[meta-lts-collab][kirkstone][PATCH 7/7] strongswan: Fix CVE-2026-35334
Nitin Wankhade <[email protected]>
| Newsgroups | org.yoctoproject.lists.yocto-patches |
|---|---|
| Message-ID | <[email protected]> |
From: Nitin Wankhade <[email protected]> Upstream-Status: Backport [https://snapshot.debian.org/archive/debian-security-debug/20260422T125423Z/pool/updates/main/s/strongswan/strongswan_6.0.1-6%2Bdeb13u5.debian.tar.xz] Signed-off-by: Nitin Wankhade <[email protected]> --- ...and-timing-leaks-in-PKCS-1-v1.5-decr.patch | 244 ++++++++++++++++++ .../strongswan/strongswan_5.9.13.bbappend | 1 + 2 files changed, 245 insertions(+) create mode 100644 meta-networking/recipes-support/strongswan/files/gmp-Avoid-crash-and-timing-leaks-in-PKCS-1-v1.5-decr.patch diff --git a/meta-networking/recipes-support/strongswan/files/gmp-Avoid-crash-and-timing-leaks-in-PKCS-1-v1.5-decr.patch b/meta-networking/recipes-support/strongswan/files/gmp-Avoid-crash-and-timing-leaks-in-PKCS-1-v1.5-decr.patch new file mode 100644 index 0000000..cb6777a --- /dev/null +++ b/meta-networking/recipes-support/strongswan/files/gmp-Avoid-crash-and-timing-leaks-in-PKCS-1-v1.5-decr.patch @@ -0,0 +1,244 @@ +From: Tobias Brunner <[email protected]> +Date: Tue, 24 Mar 2026 18:00:23 +0100 +Subject: gmp: Avoid crash and timing leaks in PKCS#1 v1.5 decryption padding + validation +MIME-Version: 1.0 +Content-Type: text/plain; charset="utf-8" +Content-Transfer-Encoding: 8bit + +This fixes a potential crash due to a null-pointer dereference if rsadp() +returns NULL (e.g. with an all-zero ciphertext). + +And it also implements the PKCS#1 v1.5 decryption padding check in +constant time. + +The timing leak caused by the previous implementation was measured at +~17.5 μs at 3 GHz, which could allow a Bleichenbacher-like attack in +LAN environments. However, because of how RSA encryption is used in +strongSwan, this is not that much of an issue in practice. The mechanism +is only used for two use cases. One is SCEP/EST via PKCS#7 enveloped +data. Fortunately, this can not be triggered in significant numbers by +an attacker. The other use case is TLS as used by EAP methods (EAP-TLS, +EAP-PEAP/TTLS) during the authentication. While the cipher suites that +use RSA encryption are still enabled by default, the TLS messages are +wrapped in EAP and encrypted by IKE, making any kind of attack difficult. + +Note that the gmp plugin isn't enabled anymore by default. And even +before that, most setups had the openssl plugin enabled, which has +priority over the gmp plugin. So it's unlikely the plugin was used in +practice. + +Also note that this patch doesn't modify libstrongswan's Makefile.am +to avoid potentially requiring autotools when patching a tarball. + +Fixes: d615ffdcf3cd ("implement gmp_rsa_private_key.decrypt()") +Fixes: CVE-2026-35334 + +CVE: CVE-2026-35334 +Upstream-Status: Backport [https://snapshot.debian.org/archive/debian-security-debug/20260422T125423Z/pool/updates/main/s/strongswan/strongswan_6.0.1-6%2Bdeb13u5.debian.tar.xz] +Signed-off-by: Nitin Wankhade <[email protected]> +=== +diff --git a/src/libstrongswan/plugins/gmp/gmp_rsa_private_key.c b/src/libstrongswan/plugins/gmp/gmp_rsa_private_key.c +index 47784b6..08c5eee 100644 +--- a/src/libstrongswan/plugins/gmp/gmp_rsa_private_key.c ++++ b/src/libstrongswan/plugins/gmp/gmp_rsa_private_key.c +@@ -495,8 +495,8 @@ METHOD(private_key_t, decrypt, bool, + private_gmp_rsa_private_key_t *this, encryption_scheme_t scheme, + void *params, chunk_t crypto, chunk_t *plain) + { +- chunk_t em, stripped; +- bool success = FALSE; ++ chunk_t em; ++ u_int valid, i, j, found_sep = 0, sep_index = 0, m_index; + + if (scheme != ENCRYPT_RSA_PKCS1) + { +@@ -505,33 +505,51 @@ METHOD(private_key_t, decrypt, bool, + return FALSE; + } + /* rsa decryption using PKCS#1 RSADP */ +- stripped = em = rsadp(this, crypto); ++ em = rsadp(this, crypto); ++ if (em.len != this->k) ++ { ++ return FALSE; ++ } + +- /* PKCS#1 v1.5 8.1 encryption-block formatting (EB = 00 || 02 || PS || 00 || D) */ ++ /* PKCS#1 v1.5, RFC 8017, section 7.2.2 message structure: ++ * EM = 00 || 02 || PS || 00 || M */ + + /* check for hex pattern 00 02 in decrypted message */ +- if ((*stripped.ptr++ != 0x00) || (*(stripped.ptr++) != 0x02)) ++ valid = constant_time_eq(em.ptr[0], 0x00); ++ valid &= constant_time_eq(em.ptr[1], 0x02); ++ ++ /* the plaintext data starts after first 0x00 byte */ ++ for (i = 2; i < em.len; i++) + { +- DBG1(DBG_LIB, "incorrect padding - probably wrong rsa key"); +- goto end; ++ u_int zero = constant_time_eq(em.ptr[i], 0x00); ++ ++ sep_index = constant_time_select(i, sep_index, ~found_sep & zero); ++ found_sep |= zero; + } +- stripped.len -= 2; + +- /* the plaintext data starts after first 0x00 byte */ +- while (stripped.len-- > 0 && *stripped.ptr++ != 0x00) ++ /* make sure PS is at least eight bytes long (plus the initial bytes) */ ++ valid &= constant_time_ge(sep_index, 10); + +- if (stripped.len == 0) ++ /* instead of copying the message directly, we try not to reveal the message ++ * length i.e. where the 0x00 byte was. and since clearing a chunk is ++ * relatively efficient, i.e. doesn't leak much, we always allocate and copy ++ * a value and then clear it if the structure was invalid */ ++ m_index = constant_time_select(sep_index + 1, 11, valid); ++ ++ *plain = chunk_alloc(this->k); ++ for (i = 0, j = 0; i < em.len; i++) + { +- DBG1(DBG_LIB, "no plaintext data"); +- goto end; ++ plain->ptr[j] = em.ptr[i]; ++ j += constant_time_ge(i, m_index); + } ++ plain->len = j; + +- *plain = chunk_clone(stripped); +- success = TRUE; +- +-end: ++ if (!valid) ++ { ++ chunk_clear(plain); ++ } + chunk_clear(&em); +- return success; ++ return valid; + } + + METHOD(private_key_t, get_keysize, int, +diff --git a/src/libstrongswan/utils/utils.h b/src/libstrongswan/utils/utils.h +index 40fe76a..80199a9 100644 +--- a/src/libstrongswan/utils/utils.h ++++ b/src/libstrongswan/utils/utils.h +@@ -53,6 +53,7 @@ + #include "utils/atomics.h" + #include "utils/align.h" + #include "utils/byteorder.h" ++#include "utils/constant_time.h" + #include "utils/string.h" + #include "utils/memory.h" + #include "utils/strerror.h" +diff --git a/src/libstrongswan/utils/utils/constant_time.h b/src/libstrongswan/utils/utils/constant_time.h +new file mode 100644 +index 0000000..30a8549 +--- /dev/null ++++ b/src/libstrongswan/utils/utils/constant_time.h +@@ -0,0 +1,103 @@ ++/* ++ * Copyright (C) 2026 Tobias Brunner ++ * ++ * Copyright (C) secunet Security Networks AG ++ * ++ * This program is free software; you can redistribute it and/or modify it ++ * under the terms of the GNU General Public License as published by the ++ * Free Software Foundation; either version 2 of the License, or (at your ++ * option) any later version. See <http://www.fsf.org/copyleft/gpl.txt>. ++ * ++ * This program is distributed in the hope that it will be useful, but ++ * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY ++ * or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License ++ * for more details. ++ */ ++ ++/** ++ * @defgroup constant_time_i constant_time ++ * @{ @ingroup constant_time_i ++ */ ++ ++#ifndef CONSTANT_TIME_H_ ++#define CONSTANT_TIME_H_ ++ ++#include <stdint.h> ++ ++/** ++ * Check if the given values are not equal in constant time. ++ * ++ * @param x first value to check ++ * @param y second value to check ++ * @return 1 if values are not equal, 0 otherwise ++ */ ++static inline u_int constant_time_neq(uint32_t x, uint32_t y) ++{ ++ return ((x-y) | (y-x)) >> 31; ++} ++ ++/** ++ * Check if the given values are equal in constant time. ++ * ++ * @param x first value to check ++ * @param y second value to check ++ * @return 1 if values are equal, 0 otherwise ++ */ ++static inline u_int constant_time_eq(uint32_t x, uint32_t y) ++{ ++ return 1 ^ constant_time_neq(x, y); ++} ++ ++/** ++ * Compare the two values and return 1 if the first argument is lower than ++ * the second in constant time. ++ * ++ * @param x first value to check ++ * @param y second value to check ++ * @return 1 if first value is lower than second ++ */ ++static inline u_int constant_time_lt(uint32_t x, uint32_t y) ++{ ++ return (x ^ ((x^y) | ((x-y) ^ y))) >> 31; ++} ++ ++/** ++ * Compare the two values and return 1 if the first argument greater or equal to ++ * the second in constant time. ++ * ++ * @param x first value to check ++ * @param y second value to check ++ * @return 1 if first value is greater or equal to the second ++ */ ++static inline u_int constant_time_ge(uint32_t x, uint32_t y) ++{ ++ return 1 ^ constant_time_lt(x, y); ++} ++ ++/** ++ * Return a 32-bit all bit-set mask if the given value is not 0. ++ * ++ * @param x value to check ++ * @return 0xffffffff if value is != 0, 0 otherwise ++ */ ++static inline uint32_t constant_time_mask(uint32_t x) ++{ ++ return -(uint32_t)constant_time_neq(x, 0); ++} ++ ++/** ++ * Select one of two values depending on whether the condition is != 0 or not. ++ * Basically equivalent to 'c ? x : y'. ++ * ++ * @param x first value to select ++ * @param y second value to select ++ * @param c condition ++ * @return x if c is != 0, y otherwise ++ */ ++static inline uint32_t constant_time_select(uint32_t x, uint32_t y, uint32_t c) ++{ ++ uint32_t m = constant_time_mask(c); ++ return (x & m) | (y & ~m); ++} ++ ++#endif /** CONSTANT_TIME_H_ @} */ diff --git a/meta-networking/recipes-support/strongswan/strongswan_5.9.13.bbappend b/meta-networking/recipes-support/strongswan/strongswan_5.9.13.bbappend index 8d22b60..a452a92 100644 --- a/meta-networking/recipes-support/strongswan/strongswan_5.9.13.bbappend +++ b/meta-networking/recipes-support/strongswan/strongswan_5.9.13.bbappend @@ -5,4 +5,5 @@ SRC_URI += "\ file://constraints-Case-insensitive-matching-and-reject-exc.patch \ file://tls-server-Only-accept-non-empty-ECDH-public-keys-wi.patch \ file://libradius-Reject-undersized-attributes-in-enumerator.patch \ + file://gmp-Avoid-crash-and-timing-leaks-in-PKCS-1-v1.5-decr.patch \ " -- 2.34.1