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      1 =pod
      2 
      3 =head1 NAME
      4 
      5 ASN1_item_sign, ASN1_item_sign_ex, ASN1_item_sign_ctx,
      6 ASN1_item_verify, ASN1_item_verify_ex, ASN1_item_verify_ctx -
      7 ASN1 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 
     42 ASN1_item_sign_ex() is used to sign arbitrary ASN1 data using a data object
     43 I<data>, the ASN.1 structure I<it>, private key I<pkey> and message digest I<md>.
     44 The data that is signed is formed by taking the data object in I<data> and
     45 converting it to der format using the ASN.1 structure I<it>.
     46 The I<data> that will be signed, and a structure containing the signature may
     47 both have a copy of the B<X509_ALGOR>. The ASN1_item_sign_ex() function will
     48 write the correct B<X509_ALGOR> to the structs based on the algorithms and
     49 parameters that have been set up. If one of I<algor1> or I<algor2> points to the
     50 B<X509_ALGOR> of the I<data> to be signed, then that B<X509_ALGOR> will first be
     51 written before the signature is generated.
     52 Examples of valid values that can be used by the ASN.1 structure I<it> are
     53 ASN1_ITEM_rptr(X509_CINF), ASN1_ITEM_rptr(X509_REQ_INFO) and
     54 ASN1_ITEM_rptr(X509_CRL_INFO).
     55 The B<OSSL_LIB_CTX> specified in I<libctx> and the property query string
     56 specified in I<props> are used when searching for algorithms in providers.
     57 The generated signature is set into I<signature>.
     58 The optional parameter I<id> can be NULL, but can be set for special key types.
     59 See EVP_PKEY_CTX_set1_id() for further info. The output parameters <algor1> and
     60 I<algor2> are ignored if they are NULL.
     61 
     62 ASN1_item_sign() is similar to ASN1_item_sign_ex() but uses default values of
     63 NULL for the I<id>, I<libctx> and I<propq>.
     64 
     65 ASN1_item_sign_ctx() is similar to ASN1_item_sign() but uses the parameters
     66 contained in digest context I<ctx>.
     67 
     68 ASN1_item_verify_ex() is used to verify the signature I<signature> of internal
     69 data I<data> using the public key I<pkey> and algorithm identifier I<alg>.
     70 The data that is verified is formed by taking the data object in I<data> and
     71 converting it to der format using the ASN.1 structure I<it>.
     72 The B<OSSL_LIB_CTX> specified in I<libctx> and the property query string
     73 specified in I<props> are used when searching for algorithms in providers.
     74 The optional parameter I<id> can be NULL, but can be set for special key types.
     75 See EVP_PKEY_CTX_set1_id() for further info.
     76 
     77 ASN1_item_verify() is similar to ASN1_item_verify_ex() but uses default values of
     78 NULL for the I<id>, I<libctx> and I<propq>.
     79 
     80 ASN1_item_verify_ctx() is similar to ASN1_item_verify() but uses the parameters
     81 contained in digest context I<ctx>.
     82 
     83 
     84 =head1 RETURN VALUES
     85 
     86 All sign functions return the size of the signature in bytes for success and
     87 zero for failure.
     88 
     89 All verify functions return 1 if the signature is valid and 0 if the signature
     90 check fails. If the signature could not be checked at all because it was
     91 ill-formed or some other error occurred then -1 is returned.
     92 
     93 =head1 EXAMPLES
     94 
     95 In the following example a 'MyObject' object is signed using the key contained
     96 in an EVP_MD_CTX. The signature is written to MyObject.signature. The object is
     97 then 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);
    199 err:
    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 
    210 L<X509_sign(3)>,
    211 L<X509_verify(3)>
    212 
    213 =head1 HISTORY
    214 
    215 ASN1_item_sign_ex() and ASN1_item_verify_ex() were added in OpenSSL 3.0.
    216 
    217 =head1 COPYRIGHT
    218 
    219 Copyright 2020-2022 The OpenSSL Project Authors. All Rights Reserved.
    220 
    221 Licensed under the Apache License 2.0 (the "License").  You may not use
    222 this file except in compliance with the License.  You can obtain a copy
    223 in the file LICENSE in the source distribution or at
    224 L<https://www.openssl.org/source/license.html>.
    225 
    226 =cut
    227