91 lines
2.7 KiB
Text
91 lines
2.7 KiB
Text
=pod
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=head1 NAME
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EVP_PKEY_verify_init, EVP_PKEY_verify - signature verification using a public key algorithm
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=head1 SYNOPSIS
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#include <openssl/evp.h>
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int EVP_PKEY_verify_init(EVP_PKEY_CTX *ctx);
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int EVP_PKEY_verify(EVP_PKEY_CTX *ctx,
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const unsigned char *sig, size_t siglen,
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const unsigned char *tbs, size_t tbslen);
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=head1 DESCRIPTION
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The EVP_PKEY_verify_init() function initializes a public key algorithm
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context using key B<pkey> for a signature verification operation.
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The EVP_PKEY_verify() function performs a public key verification operation
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using B<ctx>. The signature is specified using the B<sig> and
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B<siglen> parameters. The verified data (i.e. the data believed originally
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signed) is specified using the B<tbs> and B<tbslen> parameters.
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=head1 NOTES
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After the call to EVP_PKEY_verify_init() algorithm specific control
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operations can be performed to set any appropriate parameters for the
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operation.
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The function EVP_PKEY_verify() can be called more than once on the same
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context if several operations are performed using the same parameters.
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=head1 RETURN VALUES
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EVP_PKEY_verify_init() and EVP_PKEY_verify() return 1 if the verification was
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successful and 0 if it failed. Unlike other functions the return value 0 from
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EVP_PKEY_verify() only indicates that the signature did not not verify
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successfully (that is tbs did not match the original data or the signature was
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of invalid form) it is not an indication of a more serious error.
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A negative value indicates an error other that signature verification failure.
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In particular a return value of -2 indicates the operation is not supported by
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the public key algorithm.
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=head1 EXAMPLE
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Verify signature using PKCS#1 and SHA256 digest:
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#include <openssl/evp.h>
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#include <openssl/rsa.h>
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EVP_PKEY_CTX *ctx;
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unsigned char *md, *sig;
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size_t mdlen, siglen;
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EVP_PKEY *verify_key;
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/* NB: assumes verify_key, sig, siglen md and mdlen are already set up
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* and that verify_key is an RSA public key
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*/
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ctx = EVP_PKEY_CTX_new(verify_key);
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if (!ctx)
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/* Error occurred */
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if (EVP_PKEY_verify_init(ctx) <= 0)
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/* Error */
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if (EVP_PKEY_CTX_set_rsa_padding(ctx, RSA_PKCS1_PADDING) <= 0)
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/* Error */
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if (EVP_PKEY_CTX_set_signature_md(ctx, EVP_sha256()) <= 0)
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/* Error */
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/* Perform operation */
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ret = EVP_PKEY_verify(ctx, md, mdlen, sig, siglen);
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/* ret == 1 indicates success, 0 verify failure and < 0 for some
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* other error.
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*/
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=head1 SEE ALSO
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L<EVP_PKEY_CTX_new(3)|EVP_PKEY_CTX_new(3)>,
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L<EVP_PKEY_encrypt(3)|EVP_PKEY_encrypt(3)>,
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L<EVP_PKEY_decrypt(3)|EVP_PKEY_decrypt(3)>,
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L<EVP_PKEY_sign(3)|EVP_PKEY_sign(3)>,
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L<EVP_PKEY_verifyrecover(3)|EVP_PKEY_verifyrecover(3)>,
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L<EVP_PKEY_derive(3)|EVP_PKEY_derive(3)>
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=head1 HISTORY
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These functions were first added to OpenSSL 0.9.9.
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=cut
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