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diff --git a/src/lib/libcrypto/doc/EVP_SignInit.pod b/src/lib/libcrypto/doc/EVP_SignInit.pod new file mode 100644 index 0000000000..781d43e401 --- /dev/null +++ b/src/lib/libcrypto/doc/EVP_SignInit.pod  | |||
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| 1 | =pod | ||
| 2 | |||
| 3 | =head1 NAME | ||
| 4 | |||
| 5 | EVP_SignInit, EVP_SignUpdate, EVP_SignFinal - EVP signing functions | ||
| 6 | |||
| 7 | =head1 SYNOPSIS | ||
| 8 | |||
| 9 | #include <openssl/evp.h> | ||
| 10 | |||
| 11 | int EVP_SignInit_ex(EVP_MD_CTX *ctx, const EVP_MD *type, ENGINE *impl); | ||
| 12 | int EVP_SignUpdate(EVP_MD_CTX *ctx, const void *d, unsigned int cnt); | ||
| 13 | int EVP_SignFinal(EVP_MD_CTX *ctx,unsigned char *sig,unsigned int *s, EVP_PKEY *pkey); | ||
| 14 | |||
| 15 | void EVP_SignInit(EVP_MD_CTX *ctx, const EVP_MD *type); | ||
| 16 | |||
| 17 | int EVP_PKEY_size(EVP_PKEY *pkey); | ||
| 18 | |||
| 19 | =head1 DESCRIPTION | ||
| 20 | |||
| 21 | The EVP signature routines are a high level interface to digital | ||
| 22 | signatures. | ||
| 23 | |||
| 24 | EVP_SignInit_ex() sets up signing context B<ctx> to use digest | ||
| 25 | B<type> from ENGINE B<impl>. B<ctx> must be initialized with | ||
| 26 | EVP_MD_CTX_init() before calling this function. | ||
| 27 | |||
| 28 | EVP_SignUpdate() hashes B<cnt> bytes of data at B<d> into the | ||
| 29 | signature context B<ctx>. This function can be called several times on the | ||
| 30 | same B<ctx> to include additional data. | ||
| 31 | |||
| 32 | EVP_SignFinal() signs the data in B<ctx> using the private key B<pkey> and | ||
| 33 | places the signature in B<sig>. The number of bytes of data written (i.e. the | ||
| 34 | length of the signature) will be written to the integer at B<s>, at most | ||
| 35 | EVP_PKEY_size(pkey) bytes will be written. | ||
| 36 | |||
| 37 | EVP_SignInit() initializes a signing context B<ctx> to use the default | ||
| 38 | implementation of digest B<type>. | ||
| 39 | |||
| 40 | EVP_PKEY_size() returns the maximum size of a signature in bytes. The actual | ||
| 41 | signature returned by EVP_SignFinal() may be smaller. | ||
| 42 | |||
| 43 | =head1 RETURN VALUES | ||
| 44 | |||
| 45 | EVP_SignInit_ex(), EVP_SignUpdate() and EVP_SignFinal() return 1 | ||
| 46 | for success and 0 for failure. | ||
| 47 | |||
| 48 | EVP_PKEY_size() returns the maximum size of a signature in bytes. | ||
| 49 | |||
| 50 | The error codes can be obtained by L<ERR_get_error(3)|ERR_get_error(3)>. | ||
| 51 | |||
| 52 | =head1 NOTES | ||
| 53 | |||
| 54 | The B<EVP> interface to digital signatures should almost always be used in | ||
| 55 | preference to the low level interfaces. This is because the code then becomes | ||
| 56 | transparent to the algorithm used and much more flexible. | ||
| 57 | |||
| 58 | Due to the link between message digests and public key algorithms the correct | ||
| 59 | digest algorithm must be used with the correct public key type. A list of | ||
| 60 | algorithms and associated public key algorithms appears in | ||
| 61 | L<EVP_DigestInit(3)|EVP_DigestInit(3)>. | ||
| 62 | |||
| 63 | When signing with DSA private keys the random number generator must be seeded | ||
| 64 | or the operation will fail. The random number generator does not need to be | ||
| 65 | seeded for RSA signatures. | ||
| 66 | |||
| 67 | The call to EVP_SignFinal() internally finalizes a copy of the digest context. | ||
| 68 | This means that calls to EVP_SignUpdate() and EVP_SignFinal() can be called | ||
| 69 | later to digest and sign additional data. | ||
| 70 | |||
| 71 | Since only a copy of the digest context is ever finalized the context must | ||
| 72 | be cleaned up after use by calling EVP_MD_CTX_cleanup() or a memory leak | ||
| 73 | will occur. | ||
| 74 | |||
| 75 | =head1 BUGS | ||
| 76 | |||
| 77 | Older versions of this documentation wrongly stated that calls to | ||
| 78 | EVP_SignUpdate() could not be made after calling EVP_SignFinal(). | ||
| 79 | |||
| 80 | Since the private key is passed in the call to EVP_SignFinal() any error | ||
| 81 | relating to the private key (for example an unsuitable key and digest | ||
| 82 | combination) will not be indicated until after potentially large amounts of | ||
| 83 | data have been passed through EVP_SignUpdate(). | ||
| 84 | |||
| 85 | It is not possible to change the signing parameters using these function. | ||
| 86 | |||
| 87 | The previous two bugs are fixed in the newer EVP_SignDigest*() function. | ||
| 88 | |||
| 89 | =head1 SEE ALSO | ||
| 90 | |||
| 91 | L<EVP_VerifyInit(3)|EVP_VerifyInit(3)>, | ||
| 92 | L<EVP_DigestInit(3)|EVP_DigestInit(3)>, L<ERR_get_error(3)|ERR_get_error(3)>, | ||
| 93 | L<evp(3)|evp(3)>, L<HMAC(3)|HMAC(3)>, L<MD2(3)|MD2(3)>, | ||
| 94 | L<MD5(3)|MD5(3)>, L<MDC2(3)|MDC2(3)>, L<RIPEMD(3)|RIPEMD(3)>, | ||
| 95 | L<SHA1(3)|SHA1(3)>, L<digest(1)|digest(1)> | ||
| 96 | |||
| 97 | =head1 HISTORY | ||
| 98 | |||
| 99 | EVP_SignInit(), EVP_SignUpdate() and EVP_SignFinal() are | ||
| 100 | available in all versions of SSLeay and OpenSSL. | ||
| 101 | |||
| 102 | EVP_SignInit_ex() was added in OpenSSL 0.9.7. | ||
| 103 | |||
| 104 | =cut | ||
