commit 01ea23906616c546d63af750c9b07e6ed69dd873
author Demi Marie Obenour <demiobenour@gmail.com> Thu Jan 19 09:50:16 2023 -0500
committer Demi Marie Obenour <demiobenour@gmail.com> Mon Feb 27 14:08:28 2023 -0500
tree 6f9a1d12387c291b514fec2bac0ae83d289af2bb
parent 221a64824f682e227d7da6718960761a68006c09

refactor(auth): clean up certificate length checks

The previous code was correct but unnecessarily verbose.

Change-Id: Ia19c667811a7c3b6957a0274d36076b0b16e36b7
Signed-off-by: Demi Marie Obenour <demiobenour@gmail.com>

drivers/auth/mbedtls/mbedtls_x509_parser.c

diff --git a/drivers/auth/mbedtls/mbedtls_x509_parser.c b/drivers/auth/mbedtls/mbedtls_x509_parser.c
index 41024aa..b538c78 100644
--- a/drivers/auth/mbedtls/mbedtls_x509_parser.c
+++ b/drivers/auth/mbedtls/mbedtls_x509_parser.c
@@ -161,7 +161,8 @@
 
 	p = (unsigned char *)img;
 	len = img_len;
-	end = p + len;
+	crt_end = p + len;
+	end = crt_end;
 
 	/*
 	 * Certificate  ::=  SEQUENCE  {
@@ -171,15 +172,10 @@
 	 */
 	ret = mbedtls_asn1_get_tag(&p, end, &len, MBEDTLS_ASN1_CONSTRUCTED |
 				   MBEDTLS_ASN1_SEQUENCE);
-	if (ret != 0) {
+	if ((ret != 0) || ((p + len) != end)) {
 		return IMG_PARSER_ERR_FORMAT;
 	}
 
-	if (len != (size_t)(end - p)) {
-		return IMG_PARSER_ERR_FORMAT;
-	}
-	crt_end = p + len;
-
 	/*
 	 * TBSCertificate  ::=  SEQUENCE  {
 	 */
@@ -220,9 +216,6 @@
 	if (ret != 0) {
 		return IMG_PARSER_ERR_FORMAT;
 	}
-	if ((end - p) < 1) {
-		return IMG_PARSER_ERR_FORMAT;
-	}
 	sig_alg1.len = (p + len) - sig_alg1.p;
 	p += len;
 
@@ -408,19 +401,14 @@
 
 	/*
 	 * signatureValue       BIT STRING
+	 * } -- must consume all bytes
 	 */
 	signature.p = p;
 	ret = mbedtls_asn1_get_bitstring_null(&p, end, &len);
-	if (ret != 0) {
-		return IMG_PARSER_ERR_FORMAT;
-	}
-	signature.len = (p + len) - signature.p;
-	p += len;
-
-	/* Check certificate length */
-	if (p != end) {
+	if ((ret != 0) || ((p + len) != end)) {
 		return IMG_PARSER_ERR_FORMAT;
 	}
+	signature.len = end - signature.p;
 
 	return IMG_PARSER_OK;
 }