Reimplement DSA_size without crypto/asn1.
BUG=499653
Change-Id: I16963fb198609d7fc0df6c57923cda3e13350753
Reviewed-on: https://boringssl-review.googlesource.com/6875
Reviewed-by: Adam Langley <agl@google.com>
diff --git a/crypto/dsa/dsa.c b/crypto/dsa/dsa.c
index 3b269d4..aaa763f 100644
--- a/crypto/dsa/dsa.c
+++ b/crypto/dsa/dsa.c
@@ -61,7 +61,6 @@
#include <string.h>
-#include <openssl/asn1.h>
#include <openssl/bn.h>
#include <openssl/dh.h>
#include <openssl/digest.h>
@@ -754,24 +753,38 @@
return ret;
}
+/* der_len_len returns the number of bytes needed to represent a length of |len|
+ * in DER. */
+static size_t der_len_len(size_t len) {
+ if (len < 0x80) {
+ return 1;
+ }
+ size_t ret = 1;
+ while (len > 0) {
+ ret++;
+ len >>= 8;
+ }
+ return ret;
+}
+
int DSA_size(const DSA *dsa) {
- int ret, i;
- ASN1_INTEGER bs;
- unsigned char buf[4]; /* 4 bytes looks really small.
- However, i2d_ASN1_INTEGER() will not look
- beyond the first byte, as long as the second
- parameter is NULL. */
-
- i = BN_num_bits(dsa->q);
- bs.length = (i + 7) / 8;
- bs.data = buf;
- bs.type = V_ASN1_INTEGER;
- /* If the top bit is set the asn1 encoding is 1 larger. */
- buf[0] = 0xff;
-
- i = i2d_ASN1_INTEGER(&bs, NULL);
- i += i; /* r and s */
- ret = ASN1_object_size(1, i, V_ASN1_SEQUENCE);
+ size_t order_len = BN_num_bytes(dsa->q);
+ /* Compute the maximum length of an |order_len| byte integer. Defensively
+ * assume that the leading 0x00 is included. */
+ size_t integer_len = 1 /* tag */ + der_len_len(order_len + 1) + 1 + order_len;
+ if (integer_len < order_len) {
+ return 0;
+ }
+ /* A DSA signature is two INTEGERs. */
+ size_t value_len = 2 * integer_len;
+ if (value_len < integer_len) {
+ return 0;
+ }
+ /* Add the header. */
+ size_t ret = 1 /* tag */ + der_len_len(value_len) + value_len;
+ if (ret < value_len) {
+ return 0;
+ }
return ret;
}
