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X509_sign, X509_sign_ctx, X509_verify_ex, X509_verify, X509_REQ_sign, X509_REQ_sign_ctx, X509_REQ_verify_ex, X509_REQ_verify, X509_CRL_sign, X509_CRL_sign_ctx, X509_CRL_verify - sign or verify certificate, certificate request or CRL signature


 #include <openssl/x509.h>

 int X509_sign(X509 *x, EVP_PKEY *pkey, const EVP_MD *md);
 int X509_sign_ctx(X509 *x, EVP_MD_CTX *ctx);
 int X509_verify_ex(X509 *x, EVP_PKEY *pkey, OPENSSL_CTX *libctx, const char *propq);
 int X509_verify(X509 *x, EVP_PKEY *pkey;

 int X509_REQ_sign(X509_REQ *x, EVP_PKEY *pkey, const EVP_MD *md);
 int X509_REQ_sign_ctx(X509_REQ *x, EVP_MD_CTX *ctx);
 int X509_REQ_verify_ex(X509_REQ *a, EVP_PKEY *pkey, OPENSSL_CTX *libctx,
                        const char *propq);
 int X509_REQ_verify(X509_REQ *a, EVP_PKEY *pkey);

 int X509_CRL_sign(X509_CRL *x, EVP_PKEY *pkey, const EVP_MD *md);
 int X509_CRL_sign_ctx(X509_CRL *x, EVP_MD_CTX *ctx);
 int X509_CRL_verify(X509_CRL *a, EVP_PKEY *pkey);


X509_sign() signs certificate x using private key pkey and message digest md and sets the signature in x. X509_sign_ctx() also signs certificate x but uses the parameters contained in digest context ctx.

X509_verify_ex() verifies the signature of certificate x using public key pkey. Any cryptographic algorithms required for the verification are fetched using the library context libctx and the property query string propq. Only the signature is checked: no other checks (such as certificate chain validity) are performed.

X509_verify() is the same as X509_verify_ex() except that the default library context and property query string are used.

X509_REQ_sign(), X509_REQ_sign_ctx(), X509_REQ_verify_ex(), X509_REQ_verify(), X509_CRL_sign(), X509_CRL_sign_ctx() and X509_CRL_verify() sign and verify certificate requests and CRLs respectively.


X509_sign_ctx() is used where the default parameters for the corresponding public key and digest are not suitable. It can be used to sign keys using RSA-PSS for example.

For efficiency reasons and to work around ASN.1 encoding issues the encoding of the signed portion of a certificate, certificate request and CRL is cached internally. If the signed portion of the structure is modified the encoding is not always updated meaning a stale version is sometimes used. This is not normally a problem because modifying the signed portion will invalidate the signature and signing will always update the encoding.


X509_sign(), X509_sign_ctx(), X509_REQ_sign(), X509_REQ_sign_ctx(), X509_CRL_sign() and X509_CRL_sign_ctx() return the size of the signature in bytes for success and zero for failure.

X509_verify_ex(), X509_verify(), X509_REQ_verify_ex(), X509_REQ_verify() and X509_CRL_verify() return 1 if the signature is valid and 0 if the signature check fails. If the signature could not be checked at all because it was invalid or some other error occurred then -1 is returned.


d2i_X509(3), ERR_get_error(3), X509_CRL_get0_by_serial(3), X509_get0_signature(3), X509_get_ext_d2i(3), X509_get_extension_flags(3), X509_get_pubkey(3), X509_get_subject_name(3), X509_get_version(3), X509_NAME_add_entry_by_txt(3), X509_NAME_ENTRY_get_object(3), X509_NAME_get_index_by_NID(3), X509_NAME_print_ex(3), X509_new(3), X509V3_get_d2i(3), X509_verify_cert(3), OPENSSL_CTX(3)


The X509_sign(), X509_REQ_sign() and X509_CRL_sign() functions are available in all versions of OpenSSL.

The X509_sign_ctx(), X509_REQ_sign_ctx() and X509_CRL_sign_ctx() functions were added OpenSSL 1.0.1.

X509_verify_ex() and X509_REQ_verify_ex() were added in OpenSSL 3.0.


Copyright 2015-2020 The OpenSSL Project Authors. All Rights Reserved.

Licensed under the Apache License 2.0 (the "License"). You may not use this file except in compliance with the License. You can obtain a copy in the file LICENSE in the source distribution or at <>.

2020-07-06 3.0.0-alpha4