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, "\en"); 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,"\en"); 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,"\en"); 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\en",ok); return(ok); } .Ve