lib: rsa: fix allocated size for rr and rrtmp in rsa_gen_key_prop()

When calculating rrtmp/rr rsa_gen_key_prop() tries to make
(((rlen + 31) >> 5) + 1) steps in the rr uint32_t array and
(((rlen + 7) >> 3) + 1) / 4 steps in uint32_t rrtmp[]
with rlen being num_bits * 2

On a 4096bit key this comes down to to 257 uint32_t elements
in rr and 256 elements in rrtmp but with the current allocation
rr and rrtmp only have 129 uint32_t elements.

On 2048bit keys this works by chance as the defined max_rsa_size=4096
allocates a suitable number of elements, but with an actual 4096bit key
this results in other memory parts getting overwritten.

So as suggested by Heinrich Schuchardt just use the actual bit-size
of the key as base for the size calculation, in turn making the code
compatible to any future keysizes.

Suggested-by: Heinrich Schuchardt <xypron.debian@gmx.de>
Signed-off-by: Heiko Stuebner <heiko.stuebner@theobroma-systems.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
rrtmp needs 2 + (((*prop)->num_bits * 2) >> 5) array elements.

Reviewed-by: Heinrich Schuchardt <xypron.glpk@gmx.de>

diff --git a/lib/rsa/rsa-keyprop.c b/lib/rsa/rsa-keyprop.c
index 4b54db44c438507f44f5d88f4ff86cf0ff0b2daf..cc0d2f90669e42dc7dedc57105727d635d7cba5d 100644 (file)
--- a/lib/rsa/rsa-keyprop.c
+++ b/lib/rsa/rsa-keyprop.c
@@ -654,14 +654,10 @@ int rsa_gen_key_prop(const void *key, uint32_t keylen, struct key_prop **prop)
 {
        struct rsa_key rsa_key;
        uint32_t *n = NULL, *rr = NULL, *rrtmp = NULL;
-       const int max_rsa_size = 4096;
        int rlen, i, ret;
 
        *prop = calloc(sizeof(**prop), 1);
-       n = calloc(sizeof(uint32_t), 1 + (max_rsa_size >> 5));
-       rr = calloc(sizeof(uint32_t), 1 + (max_rsa_size >> 5));
-       rrtmp = calloc(sizeof(uint32_t), 1 + (max_rsa_size >> 5));
-       if (!(*prop) || !n || !rr || !rrtmp) {
+       if (!(*prop)) {
                ret = -ENOMEM;
                goto err;
        }
@@ -682,6 +678,14 @@ int rsa_gen_key_prop(const void *key, uint32_t keylen, struct key_prop **prop)
        }
        memcpy((void *)(*prop)->modulus, &rsa_key.n[i], rsa_key.n_sz - i);
 
+       n = calloc(sizeof(uint32_t), 1 + ((*prop)->num_bits >> 5));
+       rr = calloc(sizeof(uint32_t), 1 + (((*prop)->num_bits * 2) >> 5));
+       rrtmp = calloc(sizeof(uint32_t), 2 + (((*prop)->num_bits * 2) >> 5));
+       if (!n || !rr || !rrtmp) {
+               ret = -ENOMEM;
+               goto err;
+       }
+
        /* exponent */
        (*prop)->public_exponent = calloc(1, sizeof(uint64_t));
        if (!(*prop)->public_exponent) {