xref: /openssl/doc/man3/ASN1_item_sign.pod (revision fecb3aae) 
1=pod
2
3=head1 NAME
4
5ASN1_item_sign, ASN1_item_sign_ex, ASN1_item_sign_ctx,
6ASN1_item_verify, ASN1_item_verify_ex, ASN1_item_verify_ctx -
7ASN1 sign and verify
8
9=head1 SYNOPSIS
10
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
40=head1 DESCRIPTION
41
42ASN1_item_sign_ex() is used to sign arbitrary ASN1 data using a data object
43I<data>, the ASN.1 structure I<it>, private key I<pkey> and message digest I<md>.
44The data that is signed is formed by taking the data object in I<data> and
45converting it to der format using the ASN.1 structure I<it>.
46The I<data> that will be signed, and a structure containing the signature may
47both have a copy of the B<X509_ALGOR>. The ASN1_item_sign_ex() function will
48write the correct B<X509_ALGOR> to the structs based on the algorithms and
49parameters that have been set up. If one of I<algor1> or I<algor2> points to the
50B<X509_ALGOR> of the I<data> to be signed, then that B<X509_ALGOR> will first be
51written before the signature is generated.
52Examples of valid values that can be used by the ASN.1 structure I<it> are
53ASN1_ITEM_rptr(X509_CINF), ASN1_ITEM_rptr(X509_REQ_INFO) and
54ASN1_ITEM_rptr(X509_CRL_INFO).
55The B<OSSL_LIB_CTX> specified in I<libctx> and the property query string
56specified in I<props> are used when searching for algorithms in providers.
57The generated signature is set into I<signature>.
58The optional parameter I<id> can be NULL, but can be set for special key types.
59See EVP_PKEY_CTX_set1_id() for further info. The output parameters <algor1> and
60I<algor2> are ignored if they are NULL.
61
62ASN1_item_sign() is similar to ASN1_item_sign_ex() but uses default values of
63NULL for the I<id>, I<libctx> and I<propq>.
64
65ASN1_item_sign_ctx() is similar to ASN1_item_sign() but uses the parameters
66contained in digest context I<ctx>.
67
68ASN1_item_verify_ex() is used to verify the signature I<signature> of internal
69data I<data> using the public key I<pkey> and algorithm identifier I<alg>.
70The data that is verified is formed by taking the data object in I<data> and
71converting it to der format using the ASN.1 structure I<it>.
72The B<OSSL_LIB_CTX> specified in I<libctx> and the property query string
73specified in I<props> are used when searching for algorithms in providers.
74The optional parameter I<id> can be NULL, but can be set for special key types.
75See EVP_PKEY_CTX_set1_id() for further info.
76
77ASN1_item_verify() is similar to ASN1_item_verify_ex() but uses default values of
78NULL for the I<id>, I<libctx> and I<propq>.
79
80ASN1_item_verify_ctx() is similar to ASN1_item_verify() but uses the parameters
81contained in digest context I<ctx>.
82
83
84=head1 RETURN VALUES
85
86All sign functions return the size of the signature in bytes for success and
87zero for failure.
88
89All verify functions return 1 if the signature is valid and 0 if the signature
90check fails. If the signature could not be checked at all because it was
91ill-formed or some other error occurred then -1 is returned.
92
93=head1 EXAMPLES
94
95In the following example a 'MyObject' object is signed using the key contained
96in an EVP_MD_CTX. The signature is written to MyObject.signature. The object is
97then output in DER format and then loaded back in and verified.
98
99 #include <openssl/x509.h>
100 #include <openssl/asn1t.h>
101
102 /* An object used to store the ASN1 data fields that will be signed */
103 typedef struct MySignInfoObject_st
104 {
105     ASN1_INTEGER *version;
106     X509_ALGOR sig_alg;
107 } MySignInfoObject;
108
109 DECLARE_ASN1_FUNCTIONS(MySignInfoObject)
110 /*
111  * A higher level object containing the ASN1 fields, signature alg and
112  * output signature.
113  */
114 typedef struct MyObject_st
115 {
116     MySignInfoObject info;
117     X509_ALGOR sig_alg;
118     ASN1_BIT_STRING *signature;
119 } MyObject;
120
121 DECLARE_ASN1_FUNCTIONS(MyObject)
122
123 /* The ASN1 definition of MySignInfoObject */
124 ASN1_SEQUENCE_cb(MySignInfoObject, NULL) = {
125     ASN1_SIMPLE(MySignInfoObject, version, ASN1_INTEGER)
126     ASN1_EMBED(MySignInfoObject, sig_alg, X509_ALGOR),
127 } ASN1_SEQUENCE_END_cb(MySignInfoObject, MySignInfoObject)
128
129 /* new, free, d2i & i2d functions for MySignInfoObject */
130 IMPLEMENT_ASN1_FUNCTIONS(MySignInfoObject)
131
132 /* The ASN1 definition of MyObject */
133 ASN1_SEQUENCE_cb(MyObject, NULL) = {
134     ASN1_EMBED(MyObject, info, MySignInfoObject),
135     ASN1_EMBED(MyObject, sig_alg, X509_ALGOR),
136     ASN1_SIMPLE(MyObject, signature, ASN1_BIT_STRING)
137 } ASN1_SEQUENCE_END_cb(MyObject, MyObject)
138
139 /* new, free, d2i & i2d functions for MyObject */
140 IMPLEMENT_ASN1_FUNCTIONS(MyObject)
141
142 int test_asn1_item_sign_verify(const char *mdname, EVP_PKEY *pkey, long version)
143 {
144    int ret = 0;
145    unsigned char *obj_der = NULL;
146    const unsigned char *p = NULL;
147    MyObject *obj = NULL, *loaded_obj = NULL;
148    const ASN1_ITEM *it = ASN1_ITEM_rptr(MySignInfoObject);
149    EVP_MD_CTX *sctx = NULL, *vctx = NULL;
150    int len;
151
152    /* Create MyObject and set its version */
153    obj = MyObject_new();
154    if (obj == NULL)
155        goto err;
156    if (!ASN1_INTEGER_set(obj->info.version, version))
157        goto err;
158
159    /* Set the key and digest used for signing */
160    sctx = EVP_MD_CTX_new();
161    if (sctx == NULL
162        || !EVP_DigestSignInit_ex(sctx, NULL, mdname, NULL, NULL, pkey))
163        goto err;
164
165    /*
166     * it contains the mapping between ASN.1 data and an object MySignInfoObject
167     * obj->info is the 'MySignInfoObject' object that will be
168     *   converted into DER data and then signed.
169     * obj->signature will contain the output signature.
170     * obj->sig_alg is filled with the private key's signing algorithm id.
171     * obj->info.sig_alg is another copy of the signing algorithm id that sits
172     * within MyObject.
173     */
174    len = ASN1_item_sign_ctx(it, &obj->sig_alg, &obj->info.sig_alg,
175                             obj->signature, &obj->info, sctx);
176    if (len <= 0
177        || X509_ALGOR_cmp(&obj->sig_alg, &obj->info.sig_alg) != 0)
178        goto err;
179
180    /* Output MyObject in der form */
181    len = i2d_MyObject(obj, &obj_der);
182    if (len <= 0)
183        goto err;
184
185    /* Set the key and digest used for verifying */
186    vctx = EVP_MD_CTX_new();
187    if (vctx == NULL
188        || !EVP_DigestVerifyInit_ex(vctx, NULL, mdname, NULL, NULL, pkey))
189        goto err;
190
191    /* Load the der data back into an object */
192    p = obj_der;
193    loaded_obj = d2i_MyObject(NULL, &p, len);
194    if (loaded_obj == NULL)
195        goto err;
196    /* Verify the loaded object */
197    ret = ASN1_item_verify_ctx(it, &loaded_obj->sig_alg, loaded_obj->signature,
198                               &loaded_obj->info, vctx);
199err:
200    OPENSSL_free(obj_der);
201    MyObject_free(loaded_obj);
202    MyObject_free(obj);
203    EVP_MD_CTX_free(sctx);
204    EVP_MD_CTX_free(vctx);
205    return ret;
206 }
207
208=head1 SEE ALSO
209
210L<X509_sign(3)>,
211L<X509_verify(3)>
212
213=head1 HISTORY
214
215ASN1_item_sign_ex() and ASN1_item_verify_ex() were added in OpenSSL 3.0.
216
217=head1 COPYRIGHT
218
219Copyright 2020-2022 The OpenSSL Project Authors. All Rights Reserved.
220
221Licensed under the Apache License 2.0 (the "License").  You may not use
222this file except in compliance with the License.  You can obtain a copy
223in the file LICENSE in the source distribution or at
224L<https://www.openssl.org/source/license.html>.
225
226=cut
227