1ASN1_ITEM_SIGN(3ossl)               OpenSSL              ASN1_ITEM_SIGN(3ossl)
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NAME

6       ASN1_item_sign, ASN1_item_sign_ex, ASN1_item_sign_ctx,
7       ASN1_item_verify, ASN1_item_verify_ex, ASN1_item_verify_ctx - ASN1 sign
8       and verify
9

SYNOPSIS

11        #include <openssl/x509.h>
12
13        int ASN1_item_sign_ex(const ASN1_ITEM *it, X509_ALGOR *algor1,
14                              X509_ALGOR *algor2, ASN1_BIT_STRING *signature,
15                              const void *data, const ASN1_OCTET_STRING *id,
16                              EVP_PKEY *pkey, const EVP_MD *md, OSSL_LIB_CTX *libctx,
17                              const char *propq);
18
19        int ASN1_item_sign(const ASN1_ITEM *it, X509_ALGOR *algor1, X509_ALGOR *algor2,
20                           ASN1_BIT_STRING *signature, const void *data,
21                           EVP_PKEY *pkey, const EVP_MD *md);
22
23        int ASN1_item_sign_ctx(const ASN1_ITEM *it, X509_ALGOR *algor1,
24                               X509_ALGOR *algor2, ASN1_BIT_STRING *signature,
25                               const void *data, EVP_MD_CTX *ctx);
26
27        int ASN1_item_verify_ex(const ASN1_ITEM *it, const X509_ALGOR *alg,
28                                const ASN1_BIT_STRING *signature, const void *data,
29                                const ASN1_OCTET_STRING *id, EVP_PKEY *pkey,
30                                OSSL_LIB_CTX *libctx, const char *propq);
31
32        int ASN1_item_verify(const ASN1_ITEM *it, const X509_ALGOR *alg,
33                             const ASN1_BIT_STRING *signature, const void *data,
34                             EVP_PKEY *pkey);
35
36        int ASN1_item_verify_ctx(const ASN1_ITEM *it, const X509_ALGOR *alg,
37                                 const ASN1_BIT_STRING *signature, const void *data,
38                                 EVP_MD_CTX *ctx);
39

DESCRIPTION

41       ASN1_item_sign_ex() is used to sign arbitrary ASN1 data using a data
42       object data, the ASN.1 structure it, private key pkey and message
43       digest md.  The data that is signed is formed by taking the data object
44       in data and converting it to der format using the ASN.1 structure it.
45       The data that will be signed, and a structure containing the signature
46       may both have a copy of the X509_ALGOR. The ASN1_item_sign_ex()
47       function will write the correct X509_ALGOR to the structs based on the
48       algorithms and parameters that have been set up. If one of algor1 or
49       algor2 points to the X509_ALGOR of the data to be signed, then that
50       X509_ALGOR will first be written before the signature is generated.
51       Examples of valid values that can be used by the ASN.1 structure it are
52       ASN1_ITEM_rptr(X509_CINF), ASN1_ITEM_rptr(X509_REQ_INFO) and
53       ASN1_ITEM_rptr(X509_CRL_INFO).  The OSSL_LIB_CTX specified in libctx
54       and the property query string specified in props are used when
55       searching for algorithms in providers.  The generated signature is set
56       into signature.  The optional parameter id can be NULL, but can be set
57       for special key types.  See EVP_PKEY_CTX_set1_id() for further info.
58       The output parameters <algor1> and algor2 are ignored if they are NULL.
59
60       ASN1_item_sign() is similar to ASN1_item_sign_ex() but uses default
61       values of NULL for the id, libctx and propq.
62
63       ASN1_item_sign_ctx() is similiar to ASN1_item_sign() but uses the
64       parameters contained in digest context ctx.
65
66       ASN1_item_verify_ex() is used to verify the signature signature of
67       internal data data using the public key pkey and algorithm identifier
68       alg.  The data that is verified is formed by taking the data object in
69       data and converting it to der format using the ASN.1 structure it.  The
70       OSSL_LIB_CTX specified in libctx and the property query string
71       specified in props are used when searching for algorithms in providers.
72       The optional parameter id can be NULL, but can be set for special key
73       types.  See EVP_PKEY_CTX_set1_id() for further info.
74
75       ASN1_item_verify() is similar to ASN1_item_verify_ex() but uses default
76       values of NULL for the id, libctx and propq.
77
78       ASN1_item_verify_ctx() is similiar to ASN1_item_verify() but uses the
79       parameters contained in digest context ctx.
80

RETURN VALUES

82       All sign functions return the size of the signature in bytes for
83       success and zero for failure.
84
85       All verify functions return 1 if the signature is valid and 0 if the
86       signature check fails. If the signature could not be checked at all
87       because it was ill-formed or some other error occurred then -1 is
88       returned.
89

EXAMPLES

91       In the following example a 'MyObject' object is signed using the key
92       contained in an EVP_MD_CTX. The signature is written to
93       MyObject.signature. The object is then output in DER format and then
94       loaded back in and verified.
95
96        #include <openssl/x509.h>
97        #include <openssl/asn1t.h>
98
99        /* An object used to store the ASN1 data fields that will be signed */
100        typedef struct MySignInfoObject_st
101        {
102            ASN1_INTEGER *version;
103            X509_ALGOR sig_alg;
104        } MySignInfoObject;
105
106        DECLARE_ASN1_FUNCTIONS(MySignInfoObject)
107        /*
108         * A higher level object containing the ASN1 fields, signature alg and
109         * output signature.
110         */
111        typedef struct MyObject_st
112        {
113            MySignInfoObject info;
114            X509_ALGOR sig_alg;
115            ASN1_BIT_STRING *signature;
116        } MyObject;
117
118        DECLARE_ASN1_FUNCTIONS(MyObject)
119
120        /* The ASN1 definition of MySignInfoObject */
121        ASN1_SEQUENCE_cb(MySignInfoObject, NULL) = {
122            ASN1_SIMPLE(MySignInfoObject, version, ASN1_INTEGER)
123            ASN1_EMBED(MySignInfoObject, sig_alg, X509_ALGOR),
124        } ASN1_SEQUENCE_END_cb(MySignInfoObject, MySignInfoObject)
125
126        /* new, free, d2i & i2d functions for MySignInfoObject */
127        IMPLEMENT_ASN1_FUNCTIONS(MySignInfoObject)
128
129        /* The ASN1 definition of MyObject */
130        ASN1_SEQUENCE_cb(MyObject, NULL) = {
131            ASN1_EMBED(MyObject, info, MySignInfoObject),
132            ASN1_EMBED(MyObject, sig_alg, X509_ALGOR),
133            ASN1_SIMPLE(MyObject, signature, ASN1_BIT_STRING)
134        } ASN1_SEQUENCE_END_cb(MyObject, MyObject)
135
136        /* new, free, d2i & i2d functions for MyObject */
137        IMPLEMENT_ASN1_FUNCTIONS(MyObject)
138
139        int test_asn1_item_sign_verify(const char *mdname, EVP_PKEY *pkey, long version)
140        {
141           int ret = 0;
142           unsigned char *obj_der = NULL;
143           const unsigned char *p = NULL;
144           MyObject *obj = NULL, *loaded_obj = NULL;
145           const ASN1_ITEM *it = ASN1_ITEM_rptr(MySignInfoObject);
146           EVP_MD_CTX *sctx = NULL, *vctx = NULL;
147           int len;
148
149           /* Create MyObject and set its version */
150           obj = MyObject_new();
151           if (obj == NULL)
152               goto err;
153           if (!ASN1_INTEGER_set(obj->info.version, version))
154               goto err;
155
156           /* Set the key and digest used for signing */
157           sctx = EVP_MD_CTX_new();
158           if (sctx == NULL
159               || !EVP_DigestSignInit_ex(sctx, NULL, mdname, NULL, NULL, pkey))
160               goto err;
161
162           /*
163            * it contains the mapping between ASN.1 data and an object MySignInfoObject
164            * obj->info is the 'MySignInfoObject' object that will be
165            *   converted into DER data and then signed.
166            * obj->signature will contain the output signature.
167            * obj->sig_alg is filled with the private key's signing algorithm id.
168            * obj->info.sig_alg is another copy of the signing algorithm id that sits
169            * within MyObject.
170            */
171           len = ASN1_item_sign_ctx(it, &obj->sig_alg, &obj->info.sig_alg,
172                                    obj->signature, &obj->info, sctx);
173           if (len <= 0
174               || X509_ALGOR_cmp(&obj->sig_alg, &obj->info.sig_alg) != 0)
175               goto err;
176
177           /* Output MyObject in der form */
178           len = i2d_MyObject(obj, &obj_der);
179           if (len <= 0)
180               goto err;
181
182           /* Set the key and digest used for verifying */
183           vctx = EVP_MD_CTX_new();
184           if (vctx == NULL
185               || !EVP_DigestVerifyInit_ex(vctx, NULL, mdname, NULL, NULL, pkey))
186               goto err;
187
188           /* Load the der data back into an object */
189           p = obj_der;
190           loaded_obj = d2i_MyObject(NULL, &p, len);
191           if (loaded_obj == NULL)
192               goto err;
193           /* Verify the loaded object */
194           ret = ASN1_item_verify_ctx(it, &loaded_obj->sig_alg, loaded_obj->signature,
195                                      &loaded_obj->info, vctx);
196       err:
197           OPENSSL_free(obj_der);
198           MyObject_free(loaded_obj);
199           MyObject_free(obj);
200           EVP_MD_CTX_free(sctx);
201           EVP_MD_CTX_free(vctx);
202           return ret;
203        }
204

SEE ALSO

206       X509_sign(3), X509_verify(3)
207

HISTORY

209       ASN1_item_sign_ex() and ASN1_item_verify_ex() were added in OpenSSL
210       3.0.
211
213       Copyright 2020-2021 The OpenSSL Project Authors. All Rights Reserved.
214
215       Licensed under the Apache License 2.0 (the "License").  You may not use
216       this file except in compliance with the License.  You can obtain a copy
217       in the file LICENSE in the source distribution or at
218       <https://www.openssl.org/source/license.html>.
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2223.0.5                             2022-11-01             ASN1_ITEM_SIGN(3ossl)
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