crypto: dh - fix calculating encoded key size

It was forgotten to increase DH_KPP_SECRET_MIN_SIZE to include 'q_size',
causing an out-of-bounds write of 4 bytes in crypto_dh_encode_key(), and
an out-of-bounds read of 4 bytes in crypto_dh_decode_key().  Fix it, and
fix the lengths of the test vectors to match this.

Reported-by: syzbot+6d38d558c25b53b8f4ed@syzkaller.appspotmail.com
Fixes: e3fe0ae ("crypto: dh - add public key verification test")
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

Author: ebiggers

crypto/dh_helper.c

@@ -14,7 +14,7 @@
 #include <crypto/dh.h>
 #include <crypto/kpp.h>
 
-#define DH_KPP_SECRET_MIN_SIZE (sizeof(struct kpp_secret) + 3 * sizeof(int))
+#define DH_KPP_SECRET_MIN_SIZE (sizeof(struct kpp_secret) + 4 * sizeof(int))
 
 static inline u8 *dh_pack_data(void *dst, const void *src, size_t size)
 {

crypto/testmgr.h

@@ -641,14 +641,14 @@ static const struct kpp_testvec dh_tv_template[] = {
 	.secret =
 #ifdef __LITTLE_ENDIAN
 	"\x01\x00" /* type */
-	"\x11\x02" /* len */
+	"\x15\x02" /* len */
 	"\x00\x01\x00\x00" /* key_size */
 	"\x00\x01\x00\x00" /* p_size */
 	"\x00\x00\x00\x00" /* q_size */
 	"\x01\x00\x00\x00" /* g_size */
 #else
 	"\x00\x01" /* type */
-	"\x02\x11" /* len */
+	"\x02\x15" /* len */
 	"\x00\x00\x01\x00" /* key_size */
 	"\x00\x00\x01\x00" /* p_size */
 	"\x00\x00\x00\x00" /* q_size */
@@ -741,7 +741,7 @@ static const struct kpp_testvec dh_tv_template[] = {
 	"\xd3\x34\x49\xad\x64\xa6\xb1\xc0\x59\x28\x75\x60\xa7\x8a\xb0\x11"
 	"\x56\x89\x42\x74\x11\xf5\xf6\x5e\x6f\x16\x54\x6a\xb1\x76\x4d\x50"
 	"\x8a\x68\xc1\x5b\x82\xb9\x0d\x00\x32\x50\xed\x88\x87\x48\x92\x17",
-	.secret_size = 529,
+	.secret_size = 533,
 	.b_public_size = 256,
 	.expected_a_public_size = 256,
 	.expected_ss_size = 256,
@@ -750,14 +750,14 @@ static const struct kpp_testvec dh_tv_template[] = {
 	.secret =
 #ifdef __LITTLE_ENDIAN
 	"\x01\x00" /* type */
-	"\x11\x02" /* len */
+	"\x15\x02" /* len */
 	"\x00\x01\x00\x00" /* key_size */
 	"\x00\x01\x00\x00" /* p_size */
 	"\x00\x00\x00\x00" /* q_size */
 	"\x01\x00\x00\x00" /* g_size */
 #else
 	"\x00\x01" /* type */
-	"\x02\x11" /* len */
+	"\x02\x15" /* len */
 	"\x00\x00\x01\x00" /* key_size */
 	"\x00\x00\x01\x00" /* p_size */
 	"\x00\x00\x00\x00" /* q_size */
@@ -850,7 +850,7 @@ static const struct kpp_testvec dh_tv_template[] = {
 	"\x5e\x5a\x64\xbd\xf6\x85\x04\xe8\x28\x6a\xac\xef\xce\x19\x8e\x9a"
 	"\xfe\x75\xc0\x27\x69\xe3\xb3\x7b\x21\xa7\xb1\x16\xa4\x85\x23\xee"
 	"\xb0\x1b\x04\x6e\xbd\xab\x16\xde\xfd\x86\x6b\xa9\x95\xd7\x0b\xfd",
-	.secret_size = 529,
+	.secret_size = 533,
 	.b_public_size = 256,
 	.expected_a_public_size = 256,
 	.expected_ss_size = 256,