From 0594486b639849b47d762c76f28730edbf648dc7 Mon Sep 17 00:00:00 2001 From: Stefan Berger Date: Wed, 6 Nov 2019 16:36:00 -0500 Subject: tcgbios: Check for enough bytes returned from TPM2_GetCapability MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit When querying a TPM 2.0 for its PCRs, make sure that we get enough bytes from it in a response that did not indicate a failure. Basically we are defending against a TPM 2.0 sending responses that are not compliant to the specs. Reviewed-by: Marc-André Lureau Reviewed-by: Philippe Mathieu-Daudé Signed-off-by: Stefan Berger --- src/tcgbios.c | 13 +++++++++++-- 1 file changed, 11 insertions(+), 2 deletions(-) (limited to 'src/tcgbios.c') diff --git a/src/tcgbios.c b/src/tcgbios.c index 2e503f93..95c1e943 100644 --- a/src/tcgbios.c +++ b/src/tcgbios.c @@ -481,8 +481,17 @@ tpm20_get_pcrbanks(void) if (ret) return ret; - u32 size = be32_to_cpu(trg->hdr.totlen) - - offsetof(struct tpm2_res_getcapability, data); + /* defend against (broken) TPM sending packets that are too short */ + u32 resplen = be32_to_cpu(trg->hdr.totlen); + if (resplen <= offsetof(struct tpm2_res_getcapability, data)) + return -1; + + u32 size = resplen - offsetof(struct tpm2_res_getcapability, data); + /* we need a valid tpml_pcr_selection up to and including sizeOfSelect */ + if (size < offsetof(struct tpml_pcr_selection, selections) + + offsetof(struct tpms_pcr_selection, pcrSelect)) + return -1; + tpm20_pcr_selection = malloc_high(size); if (tpm20_pcr_selection) { memcpy(tpm20_pcr_selection, &trg->data, size); -- cgit