| 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_PKEY_verify_init, EVP_PKEY_verify - signature verification using a public key algorithm
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| 6 |
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| 7 | =head1 SYNOPSIS
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| 8 |
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| 9 | #include <openssl/evp.h>
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| 10 |
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| 11 | int EVP_PKEY_verify_init(EVP_PKEY_CTX *ctx);
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| 12 | int EVP_PKEY_verify(EVP_PKEY_CTX *ctx,
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| 13 | const unsigned char *sig, size_t siglen,
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| 14 | const unsigned char *tbs, size_t tbslen);
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| 15 |
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| 16 | =head1 DESCRIPTION
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| 17 |
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| 18 | The EVP_PKEY_verify_init() function initializes a public key algorithm
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| 19 | context using key B<pkey> for a signature verification operation.
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| 20 |
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| 21 | The EVP_PKEY_verify() function performs a public key verification operation
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| 22 | using B<ctx>. The signature is specified using the B<sig> and
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| 23 | B<siglen> parameters. The verified data (i.e. the data believed originally
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| 24 | signed) is specified using the B<tbs> and B<tbslen> parameters.
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| 25 |
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| 26 | =head1 NOTES
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| 27 |
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| 28 | After the call to EVP_PKEY_verify_init() algorithm specific control
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| 29 | operations can be performed to set any appropriate parameters for the
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| 30 | operation.
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| 31 |
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| 32 | The function EVP_PKEY_verify() can be called more than once on the same
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| 33 | context if several operations are performed using the same parameters.
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| 34 |
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| 35 | =head1 RETURN VALUES
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| 36 |
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| 37 | EVP_PKEY_verify_init() and EVP_PKEY_verify() return 1 if the verification was
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| 38 | successful and 0 if it failed. Unlike other functions the return value 0 from
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| 39 | EVP_PKEY_verify() only indicates that the signature did not verify
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| 40 | successfully (that is tbs did not match the original data or the signature was
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| 41 | of invalid form) it is not an indication of a more serious error.
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| 42 |
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| 43 | A negative value indicates an error other that signature verification failure.
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| 44 | In particular a return value of -2 indicates the operation is not supported by
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| 45 | the public key algorithm.
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| 46 |
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| 47 | =head1 EXAMPLES
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| 48 |
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| 49 | Verify signature using PKCS#1 and SHA256 digest:
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| 50 |
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| 51 | #include <openssl/evp.h>
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| 52 | #include <openssl/rsa.h>
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| 53 |
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| 54 | EVP_PKEY_CTX *ctx;
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| 55 | unsigned char *md, *sig;
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| 56 | size_t mdlen, siglen;
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| 57 | EVP_PKEY *verify_key;
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| 58 |
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| 59 | /*
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| 60 | * NB: assumes verify_key, sig, siglen md and mdlen are already set up
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| 61 | * and that verify_key is an RSA public key
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| 62 | */
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| 63 | ctx = EVP_PKEY_CTX_new(verify_key, NULL /* no engine */);
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| 64 | if (!ctx)
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| 65 | /* Error occurred */
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| 66 | if (EVP_PKEY_verify_init(ctx) <= 0)
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| 67 | /* Error */
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| 68 | if (EVP_PKEY_CTX_set_rsa_padding(ctx, RSA_PKCS1_PADDING) <= 0)
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| 69 | /* Error */
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| 70 | if (EVP_PKEY_CTX_set_signature_md(ctx, EVP_sha256()) <= 0)
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| 71 | /* Error */
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| 72 |
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| 73 | /* Perform operation */
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| 74 | ret = EVP_PKEY_verify(ctx, sig, siglen, md, mdlen);
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| 75 |
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| 76 | /*
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| 77 | * ret == 1 indicates success, 0 verify failure and < 0 for some
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| 78 | * other error.
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| 79 | */
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| 80 |
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| 81 | =head1 SEE ALSO
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| 82 |
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| 83 | L<EVP_PKEY_CTX_new(3)>,
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| 84 | L<EVP_PKEY_encrypt(3)>,
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| 85 | L<EVP_PKEY_decrypt(3)>,
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| 86 | L<EVP_PKEY_sign(3)>,
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| 87 | L<EVP_PKEY_verify_recover(3)>,
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| 88 | L<EVP_PKEY_derive(3)>
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| 89 |
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| 90 | =head1 HISTORY
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| 91 |
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| 92 | These functions were added in OpenSSL 1.0.0.
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| 93 |
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| 94 | =head1 COPYRIGHT
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| 95 |
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| 96 | Copyright 2006-2019 The OpenSSL Project Authors. All Rights Reserved.
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| 97 |
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| 98 | Licensed under the OpenSSL license (the "License"). You may not use
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| 99 | this file except in compliance with the License. You can obtain a copy
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| 100 | in the file LICENSE in the source distribution or at
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| 101 | L<https://www.openssl.org/source/license.html>.
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| 102 |
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| 103 | =cut
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