[PATCH 2/4] rsa.c: Factor out constructing the EMSA-PKCS1 message representative.
Ian Jackson
ijackson at chiark.greenend.org.uk
Mon Jul 22 00:19:39 BST 2013
From: Mark Wooding <mdw at distorted.org.uk>
This was done in two different places for no reason I could understand.
Replace them both with a single implementation.
Signed-off-by: Mark Wooding <mdw at distorted.org.uk>
---
rsa.c | 47 ++++++++++++++++++-----------------------------
1 files changed, 18 insertions(+), 29 deletions(-)
diff --git a/rsa.c b/rsa.c
index fed468d..0ca5d19 100644
--- a/rsa.c
+++ b/rsa.c
@@ -36,16 +36,11 @@ struct rsapub {
static const char *hexchars="0123456789abcdef";
-static string_t rsa_sign(void *sst, uint8_t *data, int32_t datalen)
+static void emsa_pkcs1(MP_INT *n, MP_INT *m,
+ const uint8_t *data, int32_t datalen)
{
- struct rsapriv *st=sst;
- MP_INT a, b, u, v, tmp, tmp2;
char buff[2048];
int msize, i;
- string_t signature;
-
- mpz_init(&a);
- mpz_init(&b);
/* RSA PKCS#1 v1.5 signature padding:
*
@@ -65,7 +60,7 @@ static string_t rsa_sign(void *sst, uint8_t *data, int32_t datalen)
* -iwj 17.9.2002
*/
- msize=mpz_sizeinbase(&st->n, 16);
+ msize=mpz_sizeinbase(n, 16);
if (datalen*2+6>=msize) {
fatal("rsa_sign: message too big");
@@ -86,7 +81,20 @@ static string_t rsa_sign(void *sst, uint8_t *data, int32_t datalen)
buff[msize]=0;
- mpz_set_str(&a, buff, 16);
+ mpz_set_str(m, buff, 16);
+}
+
+static string_t rsa_sign(void *sst, uint8_t *data, int32_t datalen)
+{
+ struct rsapriv *st=sst;
+ MP_INT a, b, u, v, tmp, tmp2;
+ string_t signature;
+
+ mpz_init(&a);
+ mpz_init(&b);
+
+ /* Construct the message representative. */
+ emsa_pkcs1(&st->n, &a, data, datalen);
/*
* Produce an RSA signature (a^d mod n) using the Chinese
@@ -135,32 +143,13 @@ static bool_t rsa_sig_check(void *sst, uint8_t *data, int32_t datalen,
{
struct rsapub *st=sst;
MP_INT a, b, c;
- char buff[2048];
- int msize, i;
bool_t ok;
mpz_init(&a);
mpz_init(&b);
mpz_init(&c);
- msize=mpz_sizeinbase(&st->n, 16);
-
- strcpy(buff,"0001");
-
- for (i=0; i<datalen; i++) {
- buff[msize+(-datalen+i)*2]=hexchars[(data[i]&0xf0)>>4];
- buff[msize+(-datalen+i)*2+1]=hexchars[data[i]&0xf];
- }
-
- buff[msize-datalen*2-2]= '0';
- buff[msize-datalen*2-1]= '0';
-
- for (i=4; i<msize-datalen*2-2; i++)
- buff[i]='f';
-
- buff[msize]=0;
-
- mpz_set_str(&a, buff, 16);
+ emsa_pkcs1(&st->n, &a, data, datalen);
mpz_set_str(&b, signature, 16);
--
1.7.2.5
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