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Fail EVP_DigestSignFinal() for ECDSA when buffer is too small #11924

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Fail EVP_DigestSignFinal() for ECDSA when buffer is too small #11924

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0a71909
Fail EVP_DigestSignFinal() for ECDSA when the buffer is too small
julek-wolfssl Oct 28, 2026
ea17e70
Address review: skip Brainpool sig size test on FIPS v6+
julek-wolfssl Oct 30, 2026
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43 changes: 43 additions & 0 deletions tests/api/test_evp_pkey.c
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Original file line number Diff line number Diff line change
Expand Up @@ -2440,6 +2440,12 @@ int test_wolfSSL_EVP_MD_ecc_signing(void)
(unsigned int)XSTRLEN(testData)), 1);
checkSz = sizeof(check);
ExpectIntEQ(wolfSSL_EVP_DigestSignFinal(&mdCtx, NULL, &checkSz), 1);
ExpectIntEQ((int)checkSz, wolfSSL_EVP_PKEY_size(privKey));
/* A buffer too small for the signature is an error. */
checkSz = 8;
ExpectIntEQ(wolfSSL_EVP_DigestSignFinal(&mdCtx, check, &checkSz), 0);
ExpectIntEQ((int)checkSz, 8);
ExpectIntEQ(check[0], 0);
checkSz = sizeof(check);
ExpectIntEQ(wolfSSL_EVP_DigestSignFinal(&mdCtx, check, &checkSz), 1);
ret = wolfSSL_EVP_MD_CTX_cleanup(&mdCtx);
Expand Down Expand Up @@ -2487,6 +2493,43 @@ int test_wolfSSL_EVP_MD_ecc_signing(void)
return EXPECT_RESULT();
}

int test_wolfSSL_EVP_DigestSignFinal_ecc_size(void)
{
EXPECT_DECLS;
#if defined(OPENSSL_EXTRA) && defined(HAVE_ECC) && !defined(NO_SHA256) && \
defined(HAVE_ECC_BRAINPOOL) && \
(defined(HAVE_ECC512) || defined(HAVE_ALL_CURVES)) && \
ECC_MIN_KEY_SZ <= 512 && FIPS_VERSION3_LT(6,0,0)
WOLFSSL_EC_KEY* ecKey = NULL;
WOLFSSL_EVP_PKEY* pkey = NULL;
WOLFSSL_EVP_MD_CTX mdCtx;
size_t sigSz = 0;
int ret;

ExpectNotNull(ecKey = wolfSSL_EC_KEY_new_by_curve_name(
NID_brainpoolP512r1));
ExpectIntEQ(wolfSSL_EC_KEY_generate_key(ecKey), 1);
ExpectNotNull(pkey = wolfSSL_EVP_PKEY_new());
ExpectIntEQ(wolfSSL_EVP_PKEY_assign_EC_KEY(pkey, ecKey), WOLFSSL_SUCCESS);
if (EXPECT_FAIL()) {
wolfSSL_EC_KEY_free(ecKey);
}

wolfSSL_EVP_MD_CTX_init(&mdCtx);
ExpectIntEQ(wolfSSL_EVP_DigestSignInit(&mdCtx, NULL, wolfSSL_EVP_sha256(),
NULL, pkey), 1);
ExpectIntEQ(wolfSSL_EVP_DigestSignFinal(&mdCtx, NULL, &sigSz), 1);
/* r and s may need a leading zero and the SEQ length is two bytes. */
ExpectIntEQ((int)sigSz, 137);
ExpectIntEQ((int)sigSz, wolfSSL_EVP_PKEY_size(pkey));
ret = wolfSSL_EVP_MD_CTX_cleanup(&mdCtx);
ExpectIntEQ(ret, 1);

wolfSSL_EVP_PKEY_free(pkey);
#endif
return EXPECT_RESULT();
}


int test_wolfSSL_EVP_DigestSign(void)
{
Expand Down
2 changes: 2 additions & 0 deletions tests/api/test_evp_pkey.h
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Original file line number Diff line number Diff line change
Expand Up @@ -65,6 +65,7 @@ int test_wolfSSL_EVP_PKEY_verify_dsa_len(void);
int test_wolfSSL_EVP_MD_rsa_signing(void);
int test_wc_RsaPSS_DigitalSignVerify(void);
int test_wolfSSL_EVP_MD_ecc_signing(void);
int test_wolfSSL_EVP_DigestSignFinal_ecc_size(void);
int test_wolfSSL_EVP_DigestSign(void);
int test_wolfSSL_EVP_DigestSign_ecc(void);
int test_wolfSSL_EVP_PKEY_encrypt(void);
Expand Down Expand Up @@ -126,6 +127,7 @@ int test_wolfSSL_CTX_use_PrivateKey_pkcs8_repopulate(void);
TEST_DECL_GROUP("evp_pkey", test_wolfSSL_EVP_MD_rsa_signing), \
TEST_DECL_GROUP("evp_pkey", test_wc_RsaPSS_DigitalSignVerify), \
TEST_DECL_GROUP("evp_pkey", test_wolfSSL_EVP_MD_ecc_signing), \
TEST_DECL_GROUP("evp_pkey", test_wolfSSL_EVP_DigestSignFinal_ecc_size), \
TEST_DECL_GROUP("evp_pkey", test_wolfSSL_EVP_DigestSign), \
TEST_DECL_GROUP("evp_pkey", test_wolfSSL_EVP_DigestSign_ecc), \
TEST_DECL_GROUP("evp_pkey", test_wolfSSL_EVP_PKEY_encrypt), \
Expand Down
18 changes: 14 additions & 4 deletions wolfcrypt/src/evp.c
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Original file line number Diff line number Diff line change
Expand Up @@ -5225,9 +5225,17 @@ int wolfSSL_EVP_DigestSignFinal(WOLFSSL_EVP_MD_CTX *ctx, unsigned char *sig,
#ifdef HAVE_ECC
else if (ctx->pctx->pkey->type == WC_EVP_PKEY_EC) {
if (sig == NULL) {
/* SEQ + INT + INT */
*siglen = (size_t)ecc_sets[ctx->pctx->pkey->ecc->group->curve_idx].
size * 2 + 8;
WOLFSSL_EC_KEY* key = ctx->pctx->pkey->ecc;
int sigSz;

if (key == NULL || (key->inSet == 0 &&
SetECKeyInternal(key) != WOLFSSL_SUCCESS)) {
return WOLFSSL_FAILURE;
}
sigSz = wc_ecc_sig_size((ecc_key*)key->internal);
if (sigSz <= 0)
return WOLFSSL_FAILURE;
*siglen = (size_t)sigSz;
return WOLFSSL_SUCCESS;
}
}
Expand Down Expand Up @@ -5277,8 +5285,10 @@ int wolfSSL_EVP_DigestSignFinal(WOLFSSL_EVP_MD_CTX *ctx, unsigned char *sig,
len = wolfSSL_i2d_ECDSA_SIG(ecdsaSig, NULL);
if (len > 0 && (size_t)len <= *siglen)
len = wolfSSL_i2d_ECDSA_SIG(ecdsaSig, &sig);
else
len = 0;
wolfSSL_ECDSA_SIG_free(ecdsaSig);
if (len == 0)
if (len <= 0)
break;
*siglen = (size_t)len;
ret = WOLFSSL_SUCCESS;
Expand Down
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