From: Jarkko Sakkinen jarkko@kernel.org
For a heap makes sense to leave its contents "unmeasured" in the SGX enclave build process, meaning that they won't contribute to the cryptographic signature (a RSA-3072 signed SHA56 hash) of the enclave.
Enclaves are signed blobs where the signature is calculated both from page data and also from "structural properties" of the pages. For instance a page offset of *every* page added to the enclave is hashed.
For data, this is optional, not least because hashing a page has a significant contribution to the enclave load time. Thus, where there is no reason to hash, do not. The SGX ioctl interface supports this with SGX_PAGE_MEASURE flag. Only when the flag is *set*, data is measured.
Add seg->measure boolean flag to struct encl_segment. Only when the flag is set, include the segment data to the signature (represented by SIGSTRUCT architectural structure).
Signed-off-by: Jarkko Sakkinen jarkko@kernel.org Signed-off-by: Reinette Chatre reinette.chatre@intel.com --- tools/testing/selftests/sgx/load.c | 6 +++++- tools/testing/selftests/sgx/main.h | 1 + tools/testing/selftests/sgx/sigstruct.c | 6 ++++-- 3 files changed, 10 insertions(+), 3 deletions(-)
diff --git a/tools/testing/selftests/sgx/load.c b/tools/testing/selftests/sgx/load.c index 5605474aab73..f1be78984c50 100644 --- a/tools/testing/selftests/sgx/load.c +++ b/tools/testing/selftests/sgx/load.c @@ -111,7 +111,10 @@ static bool encl_ioc_add_pages(struct encl *encl, struct encl_segment *seg) ioc.offset = seg->offset; ioc.length = seg->size; ioc.secinfo = (unsigned long)&secinfo; - ioc.flags = SGX_PAGE_MEASURE; + if (seg->measure) + ioc.flags = SGX_PAGE_MEASURE; + else + ioc.flags = 0;
rc = ioctl(encl->fd, SGX_IOC_ENCLAVE_ADD_PAGES, &ioc); if (rc < 0) { @@ -230,6 +233,7 @@ bool encl_load(const char *path, struct encl *encl) seg->offset = (phdr->p_offset & PAGE_MASK) - src_offset; seg->size = (phdr->p_filesz + PAGE_SIZE - 1) & PAGE_MASK; seg->src = encl->src + seg->offset; + seg->measure = true;
j++; } diff --git a/tools/testing/selftests/sgx/main.h b/tools/testing/selftests/sgx/main.h index 452d11dc4889..aebc69e7cdc8 100644 --- a/tools/testing/selftests/sgx/main.h +++ b/tools/testing/selftests/sgx/main.h @@ -12,6 +12,7 @@ struct encl_segment { size_t size; unsigned int prot; unsigned int flags; + bool measure; };
struct encl { diff --git a/tools/testing/selftests/sgx/sigstruct.c b/tools/testing/selftests/sgx/sigstruct.c index 202a96fd81bf..50c5ab1aa6fa 100644 --- a/tools/testing/selftests/sgx/sigstruct.c +++ b/tools/testing/selftests/sgx/sigstruct.c @@ -296,8 +296,10 @@ static bool mrenclave_segment(EVP_MD_CTX *ctx, struct encl *encl, if (!mrenclave_eadd(ctx, seg->offset + offset, seg->flags)) return false;
- if (!mrenclave_eextend(ctx, seg->offset + offset, seg->src + offset)) - return false; + if (seg->measure) { + if (!mrenclave_eextend(ctx, seg->offset + offset, seg->src + offset)) + return false; + } }
return true;