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push --signed: tighten what the receiving end can ask to sign 

Instead of blindly trusting the receiving side to give us a sensible
nonce to sign, limit the length (max 256 bytes) and the alphabet
(alnum and a few selected punctuations, enough to encode in base64)
that can be used in nonce.

Signed-off-by: Junio C Hamano <gitster@pobox.com>
This commit is contained in:
Junio C Hamano 2015-04-01 18:00:36 -07:00
parent 45917f0f99
commit afcb6ee30a
1 changed files with 23 additions and 0 deletions
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23
send-pack.c
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@ -279,6 +279,28 @@ static int generate_push_cert(struct strbuf *req_buf,
return update_seen;
}
#define NONCE_LEN_LIMIT 256
static void reject_invalid_nonce(const char *nonce, int len)
{
int i = 0;
if (NONCE_LEN_LIMIT <= len)
die("the receiving end asked to sign an invalid nonce <%.*s>",
len, nonce);
for (i = 0; i < len; i++) {
int ch = nonce[i] & 0xFF;
if (isalnum(ch) ||
ch == '-' || ch == '.' ||
ch == '/' || ch == '+' ||
ch == '=' || ch == '_')
continue;
die("the receiving end asked to sign an invalid nonce <%.*s>",
len, nonce);
}
}
int send_pack(struct send_pack_args *args,
int fd[], struct child_process *conn,
struct ref *remote_refs,
@ -321,6 +343,7 @@ int send_pack(struct send_pack_args *args,
push_cert_nonce = server_feature_value("push-cert", &len);
if (!push_cert_nonce)
die(_("the receiving end does not support --signed push"));
reject_invalid_nonce(push_cert_nonce, len);
push_cert_nonce = xmemdupz(push_cert_nonce, len);
}