From 2be4076efedd845c04db91d7cbbf57cd86353465 Mon Sep 17 00:00:00 2001
From: Greg Hudson <ghudson@mit.edu>
Date: Mon, 9 Jan 2012 21:03:58 +0000
Subject: Make dh_key_info encoder and decoder symmetric

The dh_key_info encoder expects subjectPublicKey to contain the
contents of a bit string, but the decoder outputs the DER encoding of
the bit string including tag.  The PKINIT client code expects this, so
everything works, but the encoder and decoder should be symmetric.
Change the decoder to process the bit string (adding a bit string
decoding primitive) and modify the PKINIT client code to expect only
the bit string contents.

git-svn-id: svn://anonsvn.mit.edu/krb5/trunk@25626 dc483132-0cff-0310-8789-dd5450dbe970
---
 src/lib/krb5/asn.1/asn1_decode.c   | 26 ++++++++++++++++++++++++++
 src/lib/krb5/asn.1/asn1_decode.h   |  3 +++
 src/lib/krb5/asn.1/asn1_k_decode.c | 11 ++++++-----
 3 files changed, 35 insertions(+), 5 deletions(-)

(limited to 'src/lib')

diff --git a/src/lib/krb5/asn.1/asn1_decode.c b/src/lib/krb5/asn.1/asn1_decode.c
index 53e204549..1ded579b8 100644
--- a/src/lib/krb5/asn.1/asn1_decode.c
+++ b/src/lib/krb5/asn.1/asn1_decode.c
@@ -197,6 +197,32 @@ asn1_decode_generalstring(asn1buf *buf, unsigned int *retlen, char **val)
     cleanup();
 }
 
+asn1_error_code
+asn1_decode_bitstring(asn1buf *buf, unsigned int *retlen, char **val)
+{
+    setup();
+    asn1_octet unused;
+
+    tag(ASN1_BITSTRING);
+
+    /* Get the number of unused bits in the last byte (0-7). */
+    retval = asn1buf_remove_octet(buf, &unused);
+    if (retval)
+        return retval;
+    if (unused > 7)
+        return ASN1_BAD_FORMAT;
+
+    retval = asn1buf_remove_charstring(buf, length - 1, val);
+    if (retval)
+        return retval;
+
+    /* Mask out unused bits (unnecessary for correct DER, but be safe). */
+    if (length > 1)
+        (*val)[length - 2] &= (0xff << unused);
+
+    *retlen = length - 1;
+    return 0;
+}
 
 asn1_error_code
 asn1_decode_null(asn1buf *buf)
diff --git a/src/lib/krb5/asn.1/asn1_decode.h b/src/lib/krb5/asn.1/asn1_decode.h
index 0e14491de..7573b4fb7 100644
--- a/src/lib/krb5/asn.1/asn1_decode.h
+++ b/src/lib/krb5/asn.1/asn1_decode.h
@@ -45,6 +45,7 @@
  *  asn1_decode_octetstring
  *  asn1_decode_charstring
  *  asn1_decode_generalstring
+ *  asn1_decode_bitstring
  *  asn1_decode_null
  *  asn1_decode_printablestring
  *  asn1_decode_ia5string
@@ -72,6 +73,8 @@ asn1_error_code asn1_decode_octetstring(asn1buf *buf, unsigned int *retlen,
                                         asn1_octet **val);
 asn1_error_code asn1_decode_generalstring(asn1buf *buf, unsigned int *retlen,
                                           char **val);
+asn1_error_code asn1_decode_bitstring(asn1buf *buf, unsigned int *retlen,
+                                      char **val);
 asn1_error_code asn1_decode_charstring(asn1buf *buf, unsigned int *retlen,
                                        char **val);
 /*
diff --git a/src/lib/krb5/asn.1/asn1_k_decode.c b/src/lib/krb5/asn.1/asn1_k_decode.c
index b2471004a..e0c827c4f 100644
--- a/src/lib/krb5/asn.1/asn1_k_decode.c
+++ b/src/lib/krb5/asn.1/asn1_k_decode.c
@@ -1515,11 +1515,12 @@ asn1_decode_kdc_dh_key_info(asn1buf *buf, krb5_kdc_dh_key_info *val)
     setup();
     val->subjectPublicKey.data = NULL;
     { begin_structure();
-        retval = asn1buf_remove_charstring(&subbuf, taglen,
-                                           &val->subjectPublicKey.data);
-        if (retval) clean_return(retval);
-        val->subjectPublicKey.length = taglen;
-        next_tag();
+        /* Special handling for [0] IMPLICIT BIT STRING */
+        error_if_bad_tag(0);
+        if (asn1class != CONTEXT_SPECIFIC || construction != CONSTRUCTED)
+            clean_return(ASN1_BAD_ID);
+        get_lenfield_body(val->subjectPublicKey.length,
+                          val->subjectPublicKey.data, asn1_decode_bitstring);
         get_field(val->nonce, 1, asn1_decode_int32);
         opt_field(val->dhKeyExpiration, 2, asn1_decode_kerberos_time, 0);
         end_structure();
-- 
cgit