From c9fb704cf3af5524eb8e79961e31b60eee8c3c47 Mon Sep 17 00:00:00 2001 From: Matt Caswell Date: Tue, 2 Feb 2021 17:17:23 +0000 Subject: Don't overflow the output length in EVP_CipherUpdate calls CVE-2021-23840 Reviewed-by: Paul Dale --- crypto/evp/evp_enc.c | 26 ++++++++++++++++++++++++++ 1 file changed, 26 insertions(+) (limited to 'crypto/evp/evp_enc.c') diff --git a/crypto/evp/evp_enc.c b/crypto/evp/evp_enc.c index b804d74914..f049cb40bb 100644 --- a/crypto/evp/evp_enc.c +++ b/crypto/evp/evp_enc.c @@ -11,6 +11,7 @@ #define OPENSSL_SUPPRESS_DEPRECATED #include +#include #include #include "internal/cryptlib.h" #include @@ -511,6 +512,18 @@ static int evp_EncryptDecryptUpdate(EVP_CIPHER_CTX *ctx, return 1; } else { j = bl - i; + + /* + * Once we've processed the first j bytes from in, the amount of + * data left that is a multiple of the block length is: + * (inl - j) & ~(bl - 1) + * We must ensure that this amount of data, plus the one block that + * we process from ctx->buf does not exceed INT_MAX + */ + if (((inl - j) & ~(bl - 1)) > INT_MAX - bl) { + ERR_raise(ERR_LIB_EVP, EVP_R_OUTPUT_WOULD_OVERFLOW); + return 0; + } memcpy(&(ctx->buf[i]), in, j); inl -= j; in += j; @@ -771,6 +784,19 @@ int EVP_DecryptUpdate(EVP_CIPHER_CTX *ctx, unsigned char *out, int *outl, ERR_raise(ERR_LIB_EVP, EVP_R_PARTIALLY_OVERLAPPING); return 0; } + /* + * final_used is only ever set if buf_len is 0. Therefore the maximum + * length output we will ever see from evp_EncryptDecryptUpdate is + * the maximum multiple of the block length that is <= inl, or just: + * inl & ~(b - 1) + * Since final_used has been set then the final output length is: + * (inl & ~(b - 1)) + b + * This must never exceed INT_MAX + */ + if ((inl & ~(b - 1)) > INT_MAX - b) { + ERR_raise(ERR_LIB_EVP, EVP_R_OUTPUT_WOULD_OVERFLOW); + return 0; + } memcpy(out, ctx->final, b); out += b; fix_len = 1; -- cgit v1.2.3