Fix CVE-2018-6003: https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2018-6003 https://lists.gnu.org/archive/html/help-libtasn1/2018-01/msg00000.html Patch copied from upstream source repository: https://gitlab.com/gnutls/libtasn1/commit/c593ae84cfcde8fea45787e53950e0ac71e9ca97 From c593ae84cfcde8fea45787e53950e0ac71e9ca97 Mon Sep 17 00:00:00 2001 From: Nikos Mavrogiannopoulos Date: Thu, 4 Jan 2018 10:52:05 +0100 Subject: [PATCH] _asn1_decode_simple_ber: restrict the levels of recursion to 3 On indefinite string decoding, setting a maximum level of recursions protects the BER decoder from a stack exhaustion due to large amounts of recursion. Signed-off-by: Nikos Mavrogiannopoulos --- lib/decoding.c | 21 +++++++++++++++++++-- 1 file changed, 19 insertions(+), 2 deletions(-) diff --git a/lib/decoding.c b/lib/decoding.c index 2240b09..0ee35d3 100644 --- a/lib/decoding.c +++ b/lib/decoding.c @@ -45,6 +45,13 @@ #define DECODE_FLAG_HAVE_TAG 1 #define DECODE_FLAG_INDEFINITE (1<<1) +/* On indefinite string decoding, allow this maximum levels + * of recursion. Allowing infinite recursion, makes the BER + * decoder susceptible to stack exhaustion due to that recursion. + */ +#define DECODE_FLAG_LEVEL1 (1<<2) +#define DECODE_FLAG_LEVEL2 (1<<3) +#define DECODE_FLAG_LEVEL3 (1<<4) #define DECR_LEN(l, s) do { \ l -= s; \ @@ -2216,7 +2223,8 @@ _asn1_decode_simple_ber (unsigned int etype, const unsigned char *der, } /* indefinite constructed */ - if (((dflags & DECODE_FLAG_INDEFINITE) || class == ASN1_CLASS_STRUCTURED) && ETYPE_IS_STRING(etype)) + if ((((dflags & DECODE_FLAG_INDEFINITE) || class == ASN1_CLASS_STRUCTURED) && ETYPE_IS_STRING(etype)) && + !(dflags & DECODE_FLAG_LEVEL3)) { len_len = 1; @@ -2236,8 +2244,17 @@ _asn1_decode_simple_ber (unsigned int etype, const unsigned char *der, do { unsigned tmp_len; + unsigned flags = DECODE_FLAG_HAVE_TAG; + + if (dflags & DECODE_FLAG_LEVEL1) + flags |= DECODE_FLAG_LEVEL2; + else if (dflags & DECODE_FLAG_LEVEL2) + flags |= DECODE_FLAG_LEVEL3; + else + flags |= DECODE_FLAG_LEVEL1; - result = asn1_decode_simple_ber(etype, p, der_len, &out, &out_len, &tmp_len); + result = _asn1_decode_simple_ber(etype, p, der_len, &out, &out_len, &tmp_len, + flags); if (result != ASN1_SUCCESS) { warn(); -- libgit2 0.26.0