[PATCH 2/5] pki_gcrypt: Add a little more ASN1 infrastructure

[Justus Winter <justus@xxxxxxxxxxx>]

* src/pki_gcrypt.c (ASN1_OCTET_STRING): New macro.
(ASN1_OBJECT_IDENTIFIER): Likewise.
(asn1_check_tag): New function.

Signed-off-by: Justus Winter <justus@xxxxxxxxxxx>
---
 src/pki_gcrypt.c | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/src/pki_gcrypt.c b/src/pki_gcrypt.c
index 982e3f4..acfed2e 100644
--- a/src/pki_gcrypt.c
+++ b/src/pki_gcrypt.c
@@ -50,6 +50,8 @@
 #define MAX_PASSPHRASE_SIZE 1024
 #define ASN1_INTEGER 2
 #define ASN1_BIT_STRING 3
+#define ASN1_OCTET_STRING 4
+#define ASN1_OBJECT_IDENTIFIER 6
 #define ASN1_SEQUENCE 48
 #define PKCS5_SALT_LEN 8
 
@@ -228,6 +230,17 @@ static int asn1_check_sequence(ssh_buffer buffer) {
   return 1;
 }
 
+static int asn1_check_tag(ssh_buffer buffer, unsigned char tag) {
+  unsigned char tmp;
+
+  if (ssh_buffer_get_data(buffer, &tmp, 1) == 0 || tmp != tag) {
+    return 0;
+  }
+
+  (void) asn1_get_len(buffer);
+  return 1;
+}
+
 static int passphrase_to_key(char *data, unsigned int datalen,
     unsigned char *salt, unsigned char *key, unsigned int keylen) {
   MD5CTX md;
-- 
2.8.1