Commit fdf0819afb (rsa: fix alignment issue when getting public exponent) changed the logic to avoid doing an 8-byte access to a possibly-not-8-byte-aligned address.
However, using rsa_convert_big_endian is wrong: That function converts an array of big-endian (32-bit) words with the most significant word first (aka a BE byte array) to an array of cpu-endian words with the least significant word first. While the exponent is indeed _stored_ as a big-endian 64-bit word (two BE words with MSW first), we want to extract it as a cpu-endian 64 bit word. On a little-endian host, swapping the words and byte-swapping each 32-bit word works, because that's the same as byte-swapping the whole 64 bit word. But on a big-endian host, the fdt32_to_cpu are no-ops, but rsa_convert_big_endian() still does the word-swapping, breaking verified boot.
To fix that, while still ensuring we don't do unaligned accesses, add a little helper that first memcpy's the bytes to a local fdt64_t, then applies fdt64_to_cpu(). [The name is chosen based on the [bl]eXX_to_cpup in linux/byteorder/generic.h].
Fixes: fdf0819afb ("rsa: fix alignment issue when getting public exponent") Signed-off-by: Rasmus Villemoes rasmus.villemoes@prevas.dk --- lib/rsa/rsa-mod-exp.c | 11 +++++++++-- 1 file changed, 9 insertions(+), 2 deletions(-)
diff --git a/lib/rsa/rsa-mod-exp.c b/lib/rsa/rsa-mod-exp.c index a437cbe26f..78c688d14c 100644 --- a/lib/rsa/rsa-mod-exp.c +++ b/lib/rsa/rsa-mod-exp.c @@ -25,6 +25,14 @@ #define get_unaligned_be32(a) fdt32_to_cpu(*(uint32_t *)a) #define put_unaligned_be32(a, b) (*(uint32_t *)(b) = cpu_to_fdt32(a))
+static inline uint64_t fdt64_to_cpup(const void *p) +{ + fdt64_t w; + + memcpy(&w, p, sizeof(w)); + return fdt64_to_cpu(w); +} + /* Default public exponent for backward compatibility */ #define RSA_DEFAULT_PUBEXP 65537
@@ -263,8 +271,7 @@ int rsa_mod_exp_sw(const uint8_t *sig, uint32_t sig_len, if (!prop->public_exponent) key.exponent = RSA_DEFAULT_PUBEXP; else - rsa_convert_big_endian((uint32_t *)&key.exponent, - prop->public_exponent, 2); + key.exponent = fdt64_to_cpup(prop->public_exponent);
if (!key.len || !prop->modulus || !prop->rr) { debug("%s: Missing RSA key info", __func__);