From 221d65ba534d23a240ccadd0c2679b222aae35b1 Mon Sep 17 00:00:00 2001 From: Benjamin Kaduk Date: Mon, 2 May 2022 10:40:57 -0700 Subject: [PATCH] evp_md: assert digest is provided for algctx reuse When reusing an algctx (it was always freed on reinitialization, prior to #18105), assert that the associated digest is provided. We implicitly rely on this for algctx reuse to be safe (since an implicit fetch could potentially change the digest object used, including provider, which accordingly could change the layout of the algctx object. From code inspection, this is currently always the case -- the only way to set an algctx requires the provider to be set, and the only ways to change or remove a provider without destroying the entier EVP_MD_CTX will also free the algctx. Adding an assertion will help ensure that this remains true as the code evolves. Reviewed-by: Tomas Mraz Reviewed-by: Paul Dale (Merged from https://github.com/openssl/openssl/pull/18224) --- crypto/evp/digest.c | 11 +++++++++-- 1 file changed, 9 insertions(+), 2 deletions(-) diff --git a/crypto/evp/digest.c b/crypto/evp/digest.c index 02e8c4c47d2..e055c70a5f5 100644 --- a/crypto/evp/digest.c +++ b/crypto/evp/digest.c @@ -245,8 +245,15 @@ static int evp_md_init_internal(EVP_MD_CTX *ctx, const EVP_MD *type, cleanup_old_md_data(ctx, 1); /* Start of non-legacy code below */ - if (ctx->digest != type && !evp_md_ctx_free_algctx(ctx)) - return 0; + if (ctx->digest == type) { + if (!ossl_assert(type->prov != NULL)) { + ERR_raise(ERR_LIB_EVP, EVP_R_INITIALIZATION_ERROR); + return 0; + } + } else { + if (!evp_md_ctx_free_algctx(ctx)) + return 0; + } if (type->prov == NULL) { #ifdef FIPS_MODULE -- 2.47.2