lib/digsig: additional sanity checks against badly formated key payload

Added sanity checks for possible wrongly formatted key payload data:
- minimum key payload size
- zero modulus length
- corrected upper key payload boundary.

Signed-off-by: Dmitry Kasatkin <[email protected]>
Reviewed-by: Tetsuo Handa <[email protected]>
Signed-off-by: James Morris <[email protected]>

diff --git a/lib/digsig.c b/lib/digsig.c
index fd2402f67f89a0d740fc5cc1fbb4a27dbe420a39..5d840ac64fb1c26036e101693c6d2006f1c062c8 100644 (file)
--- a/lib/digsig.c
+++ b/lib/digsig.c
@@ -105,6 +105,10 @@ static int digsig_verify_rsa(struct key *key,
 
        down_read(&key->sem);
        ukp = key->payload.data;
+
+       if (ukp->datalen < sizeof(*pkh))
+               goto err1;
+
        pkh = (struct pubkey_hdr *)ukp->data;
 
        if (pkh->version != 1)
@@ -117,7 +121,7 @@ static int digsig_verify_rsa(struct key *key,
                goto err1;
 
        datap = pkh->mpi;
-       endp = datap + ukp->datalen;
+       endp = ukp->data + ukp->datalen;
 
        for (i = 0; i < pkh->nmpi; i++) {
                unsigned int remaining = endp - datap;
@@ -128,7 +132,8 @@ static int digsig_verify_rsa(struct key *key,
        mblen = mpi_get_nbits(pkey[0]);
        mlen = (mblen + 7)/8;
 
-       err = -ENOMEM;
+       if (mlen == 0)
+               goto err;
 
        out1 = kzalloc(mlen, GFP_KERNEL);
        if (!out1)