1 files changed, 33 insertions, 16 deletions

diff --git a/crypto/asymmetric_keys/verify_pefile.c b/crypto/asymmetric_keys/verify_pefile.c
index 79175e6ea0b2..2421f46184ce 100644
--- a/crypto/asymmetric_keys/verify_pefile.c
+++ b/crypto/asymmetric_keys/verify_pefile.c
@@ -128,6 +128,7 @@ static int pefile_strip_sig_wrapper(const void *pebuf,
 {
         struct win_certificate wrapper;
         const u8 *pkcs7;
+        unsigned len;
 
         if (ctx->sig_len < sizeof(wrapper)) {
                 pr_debug("Signature wrapper too short\n");
@@ -154,33 +155,49 @@ static int pefile_strip_sig_wrapper(const void *pebuf,
                 return -ENOTSUPP;
         }
 
-        /* Looks like actual pkcs signature length is in wrapper->length.
-         * size obtained from data dir entries lists the total size of
-         * certificate table which is also aligned to octawrod boundary.
-         *
-         * So set signature length field appropriately.
+        /* It looks like the pkcs signature length in wrapper->length and the
+         * size obtained from the data dir entries, which lists the total size
+         * of certificate table, are both aligned to an octaword boundary, so
+         * we may have to deal with some padding.
          */
         ctx->sig_len = wrapper.length;
         ctx->sig_offset += sizeof(wrapper);
         ctx->sig_len -= sizeof(wrapper);
-        if (ctx->sig_len == 0) {
+        if (ctx->sig_len < 4) {
                 pr_debug("Signature data missing\n");
                 return -EKEYREJECTED;
         }
 
-        /* What's left should a PKCS#7 cert */
+        /* What's left should be a PKCS#7 cert */
         pkcs7 = pebuf + ctx->sig_offset;
-        if (pkcs7[0] == (ASN1_CONS_BIT | ASN1_SEQ)) {
-                if (pkcs7[1] == 0x82 &&
-                    pkcs7[2] == (((ctx->sig_len - 4) >> 8) & 0xff) &&
-                    pkcs7[3] ==  ((ctx->sig_len - 4)       & 0xff))
-                        return 0;
-                if (pkcs7[1] == 0x80)
-                        return 0;
-                if (pkcs7[1] > 0x82)
-                        return -EMSGSIZE;
+        if (pkcs7[0] != (ASN1_CONS_BIT | ASN1_SEQ))
+                goto not_pkcs7;
+
+        switch (pkcs7[1]) {
+        case 0 ... 0x7f:
+                len = pkcs7[1] + 2;
+                goto check_len;
+        case ASN1_INDEFINITE_LENGTH:
+                return 0;
+        case 0x81:
+                len = pkcs7[2] + 3;
+                goto check_len;
+        case 0x82:
+                len = ((pkcs7[2] << 8) | pkcs7[3]) + 4;
+                goto check_len;
+        case 0x83 ... 0xff:
+                return -EMSGSIZE;
+        default:
+                goto not_pkcs7;
         }
 
+check_len:
+        if (len <= ctx->sig_len) {
+                /* There may be padding */
+                ctx->sig_len = len;
+                return 0;
+        }
+not_pkcs7:
         pr_debug("Signature data not PKCS#7\n");
         return -ELIBBAD;
 }