expr: fix buffer overflows in data value setters

The data value setters memcpy() to a fixed-size buffer, but its very easy
to make nft pass too-larger values.  Example:
  @th,160,1272 gt 0

ERROR: AddressSanitizer: heap-buffer-overflow on address 0x60b000[..]

Truncate the copy instead of corrupting the heap.
This needs additional fixes on nft side to reject such statements with a
proper error message.

Signed-off-by: Florian Westphal <fw@strlen.de>

6 files changed, 23 insertions, 21 deletions

diff --git a/include/data_reg.h b/include/data_reg.h
index 6d2dc66..5ee7080 100644
--- a/include/data_reg.h
+++ b/include/data_reg.h
@@ -37,4 +37,6 @@ struct nlattr;
 int nftnl_parse_data(union nftnl_data_reg *data, struct nlattr *attr, int *type);
 void nftnl_free_verdict(const union nftnl_data_reg *data);
 
+int nftnl_data_cpy(union nftnl_data_reg *dreg, const void *src, uint32_t len);
+
 #endif
diff --git a/src/expr/bitwise.c b/src/expr/bitwise.c
index 2d27233..e5dba82 100644
--- a/src/expr/bitwise.c
+++ b/src/expr/bitwise.c
@@ -51,17 +51,11 @@ nftnl_expr_bitwise_set(struct nftnl_expr *e, uint16_t type,
 		memcpy(&bitwise->len, data, sizeof(bitwise->len));
 		break;
 	case NFTNL_EXPR_BITWISE_MASK:
-		memcpy(&bitwise->mask.val, data, data_len);
-		bitwise->mask.len = data_len;
-		break;
+		return nftnl_data_cpy(&bitwise->mask, data, data_len);
 	case NFTNL_EXPR_BITWISE_XOR:
-		memcpy(&bitwise->xor.val, data, data_len);
-		bitwise->xor.len = data_len;
-		break;
+		return nftnl_data_cpy(&bitwise->xor, data, data_len);
 	case NFTNL_EXPR_BITWISE_DATA:
-		memcpy(&bitwise->data.val, data, data_len);
-		bitwise->data.len = data_len;
-		break;
+		return nftnl_data_cpy(&bitwise->data, data, data_len);
 	default:
 		return -1;
 	}
diff --git a/src/expr/cmp.c b/src/expr/cmp.c
index f9d15bb..1d396e8 100644
--- a/src/expr/cmp.c
+++ b/src/expr/cmp.c
@@ -42,9 +42,7 @@ nftnl_expr_cmp_set(struct nftnl_expr *e, uint16_t type,
 		memcpy(&cmp->op, data, sizeof(cmp->op));
 		break;
 	case NFTNL_EXPR_CMP_DATA:
-		memcpy(&cmp->data.val, data, data_len);
-		cmp->data.len = data_len;
-		break;
+		return nftnl_data_cpy(&cmp->data, data, data_len);
 	default:
 		return -1;
 	}
diff --git a/src/expr/data_reg.c b/src/expr/data_reg.c
index 2633a77..690b23d 100644
--- a/src/expr/data_reg.c
+++ b/src/expr/data_reg.c
@@ -217,3 +217,17 @@ void nftnl_free_verdict(const union nftnl_data_reg *data)
 		break;
 	}
 }
+
+int nftnl_data_cpy(union nftnl_data_reg *dreg, const void *src, uint32_t len)
+{
+	int ret = 0;
+
+	if (len > sizeof(dreg->val)) {
+		len = sizeof(dreg->val);
+		ret = -1;
+	}
+
+	memcpy(dreg->val, src, len);
+	dreg->len = len;
+	return ret;
+}
diff --git a/src/expr/immediate.c b/src/expr/immediate.c
index 5d477a8..f56aa8f 100644
--- a/src/expr/immediate.c
+++ b/src/expr/immediate.c
@@ -36,9 +36,7 @@ nftnl_expr_immediate_set(struct nftnl_expr *e, uint16_t type,
 		memcpy(&imm->dreg, data, sizeof(imm->dreg));
 		break;
 	case NFTNL_EXPR_IMM_DATA:
-		memcpy(&imm->data.val, data, data_len);
-		imm->data.len = data_len;
-		break;
+		return nftnl_data_cpy(&imm->data, data, data_len);
 	case NFTNL_EXPR_IMM_VERDICT:
 		memcpy(&imm->data.verdict, data, sizeof(imm->data.verdict));
 		break;
diff --git a/src/expr/range.c b/src/expr/range.c
index 473add8..5a30e48 100644
--- a/src/expr/range.c
+++ b/src/expr/range.c
@@ -40,13 +40,9 @@ static int nftnl_expr_range_set(struct nftnl_expr *e, uint16_t type,
 		memcpy(&range->op, data, sizeof(range->op));
 		break;
 	case NFTNL_EXPR_RANGE_FROM_DATA:
-		memcpy(&range->data_from.val, data, data_len);
-		range->data_from.len = data_len;
-		break;
+		return nftnl_data_cpy(&range->data_from, data, data_len);
 	case NFTNL_EXPR_RANGE_TO_DATA:
-		memcpy(&range->data_to.val, data, data_len);
-		range->data_to.len = data_len;
-		break;
+		return nftnl_data_cpy(&range->data_to, data, data_len);
 	default:
 		return -1;
 	}