From 50788b8b3618888f3974962cf19fd1e61d780c7d Mon Sep 17 00:00:00 2001 From: Bernd Edlinger Date: Fri, 1 Mar 2019 09:27:32 +0100 Subject: Update documentation regarding required output buffer memory size of RSA_private_decrypt/RSA_public_encrypt. Reviewed-by: Kurt Roeckx (Merged from https://github.com/openssl/openssl/pull/8365) (cherry picked from commit b89fdeb2f7d4471cbfd8a579945754327a4e06a8) --- doc/man3/RSA_public_encrypt.pod | 38 ++++++++++++++++++++++++++------------ 1 file changed, 26 insertions(+), 12 deletions(-) (limited to 'doc') diff --git a/doc/man3/RSA_public_encrypt.pod b/doc/man3/RSA_public_encrypt.pod index 91c176e24c..d91c6884b1 100644 --- a/doc/man3/RSA_public_encrypt.pod +++ b/doc/man3/RSA_public_encrypt.pod @@ -8,10 +8,10 @@ RSA_public_encrypt, RSA_private_decrypt - RSA public key cryptography #include - int RSA_public_encrypt(int flen, unsigned char *from, + int RSA_public_encrypt(int flen, const unsigned char *from, unsigned char *to, RSA *rsa, int padding); - int RSA_private_decrypt(int flen, unsigned char *from, + int RSA_private_decrypt(int flen, const unsigned char *from, unsigned char *to, RSA *rsa, int padding); =head1 DESCRIPTION @@ -27,6 +27,8 @@ B denotes one of the following modes: =item RSA_PKCS1_PADDING PKCS #1 v1.5 padding. This currently is the most widely used mode. +However, it is highly recommended to use RSA_PKCS1_OAEP_PADDING in +new applications. SEE WARNING BELOW. =item RSA_PKCS1_OAEP_PADDING @@ -46,23 +48,35 @@ Encrypting user data directly with RSA is insecure. =back -B must be less than RSA_size(B) - 11 for the PKCS #1 v1.5 -based padding modes, less than RSA_size(B) - 41 for +B must not be more than RSA_size(B) - 11 for the PKCS #1 v1.5 +based padding modes, not more than RSA_size(B) - 42 for RSA_PKCS1_OAEP_PADDING and exactly RSA_size(B) for RSA_NO_PADDING. -The random number generator must be seeded prior to calling -RSA_public_encrypt(). +When a padding mode other than RSA_NO_PADDING is in use, then +RSA_public_encrypt() will include some random bytes into the ciphertext +and therefore the ciphertext will be different each time, even if the +plaintext and the public key are exactly identical. +The returned ciphertext in B will always be zero padded to exactly +RSA_size(B) bytes. +B and B may overlap. RSA_private_decrypt() decrypts the B bytes at B using the -private key B and stores the plaintext in B. B must point -to a memory section large enough to hold the decrypted data (which is -smaller than RSA_size(B)). B is the padding mode that -was used to encrypt the data. +private key B and stores the plaintext in B. B should +be equal to RSA_size(B) but may be smaller, when leading zero +bytes are in the ciphertext. Those are not important and may be removed, +but RSA_public_encrypt() does not do that. B must point +to a memory section large enough to hold the maximal possible decrypted +data (which is equal to RSA_size(B) for RSA_NO_PADDING, +RSA_size(B) - 11 for the PKCS #1 v1.5 based padding modes and +RSA_size(B) - 42 for RSA_PKCS1_OAEP_PADDING). +B is the padding mode that was used to encrypt the data. +B and B may overlap. =head1 RETURN VALUES RSA_public_encrypt() returns the size of the encrypted data (i.e., RSA_size(B)). RSA_private_decrypt() returns the size of the -recovered plaintext. +recovered plaintext. A return value of 0 is not an error and +means only that the plaintext was empty. On error, -1 is returned; the error codes can be obtained by L. @@ -85,7 +99,7 @@ L =head1 COPYRIGHT -Copyright 2000-2016 The OpenSSL Project Authors. All Rights Reserved. +Copyright 2000-2019 The OpenSSL Project Authors. All Rights Reserved. Licensed under the OpenSSL license (the "License"). You may not use this file except in compliance with the License. You can obtain a copy -- cgit v1.2.3