X509_sign.3ssl - Man Page

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(X509 *a, EVP_PKEY *r);

 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(X509_REQ *a, EVP_PKEY *r);

 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 *r);


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() verifies the signature of certificate x using public key pkey. Only the signature is checked: no other checks (such as certificate chain validity) are performed.

X509_REQ_sign(), X509_REQ_sign_ctx(), 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.

Return Values

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(), 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.

See Also

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)


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.

Referenced By

EVP_PKEY_ASN1_METHOD.3ssl(3), i2d_re_X509_tbs.3ssl(3), X509_CRL_get0_by_serial.3ssl(3), X509_get0_notBefore.3ssl(3), X509_get0_signature.3ssl(3), X509_get0_uids.3ssl(3), X509_get_pubkey.3ssl(3), X509_get_serialNumber.3ssl(3), X509_get_subject_name.3ssl(3), X509_get_version.3ssl(3), X509_new.3ssl(3), X509V3_get_d2i.3ssl(3).

The man pages X509_CRL_sign.3ssl(3), X509_CRL_sign_ctx.3ssl(3), X509_CRL_verify.3ssl(3), X509_REQ_sign.3ssl(3), X509_REQ_sign_ctx.3ssl(3), X509_REQ_verify.3ssl(3), X509_sign_ctx.3ssl(3) and X509_verify.3ssl(3) are aliases of X509_sign.3ssl(3).

2023-07-20 1.1.1q OpenSSL