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OER: check unused bit count while parsing bit string

This commit is contained in:
Michał Kaźmierowski 2021-05-19 09:10:04 +02:00
parent e10f761362
commit df508537be
1 changed files with 9 additions and 2 deletions
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11
epan/dissectors/packet-oer.c
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@ -398,6 +398,10 @@ dissect_oer_bit_string_unconstr(tvbuff_t *tvb, guint32 offset _U_, asn1_ctx_t *a
offset = dissect_oer_length_determinant(tvb, offset, actx, tree, -1 /*Don't show length value as internal field*/, &length);
if (length > 0) {
unused_bit_count = tvb_get_guint8(tvb, offset);
if (unused_bit_count > 7) {
dissect_oer_not_decoded_yet(tree, actx->pinfo, tvb, "too high unused bit count");
return offset + length;
}
offset += 1;
length -= 1;
}
@ -409,10 +413,13 @@ dissect_oer_bit_string_unconstr(tvbuff_t *tvb, guint32 offset _U_, asn1_ctx_t *a
dissect_oer_not_decoded_yet(tree, actx->pinfo, tvb, "too many bitstring elements");
}
for (int i = 0; i < length; i++) {
values[i] = tvb_get_guint8(tvb, offset);
guint8 value = tvb_get_guint8(tvb, offset);
if (i + 1 == length) {
/* unused bits of the last octet shall be set to zeros */
values[i] &= (0xFF << unused_bit_count);
value &= (0xFF << unused_bit_count);
}
if (i < values_size) {
values[i] = value;
}
offset += 1;
}