Index: openssl/doc/crypto/EVP_PKEY_verifyrecover.pod |
=================================================================== |
--- openssl/doc/crypto/EVP_PKEY_verifyrecover.pod (revision 0) |
+++ openssl/doc/crypto/EVP_PKEY_verifyrecover.pod (revision 0) |
@@ -0,0 +1,103 @@ |
+=pod |
+ |
+=head1 NAME |
+ |
+EVP_PKEY_verifyrecover_init, EVP_PKEY_verifyrecover - recover signature using a public key algorithm |
+ |
+=head1 SYNOPSIS |
+ |
+ #include <openssl/evp.h> |
+ |
+ int EVP_PKEY_verifyrecover_init(EVP_PKEY_CTX *ctx); |
+ int EVP_PKEY_verifyrecover(EVP_PKEY_CTX *ctx, |
+ unsigned char *rout, size_t *routlen, |
+ const unsigned char *sig, size_t siglen); |
+ |
+=head1 DESCRIPTION |
+ |
+The EVP_PKEY_verifyrecover_init() function initializes a public key algorithm |
+context using key B<pkey> for a verify recover operation. |
+ |
+The EVP_PKEY_verifyrecover() function recovers signed data |
+using B<ctx>. The signature is specified using the B<sig> and |
+B<siglen> parameters. If B<rout> is B<NULL> then the maximum size of the output |
+buffer is written to the B<routlen> parameter. If B<rout> is not B<NULL> then |
+before the call the B<routlen> parameter should contain the length of the |
+B<rout> buffer, if the call is successful recovered data is written to |
+B<rout> and the amount of data written to B<routlen>. |
+ |
+=head1 NOTES |
+ |
+Normally an application is only interested in whether a signature verification |
+operation is successful in those cases the EVP_verify() function should be |
+used. |
+ |
+Sometimes however it is useful to obtain the data originally signed using a |
+signing operation. Only certain public key algorithms can recover a signature |
+in this way (for example RSA in PKCS padding mode). |
+ |
+After the call to EVP_PKEY_verifyrecover_init() algorithm specific control |
+operations can be performed to set any appropriate parameters for the |
+operation. |
+ |
+The function EVP_PKEY_verifyrecover() can be called more than once on the same |
+context if several operations are performed using the same parameters. |
+ |
+=head1 RETURN VALUES |
+ |
+EVP_PKEY_verifyrecover_init() and EVP_PKEY_verifyrecover() return 1 for success |
+and 0 or a negative value for failure. In particular a return value of -2 |
+indicates the operation is not supported by the public key algorithm. |
+ |
+=head1 EXAMPLE |
+ |
+Recover digest originally signed using PKCS#1 and SHA256 digest: |
+ |
+ #include <openssl/evp.h> |
+ #include <openssl/rsa.h> |
+ |
+ EVP_PKEY_CTX *ctx; |
+ unsigned char *rout, *sig; |
+ size_t routlen, siglen; |
+ EVP_PKEY *verify_key; |
+ /* NB: assumes verify_key, sig and siglen are already set up |
+ * and that verify_key is an RSA public key |
+ */ |
+ ctx = EVP_PKEY_CTX_new(verify_key); |
+ if (!ctx) |
+ /* Error occurred */ |
+ if (EVP_PKEY_verifyrecover_init(ctx) <= 0) |
+ /* Error */ |
+ if (EVP_PKEY_CTX_set_rsa_padding(ctx, RSA_PKCS1_PADDING) <= 0) |
+ /* Error */ |
+ if (EVP_PKEY_CTX_set_signature_md(ctx, EVP_sha256()) <= 0) |
+ /* Error */ |
+ |
+ /* Determine buffer length */ |
+ if (EVP_PKEY_verifyrecover(ctx, NULL, &routlen, sig, siglen) <= 0) |
+ /* Error */ |
+ |
+ rout = OPENSSL_malloc(routlen); |
+ |
+ if (!rout) |
+ /* malloc failure */ |
+ |
+ if (EVP_PKEY_verifyrecover(ctx, rout, &routlen, sig, siglen) <= 0) |
+ /* Error */ |
+ |
+ /* Recovered data is routlen bytes written to buffer rout */ |
+ |
+=head1 SEE ALSO |
+ |
+L<EVP_PKEY_CTX_new(3)|EVP_PKEY_CTX_new(3)>, |
+L<EVP_PKEY_encrypt(3)|EVP_PKEY_encrypt(3)>, |
+L<EVP_PKEY_decrypt(3)|EVP_PKEY_decrypt(3)>, |
+L<EVP_PKEY_sign(3)|EVP_PKEY_sign(3)>, |
+L<EVP_PKEY_verify(3)|EVP_PKEY_verify(3)>, |
+L<EVP_PKEY_derive(3)|EVP_PKEY_derive(3)> |
+ |
+=head1 HISTORY |
+ |
+These functions were first added to OpenSSL 1.0.0. |
+ |
+=cut |