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Commit dbadc176 authored by David Howells's avatar David Howells Committed by Rusty Russell
Browse files

X.509: Fix indefinite length element skip error handling 



asn1_find_indefinite_length() returns an error indicator of -1, which the
caller asn1_ber_decoder() places in a size_t (which is usually unsigned) and
then checks to see whether it is less than 0 (which it can't be).  This can
lead to the following warning:

	lib/asn1_decoder.c:320 asn1_ber_decoder()
		warn: unsigned 'len' is never less than zero.

Instead, asn1_find_indefinite_length() update the caller's idea of the data
cursor and length separately from returning the error code.

Reported-by: default avatarDan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: default avatarDavid Howells <dhowells@redhat.com>
Signed-off-by: default avatarRusty Russell <rusty@rustcorp.com.au>
parent 2f1c4fef

lib/asn1_decoder.c

+19 −9
Original line number Diff line number Diff line
@@ -46,12 +46,18 @@ static const unsigned char asn1_op_lengths[ASN1_OP__NR] = { 


/*

 * Find the length of an indefinite length object

 * @data: The data buffer

 * @datalen: The end of the innermost containing element in the buffer

 * @_dp: The data parse cursor (updated before returning)

 * @_len: Where to return the size of the element.

 * @_errmsg: Where to return a pointer to an error message on error

 */

static int asn1_find_indefinite_length(const unsigned char *data, size_t datalen,

				       const char **_errmsg, size_t *_err_dp)

				       size_t *_dp, size_t *_len,

				       const char **_errmsg)

{

	unsigned char tag, tmp;

	size_t dp = 0, len, n;

	size_t dp = *_dp, len, n;

	int indef_level = 1;



next_tag:
@@ -67,8 +73,11 @@ next_tag: 
		/* It appears to be an EOC. */

		if (data[dp++] != 0)

			goto invalid_eoc;

		if (--indef_level <= 0)

			return dp;

		if (--indef_level <= 0) {

			*_len = dp - *_dp;

			*_dp = dp;

			return 0;

		}

		goto next_tag;

	}
@@ -122,7 +131,7 @@ data_overrun_error: 
missing_eoc:

	*_errmsg = "Missing EOC in indefinite len cons";

error:

	*_err_dp = dp;

	*_dp = dp;

	return -1;

}
@@ -315,13 +324,14 @@ next_op: 
	skip_data:

		if (!(flags & FLAG_CONS)) {

			if (flags & FLAG_INDEFINITE_LENGTH) {

				len = asn1_find_indefinite_length(

					data + dp, datalen - dp, &errmsg, &dp);

				if (len < 0)

				ret = asn1_find_indefinite_length(

					data, datalen, &dp, &len, &errmsg);

				if (ret < 0)

					goto error;

			} else {

				dp += len;

			}

			pr_debug("- LEAF: %zu\n", len);

			dp += len;

		}

		pc += asn1_op_lengths[op];

		goto next_op;