Viktor, Thank you for taking a look.
We are not invoking either of the API X509_STORE_CTX_get0_chain/X509_STORE_CTX_get1_chain We invoke X509_verify_cert() during the certification verification and this fails (expectedly due to the missing CA certificate), so we invoke X509_STORE_CTX_free to clean up the "X509_STORE_CTX" context and hit this crash (this is not seen always) X509_STORE_new() X509_STORE_CTX_new() X509_STORE_set_verify_cb_func X509_STORE_set_default_paths X509_STORE_load_locations X509_STORE_CTX_init X509_STORE_CTX_set_flags X509_verify_cert --------------------> Fails with error X509_V_ERR_UNABLE_TO_GET_ISSUER_CERT_LOCALLY as CA certificate is not present. /* Cleanup. */ X509_STORE_CTX_free(pContext); -------------------->Crash seen here in sk_X509_pop_free 360 void OPENSSL_sk_pop_free(OPENSSL_STACK *st, OPENSSL_sk_freefunc func) 361 { 362 int i; 363 364 if (st == NULL) 365 return; 366 for (i = 0; i < st->num; i++) 367 if (st->data[i] != NULL)---------------------> Crash seen here 368 func((char *)st->data[i]); 369 OPENSSL_sk_free(st); 370 } Thanks Bala On Monday, 16 August, 2021, 11:40:24 pm IST, Viktor Dukhovni <openssl-us...@dukhovni.org> wrote: > On 16 Aug 2021, at 5:58 am, Bala Duvvuri via openssl-users > <openssl-users@openssl.org> wrote: > > We are using OpenSSl version 1.1.1d in our program and crash is being seen in > "OPENSSL_sk_pop_free" API, we invoke this API in our certificate verification > API. Since crash is not seen always, trying to understand from OpenSSL code, > when can this occur? > > Below is the bt of the crash > > #0 0x0f31f438 in OPENSSL_sk_pop_free (st=0x1041de20, func=0xf34d5b0 > <X509_free>) at crypto/stack/stack.c:367 > #1 0x0f344c74 in sk_X509_pop_free (freefunc=<optimized out>, sk=<optimized > out>) at include/openssl/x509.h:99 > #2 X509_STORE_CTX_cleanup (ctx=ctx@entry=0x1041ba70) at > crypto/x509/x509_vfy.c:2454 > #3 0x0f344cf4 in X509_STORE_CTX_free (ctx=ctx@entry=0x1041ba70) at > crypto/x509/x509_vfy.c:2281 The call in question frees the certificate chain built by X509_verify_cert(). sk_X509_pop_free(ctx->chain, X509_free); That chain is owned by the X509_STORE_CTX. You probably made the mistake of freeing it (or one of the certificates in question) yourself. There are two functions for accessing the built chain: STACK_OF(X509) *X509_STORE_CTX_get0_chain(X509_STORE_CTX *ctx) { return ctx->chain; } STACK_OF(X509) *X509_STORE_CTX_get1_chain(X509_STORE_CTX *ctx) { if (!ctx->chain) return NULL; return X509_chain_up_ref(ctx->chain); } If you call X509_STORE_CTX_get0_chain(3), you MUST NOT free the result. If you call X509_STORE_CTX_get1_chain(3), you own the chain copy, and should free the result when you no longer need it. -- Viktor.