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Fix a segfault in parsing OpenSSH private key files.

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The initial test for a line ending with "PRIVATE KEY-----" failed to
take into account the possibility that the line might be shorter than
that. Fixed by introducing a new library function strendswith(), and
strstartswith() for good measure, and using that.

Thanks to Hanno Böck for spotting this, with the aid of AFL.
This commit is contained in:
Simon Tatham 2015-11-10 18:47:55 +00:00
parent a454399ec8
commit fa7b23ce90
3 changed files with 17 additions and 4 deletions
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8
import.c
View File

@ -383,8 +383,8 @@ static struct openssh_pem_key *load_openssh_pem_key(const Filename *filename,
goto error;
}
strip_crlf(line);
if (0 != strncmp(line, "-----BEGIN ", 11) ||
0 != strcmp(line+strlen(line)-16, "PRIVATE KEY-----")) {
if (!strstartswith(line, "-----BEGIN ") ||
!strendswith(line, "PRIVATE KEY-----")) {
errmsg = "file does not begin with OpenSSH key header";
goto error;
}
@ -421,8 +421,8 @@ static struct openssh_pem_key *load_openssh_pem_key(const Filename *filename,
goto error;
}
strip_crlf(line);
if (0 == strncmp(line, "-----END ", 9) &&
0 == strcmp(line+strlen(line)-16, "PRIVATE KEY-----")) {
if (strstartswith(line, "-----END ") &&
strendswith(line, "PRIVATE KEY-----")) {
sfree(line);
line = NULL;
break; /* done */

11
misc.c
View File

@ -1087,3 +1087,14 @@ int get_ssh_uint32(int *datalen, const void **data, unsigned *ret)
*data = (const char *)*data + 4;
return TRUE;
}
int strstartswith(const char *s, const char *t)
{
return !memcmp(s, t, strlen(t));
}
int strendswith(const char *s, const char *t)
{
size_t slen = strlen(s), tlen = strlen(t);
return slen >= tlen && !strcmp(s + (slen - tlen), t);
}

2
misc.h
View File

@ -52,6 +52,8 @@ int toint(unsigned);
char *fgetline(FILE *fp);
char *chomp(char *str);
int strstartswith(const char *s, const char *t);
int strendswith(const char *s, const char *t);
void base64_encode_atom(const unsigned char *data, int n, char *out);
int base64_decode_atom(const char *atom, unsigned char *out);