diff options
Diffstat (limited to 'secure/lib/libssl/man/SSL_CTX_set_verify.3')
-rw-r--r-- | secure/lib/libssl/man/SSL_CTX_set_verify.3 | 418 |
1 files changed, 418 insertions, 0 deletions
diff --git a/secure/lib/libssl/man/SSL_CTX_set_verify.3 b/secure/lib/libssl/man/SSL_CTX_set_verify.3 new file mode 100644 index 0000000..2a49511 --- /dev/null +++ b/secure/lib/libssl/man/SSL_CTX_set_verify.3 @@ -0,0 +1,418 @@ +.\" Automatically generated by Pod::Man 2.28 (Pod::Simple 3.30) +.\" +.\" Standard preamble: +.\" ======================================================================== +.de Sp \" Vertical space (when we can't use .PP) +.if t .sp .5v +.if n .sp +.. +.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. \*(C+ will +.\" give a nicer C++. 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Always turn off hyphenation; it makes +.\" way too many mistakes in technical documents. +.if n .ad l +.nh +.SH "NAME" +SSL_CTX_set_verify, SSL_set_verify, SSL_CTX_set_verify_depth, SSL_set_verify_depth \- set peer certificate verification parameters +.SH "SYNOPSIS" +.IX Header "SYNOPSIS" +.Vb 1 +\& #include <openssl/ssl.h> +\& +\& void SSL_CTX_set_verify(SSL_CTX *ctx, int mode, +\& int (*verify_callback)(int, X509_STORE_CTX *)); +\& void SSL_set_verify(SSL *s, int mode, +\& int (*verify_callback)(int, X509_STORE_CTX *)); +\& void SSL_CTX_set_verify_depth(SSL_CTX *ctx,int depth); +\& void SSL_set_verify_depth(SSL *s, int depth); +\& +\& int verify_callback(int preverify_ok, X509_STORE_CTX *x509_ctx); +.Ve +.SH "DESCRIPTION" +.IX Header "DESCRIPTION" +\&\fISSL_CTX_set_verify()\fR sets the verification flags for \fBctx\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. +.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 time \fBssl\fR was created with +\&\fISSL_new\fR\|(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 \fISSL_get_verify_result\fR\|(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 +\&\fISSL_CTX_set_cert_verify_callback\fR\|(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 100, +allowing for the peer certificate and additional 100 \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 not be terminated with respect to verification +failures and the connection will be established. The calling process can +however retrieve the error code of the last verification error using +\&\fISSL_get_verify_result\fR\|(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; information about the certificate chain +is 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 \fISSL_get_ex_new_index\fR\|(3), +\&\fISSL_get_ex_data_X509_STORE_CTX_idx\fR\|(3)). +.PP +.Vb 10 +\& ... +\& 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; +\& +\& err_cert = X509_STORE_CTX_get_current_cert(ctx); +\& err = X509_STORE_CTX_get_error(ctx); +\& depth = X509_STORE_CTX_get_error_depth(ctx); +\& +\& /* +\& * 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); +\& +\& X509_NAME_oneline(X509_get_subject_name(err_cert), buf, 256); +\& +\& /* +\& * 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); +\& } +\& +\& /* +\& * 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); +\& } +\& +\& if (mydata\->always_continue) +\& return 1; +\& else +\& return preverify_ok; +\& } +\& ... +\& +\& mydata_t mydata; +\& +\& ... +\& mydata_index = SSL_get_ex_new_index(0, "mydata index", NULL, NULL, NULL); +\& +\& ... +\& SSL_CTX_set_verify(ctx, SSL_VERIFY_PEER|SSL_VERIFY_CLIENT_ONCE, +\& verify_callback); +\& +\& /* +\& * 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); +\& +\& /* +\& * 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); +\& +\& ... +\& 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" +\&\fIssl\fR\|(3), \fISSL_new\fR\|(3), +\&\fISSL_CTX_get_verify_mode\fR\|(3), +\&\fISSL_get_verify_result\fR\|(3), +\&\fISSL_CTX_load_verify_locations\fR\|(3), +\&\fISSL_get_peer_certificate\fR\|(3), +\&\fISSL_CTX_set_cert_verify_callback\fR\|(3), +\&\fISSL_get_ex_data_X509_STORE_CTX_idx\fR\|(3), +\&\fISSL_get_ex_new_index\fR\|(3) |