diff options
| -rw-r--r-- | crypto/asymmetric_keys/verify_pefile.c | 71 |
1 files changed, 71 insertions, 0 deletions
diff --git a/crypto/asymmetric_keys/verify_pefile.c b/crypto/asymmetric_keys/verify_pefile.c index aec7c509404e..2f5268cb843d 100644 --- a/crypto/asymmetric_keys/verify_pefile.c +++ b/crypto/asymmetric_keys/verify_pefile.c @@ -15,6 +15,7 @@ #include <linux/slab.h> #include <linux/err.h> #include <linux/pe.h> +#include <linux/asn1.h> #include <crypto/pkcs7.h> #include <crypto/hash.h> #include "verify_pefile.h" @@ -118,6 +119,72 @@ static int pefile_parse_binary(const void *pebuf, unsigned int pelen, return 0; } +/* + * Check and strip the PE wrapper from around the signature and check that the + * remnant looks something like PKCS#7. + */ +static int pefile_strip_sig_wrapper(const void *pebuf, + struct pefile_context *ctx) +{ + struct win_certificate wrapper; + const u8 *pkcs7; + + if (ctx->sig_len < sizeof(wrapper)) { + pr_debug("Signature wrapper too short\n"); + return -ELIBBAD; + } + + memcpy(&wrapper, pebuf + ctx->sig_offset, sizeof(wrapper)); + pr_debug("sig wrapper = { %x, %x, %x }\n", + wrapper.length, wrapper.revision, wrapper.cert_type); + + /* Both pesign and sbsign round up the length of certificate table + * (in optional header data directories) to 8 byte alignment. + */ + if (round_up(wrapper.length, 8) != ctx->sig_len) { + pr_debug("Signature wrapper len wrong\n"); + return -ELIBBAD; + } + if (wrapper.revision != WIN_CERT_REVISION_2_0) { + pr_debug("Signature is not revision 2.0\n"); + return -ENOTSUPP; + } + if (wrapper.cert_type != WIN_CERT_TYPE_PKCS_SIGNED_DATA) { + pr_debug("Signature certificate type is not PKCS\n"); + 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. + */ + ctx->sig_len = wrapper.length; + ctx->sig_offset += sizeof(wrapper); + ctx->sig_len -= sizeof(wrapper); + if (ctx->sig_len == 0) { + pr_debug("Signature data missing\n"); + return -EKEYREJECTED; + } + + /* What's left should 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; + } + + pr_debug("Signature data not PKCS#7\n"); + return -ELIBBAD; +} + /** * verify_pefile_signature - Verify the signature on a PE binary image * @pebuf: Buffer containing the PE binary image @@ -159,5 +226,9 @@ int verify_pefile_signature(const void *pebuf, unsigned pelen, if (ret < 0) return ret; + ret = pefile_strip_sig_wrapper(pebuf, &ctx); + if (ret < 0) + return ret; + return -ENOANO; // Not yet complete } |