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authorHerbert Xu <herbert@gondor.apana.org.au>2016-06-29 19:32:21 +0800
committerHerbert Xu <herbert@gondor.apana.org.au>2016-07-01 23:45:18 +0800
commit9b45b7bba3d22de52e09df63c50f390a193a3f53 (patch)
tree589fa304ec152558fc189f2da773154bd334e64c /lib
parent50d2b643ea6675927435743633a57c2a9cfd8d83 (diff)
downloadlinux-stericsson-9b45b7bba3d22de52e09df63c50f390a193a3f53.tar.gz
crypto: rsa - Generate fixed-length output
Every implementation of RSA that we have naturally generates output with leading zeroes. The one and only user of RSA, pkcs1pad wants to have those leading zeroes in place, in fact because they are currently absent it has to write those zeroes itself. So we shouldn't be stripping leading zeroes in the first place. In fact this patch makes rsa-generic produce output with fixed length so that pkcs1pad does not need to do any extra work. This patch also changes DH to use the new interface. Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Diffstat (limited to 'lib')
-rw-r--r--lib/mpi/mpicoder.c55
1 files changed, 26 insertions, 29 deletions
diff --git a/lib/mpi/mpicoder.c b/lib/mpi/mpicoder.c
index 823cf5f5196b..7150e5c23604 100644
--- a/lib/mpi/mpicoder.c
+++ b/lib/mpi/mpicoder.c
@@ -237,16 +237,13 @@ EXPORT_SYMBOL_GPL(mpi_get_buffer);
* @a: a multi precision integer
* @sgl: scatterlist to write to. Needs to be at least
* mpi_get_size(a) long.
- * @nbytes: in/out param - it has the be set to the maximum number of
- * bytes that can be written to sgl. This has to be at least
- * the size of the integer a. On return it receives the actual
- * length of the data written on success or the data that would
- * be written if buffer was too small.
+ * @nbytes: the number of bytes to write. Leading bytes will be
+ * filled with zero.
* @sign: if not NULL, it will be set to the sign of a.
*
* Return: 0 on success or error code in case of error
*/
-int mpi_write_to_sgl(MPI a, struct scatterlist *sgl, unsigned *nbytes,
+int mpi_write_to_sgl(MPI a, struct scatterlist *sgl, unsigned nbytes,
int *sign)
{
u8 *p, *p2;
@@ -258,43 +255,44 @@ int mpi_write_to_sgl(MPI a, struct scatterlist *sgl, unsigned *nbytes,
#error please implement for this limb size.
#endif
unsigned int n = mpi_get_size(a);
- int i, x, y = 0, lzeros, buf_len;
-
- if (!nbytes)
- return -EINVAL;
+ int i, x, buf_len;
if (sign)
*sign = a->sign;
- lzeros = count_lzeros(a);
-
- if (*nbytes < n - lzeros) {
- *nbytes = n - lzeros;
+ if (nbytes < n)
return -EOVERFLOW;
- }
- *nbytes = n - lzeros;
buf_len = sgl->length;
p2 = sg_virt(sgl);
- for (i = a->nlimbs - 1 - lzeros / BYTES_PER_MPI_LIMB,
- lzeros %= BYTES_PER_MPI_LIMB;
- i >= 0; i--) {
+ while (nbytes > n) {
+ if (!buf_len) {
+ sgl = sg_next(sgl);
+ if (!sgl)
+ return -EINVAL;
+ buf_len = sgl->length;
+ p2 = sg_virt(sgl);
+ }
+
+ i = min_t(unsigned, nbytes - n, buf_len);
+ memset(p2, 0, i);
+ p2 += i;
+ buf_len -= i;
+ nbytes -= i;
+ }
+
+ for (i = a->nlimbs - 1; i >= 0; i--) {
#if BYTES_PER_MPI_LIMB == 4
- alimb = cpu_to_be32(a->d[i]);
+ alimb = a->d[i] ? cpu_to_be32(a->d[i]) : 0;
#elif BYTES_PER_MPI_LIMB == 8
- alimb = cpu_to_be64(a->d[i]);
+ alimb = a->d[i] ? cpu_to_be64(a->d[i]) : 0;
#else
#error please implement for this limb size.
#endif
- if (lzeros) {
- y = lzeros;
- lzeros = 0;
- }
-
- p = (u8 *)&alimb + y;
+ p = (u8 *)&alimb;
- for (x = 0; x < sizeof(alimb) - y; x++) {
+ for (x = 0; x < sizeof(alimb); x++) {
if (!buf_len) {
sgl = sg_next(sgl);
if (!sgl)
@@ -305,7 +303,6 @@ int mpi_write_to_sgl(MPI a, struct scatterlist *sgl, unsigned *nbytes,
*p2++ = *p++;
buf_len--;
}
- y = 0;
}
return 0;
}