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kern uuid: break format validation out into a separate KPI

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This new KPI, validate_uuid, strictly validates the formatting of the input
UUID and, optionally, populates a given struct uuid.

As noted in the header, the key differences are that the new KPI won't
recognize an empty string as a nil UUID and it won't do any kind of semantic
validation on it. Also key is that populating a struct uuid is optional, so
the caller doesn't necessarily need to allocate a bogus one on the stack
just to validate the string.

This KPI has specifically been broken out in support of D24288, which will
preload /etc/hostid in loader so that early boot hostuuid users (e.g.
anything that calls ether_gen_addr) can have a valid hostuuid to work with
once it's been stashed in /etc/hostid.
This commit is contained in:
kevans 2020-04-15 03:59:26 +00:00
parent b90518c84c
commit 9da994e5cc
2 changed files with 53 additions and 18 deletions
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56
sys/kern/kern_uuid.c
View File

@ -382,19 +382,16 @@ be_uuid_dec(void const *buf, struct uuid *uuid)
}
int
parse_uuid(const char *str, struct uuid *uuid)
validate_uuid(const char *str, size_t size, struct uuid *uuid)
{
u_int c[11];
int n;
/* An empty string represents a nil UUID. */
if (*str == '\0') {
bzero(uuid, sizeof(*uuid));
return (0);
}
if (size == 0 || *str == '\0')
return (EINVAL);
/* The UUID string representation has a fixed length. */
if (strlen(str) != 36)
if (size != 36)
return (EINVAL);
/*
@ -406,25 +403,48 @@ parse_uuid(const char *str, struct uuid *uuid)
if (str[8] != '-')
return (EINVAL);
/* Now check the format. */
n = sscanf(str, "%8x-%4x-%4x-%2x%2x-%2x%2x%2x%2x%2x%2x", c + 0, c + 1,
c + 2, c + 3, c + 4, c + 5, c + 6, c + 7, c + 8, c + 9, c + 10);
/* Make sure we have all conversions. */
if (n != 11)
return (EINVAL);
/* Successful scan. Build the UUID. */
uuid->time_low = c[0];
uuid->time_mid = c[1];
uuid->time_hi_and_version = c[2];
uuid->clock_seq_hi_and_reserved = c[3];
uuid->clock_seq_low = c[4];
for (n = 0; n < 6; n++)
uuid->node[n] = c[n + 5];
/* Successful scan. Build the UUID if requested. */
if (uuid != NULL) {
uuid->time_low = c[0];
uuid->time_mid = c[1];
uuid->time_hi_and_version = c[2];
uuid->clock_seq_hi_and_reserved = c[3];
uuid->clock_seq_low = c[4];
for (n = 0; n < 6; n++)
uuid->node[n] = c[n + 5];
}
return (0);
}
int
parse_uuid(const char *str, struct uuid *uuid)
{
unsigned int clock_seq;
int ret;
/* An empty string represents a nil UUID. */
if (*str == '\0') {
bzero(uuid, sizeof(*uuid));
return (0);
}
ret = validate_uuid(str, strlen(str), uuid);
if (ret != 0)
return (ret);
/* Check semantics... */
return (((c[3] & 0x80) != 0x00 && /* variant 0? */
(c[3] & 0xc0) != 0x80 && /* variant 1? */
(c[3] & 0xe0) != 0xc0) ? EINVAL : 0); /* variant 2? */
clock_seq = uuid->clock_seq_hi_and_reserved;
return (((clock_seq & 0x80) != 0x00 && /* variant 0? */
(clock_seq & 0xc0) != 0x80 && /* variant 1? */
(clock_seq & 0xe0) != 0xc0) ? EINVAL : 0); /* variant 2? */
}
int

15
sys/sys/uuid.h
View File

@ -66,6 +66,21 @@ int uuid_ether_del(const uint8_t *);
int snprintf_uuid(char *, size_t, struct uuid *);
int printf_uuid(struct uuid *);
int sbuf_printf_uuid(struct sbuf *, struct uuid *);
/*
* There are a few key differences between validate_uuid and parse_uuid:
*
* - The struct uuid * parameter to validate_uuid is optional, so the caller
* can simply validate UUID format without doing anything with the result.
* - validate_uuid will not pass an empty string as a valid UUID, as it doesn't
* strictly meet the formatting requirements. parse_uuid will accept an
* empty string and zero out the uuid struct accordingly.
* - parse_uuid does additional semantic checks on clock_seq_hi_and_reserved
* that validate_uuid will not do.
*
* validate_uuid is intended to strictly check that it's a well-formed uuid.
*/
int validate_uuid(const char *, size_t, struct uuid *);
int parse_uuid(const char *, struct uuid *);
int uuidcmp(const struct uuid *, const struct uuid *);