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cgtest: update OpenSSH fingerprinting mechanism.

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We can only get fingerprints compatible with our own system by passing
the '-E md5' option to ssh-keygen. Also, we must strip the "MD5:"
prefix from the hash component of the returned fingerprint.

Since that hash appears in the middle of the string we were previously
extracting, I've reworked the whole cleanup_fp function to use the new
ptrlen_get_word, which makes it easy to extract two words from the
string and then strip a prefix off the second one.
This commit is contained in:
Simon Tatham 2019-03-24 14:06:17 +00:00
parent d159a6efac
commit 8c710dddc5
1 changed files with 13 additions and 11 deletions
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24
cmdgen.c
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@ -1214,19 +1214,21 @@ void filecmp(char *file1, char *file2, char *fmt, ...)
char *cleanup_fp(char *s) char *cleanup_fp(char *s)
{ {
char *p; ptrlen pl = ptrlen_from_asciz(s);
static const char separators[] = " \n\t";
if (!strncmp(s, "ssh-", 4)) { /* Skip initial key type word if we find one */
s += strcspn(s, " \n\t"); if (ptrlen_startswith(pl, PTRLEN_LITERAL("ssh-"), NULL))
s += strspn(s, " \n\t"); ptrlen_get_word(&pl, separators);
}
p = s; /* Expect two words giving the key length and the hash */
s += strcspn(s, " \n\t"); ptrlen bits = ptrlen_get_word(&pl, separators);
s += strspn(s, " \n\t"); ptrlen hash = ptrlen_get_word(&pl, separators);
s += strcspn(s, " \n\t");
return dupprintf("%.*s", (int)(s - p), p); /* Strip "MD5:" prefix if it's present, and do nothing if it isn't */
ptrlen_startswith(hash, PTRLEN_LITERAL("MD5:"), &hash);
return dupprintf("%.*s %.*s", PTRLEN_PRINTF(bits), PTRLEN_PRINTF(hash));
} }
char *get_fp(char *filename) char *get_fp(char *filename)
@ -1316,7 +1318,7 @@ int main(int argc, char **argv)
{ {
char *cmdbuf; char *cmdbuf;
fp = NULL; fp = NULL;
cmdbuf = dupprintf("ssh-keygen -l -f '%s' > '%s'", cmdbuf = dupprintf("ssh-keygen -E md5 -l -f '%s' > '%s'",
pubfilename, tmpfilename1); pubfilename, tmpfilename1);
if (system(cmdbuf) || if (system(cmdbuf) ||
(fp = get_fp(tmpfilename1)) == NULL) { (fp = get_fp(tmpfilename1)) == NULL) {