From 5d5f04923f2df0e3c24114bcd28e2c86139e1ba8 Mon Sep 17 00:00:00 2001 From: Thomas Altenbach Date: Wed, 11 Sep 2024 17:50:15 +0200 Subject: [PATCH] bootutil: Fix AES and SHA-256 contexts not zeroized with mbedTLS For some reason, the calls to mbedtls_aes_free, mbedtls_nist_kw_free and mbedtls_sha256_free_drop were commented out which means the AES and SHA-256 contexts were not properly de-initialized after usage when mbedTLS is used. In the case of AES-KW it seems that might lead to a memory leak depending on the mbedTLS configuration, but in any case and independently of the mbedTLS configuration, this leads to the contexts not be zeroized after usage. Not zeroizing a context means it stays in RAM an undefined amount of time, which might enable an attacker to access it and to dump the sensitive data it contains. Signed-off-by: Thomas Altenbach --- boot/bootutil/include/bootutil/crypto/aes_ctr.h | 4 +--- boot/bootutil/include/bootutil/crypto/aes_kw.h | 4 +--- boot/bootutil/include/bootutil/crypto/sha.h | 4 +--- 3 files changed, 3 insertions(+), 9 deletions(-) diff --git a/boot/bootutil/include/bootutil/crypto/aes_ctr.h b/boot/bootutil/include/bootutil/crypto/aes_ctr.h index e69b0372..50d36a4f 100644 --- a/boot/bootutil/include/bootutil/crypto/aes_ctr.h +++ b/boot/bootutil/include/bootutil/crypto/aes_ctr.h @@ -53,9 +53,7 @@ static inline void bootutil_aes_ctr_init(bootutil_aes_ctr_context *ctx) static inline void bootutil_aes_ctr_drop(bootutil_aes_ctr_context *ctx) { - /* XXX: config defines MBEDTLS_PLATFORM_NO_STD_FUNCTIONS so no need to free */ - /* (void)mbedtls_aes_free(ctx); */ - (void)ctx; + mbedtls_aes_free(ctx); } static inline int bootutil_aes_ctr_set_key(bootutil_aes_ctr_context *ctx, const uint8_t *k) diff --git a/boot/bootutil/include/bootutil/crypto/aes_kw.h b/boot/bootutil/include/bootutil/crypto/aes_kw.h index cf3194f9..34045c2d 100644 --- a/boot/bootutil/include/bootutil/crypto/aes_kw.h +++ b/boot/bootutil/include/bootutil/crypto/aes_kw.h @@ -45,9 +45,7 @@ static inline void bootutil_aes_kw_init(bootutil_aes_kw_context *ctx) static inline void bootutil_aes_kw_drop(bootutil_aes_kw_context *ctx) { - /* XXX: config defines MBEDTLS_PLATFORM_NO_STD_FUNCTIONS so no need to free */ - /* (void)mbedtls_aes_free(ctx); */ - (void)ctx; + mbedtls_nist_kw_free(ctx); } static inline int bootutil_aes_kw_set_unwrap_key(bootutil_aes_kw_context *ctx, const uint8_t *k, uint32_t klen) diff --git a/boot/bootutil/include/bootutil/crypto/sha.h b/boot/bootutil/include/bootutil/crypto/sha.h index 9ce54bee..704a123e 100644 --- a/boot/bootutil/include/bootutil/crypto/sha.h +++ b/boot/bootutil/include/bootutil/crypto/sha.h @@ -126,9 +126,7 @@ static inline int bootutil_sha_init(bootutil_sha_context *ctx) static inline int bootutil_sha_drop(bootutil_sha_context *ctx) { - /* XXX: config defines MBEDTLS_PLATFORM_NO_STD_FUNCTIONS so no need to free */ - /* (void)mbedtls_sha256_free(ctx); */ - (void)ctx; + mbedtls_sha256_free(ctx); return 0; }