[PATCH bpf-next v6 4/8] bpftool: Check EVP_Digest when computing excl_prog_hash

[Daniel Borkmann]

bpftool_prog_sign() ignores the return value of EVP_Digest(). If the
digest computation fails (context allocation failure, or a digest
fetch failure under OpenSSL), EVP_Digest() returns 0 and leaves the
output buffer untouched, but the function still reports success.

Fixes: 40863f4d6ef2 ("bpftool: Add support for signing BPF programs")
Signed-off-by: Daniel Borkmann <daniel at iogearbox.net>
---
 tools/bpf/bpftool/sign.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/tools/bpf/bpftool/sign.c b/tools/bpf/bpftool/sign.c
index f9b742f4bb10..1257dba8ef2f 100644
--- a/tools/bpf/bpftool/sign.c
+++ b/tools/bpf/bpftool/sign.c
@@ -175,8 +175,11 @@ int bpftool_prog_sign(struct bpf_load_and_run_opts *opts)
 		goto cleanup;
 	}
 
-	EVP_Digest(opts->insns, opts->insns_sz, opts->excl_prog_hash,
-		   &opts->excl_prog_hash_sz, EVP_sha256(), NULL);
+	if (EVP_Digest(opts->insns, opts->insns_sz, opts->excl_prog_hash,
+		       &opts->excl_prog_hash_sz, EVP_sha256(), NULL) != 1) {
+		err = -EIO;
+		goto cleanup;
+	}
 
 		bd_out = BIO_new(BIO_s_mem());
 	if (!bd_out) {
-- 
2.43.0