| 1 | =pod
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| 2 |
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| 3 | =head1 NAME
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| 4 |
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| 5 | EVP_VerifyInit_ex,
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| 6 | EVP_VerifyInit, EVP_VerifyUpdate, EVP_VerifyFinal_ex, EVP_VerifyFinal
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| 7 | - EVP signature verification functions
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| 8 |
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| 9 | =head1 SYNOPSIS
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| 10 |
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| 11 | #include <openssl/evp.h>
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| 12 |
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| 13 | int EVP_VerifyInit_ex(EVP_MD_CTX *ctx, const EVP_MD *type, ENGINE *impl);
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| 14 | int EVP_VerifyUpdate(EVP_MD_CTX *ctx, const void *d, unsigned int cnt);
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| 15 | int EVP_VerifyFinal_ex(EVP_MD_CTX *ctx, const unsigned char *sigbuf,
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| 16 | unsigned int siglen, EVP_PKEY *pkey,
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| 17 | OSSL_LIB_CTX *libctx, const char *propq);
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| 18 | int EVP_VerifyFinal(EVP_MD_CTX *ctx, unsigned char *sigbuf, unsigned int siglen,
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| 19 | EVP_PKEY *pkey);
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| 20 |
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| 21 | int EVP_VerifyInit(EVP_MD_CTX *ctx, const EVP_MD *type);
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| 22 |
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| 23 | =head1 DESCRIPTION
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| 24 |
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| 25 | The EVP signature verification routines are a high-level interface to digital
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| 26 | signatures.
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| 27 |
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| 28 | EVP_VerifyInit_ex() sets up verification context I<ctx> to use digest
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| 29 | I<type> from ENGINE I<impl>. I<ctx> must be created by calling
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| 30 | EVP_MD_CTX_new() before calling this function.
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| 31 |
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| 32 | EVP_VerifyUpdate() hashes I<cnt> bytes of data at I<d> into the
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| 33 | verification context I<ctx>. This function can be called several times on the
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| 34 | same I<ctx> to include additional data.
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| 35 |
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| 36 | EVP_VerifyFinal_ex() verifies the data in I<ctx> using the public key
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| 37 | I<pkey> and I<siglen> bytes in I<sigbuf>.
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| 38 | The library context I<libctx> and property query I<propq> are used when creating
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| 39 | a context to use with the key I<pkey>.
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| 40 |
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| 41 | EVP_VerifyFinal() is similar to EVP_VerifyFinal_ex() but uses default
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| 42 | values of NULL for the library context I<libctx> and the property query I<propq>.
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| 43 |
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| 44 | EVP_VerifyInit() initializes verification context I<ctx> to use the default
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| 45 | implementation of digest I<type>.
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| 46 |
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| 47 | =head1 RETURN VALUES
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| 48 |
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| 49 | EVP_VerifyInit_ex() and EVP_VerifyUpdate() return 1 for success and 0 for
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| 50 | failure.
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| 51 |
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| 52 | EVP_VerifyFinal_ex() and EVP_VerifyFinal() return 1 for a correct
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| 53 | signature, 0 for failure and a negative value if some other error occurred.
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| 54 |
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| 55 | The error codes can be obtained by L<ERR_get_error(3)>.
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| 56 |
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| 57 | =head1 NOTES
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| 58 |
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| 59 | The B<EVP> interface to digital signatures should almost always be used in
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| 60 | preference to the low-level interfaces. This is because the code then becomes
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| 61 | transparent to the algorithm used and much more flexible.
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| 62 |
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| 63 | The call to EVP_VerifyFinal() internally finalizes a copy of the digest context.
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| 64 | This means that calls to EVP_VerifyUpdate() and EVP_VerifyFinal() can be called
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| 65 | later to digest and verify additional data.
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| 66 |
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| 67 | Since only a copy of the digest context is ever finalized the context must
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| 68 | be cleaned up after use by calling EVP_MD_CTX_free() or a memory leak
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| 69 | will occur.
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| 70 |
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| 71 | =head1 BUGS
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| 72 |
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| 73 | Older versions of this documentation wrongly stated that calls to
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| 74 | EVP_VerifyUpdate() could not be made after calling EVP_VerifyFinal().
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| 75 |
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| 76 | Since the public key is passed in the call to EVP_SignFinal() any error
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| 77 | relating to the private key (for example an unsuitable key and digest
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| 78 | combination) will not be indicated until after potentially large amounts of
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| 79 | data have been passed through EVP_SignUpdate().
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| 80 |
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| 81 | It is not possible to change the signing parameters using these function.
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| 82 |
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| 83 | The previous two bugs are fixed in the newer EVP_DigestVerify*() function.
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| 84 |
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| 85 | =head1 SEE ALSO
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| 86 |
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| 87 | L<evp(7)>,
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| 88 | L<EVP_SignInit(3)>,
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| 89 | L<EVP_DigestInit(3)>,
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| 90 | L<evp(7)>, L<HMAC(3)>, L<MD2(3)>,
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| 91 | L<MD5(3)>, L<MDC2(3)>, L<RIPEMD160(3)>,
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| 92 | L<SHA1(3)>, L<openssl-dgst(1)>
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| 93 |
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| 94 | =head1 HISTORY
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| 95 |
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| 96 | The function EVP_VerifyFinal_ex() was added in OpenSSL 3.0.
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| 97 |
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| 98 | =head1 COPYRIGHT
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| 99 |
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| 100 | Copyright 2000-2022 The OpenSSL Project Authors. All Rights Reserved.
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| 101 |
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| 102 | Licensed under the Apache License 2.0 (the "License"). You may not use
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| 103 | this file except in compliance with the License. You can obtain a copy
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| 104 | in the file LICENSE in the source distribution or at
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| 105 | L<https://www.openssl.org/source/license.html>.
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| 106 |
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| 107 | =cut
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