111 lines
3.4 KiB
Diff
111 lines
3.4 KiB
Diff
From 6289e2d29883d5d9510b6a15c18c597478967a42 Mon Sep 17 00:00:00 2001
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From: Juraj Vijtiuk <juraj.vijtiuk@sartura.hr>
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Date: Sun, 12 Jan 2020 12:26:18 +0100
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Subject: blobmsg: blobmsg_parse and blobmsg_parse_array oob read fixes
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MIME-Version: 1.0
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Content-Type: text/plain; charset=UTF-8
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Content-Transfer-Encoding: 8bit
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Fix out of bounds read in blobmsg_parse and blobmsg_check_name. The
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out of bounds read happens because blob_attr and blobmsg_hdr have
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flexible array members, whose size is 0 in the corresponding sizeofs.
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For example the __blob_for_each_attr macro checks whether rem >=
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sizeof(struct blob_attr). However, what LibFuzzer discovered was,
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if the input data was only 4 bytes, the data would be casted to blob_attr,
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and later on blob_data(attr) would be called even though attr->data was empty.
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The same issue could appear with data larger than 4 bytes, where data
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wasn't empty, but contained only the start of the blobmsg_hdr struct,
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and blobmsg_hdr name was empty. The bugs were discovered by fuzzing
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blobmsg_parse and blobmsg_array_parse with LibFuzzer.
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CC: Luka Perkov <luka.perkov@sartura.hr>
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Reviewed-by: Jo-Philipp Wich <jo@mein.io>
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Signed-off-by: Juraj Vijtiuk <juraj.vijtiuk@sartura.hr>
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[refactored some checks, added fuzz inputs, adjusted unit test results]
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Signed-off-by: Petr Štetiar <ynezz@true.cz>
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---
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blobmsg.c | 40 ++++++++++++++++++++++++++++++++--------
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1 file changed, 32 insertions(+), 8 deletions(-)
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--- a/blobmsg.c
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+++ b/blobmsg.c
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@@ -36,16 +36,38 @@ bool blobmsg_check_attr(const struct blo
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return blobmsg_check_attr_len(attr, name, blob_raw_len(attr));
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}
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+static const struct blobmsg_hdr* blobmsg_hdr_from_blob(const struct blob_attr *attr, size_t len)
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+{
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+ if (len < sizeof(struct blob_attr) + sizeof(struct blobmsg_hdr))
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+ return NULL;
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+
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+ return blob_data(attr);
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+}
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+
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+static bool blobmsg_hdr_valid_namelen(const struct blobmsg_hdr *hdr, size_t len)
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+{
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+ if (len < sizeof(struct blob_attr) + sizeof(struct blobmsg_hdr) + blobmsg_namelen(hdr) + 1)
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+ return false;
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+
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+ return true;
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+}
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+
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static bool blobmsg_check_name(const struct blob_attr *attr, size_t len, bool name)
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{
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char *limit = (char *) attr + len;
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const struct blobmsg_hdr *hdr;
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- hdr = blob_data(attr);
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+ hdr = blobmsg_hdr_from_blob(attr, len);
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+ if (!hdr)
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+ return false;
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+
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if (name && !hdr->namelen)
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return false;
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- if ((char *) hdr->name + blobmsg_namelen(hdr) > limit)
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+ if (name && !blobmsg_hdr_valid_namelen(hdr, len))
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+ return false;
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+
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+ if ((char *) hdr->name + blobmsg_namelen(hdr) + 1 > limit)
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return false;
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if (blobmsg_namelen(hdr) > (blob_len(attr) - sizeof(struct blobmsg_hdr)))
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@@ -79,9 +101,6 @@ bool blobmsg_check_attr_len(const struct
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size_t data_len;
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int id;
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- if (len < sizeof(struct blob_attr))
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- return false;
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-
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if (!blobmsg_check_name(attr, len, name))
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return false;
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@@ -176,11 +195,10 @@ int blobmsg_parse_array(const struct blo
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return 0;
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}
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-
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int blobmsg_parse(const struct blobmsg_policy *policy, int policy_len,
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struct blob_attr **tb, void *data, unsigned int len)
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{
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- struct blobmsg_hdr *hdr;
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+ const struct blobmsg_hdr *hdr;
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struct blob_attr *attr;
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uint8_t *pslen;
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int i;
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@@ -197,7 +215,13 @@ int blobmsg_parse(const struct blobmsg_p
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}
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__blob_for_each_attr(attr, data, len) {
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- hdr = blob_data(attr);
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+ hdr = blobmsg_hdr_from_blob(attr, len);
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+ if (!hdr)
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+ return -1;
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+
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+ if (!blobmsg_hdr_valid_namelen(hdr, len))
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+ return -1;
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+
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for (i = 0; i < policy_len; i++) {
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if (!policy[i].name)
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continue;
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