From 8d807cc21655eaa6e6a08afafeec3682c0f3f2ab Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Ond=C5=99ej=20Sur=C3=BD?= <ondrej@isc.org>
Date: Tue, 21 Jul 2020 14:42:47 +0200
Subject: [PATCH] Fix crash in pk11_numbits() when native-pkcs11 is used

When pk11_numbits() is passed a user provided input that contains all
zeroes (via crafted DNS message), it would crash with assertion
failure.  Fix that by properly handling such input.
---
 lib/dns/pkcs11dh_link.c         | 15 ++++++-
 lib/dns/pkcs11dsa_link.c        |  8 +++-
 lib/dns/pkcs11rsa_link.c        | 79 +++++++++++++++++++++++++--------
 lib/isc/include/pk11/internal.h |  3 +-
 lib/isc/pk11.c                  | 61 ++++++++++++++++---------
 5 files changed, 121 insertions(+), 45 deletions(-)

diff --git a/lib/dns/pkcs11dh_link.c b/lib/dns/pkcs11dh_link.c
index e2b60ea7c5..4cd8e32d60 100644
--- a/lib/dns/pkcs11dh_link.c
+++ b/lib/dns/pkcs11dh_link.c
@@ -748,6 +748,7 @@ pkcs11dh_fromdns(dst_key_t *key, isc_buffer_t *data) {
 	CK_BYTE *prime = NULL, *base = NULL, *pub = NULL;
 	CK_ATTRIBUTE *attr;
 	int special = 0;
+	unsigned int bits;
 	isc_result_t result;
 
 	isc_buffer_remainingregion(data, &r);
@@ -852,7 +853,11 @@ pkcs11dh_fromdns(dst_key_t *key, isc_buffer_t *data) {
 	pub = r.base;
 	isc_region_consume(&r, publen);
 
-	key->key_size = pk11_numbits(prime, plen_);
+	result = pk11_numbits(prime, plen_, &bits);
+	if (result != ISC_R_SUCCESS) {
+		goto cleanup;
+	}
+	key->key_size = bits;
 
 	dh->repr = (CK_ATTRIBUTE *) isc_mem_get(key->mctx, sizeof(*attr) * 3);
 	if (dh->repr == NULL)
@@ -1012,6 +1017,7 @@ pkcs11dh_parse(dst_key_t *key, isc_lex_t *lexer, dst_key_t *pub) {
 	dst_private_t priv;
 	isc_result_t ret;
 	int i;
+	unsigned int bits;
 	pk11_object_t *dh = NULL;
 	CK_ATTRIBUTE *attr;
 	isc_mem_t *mctx;
@@ -1082,7 +1088,12 @@ pkcs11dh_parse(dst_key_t *key, isc_lex_t *lexer, dst_key_t *pub) {
 
 	attr = pk11_attribute_bytype(dh, CKA_PRIME);
 	INSIST(attr != NULL);
-	key->key_size = pk11_numbits(attr->pValue, attr->ulValueLen);
+
+	ret = pk11_numbits(attr->pValue, attr->ulValueLen, &bits);
+	if (ret != ISC_R_SUCCESS) {
+		goto err;
+	}
+	key->key_size = bits;
 
 	return (ISC_R_SUCCESS);
 
diff --git a/lib/dns/pkcs11dsa_link.c b/lib/dns/pkcs11dsa_link.c
index 12d707a112..24d4c149ff 100644
--- a/lib/dns/pkcs11dsa_link.c
+++ b/lib/dns/pkcs11dsa_link.c
@@ -983,6 +983,7 @@ pkcs11dsa_parse(dst_key_t *key, isc_lex_t *lexer, dst_key_t *pub) {
 	dst_private_t priv;
 	isc_result_t ret;
 	int i;
+	unsigned int bits;
 	pk11_object_t *dsa = NULL;
 	CK_ATTRIBUTE *attr;
 	isc_mem_t *mctx = key->mctx;
@@ -1072,7 +1073,12 @@ pkcs11dsa_parse(dst_key_t *key, isc_lex_t *lexer, dst_key_t *pub) {
 
 	attr = pk11_attribute_bytype(dsa, CKA_PRIME);
 	INSIST(attr != NULL);
-	key->key_size = pk11_numbits(attr->pValue, attr->ulValueLen);
+
+	ret = pk11_numbits(attr->pValue, attr->ulValueLen, &bits);
+	if (ret != ISC_R_SUCCESS) {
+		goto err;
+	}
+	key->key_size = bits;
 
 	return (ISC_R_SUCCESS);
 
diff --git a/lib/dns/pkcs11rsa_link.c b/lib/dns/pkcs11rsa_link.c
index 096c1a8e91..1d10d26564 100644
--- a/lib/dns/pkcs11rsa_link.c
+++ b/lib/dns/pkcs11rsa_link.c
@@ -332,6 +332,7 @@ pkcs11rsa_createctx_verify(dst_key_t *key, unsigned int maxbits,
 		key->key_alg == DST_ALG_RSASHA256 ||
 		key->key_alg == DST_ALG_RSASHA512);
 #endif
+	REQUIRE(maxbits <= RSA_MAX_PUBEXP_BITS);
 
 	/*
 	 * Reject incorrect RSA key lengths.
@@ -376,6 +377,7 @@ pkcs11rsa_createctx_verify(dst_key_t *key, unsigned int maxbits,
 	for (attr = pk11_attribute_first(rsa);
 	     attr != NULL;
 	     attr = pk11_attribute_next(rsa, attr))
+	{
 		switch (attr->type) {
 		case CKA_MODULUS:
 			INSIST(keyTemplate[5].type == attr->type);
@@ -396,12 +398,16 @@ pkcs11rsa_createctx_verify(dst_key_t *key, unsigned int maxbits,
 			memmove(keyTemplate[6].pValue, attr->pValue,
 				attr->ulValueLen);
 			keyTemplate[6].ulValueLen = attr->ulValueLen;
-			if (pk11_numbits(attr->pValue,
-					 attr->ulValueLen) > maxbits &&
-			    maxbits != 0)
+			unsigned int bits;
+			ret = pk11_numbits(attr->pValue, attr->ulValueLen,
+					   &bits);
+			if (ret != ISC_R_SUCCESS ||
+			    (bits > maxbits && maxbits != 0)) {
 				DST_RET(DST_R_VERIFYFAILURE);
+			}
 			break;
 		}
+	}
 	pk11_ctx->object = CK_INVALID_HANDLE;
 	pk11_ctx->ontoken = false;
 	PK11_RET(pkcs_C_CreateObject,
@@ -1072,6 +1078,7 @@ pkcs11rsa_verify(dst_context_t *dctx, const isc_region_t *sig) {
 			keyTemplate[5].ulValueLen = attr->ulValueLen;
 			break;
 		case CKA_PUBLIC_EXPONENT:
+			unsigned int bits;
 			INSIST(keyTemplate[6].type == attr->type);
 			keyTemplate[6].pValue = isc_mem_get(dctx->mctx,
 							    attr->ulValueLen);
@@ -1080,10 +1087,12 @@ pkcs11rsa_verify(dst_context_t *dctx, const isc_region_t *sig) {
 			memmove(keyTemplate[6].pValue, attr->pValue,
 				attr->ulValueLen);
 			keyTemplate[6].ulValueLen = attr->ulValueLen;
-			if (pk11_numbits(attr->pValue,
-					 attr->ulValueLen)
-				> RSA_MAX_PUBEXP_BITS)
+			ret = pk11_numbits(attr->pValue, attr->ulValueLen,
+					   &bits);
+			if (ret != ISC_R_SUCCESS || bits > RSA_MAX_PUBEXP_BITS)
+			{
 				DST_RET(DST_R_VERIFYFAILURE);
+			}
 			break;
 		}
 	pk11_ctx->object = CK_INVALID_HANDLE;
@@ -1461,6 +1470,8 @@ pkcs11rsa_fromdns(dst_key_t *key, isc_buffer_t *data) {
 	CK_BYTE *exponent = NULL, *modulus = NULL;
 	CK_ATTRIBUTE *attr;
 	unsigned int length;
+	unsigned int bits;
+	isc_result_t ret = ISC_R_SUCCESS;
 
 	isc_buffer_remainingregion(data, &r);
 	if (r.length == 0)
@@ -1478,9 +1489,7 @@ pkcs11rsa_fromdns(dst_key_t *key, isc_buffer_t *data) {
 
 	if (e_bytes == 0) {
 		if (r.length < 2) {
-			isc_safe_memwipe(rsa, sizeof(*rsa));
-			isc_mem_put(key->mctx, rsa, sizeof(*rsa));
-			return (DST_R_INVALIDPUBLICKEY);
+			DST_RET(DST_R_INVALIDPUBLICKEY);
 		}
 		e_bytes = (*r.base) << 8;
 		isc_region_consume(&r, 1);
@@ -1489,16 +1498,18 @@ pkcs11rsa_fromdns(dst_key_t *key, isc_buffer_t *data) {
 	}
 
 	if (r.length < e_bytes) {
-		isc_safe_memwipe(rsa, sizeof(*rsa));
-		isc_mem_put(key->mctx, rsa, sizeof(*rsa));
-		return (DST_R_INVALIDPUBLICKEY);
+		DST_RET(DST_R_INVALIDPUBLICKEY);
 	}
 	exponent = r.base;
 	isc_region_consume(&r, e_bytes);
 	modulus = r.base;
 	mod_bytes = r.length;
 
-	key->key_size = pk11_numbits(modulus, mod_bytes);
+	ret = pk11_numbits(modulus, mod_bytes, &bits);
+	if (ret != ISC_R_SUCCESS) {
+		goto err;
+	}
+	key->key_size = bits;
 
 	isc_buffer_forward(data, length);
 
@@ -1548,9 +1559,12 @@ pkcs11rsa_fromdns(dst_key_t *key, isc_buffer_t *data) {
 			    rsa->repr,
 			    rsa->attrcnt * sizeof(*attr));
 	}
+	ret = ISC_R_NOMEMORY;
+
+    err:
 	isc_safe_memwipe(rsa, sizeof(*rsa));
 	isc_mem_put(key->mctx, rsa, sizeof(*rsa));
-	return (ISC_R_NOMEMORY);
+	return (ret);
 }
 
 static isc_result_t
@@ -1729,6 +1743,7 @@ pkcs11rsa_fetch(dst_key_t *key, const char *engine, const char *label,
 	pk11_object_t *pubrsa;
 	pk11_context_t *pk11_ctx = NULL;
 	isc_result_t ret;
+	unsigned int bits;
 
 	if (label == NULL)
 		return (DST_R_NOENGINE);
@@ -1815,7 +1830,11 @@ pkcs11rsa_fetch(dst_key_t *key, const char *engine, const char *label,
 
 	attr = pk11_attribute_bytype(rsa, CKA_MODULUS);
 	INSIST(attr != NULL);
-	key->key_size = pk11_numbits(attr->pValue, attr->ulValueLen);
+	ret = pk11_numbits(attr->pValue, attr->ulValueLen, &bits);
+	if (ret != ISC_R_SUCCESS) {
+		goto err;
+	}
+	key->key_size = bits;
 
 	return (ISC_R_SUCCESS);
 
@@ -1901,6 +1920,7 @@ pkcs11rsa_parse(dst_key_t *key, isc_lex_t *lexer, dst_key_t *pub) {
 	CK_ATTRIBUTE *attr;
 	isc_mem_t *mctx = key->mctx;
 	const char *engine = NULL, *label = NULL;
+	unsigned int bits;
 
 	/* read private key file */
 	ret = dst__privstruct_parse(key, DST_ALG_RSA, lexer, mctx, &priv);
@@ -2044,12 +2064,22 @@ pkcs11rsa_parse(dst_key_t *key, isc_lex_t *lexer, dst_key_t *pub) {
 
 	attr = pk11_attribute_bytype(rsa, CKA_MODULUS);
 	INSIST(attr != NULL);
-	key->key_size = pk11_numbits(attr->pValue, attr->ulValueLen);
+	ret = pk11_numbits(attr->pValue, attr->ulValueLen, &bits);
+	if (ret != ISC_R_SUCCESS) {
+		goto err;
+	}
+	key->key_size = bits;
 
 	attr = pk11_attribute_bytype(rsa, CKA_PUBLIC_EXPONENT);
 	INSIST(attr != NULL);
-	if (pk11_numbits(attr->pValue, attr->ulValueLen) > RSA_MAX_PUBEXP_BITS)
+
+	ret = pk11_numbits(attr->pValue, attr->ulValueLen, &bits);
+	if (ret != ISC_R_SUCCESS) {
+		goto err;
+	}
+	if (bits > RSA_MAX_PUBEXP_BITS) {
 		DST_RET(ISC_R_RANGE);
+	}
 
 	dst__privstruct_free(&priv, mctx);
 	isc_safe_memwipe(&priv, sizeof(priv));
@@ -2084,6 +2114,7 @@ pkcs11rsa_fromlabel(dst_key_t *key, const char *engine, const char *label,
 	pk11_context_t *pk11_ctx = NULL;
 	isc_result_t ret;
 	unsigned int i;
+	unsigned int bits;
 
 	UNUSED(pin);
 
@@ -2178,12 +2209,22 @@ pkcs11rsa_fromlabel(dst_key_t *key, const char *engine, const char *label,
 
 	attr = pk11_attribute_bytype(rsa, CKA_PUBLIC_EXPONENT);
 	INSIST(attr != NULL);
-	if (pk11_numbits(attr->pValue, attr->ulValueLen) > RSA_MAX_PUBEXP_BITS)
+
+	ret = pk11_numbits(attr->pValue, attr->ulValueLen, &bits);
+	if (ret != ISC_R_SUCCESS) {
+		goto err;
+	}
+	if (bits > RSA_MAX_PUBEXP_BITS) {
 		DST_RET(ISC_R_RANGE);
+	}
 
 	attr = pk11_attribute_bytype(rsa, CKA_MODULUS);
 	INSIST(attr != NULL);
-	key->key_size = pk11_numbits(attr->pValue, attr->ulValueLen);
+	ret = pk11_numbits(attr->pValue, attr->ulValueLen, &bits);
+	if (ret != ISC_R_SUCCESS) {
+		goto err;
+	}
+	key->key_size = bits;
 
 	pk11_return_session(pk11_ctx);
 	isc_safe_memwipe(pk11_ctx, sizeof(*pk11_ctx));
diff --git a/lib/isc/include/pk11/internal.h b/lib/isc/include/pk11/internal.h
index aa8907ab08..7cc8ec812b 100644
--- a/lib/isc/include/pk11/internal.h
+++ b/lib/isc/include/pk11/internal.h
@@ -25,7 +25,8 @@ void pk11_mem_put(void *ptr, size_t size);
 
 CK_SLOT_ID pk11_get_best_token(pk11_optype_t optype);
 
-unsigned int pk11_numbits(CK_BYTE_PTR data, unsigned int bytecnt);
+isc_result_t
+pk11_numbits(CK_BYTE_PTR data, unsigned int bytecnt, unsigned int *bits);
 
 CK_ATTRIBUTE *pk11_attribute_first(const pk11_object_t *obj);
 
diff --git a/lib/isc/pk11.c b/lib/isc/pk11.c
index 012afd968a..4e4052044b 100644
--- a/lib/isc/pk11.c
+++ b/lib/isc/pk11.c
@@ -962,13 +962,15 @@ pk11_get_best_token(pk11_optype_t optype) {
 	return (token->slotid);
 }
 
-unsigned int
-pk11_numbits(CK_BYTE_PTR data, unsigned int bytecnt) {
+isc_result_t
+pk11_numbits(CK_BYTE_PTR data, unsigned int bytecnt, unsigned int *bits) {
 	unsigned int bitcnt, i;
 	CK_BYTE top;
 
-	if (bytecnt == 0)
-		return (0);
+	if (bytecnt == 0) {
+		*bits = 0;
+		return (ISC_R_SUCCESS);
+	}
 	bitcnt = bytecnt * 8;
 	for (i = 0; i < bytecnt; i++) {
 		top = data[i];
@@ -976,26 +978,41 @@ pk11_numbits(CK_BYTE_PTR data, unsigned int bytecnt) {
 			bitcnt -= 8;
 			continue;
 		}
-		if (top & 0x80)
-			return (bitcnt);
-		if (top & 0x40)
-			return (bitcnt - 1);
-		if (top & 0x20)
-			return (bitcnt - 2);
-		if (top & 0x10)
-			return (bitcnt - 3);
-		if (top & 0x08)
-			return (bitcnt - 4);
-		if (top & 0x04)
-			return (bitcnt - 5);
-		if (top & 0x02)
-			return (bitcnt - 6);
-		if (top & 0x01)
-			return (bitcnt - 7);
+		if (top & 0x80) {
+			*bits = bitcnt;
+			return (ISC_R_SUCCESS);
+		}
+		if (top & 0x40) {
+			*bits = bitcnt - 1;
+			return (ISC_R_SUCCESS);
+		}
+		if (top & 0x20) {
+			*bits = bitcnt - 2;
+			return (ISC_R_SUCCESS);
+		}
+		if (top & 0x10) {
+			*bits = bitcnt - 3;
+			return (ISC_R_SUCCESS);
+		}
+		if (top & 0x08) {
+			*bits = bitcnt - 4;
+			return (ISC_R_SUCCESS);
+		}
+		if (top & 0x04) {
+			*bits = bitcnt - 5;
+			return (ISC_R_SUCCESS);
+		}
+		if (top & 0x02) {
+			*bits = bitcnt - 6;
+			return (ISC_R_SUCCESS);
+		}
+		if (top & 0x01) {
+			*bits = bitcnt - 7;
+			return (ISC_R_SUCCESS);
+		}
 		break;
 	}
-	INSIST(0);
-	ISC_UNREACHABLE();
+	return (ISC_R_RANGE);
 }
 
 CK_ATTRIBUTE *
-- 
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