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83 lines
3.2 KiB
83 lines
3.2 KiB
=pod |
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=head1 NAME |
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EVP_DigestVerifyInit, EVP_DigestVerifyUpdate, EVP_DigestVerifyFinal - EVP signature verification functions |
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=head1 SYNOPSIS |
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#include <openssl/evp.h> |
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int EVP_DigestVerifyInit(EVP_MD_CTX *ctx, EVP_PKEY_CTX **pctx, |
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const EVP_MD *type, ENGINE *e, EVP_PKEY *pkey); |
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int EVP_DigestVerifyUpdate(EVP_MD_CTX *ctx, const void *d, unsigned int cnt); |
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int EVP_DigestVerifyFinal(EVP_MD_CTX *ctx, unsigned char *sig, size_t siglen); |
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=head1 DESCRIPTION |
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The EVP signature routines are a high level interface to digital signatures. |
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EVP_DigestVerifyInit() sets up verification context B<ctx> to use digest |
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B<type> from ENGINE B<impl> and public key B<pkey>. B<ctx> must be initialized |
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with EVP_MD_CTX_init() before calling this function. If B<pctx> is not NULL the |
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EVP_PKEY_CTX of the verification operation will be written to B<*pctx>: this |
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can be used to set alternative verification options. |
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EVP_DigestVerifyUpdate() hashes B<cnt> bytes of data at B<d> into the |
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verification context B<ctx>. This function can be called several times on the |
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same B<ctx> to include additional data. This function is currently implemented |
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using a macro. |
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EVP_DigestVerifyFinal() verifies the data in B<ctx> against the signature in |
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B<sig> of length B<siglen>. |
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=head1 RETURN VALUES |
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EVP_DigestVerifyInit() and EVP_DigestVerifyUpdate() return 1 for success and 0 |
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or a negative value for failure. In particular a return value of -2 indicates |
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the operation is not supported by the public key algorithm. |
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EVP_DigestVerifyFinal() returns 1 for success; any other value indicates |
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failure. A return value of zero indicates that the signature did not verify |
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successfully (that is, tbs did not match the original data or the signature had |
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an invalid form), while other values indicate a more serious error (and |
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sometimes also indicate an invalid signature form). |
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The error codes can be obtained from L<ERR_get_error(3)|ERR_get_error(3)>. |
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=head1 NOTES |
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The B<EVP> interface to digital signatures should almost always be used in |
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preference to the low level interfaces. This is because the code then becomes |
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transparent to the algorithm used and much more flexible. |
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In previous versions of OpenSSL there was a link between message digest types |
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and public key algorithms. This meant that "clone" digests such as EVP_dss1() |
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needed to be used to sign using SHA1 and DSA. This is no longer necessary and |
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the use of clone digest is now discouraged. |
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For some key types and parameters the random number generator must be seeded |
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or the operation will fail. |
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The call to EVP_DigestVerifyFinal() internally finalizes a copy of the digest |
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context. This means that EVP_VerifyUpdate() and EVP_VerifyFinal() can |
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be called later to digest and verify additional data. |
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Since only a copy of the digest context is ever finalized the context must |
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be cleaned up after use by calling EVP_MD_CTX_cleanup() or a memory leak |
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will occur. |
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=head1 SEE ALSO |
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L<EVP_DigestSignInit(3)|EVP_DigestSignInit(3)>, |
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L<EVP_DigestInit(3)|EVP_DigestInit(3)>, L<err(3)|err(3)>, |
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L<evp(3)|evp(3)>, L<hmac(3)|hmac(3)>, L<md2(3)|md2(3)>, |
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L<md5(3)|md5(3)>, L<mdc2(3)|mdc2(3)>, L<ripemd(3)|ripemd(3)>, |
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L<sha(3)|sha(3)>, L<dgst(1)|dgst(1)> |
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=head1 HISTORY |
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EVP_DigestVerifyInit(), EVP_DigestVerifyUpdate() and EVP_DigestVerifyFinal() |
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were first added to OpenSSL 1.0.0. |
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=cut
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