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Diffstat (limited to 'secure/lib/libcrypto/man/SSL_CTX_set_verify.3')
| -rw-r--r-- | secure/lib/libcrypto/man/SSL_CTX_set_verify.3 | 434 |
1 files changed, 434 insertions, 0 deletions
diff --git a/secure/lib/libcrypto/man/SSL_CTX_set_verify.3 b/secure/lib/libcrypto/man/SSL_CTX_set_verify.3 new file mode 100644 index 0000000..bc383a5 --- /dev/null +++ b/secure/lib/libcrypto/man/SSL_CTX_set_verify.3 @@ -0,0 +1,434 @@ +.\" Automatically generated by Pod::Man version 1.15 +.\" Thu May 9 13:20:36 2002 +.\" +.\" Standard preamble: +.\" ====================================================================== +.de Sh \" Subsection heading +.br +.if t .Sp +.ne 5 +.PP +\fB\\$1\fR +.PP +.. +.de Sp \" Vertical space (when we can't use .PP) +.if t .sp .5v +.if n .sp +.. +.de Ip \" List item +.br +.ie \\n(.$>=3 .ne \\$3 +.el .ne 3 +.IP "\\$1" \\$2 +.. +.de Vb \" Begin verbatim text +.ft CW +.nf +.ne \\$1 +.. +.de Ve \" End verbatim text +.ft R + +.fi +.. +.\" Set up some character translations and predefined strings. \*(-- will +.\" give an unbreakable dash, \*(PI will give pi, \*(L" will give a left +.\" double quote, and \*(R" will give a right double quote. | will give a +.\" real vertical bar. \*(C+ will give a nicer C++. Capital omega is used +.\" to do unbreakable dashes and therefore won't be available. \*(C` and +.\" \*(C' expand to `' in nroff, nothing in troff, for use with C<> +.tr \(*W-|\(bv\*(Tr +.ds C+ C\v'-.1v'\h'-1p'\s-2+\h'-1p'+\s0\v'.1v'\h'-1p' +.ie n \{\ +. 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\} +.el\{\ +. ds -- \|\(em\| +. ds PI \(*p +. ds L" `` +. ds R" '' +'br\} +.\" +.\" If the F register is turned on, we'll generate index entries on stderr +.\" for titles (.TH), headers (.SH), subsections (.Sh), items (.Ip), and +.\" index entries marked with X<> in POD. Of course, you'll have to process +.\" the output yourself in some meaningful fashion. +.if \nF \{\ +. de IX +. tm Index:\\$1\t\\n%\t"\\$2" +.. +. nr % 0 +. rr F +.\} +.\" +.\" For nroff, turn off justification. 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If no callback function +shall be specified, the \s-1NULL\s0 pointer can be used for \fBverify_callback\fR. +.PP +\&\fISSL_set_verify()\fR sets the verification flags for \fBssl\fR to be \fBmode\fR and +specifies the \fBverify_callback\fR function to be used. If no callback function +shall be specified, the \s-1NULL\s0 pointer can be used for \fBverify_callback\fR. In +this case last \fBverify_callback\fR set specifically for this \fBssl\fR remains. If +no special \fBcallback\fR was set before, the default callback for the underlying +\&\fBctx\fR is used, that was valid at the the time \fBssl\fR was created with +SSL_new(3). +.PP +\&\fISSL_CTX_set_verify_depth()\fR sets the maximum \fBdepth\fR for the certificate chain +verification that shall be allowed for \fBctx\fR. (See the \s-1BUGS\s0 section.) +.PP +\&\fISSL_set_verify_depth()\fR sets the maximum \fBdepth\fR for the certificate chain +verification that shall be allowed for \fBssl\fR. (See the \s-1BUGS\s0 section.) +.SH "NOTES" +.IX Header "NOTES" +The verification of certificates can be controlled by a set of logically +or'ed \fBmode\fR flags: +.Ip "\s-1SSL_VERIFY_NONE\s0" 4 +.IX Item "SSL_VERIFY_NONE" +\&\fBServer mode:\fR the server will not send a client certificate request to the +client, so the client will not send a certificate. +.Sp +\&\fBClient mode:\fR if not using an anonymous cipher (by default disabled), the +server will send a certificate which will be checked. The result of the +certificate verification process can be checked after the \s-1TLS/SSL\s0 handshake +using the SSL_get_verify_result(3) function. +The handshake will be continued regardless of the verification result. +.Ip "\s-1SSL_VERIFY_PEER\s0" 4 +.IX Item "SSL_VERIFY_PEER" +\&\fBServer mode:\fR the server sends a client certificate request to the client. +The certificate returned (if any) is checked. If the verification process +fails, the \s-1TLS/SSL\s0 handshake is +immediately terminated with an alert message containing the reason for +the verification failure. +The behaviour can be controlled by the additional +\&\s-1SSL_VERIFY_FAIL_IF_NO_PEER_CERT\s0 and \s-1SSL_VERIFY_CLIENT_ONCE\s0 flags. +.Sp +\&\fBClient mode:\fR the server certificate is verified. If the verification process +fails, the \s-1TLS/SSL\s0 handshake is +immediately terminated with an alert message containing the reason for +the verification failure. If no server certificate is sent, because an +anonymous cipher is used, \s-1SSL_VERIFY_PEER\s0 is ignored. +.Ip "\s-1SSL_VERIFY_FAIL_IF_NO_PEER_CERT\s0" 4 +.IX Item "SSL_VERIFY_FAIL_IF_NO_PEER_CERT" +\&\fBServer mode:\fR if the client did not return a certificate, the \s-1TLS/SSL\s0 +handshake is immediately terminated with a \*(L"handshake failure\*(R" alert. +This flag must be used together with \s-1SSL_VERIFY_PEER\s0. +.Sp +\&\fBClient mode:\fR ignored +.Ip "\s-1SSL_VERIFY_CLIENT_ONCE\s0" 4 +.IX Item "SSL_VERIFY_CLIENT_ONCE" +\&\fBServer mode:\fR only request a client certificate on the initial \s-1TLS/SSL\s0 +handshake. Do not ask for a client certificate again in case of a +renegotiation. This flag must be used together with \s-1SSL_VERIFY_PEER\s0. +.Sp +\&\fBClient mode:\fR ignored +.PP +Exactly one of the \fBmode\fR flags \s-1SSL_VERIFY_NONE\s0 and \s-1SSL_VERIFY_PEER\s0 must be +set at any time. +.PP +The actual verification procedure is performed either using the built-in +verification procedure or using another application provided verification +function set with +SSL_CTX_set_cert_verify_callback(3). +The following descriptions apply in the case of the built-in procedure. An +application provided procedure also has access to the verify depth information +and the \fIverify_callback()\fR function, but the way this information is used +may be different. +.PP +\&\fISSL_CTX_set_verify_depth()\fR and \fISSL_set_verify_depth()\fR set the limit up +to which depth certificates in a chain are used during the verification +procedure. If the certificate chain is longer than allowed, the certificates +above the limit are ignored. Error messages are generated as if these +certificates would not be present, most likely a +X509_V_ERR_UNABLE_TO_GET_ISSUER_CERT_LOCALLY will be issued. +The depth count is \*(L"level 0:peer certificate\*(R", \*(L"level 1: \s-1CA\s0 certificate\*(R", +\&\*(L"level 2: higher level \s-1CA\s0 certificate\*(R", and so on. Setting the maximum +depth to 2 allows the levels 0, 1, and 2. The default depth limit is 9, +allowing for the peer certificate and additional 9 \s-1CA\s0 certificates. +.PP +The \fBverify_callback\fR function is used to control the behaviour when the +\&\s-1SSL_VERIFY_PEER\s0 flag is set. It must be supplied by the application and +receives two arguments: \fBpreverify_ok\fR indicates, whether the verification of +the certificate in question was passed (preverify_ok=1) or not +(preverify_ok=0). \fBx509_ctx\fR is a pointer to the complete context used +for the certificate chain verification. +.PP +The certificate chain is checked starting with the deepest nesting level +(the root \s-1CA\s0 certificate) and worked upward to the peer's certificate. +At each level signatures and issuer attributes are checked. Whenever +a verification error is found, the error number is stored in \fBx509_ctx\fR +and \fBverify_callback\fR is called with \fBpreverify_ok\fR=0. By applying +X509_CTX_store_* functions \fBverify_callback\fR can locate the certificate +in question and perform additional steps (see \s-1EXAMPLES\s0). If no error is +found for a certificate, \fBverify_callback\fR is called with \fBpreverify_ok\fR=1 +before advancing to the next level. +.PP +The return value of \fBverify_callback\fR controls the strategy of the further +verification process. If \fBverify_callback\fR returns 0, the verification +process is immediately stopped with \*(L"verification failed\*(R" state. If +\&\s-1SSL_VERIFY_PEER\s0 is set, a verification failure alert is sent to the peer and +the \s-1TLS/SSL\s0 handshake is terminated. If \fBverify_callback\fR returns 1, +the verification process is continued. If \fBverify_callback\fR always returns +1, the \s-1TLS/SSL\s0 handshake will never be terminated because of this application +experiencing a verification failure. The calling process can however +retrieve the error code of the last verification error using +SSL_get_verify_result(3) or by maintaining its +own error storage managed by \fBverify_callback\fR. +.PP +If no \fBverify_callback\fR is specified, the default callback will be used. +Its return value is identical to \fBpreverify_ok\fR, so that any verification +failure will lead to a termination of the \s-1TLS/SSL\s0 handshake with an +alert message, if \s-1SSL_VERIFY_PEER\s0 is set. +.SH "BUGS" +.IX Header "BUGS" +In client mode, it is not checked whether the \s-1SSL_VERIFY_PEER\s0 flag +is set, but whether \s-1SSL_VERIFY_NONE\s0 is not set. This can lead to +unexpected behaviour, if the \s-1SSL_VERIFY_PEER\s0 and \s-1SSL_VERIFY_NONE\s0 are not +used as required (exactly one must be set at any time). +.PP +The certificate verification depth set with SSL[_CTX]\fI_verify_depth()\fR +stops the verification at a certain depth. The error message produced +will be that of an incomplete certificate chain and not +X509_V_ERR_CERT_CHAIN_TOO_LONG as may be expected. +.SH "RETURN VALUES" +.IX Header "RETURN VALUES" +The SSL*_set_verify*() functions do not provide diagnostic information. +.SH "EXAMPLES" +.IX Header "EXAMPLES" +The following code sequence realizes an example \fBverify_callback\fR function +that will always continue the \s-1TLS/SSL\s0 handshake regardless of verification +failure, if wished. The callback realizes a verification depth limit with +more informational output. +.PP +All verification errors are printed, informations about the certificate chain +are printed on request. +The example is realized for a server that does allow but not require client +certificates. +.PP +The example makes use of the ex_data technique to store application data +into/retrieve application data from the \s-1SSL\s0 structure +(see SSL_get_ex_new_index(3), +SSL_get_ex_data_X509_STORE_CTX_idx(3)). +.PP +.Vb 15 +\& ... +\& typedef struct { +\& int verbose_mode; +\& int verify_depth; +\& int always_continue; +\& } mydata_t; +\& int mydata_index; +\& ... +\& static int verify_callback(int preverify_ok, X509_STORE_CTX *ctx) +\& { +\& char buf[256]; +\& X509 *err_cert; +\& int err, depth; +\& SSL *ssl; +\& mydata_t *mydata; +.Ve +.Vb 3 +\& err_cert = X509_STORE_CTX_get_current_cert(ctx); +\& err = X509_STORE_CTX_get_error(ctx); +\& depth = X509_STORE_CTX_get_error_depth(ctx); +.Ve +.Vb 6 +\& /* +\& * Retrieve the pointer to the SSL of the connection currently treated +\& * and the application specific data stored into the SSL object. +\& */ +\& ssl = X509_STORE_CTX_get_ex_data(ctx, SSL_get_ex_data_X509_STORE_CTX_idx()); +\& mydata = SSL_get_ex_data(ssl, mydata_index); +.Ve +.Vb 1 +\& X509_NAME_oneline(X509_get_subject_name(err_cert), buf, 256); +.Ve +.Vb 22 +\& /* +\& * Catch a too long certificate chain. The depth limit set using +\& * SSL_CTX_set_verify_depth() is by purpose set to "limit+1" so +\& * that whenever the "depth>verify_depth" condition is met, we +\& * have violated the limit and want to log this error condition. +\& * We must do it here, because the CHAIN_TOO_LONG error would not +\& * be found explicitly; only errors introduced by cutting off the +\& * additional certificates would be logged. +\& */ +\& if (depth > mydata->verify_depth) { +\& preverify_ok = 0; +\& err = X509_V_ERR_CERT_CHAIN_TOO_LONG; +\& X509_STORE_CTX_set_error(ctx, err); +\& } +\& if (!preverify_ok) { +\& printf("verify error:num=%d:%s:depth=%d:%s\en", err, +\& X509_verify_cert_error_string(err), depth, buf); +\& } +\& else if (mydata->verbose_mode) +\& { +\& printf("depth=%d:%s\en", depth, buf); +\& } +.Ve +.Vb 9 +\& /* +\& * At this point, err contains the last verification error. We can use +\& * it for something special +\& */ +\& if (!preverify_ok && (err == X509_V_ERR_UNABLE_TO_GET_ISSUER_CERT) +\& { +\& X509_NAME_oneline(X509_get_issuer_name(ctx->current_cert), buf, 256); +\& printf("issuer= %s\en", buf); +\& } +.Ve +.Vb 6 +\& if (mydata->always_continue) +\& return 1; +\& else +\& return preverify_ok; +\& } +\& ... +.Ve +.Vb 1 +\& mydata_t mydata; +.Ve +.Vb 2 +\& ... +\& mydata_index = SSL_get_ex_new_index(0, "mydata index", NULL, NULL, NULL); +.Ve +.Vb 3 +\& ... +\& SSL_CTX_set_verify(ctx, SSL_VERIFY_PEER|SSL_VERIFY_CLIENT_ONCE, +\& verify_callback); +.Ve +.Vb 5 +\& /* +\& * Let the verify_callback catch the verify_depth error so that we get +\& * an appropriate error in the logfile. +\& */ +\& SSL_CTX_set_verify_depth(verify_depth + 1); +.Ve +.Vb 6 +\& /* +\& * Set up the SSL specific data into "mydata" and store it into th SSL +\& * structure. +\& */ +\& mydata.verify_depth = verify_depth; ... +\& SSL_set_ex_data(ssl, mydata_index, &mydata); +.Ve +.Vb 9 +\& ... +\& SSL_accept(ssl); /* check of success left out for clarity */ +\& if (peer = SSL_get_peer_certificate(ssl)) +\& { +\& if (SSL_get_verify_result(ssl) == X509_V_OK) +\& { +\& /* The client sent a certificate which verified OK */ +\& } +\& } +.Ve +.SH "SEE ALSO" +.IX Header "SEE ALSO" +ssl(3), SSL_new(3), +SSL_CTX_get_verify_mode(3), +SSL_get_verify_result(3), +SSL_CTX_load_verify_locations(3), +SSL_get_peer_certificate(3), +SSL_CTX_set_cert_verify_callback(3), +SSL_get_ex_data_X509_STORE_CTX_idx(3), +SSL_get_ex_new_index(3) |
