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EVP_*Update: ensure that input NULL with length 0 isn't passed

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Even with custom ciphers, the combination in == NULL && inl == 0
should not be passed down to the backend cipher function.  The reason
is that these are the values passed by EVP_*Final, and some of the
backend cipher functions do check for these to see if a "final" call
is made.

An exception is made for CCM mode which has special handling for the case
where inl == 0: this may mean the total plaintext or ciphertext length is 0.

This is based on an original commit by Richard Levitte.

Fixes #8675

Reviewed-by: Richard Levitte <levitte@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/9057)
This commit is contained in:
Matt Caswell 2019-04-05 01:22:14 +02:00
parent aeb8d94b6b
commit 420cb707b8
1 changed files with 22 additions and 9 deletions
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31
crypto/evp/evp_enc.c
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@ -305,6 +305,17 @@ static int evp_EncryptDecryptUpdate(EVP_CIPHER_CTX *ctx,
bl = ctx->cipher->block_size;
/*
* CCM mode needs to know about the case where inl == 0 && in == NULL - it
* means the plaintext/ciphertext length is 0
*/
if (inl < 0
|| (inl == 0
&& EVP_CIPHER_mode(ctx->cipher) != EVP_CIPH_CCM_MODE)) {
*outl = 0;
return inl == 0;
}
if (ctx->cipher->flags & EVP_CIPH_FLAG_CUSTOM_CIPHER) {
/* If block size > 1 then the cipher will have to do this check */
if (bl == 1 && is_partially_overlapping(out, in, cmpl)) {
@ -320,10 +331,6 @@ static int evp_EncryptDecryptUpdate(EVP_CIPHER_CTX *ctx,
return 1;
}
if (inl <= 0) {
*outl = 0;
return inl == 0;
}
if (is_partially_overlapping(out + ctx->buf_len, in, cmpl)) {
EVPerr(EVP_F_EVP_ENCRYPTDECRYPTUPDATE, EVP_R_PARTIALLY_OVERLAPPING);
return 0;
@ -457,6 +464,17 @@ int EVP_DecryptUpdate(EVP_CIPHER_CTX *ctx, unsigned char *out, int *outl,
if (EVP_CIPHER_CTX_test_flags(ctx, EVP_CIPH_FLAG_LENGTH_BITS))
cmpl = (cmpl + 7) / 8;
/*
* CCM mode needs to know about the case where inl == 0 - it means the
* plaintext/ciphertext length is 0
*/
if (inl < 0
|| (inl == 0
&& EVP_CIPHER_mode(ctx->cipher) != EVP_CIPH_CCM_MODE)) {
*outl = 0;
return inl == 0;
}
if (ctx->cipher->flags & EVP_CIPH_FLAG_CUSTOM_CIPHER) {
if (b == 1 && is_partially_overlapping(out, in, cmpl)) {
EVPerr(EVP_F_EVP_DECRYPTUPDATE, EVP_R_PARTIALLY_OVERLAPPING);
@ -472,11 +490,6 @@ int EVP_DecryptUpdate(EVP_CIPHER_CTX *ctx, unsigned char *out, int *outl,
return 1;
}
if (inl <= 0) {
*outl = 0;
return inl == 0;
}
if (ctx->flags & EVP_CIPH_NO_PADDING)
return evp_EncryptDecryptUpdate(ctx, out, outl, in, inl);