[PATCH v4 4/7] lib: crypto: add pkcs7_digest()

AKASHI Takahiro
2020-07-17T07:16:27Z

This function was nullified when the file, pkcs7_verify.c, was imported
because it calls further linux-specific interfaces inside, hence that
could lead to more files being imported from linux.

We need this function in pkcs7_verify_one() and so simply re-implement it
here instead of re-using the code.

Signed-off-by: AKASHI Takahiro <takahiro.akashi@linaro.org>
---
lib/crypto/pkcs7_verify.c | 92 +++++++++++++++++++++++++++++++++++++--
1 file changed, 89 insertions(+), 3 deletions(-)

diff --git a/lib/crypto/pkcs7_verify.c b/lib/crypto/pkcs7_verify.c
index a893fa3b586b..a32e841cb22b 100644
--- a/lib/crypto/pkcs7_verify.c
+++ b/lib/crypto/pkcs7_verify.c
@@ -7,10 +7,12 @@

#define pr_fmt(fmt) "PKCS7: "fmt
#ifdef __UBOOT__
+#include <image.h>
#include <string.h>
#include <linux/bitops.h>
#include <linux/compat.h>
#include <linux/asn1.h>
+#include <u-boot/rsa-checksum.h>
#include <crypto/public_key.h>
#include <crypto/pkcs7_parser.h>
#else
@@ -26,15 +28,99 @@
#endif

/*
- * Digest the relevant parts of the PKCS#7 data
+ * pkcs7_digest - Digest the relevant parts of the PKCS#7 data
+ * @pkcs7: PKCS7 Signed Data
+ * @sinfo: PKCS7 Signed Info
+ *
+ * Digest the relevant parts of the PKCS#7 data, @pkcs7, using signature
+ * information in @sinfo. But if there are authentication attributes,
+ * i.e. signed image case, the digest must be calculated against
+ * the authentication attributes.
+ *
+ * Return: 0 - on success, non-zero error code - otherwise
*/
#ifdef __UBOOT__
static int pkcs7_digest(struct pkcs7_message *pkcs7,
struct pkcs7_signed_info *sinfo)
{
- return 0;
+ struct public_key_signature *sig = sinfo->sig;
+ struct image_region regions[2];
+ int ret = 0;
+
+ /* The digest was calculated already. */
+ if (sig->digest)
+ return 0;
+
+ if (!sinfo->sig->hash_algo)
+ return -ENOPKG;
+ if (!strcmp(sinfo->sig->hash_algo, "sha256"))
+ sig->digest_size = SHA256_SUM_LEN;
+ else if (!strcmp(sinfo->sig->hash_algo, "sha1"))
+ sig->digest_size = SHA1_SUM_LEN;
+ 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;
+ }
+
+ 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);
+
+ /* However, if there are authenticated attributes, there must be a
+ * message digest attribute amongst them which corresponds to the
+ * digest we just calculated.
+ */
+ if (sinfo->authattrs) {
+ u8 tag;
+
+ if (!sinfo->msgdigest) {
+ pr_warn("Sig %u: No messageDigest\n", sinfo->index);
+ ret = -EKEYREJECTED;
+ goto error;
+ }
+
+ if (sinfo->msgdigest_len != sig->digest_size) {
+ pr_debug("Sig %u: Invalid digest size (%u)\n",
+ sinfo->index, sinfo->msgdigest_len);
+ ret = -EBADMSG;
+ goto error;
+ }
+
+ if (memcmp(sig->digest, sinfo->msgdigest,
+ sinfo->msgdigest_len) != 0) {
+ pr_debug("Sig %u: Message digest doesn't match\n",
+ sinfo->index);
+ ret = -EKEYREJECTED;
+ goto error;
+ }
+
+ /* We then calculate anew, using the authenticated attributes
+ * as the contents of the digest instead. Note that we need to
+ * convert the attributes from a CONT.0 into a SET before we
+ * hash it.
+ */
+ memset(sig->digest, 0, sig->digest_size);
+
+ tag = 0x31;
+ regions[0].data = &tag;
+ regions[0].size = 1;
+ regions[1].data = sinfo->authattrs;
+ regions[1].size = sinfo->authattrs_len;
+
+ hash_calculate(sinfo->sig->hash_algo, regions, 2, sig->digest);
+
+ ret = 0;
+ }
+error:
+ return ret;
}
-#else
+#else /* !__UBOOT__ */
static int pkcs7_digest(struct pkcs7_message *pkcs7,
struct pkcs7_signed_info *sinfo)
{
--
2.27.0