diff options
Diffstat (limited to 'main/krb5/CVE-2020-28196.patch')
-rw-r--r-- | main/krb5/CVE-2020-28196.patch | 100 |
1 files changed, 100 insertions, 0 deletions
diff --git a/main/krb5/CVE-2020-28196.patch b/main/krb5/CVE-2020-28196.patch new file mode 100644 index 00000000000..4d6b4238388 --- /dev/null +++ b/main/krb5/CVE-2020-28196.patch @@ -0,0 +1,100 @@ +From 2289312180a5162114037df8eaa4f4f990d67447 Mon Sep 17 00:00:00 2001 +From: Greg Hudson <ghudson@mit.edu> +Date: Sat, 31 Oct 2020 17:07:05 -0400 +Subject: [PATCH] Add recursion limit for ASN.1 indefinite lengths + +The libkrb5 ASN.1 decoder supports BER indefinite lengths. It +computes the tag length using recursion; the lack of a recursion limit +allows an attacker to overrun the stack and cause the process to +crash. Reported by Demi Obenour. + +CVE-2020-28196: + +In MIT krb5 releases 1.11 and later, an unauthenticated attacker can +cause a denial of service for any client or server to which it can +send an ASN.1-encoded Kerberos message of sufficient length. + +ticket: 8959 (new) +tags: pullup +target_version: 1.18-next +target_version: 1.17-next + +(cherry picked from commit 57415dda6cf04e73ffc3723be518eddfae599bfd) +--- + src/lib/krb5/asn.1/asn1_encode.c | 16 +++++++++------- + 1 file changed, 9 insertions(+), 7 deletions(-) + +diff --git a/src/lib/krb5/asn.1/asn1_encode.c b/src/lib/krb5/asn.1/asn1_encode.c +index a7423b642..8c0cda852 100644 +--- a/src/lib/krb5/asn.1/asn1_encode.c ++++ b/src/lib/krb5/asn.1/asn1_encode.c +@@ -393,7 +393,7 @@ make_tag(asn1buf *buf, const taginfo *t, size_t len, size_t *retlen) + static asn1_error_code + get_tag(const unsigned char *asn1, size_t len, taginfo *tag_out, + const unsigned char **contents_out, size_t *clen_out, +- const unsigned char **remainder_out, size_t *rlen_out) ++ const unsigned char **remainder_out, size_t *rlen_out, int recursion) + { + asn1_error_code ret; + unsigned char o; +@@ -431,9 +431,11 @@ get_tag(const unsigned char *asn1, size_t len, taginfo *tag_out, + /* Indefinite form (should not be present in DER, but we accept it). */ + if (tag_out->construction != CONSTRUCTED) + return ASN1_MISMATCH_INDEF; ++ if (recursion >= 32) ++ return ASN1_OVERFLOW; + p = asn1; + while (!(len >= 2 && p[0] == 0 && p[1] == 0)) { +- ret = get_tag(p, len, &t, &c, &clen, &p, &len); ++ ret = get_tag(p, len, &t, &c, &clen, &p, &len, recursion + 1); + if (ret) + return ret; + } +@@ -652,7 +654,7 @@ split_der(asn1buf *buf, unsigned char *const *der, size_t len, + const unsigned char *contents, *remainder; + size_t clen, rlen; + +- ret = get_tag(*der, len, tag_out, &contents, &clen, &remainder, &rlen); ++ ret = get_tag(*der, len, tag_out, &contents, &clen, &remainder, &rlen, 0); + if (ret) + return ret; + if (rlen != 0) +@@ -1259,7 +1261,7 @@ decode_atype(const taginfo *t, const unsigned char *asn1, + const unsigned char *rem; + size_t rlen; + if (!tag->implicit) { +- ret = get_tag(asn1, len, &inner_tag, &asn1, &len, &rem, &rlen); ++ ret = get_tag(asn1, len, &inner_tag, &asn1, &len, &rem, &rlen, 0); + if (ret) + return ret; + /* Note: we don't check rlen (it should be 0). */ +@@ -1481,7 +1483,7 @@ decode_sequence(const unsigned char *asn1, size_t len, + for (i = 0; i < seq->n_fields; i++) { + if (len == 0) + break; +- ret = get_tag(asn1, len, &t, &contents, &clen, &asn1, &len); ++ ret = get_tag(asn1, len, &t, &contents, &clen, &asn1, &len, 0); + if (ret) + goto error; + /* +@@ -1539,7 +1541,7 @@ decode_sequence_of(const unsigned char *asn1, size_t len, + *seq_out = NULL; + *count_out = 0; + while (len > 0) { +- ret = get_tag(asn1, len, &t, &contents, &clen, &asn1, &len); ++ ret = get_tag(asn1, len, &t, &contents, &clen, &asn1, &len, 0); + if (ret) + goto error; + if (!check_atype_tag(elemtype, &t)) { +@@ -1625,7 +1627,7 @@ k5_asn1_full_decode(const krb5_data *code, const struct atype_info *a, + + *retrep = NULL; + ret = get_tag((unsigned char *)code->data, code->length, &t, &contents, +- &clen, &remainder, &rlen); ++ &clen, &remainder, &rlen, 0); + if (ret) + return ret; + /* rlen should be 0, but we don't check it (and due to padding in +-- +2.20.4 + |