RFC 2315 Section 9.3 describes the message digesting process. The digest calculated depends on whether the authenticated attributes are present. In case of a scenario where the authenticated attributes are present, the message digest that gets signed and is part of the pkcs7 message is computed from the auth attributes rather than the contents field.
Check if the auth attributes are present, and if set, use the auth attributes to compute the hash that would be compared with the encrypted hash on the pkcs7 message.
Signed-off-by: Sughosh Ganu sughosh.ganu@linaro.org --- lib/crypto/pkcs7_verify.c | 37 ++++++++++++++++++++++++++----------- 1 file changed, 26 insertions(+), 11 deletions(-)
diff --git a/lib/crypto/pkcs7_verify.c b/lib/crypto/pkcs7_verify.c index 320ba49f79..58683ef614 100644 --- a/lib/crypto/pkcs7_verify.c +++ b/lib/crypto/pkcs7_verify.c @@ -50,8 +50,15 @@ static int pkcs7_digest(struct pkcs7_message *pkcs7, struct image_region regions[2]; int ret = 0;
- /* The digest was calculated already. */ - if (sig->digest) + /* + * [RFC2315 9.3] + * If the authenticated attributes are present, + * the message-digest is calculated on the + * attributes present in the + * authenticatedAttributes field and not just + * the contents field + */ + if (!sinfo->authattrs && sig->digest) return 0;
if (!sinfo->sig->hash_algo) @@ -63,17 +70,25 @@ static int pkcs7_digest(struct pkcs7_message *pkcs7, else return -ENOPKG;
- sig->digest = calloc(1, sig->digest_size); - if (!sig->digest) { - pr_warn("Sig %u: Out of memory\n", sinfo->index); - return -ENOMEM; - } + /* + * Calculate the hash only if the data is present. + * In case of authenticated variable and capsule, + * the hash has already been calculated on the + * efi_image_regions and populated + */ + if (pkcs7->data) { + sig->digest = calloc(1, sig->digest_size); + if (!sig->digest) { + pr_warn("Sig %u: Out of memory\n", sinfo->index); + return -ENOMEM; + }
- regions[0].data = pkcs7->data; - regions[0].size = pkcs7->data_len; + regions[0].data = pkcs7->data; + regions[0].size = pkcs7->data_len;
- /* Digest the message [RFC2315 9.3] */ - hash_calculate(sinfo->sig->hash_algo, regions, 1, sig->digest); + /* Digest the message [RFC2315 9.3] */ + hash_calculate(sinfo->sig->hash_algo, regions, 1, sig->digest); + }
/* However, if there are authenticated attributes, there must be a * message digest attribute amongst them which corresponds to the