diff --git a/Add-recursion-limit-for-ASN.1-indefinite-lengths.patch b/Add-recursion-limit-for-ASN.1-indefinite-lengths.patch new file mode 100644 index 0000000..bc1229c --- /dev/null +++ b/Add-recursion-limit-for-ASN.1-indefinite-lengths.patch @@ -0,0 +1,97 @@ +From b7aca8b57422cdc67a2d2bff385f09646ca037bc Mon Sep 17 00:00:00 2001 +From: Greg Hudson +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 a160cf4fe..cd6b879f7 100644 +--- a/src/lib/krb5/asn.1/asn1_encode.c ++++ b/src/lib/krb5/asn.1/asn1_encode.c +@@ -356,7 +356,7 @@ make_tag(asn1buf *buf, const taginfo *t, size_t len) + static krb5_error_code + get_tag(const uint8_t *asn1, size_t len, taginfo *tag_out, + const uint8_t **contents_out, size_t *clen_out, +- const uint8_t **remainder_out, size_t *rlen_out) ++ const uint8_t **remainder_out, size_t *rlen_out, int recursion) + { + krb5_error_code ret; + uint8_t o; +@@ -394,9 +394,11 @@ get_tag(const uint8_t *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; + } +@@ -613,7 +615,7 @@ split_der(asn1buf *buf, uint8_t *const *der, size_t len, taginfo *tag_out) + const uint8_t *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) +@@ -1199,7 +1201,7 @@ decode_atype(const taginfo *t, const uint8_t *asn1, size_t len, + const uint8_t *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). */ +@@ -1420,7 +1422,7 @@ decode_sequence(const uint8_t *asn1, size_t len, const struct seq_info *seq, + 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; + /* +@@ -1478,7 +1480,7 @@ decode_sequence_of(const uint8_t *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)) { +@@ -1584,7 +1586,7 @@ k5_asn1_full_decode(const krb5_data *code, const struct atype_info *a, + + *retrep = NULL; + ret = get_tag((uint8_t *)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 diff --git a/krb5.spec b/krb5.spec index 3cc61cf..dd4152d 100644 --- a/krb5.spec +++ b/krb5.spec @@ -18,7 +18,7 @@ Summary: The Kerberos network authentication system Name: krb5 Version: 1.18.2 # for prerelease, should be e.g., 0.% {prerelease}.1% { ?dist } (without spaces) -Release: 28%{?dist} +Release: 29%{?dist} # rharwood has trust path to signing key and verifies on check-in Source0: https://web.mit.edu/kerberos/dist/krb5/1.18/krb5-%{version}%{prerelease}.tar.gz @@ -81,6 +81,7 @@ Patch42: Refactor-KDC-authdata-list-management-helpers.patch Patch43: Avoid-passing-DB-entry-structures-in-KDC.patch Patch44: Minimize-usage-of-tgs_server-in-KDC.patch Patch45: Fix-minor-static-analysis-defects.patch +Patch46: Add-recursion-limit-for-ASN.1-indefinite-lengths.patch License: MIT URL: https://web.mit.edu/kerberos/www/ @@ -641,6 +642,9 @@ exit 0 %{_libdir}/libkadm5srv_mit.so.* %changelog +* Thu Nov 05 2020 Robbie Harwood - 1.18.2-29 +- Add recursion limit for ASN.1 indefinite lengths (CVE-2020-28196) + * Fri Oct 23 2020 Robbie Harwood - 1.18.2-28 - Fix minor static analysis defects