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: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
diff --git a/lib/asn1_decoder.c b/lib/asn1_decoder.c
index 2e4196d..de2c8b5 100644
--- a/lib/asn1_decoder.c
+++ b/lib/asn1_decoder.c
@@ -46,12 +46,18 @@
/*
* 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 @@
/* 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 @@
missing_eoc:
*_errmsg = "Missing EOC in indefinite len cons";
error:
- *_err_dp = dp;
+ *_dp = dp;
return -1;
}
@@ -315,13 +324,14 @@
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;