crypto_wrappers: fix stack overflow caused by quote v5 cert too large

Signed-off-by: Kun Lai <[email protected]>
inclavare-containers · May 30, 2024 · 475604c · 475604c
1 parent e061a09
commit 475604c
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Showing 4 changed files with 39 additions and 18 deletions.
diff --git a/api/librats_get_attestation_certificate.c b/api/librats_get_attestation_certificate.c
@@ -44,6 +44,8 @@ rats_attester_err_t librats_get_attestation_certificate(
 	bool attester_initialized = false;
 	bool crypto_wrapper_initialized = false;
 
+	rats_cert_info_t cert_info = { 0 };
+
 	if (!privkey || !privkey_len || (*privkey && !*privkey_len) || !certificate_out ||
 	    !certificate_size_out || (!custom_claims && custom_claims_length))
 		return RATS_ATTESTER_ERR_INVALID_PARAMETER;
@@ -177,10 +179,10 @@ rats_attester_err_t librats_get_attestation_certificate(
 	RATS_DEBUG("endorsements buffer size: %zu\n", endorsements_buffer_size);
 
 	/* Prepare cert info for cert generation */
-	rats_cert_info_t cert_info = {
+	cert_info = (rats_cert_info_t) {
 		.subject = subject_name,
-		.cert_len = 0,
-		.cert_buf = { 0 },
+		.cert_bufer = NULL,
+		.cert_bufer_size = 0,
 		.evidence_buffer = evidence_buffer,
 		.evidence_buffer_size = evidence_buffer_size,
 		.endorsements_buffer = endorsements_buffer,
@@ -196,14 +198,10 @@ rats_attester_err_t librats_get_attestation_certificate(
 		goto err;
 	}
 
-	uint8_t *t = (uint8_t *)malloc(cert_info.cert_len);
-	if (!t) {
-		ret = RATS_ATTESTER_ERR_NO_MEM;
-		goto err;
-	}
-	memcpy(t, cert_info.cert_buf, cert_info.cert_len);
-	*certificate_out = t;
-	*certificate_size_out = cert_info.cert_len;
+	*certificate_out = cert_info.cert_bufer;
+	*certificate_size_out = cert_info.cert_bufer_size;
+	cert_info.cert_bufer = NULL;
+	cert_info.cert_bufer_size = 0;
 
 	ret = RATS_ATTESTER_ERR_NONE;
 err:
@@ -215,6 +213,8 @@ rats_attester_err_t librats_get_attestation_certificate(
 	    ctx.attester->opts->cleanup(ctx.attester) != RATS_ATTESTER_ERR_NONE) {
 		RATS_ERR("failed to clean up attester\n");
 	}
+	if (cert_info.cert_bufer)
+		free(cert_info.cert_bufer);
 	if (evidence_buffer)
 		free(evidence_buffer);
 	if (endorsements_buffer)

diff --git a/crypto_wrappers/openssl/gen_cert.c b/crypto_wrappers/openssl/gen_cert.c
@@ -204,12 +204,26 @@ crypto_wrapper_err_t openssl_gen_cert(crypto_wrapper_ctx_t *ctx, rats_hash_algo_
 	if (!X509_sign(cert, octx->privkey, EVP_sha256()))
 		goto err;
 
-	unsigned char *der = cert_info->cert_buf;
+	len = i2d_X509(cert, NULL);
+	if (len < 0) {
+		RATS_DEBUG("openssl failed to serialize X.509 cert\n");
+		goto err;
+	}
+
+	u_int8_t *cert_buffer = malloc(len);
+	if (cert_buffer == NULL) {
+		ret = CRYPTO_WRAPPER_ERR_NO_MEM;
+		goto err;
+	}
+
+	unsigned char *der = cert_buffer;
 	len = i2d_X509(cert, &der);
 	if (len < 0)
 		goto err;
 
-	cert_info->cert_len = len;
+	cert_info->cert_bufer = cert_buffer;
+	cert_info->cert_bufer_size = len;
+	cert_buffer = NULL;
 
 	RATS_DEBUG("self-signing certificate generated\n");
 
@@ -219,6 +233,9 @@ crypto_wrapper_err_t openssl_gen_cert(crypto_wrapper_ctx_t *ctx, rats_hash_algo_
 	if (ret != CRYPTO_WRAPPER_ERR_NONE)
 		RATS_DEBUG("failed to generate certificate %d\n", ret);
 
+	if (cert_buffer)
+		free(cert_buffer);
+
 	if (cert)
 		X509_free(cert);
 

diff --git a/include/librats/cert.h b/include/librats/cert.h
@@ -8,6 +8,7 @@
 #define _RATS_CERT_H
 
 #include <stdint.h>
+#include <stddef.h>
 
 typedef struct {
 	const char *organization;
@@ -17,8 +18,8 @@ typedef struct {
 
 typedef struct {
 	rats_cert_subject_t subject;
-	unsigned int cert_len;
-	uint8_t cert_buf[8192];
+	uint8_t *cert_bufer /* out */;
+	size_t cert_bufer_size /* out */;
 	uint8_t *evidence_buffer;
 	size_t evidence_buffer_size;
 	uint8_t *endorsements_buffer;

diff --git a/verifiers/sev-snp/verify_evidence.c b/verifiers/sev-snp/verify_evidence.c
@@ -109,10 +109,13 @@ rats_verifier_err_t sev_snp_verify_evidence(rats_verifier_ctx_t *ctx,
 		return RATS_VERIFIER_ERR_INVALID;
 #else
 		memset(evidence->snp.vcek, 0, VECK_MAX_SIZE);
-		err = sev_snp_get_vcek_der(report->chip_id, sizeof(report->chip_id),
-					   &report->current_tcb, &evidence->snp);
-		if (err != RATS_ATTESTER_ERR_NONE)
+		rats_attester_err_t attester_err =
+			sev_snp_get_vcek_der(report->chip_id, sizeof(report->chip_id),
+					     &report->current_tcb, &evidence->snp);
+		if (attester_err != RATS_ATTESTER_ERR_NONE) {
+			err = (rats_verifier_err_t)attester_err;
 			return err;
+		}
 #endif
 	}