Merge 34a8ce1e85e1901b35ee15976ca677ec94145705 into 03e1438089654fb884ac48e0f3cd0049cfe2c102

ssl: size the ECDH premaster secret by PSA alone
_pms_ecdh and _pms_ecdhe_psk are sized by PSA_RAW_KEY_AGREEMENT_OUTPUT_MAX_SIZE, with no MBEDTLS_ECP_MAX_BYTES fallback and no new public macro. The ChangeLog entry describes the user-visible failure. Signed-off-by: Paulo Santos <paulo.santos-ext@hexagon.com>
2026-10-28 18:07:34 +08:00 · 2026-10-27 18:42:00 +00:00 · 2026-10-27 15:41:52 -03:00 · 2026-05-20 14:39:00 -03:00
2 changed files with 9 additions and 2 deletions
--- a/ChangeLog.d/fix-pms-ecdh-psa-client-size.txt
+++ b/ChangeLog.d/fix-pms-ecdh-psa-client-size.txt
@ -0,0 +1,7 @@
+Bugfix
+   * Fix TLS 1.2 ECDHE handshakes failing in PSA-client-only
+     (MBEDTLS_PSA_CRYPTO_C disabled) builds when PSK
+     and ECJPAKE key-exchanges were disabled.
+     In this scenario ECDHE key agreement failed returning
+     PSA_ERROR_BUFFER_TOO_SMALL.
+     Fixes #10757.
--- a/include/mbedtls/ssl.h
+++ b/include/mbedtls/ssl.h
@ -653,13 +653,13 @@ union mbedtls_ssl_premaster_secret {
    unsigned char dummy; /* Make the union non-empty even with SSL disabled */
 #if defined(MBEDTLS_KEY_EXCHANGE_ECDHE_RSA_ENABLED)    || \
    defined(MBEDTLS_KEY_EXCHANGE_ECDHE_ECDSA_ENABLED)
-    unsigned char _pms_ecdh[MBEDTLS_ECP_MAX_BYTES];    /* RFC 4492 5.10 */
+    unsigned char _pms_ecdh[PSA_RAW_KEY_AGREEMENT_OUTPUT_MAX_SIZE];    /* RFC 4492 5.10 */
 #endif
 #if defined(MBEDTLS_KEY_EXCHANGE_PSK_ENABLED)
    unsigned char _pms_psk[4 + 2 * MBEDTLS_PSK_MAX_LEN];       /* RFC 4279 2 */
 #endif
 #if defined(MBEDTLS_KEY_EXCHANGE_ECDHE_PSK_ENABLED)
-    unsigned char _pms_ecdhe_psk[4 + MBEDTLS_ECP_MAX_BYTES
+    unsigned char _pms_ecdhe_psk[4 + PSA_RAW_KEY_AGREEMENT_OUTPUT_MAX_SIZE
                                 + MBEDTLS_PSK_MAX_LEN];       /* RFC 5489 2 */
 #endif
 #if defined(MBEDTLS_KEY_EXCHANGE_ECJPAKE_ENABLED)