BER decoding: Improve error checking for indefinite length

When an indefinite length was given, the decoder could look beyond
the end of the buffer for the 0,0 that signals the end of the value.

2 files changed, 35 insertions, 22 deletions

diff --git a/lib/asn1/c_src/asn1_erl_nif.c b/lib/asn1/c_src/asn1_erl_nif.c
index 8a0e4b1cf0..53e3aa1678 100644
--- a/lib/asn1/c_src/asn1_erl_nif.c
+++ b/lib/asn1/c_src/asn1_erl_nif.c
@@ -941,16 +941,31 @@ static int ber_decode_value(ErlNifEnv* env, ERL_NIF_TERM *value, unsigned char *
     int maybe_ret;
     unsigned int len = 0;
     unsigned int lenoflen = 0;
-    int indef = 0;
     unsigned char *tmp_out_buff;
     ERL_NIF_TERM term = 0, curr_head = 0;
 
     if (((in_buf[*ib_index]) & 0x80) == ASN1_SHORT_DEFINITE_LENGTH) {
 	len = in_buf[*ib_index];
-    } else if (in_buf[*ib_index] == ASN1_INDEFINITE_LENGTH
-    )
-	indef = 1;
-    else /* long definite length */{
+    } else if (in_buf[*ib_index] == ASN1_INDEFINITE_LENGTH) {
+	(*ib_index)++;
+	curr_head = enif_make_list(env, 0);
+	if (*ib_index+1 >= in_buf_len) {
+	    return ASN1_INDEF_LEN_ERROR;
+	}
+	while (!(in_buf[*ib_index] == 0 && in_buf[*ib_index + 1] == 0)) {
+	    maybe_ret = ber_decode(env, &term, in_buf, ib_index, in_buf_len);
+	    if (maybe_ret <= ASN1_ERROR) {
+		return maybe_ret;
+	    }
+	    curr_head = enif_make_list_cell(env, term, curr_head);
+	    if (*ib_index+1 >= in_buf_len) {
+		return ASN1_INDEF_LEN_ERROR;
+	    }
+	}
+	enif_make_reverse_list(env, curr_head, value);
+	(*ib_index) += 2; /* skip the indefinite length end bytes */
+	return ASN1_OK;
+    } else /* long definite length */{
 	lenoflen = (in_buf[*ib_index] & 0x7f); /*length of length */
 	if (lenoflen > (in_buf_len - (*ib_index + 1)))
 	    return ASN1_LEN_ERROR;
@@ -965,23 +980,7 @@ static int ber_decode_value(ErlNifEnv* env, ERL_NIF_TERM *value, unsigned char *
     if (len > (in_buf_len - (*ib_index + 1)))
 	return ASN1_VALUE_ERROR;
     (*ib_index)++;
-    if (indef == 1) { /* in this case it is desireably to check that indefinite length
-     end bytes exist in inbuffer */
-	curr_head = enif_make_list(env, 0);
-	while (!(in_buf[*ib_index] == 0 && in_buf[*ib_index + 1] == 0)) {
-	    if (*ib_index >= in_buf_len)
-		return ASN1_INDEF_LEN_ERROR;
-
-	    if ((maybe_ret = ber_decode(env, &term, in_buf, ib_index, in_buf_len))
-		    <= ASN1_ERROR
-		    )
-		return maybe_ret;
-	    curr_head = enif_make_list_cell(env, term, curr_head);
-	}
-	enif_make_reverse_list(env, curr_head, value);
-	(*ib_index) += 2; /* skip the indefinite length end bytes */
-    } else if (form == ASN1_CONSTRUCTED)
-    {
+    if (form == ASN1_CONSTRUCTED) {
 	int end_index = *ib_index + len;
 	if (end_index > in_buf_len)
 	    return ASN1_LEN_ERROR;
diff --git a/lib/asn1/test/ber_decode_error.erl b/lib/asn1/test/ber_decode_error.erl
index 8be92292ee..6fd2450c62 100644
--- a/lib/asn1/test/ber_decode_error.erl
+++ b/lib/asn1/test/ber_decode_error.erl
@@ -51,4 +51,18 @@ run([]) ->
     {error,{asn1,{invalid_value,_}}} =
 	(catch 'Constructed':decode('I', <<8,7>>)),
 
+    %% Short indefinite length. Make sure that the decoder doesn't look
+    %% beyond the end of binary when looking for a 0,0 terminator.
+    {error,{asn1,{invalid_length,_}}} =
+	(catch 'Constructed':decode('S', sub(<<8,16#80,0,0>>, 3))),
+    {error,{asn1,{invalid_length,_}}} =
+	(catch 'Constructed':decode('S', sub(<<8,16#80,0,0>>, 2))),
+    {error,{asn1,{invalid_length,_}}} =
+	(catch 'Constructed':decode('S', sub(<<40,16#80,1,1,255,0,0>>, 6))),
+    {error,{asn1,{invalid_length,_}}} =
+	(catch 'Constructed':decode('S', sub(<<40,16#80,1,1,255,0,0>>, 5))),
     ok.
+
+sub(Bin, Bytes) ->
+    <<B:Bytes/binary,_/binary>> = Bin,
+    B.