From ac596026e77244481fd68736ae7f15855803a08a Mon Sep 17 00:00:00 2001 From: hopper-vul Date: Tue, 13 Dec 2022 19:54:21 +0800 Subject: [PATCH] Add str len check in config_sortlist to avoid stack overflow In ares_set_sortlist, it calls config_sortlist(..., sortstr) to parse the input str and initialize a sortlist configuration. However, ares_set_sortlist has not any checks about the validity of the input str. It is very easy to create an arbitrary length stack overflow with the unchecked `memcpy(ipbuf, str, q-str);` and `memcpy(ipbufpfx, str, q-str);` statements in the config_sortlist call, which could potentially cause severe security impact in practical programs. This commit add necessary check for `ipbuf` and `ipbufpfx` which avoid the potential stack overflows. fixes #496 Signed-off-by: hopper-vul --- src/lib/ares_init.c | 4 ++++ test/ares-test-init.cc | 2 ++ 2 files changed, 6 insertions(+) diff --git a/src/lib/ares_init.c b/src/lib/ares_init.c index de5d86c..d5858f6 100644 --- a/src/lib/ares_init.c +++ b/src/lib/ares_init.c @@ -2243,6 +2243,8 @@ static int config_sortlist(struct apattern **sortlist, int *nsort, q = str; while (*q && *q != '/' && *q != ';' && !ISSPACE(*q)) q++; + if (q-str >= 16) + return ARES_EBADSTR; memcpy(ipbuf, str, q-str); ipbuf[q-str] = '\0'; /* Find the prefix */ @@ -2251,6 +2253,8 @@ static int config_sortlist(struct apattern **sortlist, int *nsort, const char *str2 = q+1; while (*q && *q != ';' && !ISSPACE(*q)) q++; + if (q-str >= 32) + return ARES_EBADSTR; memcpy(ipbufpfx, str, q-str); ipbufpfx[q-str] = '\0'; str = str2; diff --git a/test/ares-test-init.cc b/test/ares-test-init.cc index ff6c6c6..c3cb948 100644 --- a/test/ares-test-init.cc +++ b/test/ares-test-init.cc @@ -270,6 +270,8 @@ TEST_F(DefaultChannelTest, SetAddresses) { TEST_F(DefaultChannelTest, SetSortlistFailures) { EXPECT_EQ(ARES_ENODATA, ares_set_sortlist(nullptr, "1.2.3.4")); + EXPECT_EQ(ARES_EBADSTR, ares_set_sortlist(channel_, "111.111.111.111*/16")); + EXPECT_EQ(ARES_EBADSTR, ares_set_sortlist(channel_, "111.111.111.111/255.255.255.240*")); EXPECT_EQ(ARES_SUCCESS, ares_set_sortlist(channel_, "xyzzy ; lwk")); EXPECT_EQ(ARES_SUCCESS, ares_set_sortlist(channel_, "xyzzy ; 0x123")); } -- 2.33.0