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| 1 | =pod | ||
| 2 | |||
| 3 | =head1 NAME | ||
| 4 | |||
| 5 | EVP_VerifyInit, EVP_VerifyUpdate, EVP_VerifyFinal - EVP signature verification functions | ||
| 6 | |||
| 7 | =head1 SYNOPSIS | ||
| 8 | |||
| 9 | #include <openssl/evp.h> | ||
| 10 | |||
| 11 | int EVP_VerifyInit_ex(EVP_MD_CTX *ctx, const EVP_MD *type, ENGINE *impl); | ||
| 12 | int EVP_VerifyUpdate(EVP_MD_CTX *ctx, const void *d, unsigned int cnt); | ||
| 13 | int EVP_VerifyFinal(EVP_MD_CTX *ctx,unsigned char *sigbuf, unsigned int siglen,EVP_PKEY *pkey); | ||
| 14 | |||
| 15 | int EVP_VerifyInit(EVP_MD_CTX *ctx, const EVP_MD *type); | ||
| 16 | |||
| 17 | =head1 DESCRIPTION | ||
| 18 | |||
| 19 | The EVP signature verification routines are a high level interface to digital | ||
| 20 | signatures. | ||
| 21 | |||
| 22 | EVP_VerifyInit_ex() sets up verification context B<ctx> to use digest | ||
| 23 | B<type> from ENGINE B<impl>. B<ctx> must be initialized by calling | ||
| 24 | EVP_MD_CTX_init() before calling this function. | ||
| 25 | |||
| 26 | EVP_VerifyUpdate() hashes B<cnt> bytes of data at B<d> into the | ||
| 27 | verification context B<ctx>. This function can be called several times on the | ||
| 28 | same B<ctx> to include additional data. | ||
| 29 | |||
| 30 | EVP_VerifyFinal() verifies the data in B<ctx> using the public key B<pkey> | ||
| 31 | and against the B<siglen> bytes at B<sigbuf>. | ||
| 32 | |||
| 33 | EVP_VerifyInit() initializes verification context B<ctx> to use the default | ||
| 34 | implementation of digest B<type>. | ||
| 35 | |||
| 36 | =head1 RETURN VALUES | ||
| 37 | |||
| 38 | EVP_VerifyInit_ex() and EVP_VerifyUpdate() return 1 for success and 0 for | ||
| 39 | failure. | ||
| 40 | |||
| 41 | EVP_VerifyFinal() returns 1 for a correct signature, 0 for failure and -1 if some | ||
| 42 | other error occurred. | ||
| 43 | |||
| 44 | The error codes can be obtained by L<ERR_get_error(3)|ERR_get_error(3)>. | ||
| 45 | |||
| 46 | =head1 NOTES | ||
| 47 | |||
| 48 | The B<EVP> interface to digital signatures should almost always be used in | ||
| 49 | preference to the low level interfaces. This is because the code then becomes | ||
| 50 | transparent to the algorithm used and much more flexible. | ||
| 51 | |||
| 52 | Due to the link between message digests and public key algorithms the correct | ||
| 53 | digest algorithm must be used with the correct public key type. A list of | ||
| 54 | algorithms and associated public key algorithms appears in | ||
| 55 | L<EVP_DigestInit(3)|EVP_DigestInit(3)>. | ||
| 56 | |||
| 57 | The call to EVP_VerifyFinal() internally finalizes a copy of the digest context. | ||
| 58 | This means that calls to EVP_VerifyUpdate() and EVP_VerifyFinal() can be called | ||
| 59 | later to digest and verify additional data. | ||
| 60 | |||
| 61 | Since only a copy of the digest context is ever finalized the context must | ||
| 62 | be cleaned up after use by calling EVP_MD_CTX_cleanup() or a memory leak | ||
| 63 | will occur. | ||
| 64 | |||
| 65 | =head1 BUGS | ||
| 66 | |||
| 67 | Older versions of this documentation wrongly stated that calls to | ||
| 68 | EVP_VerifyUpdate() could not be made after calling EVP_VerifyFinal(). | ||
| 69 | |||
| 70 | =head1 SEE ALSO | ||
| 71 | |||
| 72 | L<evp(3)|evp(3)>, | ||
| 73 | L<EVP_SignInit(3)|EVP_SignInit(3)>, | ||
| 74 | L<EVP_DigestInit(3)|EVP_DigestInit(3)>, L<err(3)|err(3)>, | ||
| 75 | L<evp(3)|evp(3)>, L<hmac(3)|hmac(3)>, L<md2(3)|md2(3)>, | ||
| 76 | L<md5(3)|md5(3)>, L<mdc2(3)|mdc2(3)>, L<ripemd(3)|ripemd(3)>, | ||
| 77 | L<sha(3)|sha(3)>, L<dgst(1)|dgst(1)> | ||
| 78 | |||
| 79 | =head1 HISTORY | ||
| 80 | |||
| 81 | EVP_VerifyInit(), EVP_VerifyUpdate() and EVP_VerifyFinal() are | ||
| 82 | available in all versions of SSLeay and OpenSSL. | ||
| 83 | |||
| 84 | EVP_VerifyInit_ex() was added in OpenSSL 0.9.7 | ||
| 85 | |||
| 86 | =cut | ||
