/src/fuzzpcap/fuzz_pcap.c

Source
// Copyright (c) 2021 Catena cyber
// Author Philippe Antoine <p.antoine@catenacyber.fr>

#define _GNU_SOURCE
#include <stdint.h>
#include <stddef.h>
#include <string.h>
#include <stdlib.h>

#include <pcap/pcap.h>

#include "fuzz_pcap.h"

int FPC_IsFuzzPacketCapture(const uint8_t *Data, size_t Size) {
    if (Size < FPC0_HEADER_LEN) {
        return 0;
    }
    if (memcmp(Data, FPC0_MAGIC, FPC0_MAGIC_LEN - 1) != 0) {
        return 0;
    }
    if (FPC_datalink_to(Data[FPC0_MAGIC_LEN-1] & 0x7F) == FPC_DATALINK_ERROR) {
        return 0;
    }
    return 1;
}

uint32_t FPC_datalink_to(uint8_t in) {
    if (in == DLT_NULL || in == DLT_EN10MB) {
        return in;
    }
    return (uint32_t) FPC_DATALINK_ERROR;
}

uint8_t FPC_datalink_from(uint32_t in) {
    if (in == DLT_NULL || in == DLT_EN10MB) {
        return in;
    }
    return FPC_DATALINK_ERROR;
}

int FPC_init(FPC_buffer_t *r, const uint8_t *Data, size_t Size) {
    if (!FPC_IsFuzzPacketCapture(Data, Size)) {
        return -1;
    }
    r->Data = Data;
    r->Size = Size;
    r->datalink = FPC_datalink_to(Data[FPC0_MAGIC_LEN-1] & 0x7F);
    r->tcpSingleStream = (Data[FPC0_MAGIC_LEN-1] & 0x80);
    if (r->tcpSingleStream) {
        r->offset = FPC0_HEADER_LEN;
    } else {
        r->offset = FPC0_MAGIC_LEN;
    }
    memset(r->pkt, 0, FPC_SNAPLEN);
    r->tcpState = FPC_TCP_STATE_START;
    r->seqCliAckSrv = 0x10000000;
    r->seqSrvAckCli = 0x20000000;
    r->nb = 0;
    return 0;
}

#define FPC_TCP_FLAG_SYN 0x02
#define FPC_TCP_FLAG_ACK 0x10
#define FPC_TCP_FLAGS_NEG_OFFSET 7

#define FPC_NULL_HEADER "\x02\x00\x00\x00"
#define FPC_NULL_HEADER_LEN 4

#define FPC_ETH_HEADER "\x00\x01\x02\x03\x04\x05\x00\x01\x02\x03\x04\x05\x08\x00"
#define FPC_ETH_HEADER_LEN 14

#define FPC_IP4_HEADER "\x45\x00\xff\xff\x00\x00\x40\x00\x40\x06\x00\x00\x7f\x00\x00\x01" \
"\x7f\x00\x00\x01"
#define FPC_IP4_HEADER_LEN 20

#define FPC_TCP_HEADER_END "\xFF\xFF\x00\x00\x00\x00"
#define FPC_TCP_HEADER_END_LEN 6

static bpf_u_int32 buildTCPpacket(FPC_buffer_t *pkts, bool s2c, size_t plen) {
    bpf_u_int32 r = 0;
    if (pkts->datalink == DLT_NULL) {
        memcpy(pkts->pkt, FPC_NULL_HEADER, FPC_NULL_HEADER_LEN);
        r = FPC_NULL_HEADER_LEN;
    } else if (pkts->datalink == DLT_EN10MB) {
        memcpy(pkts->pkt, FPC_ETH_HEADER, FPC_ETH_HEADER_LEN);
        r = FPC_ETH_HEADER_LEN;
    } else {
        //unreachable
        abort();
    }
    memcpy(pkts->pkt+r, FPC_IP4_HEADER, FPC_IP4_HEADER_LEN);
    pkts->pkt[r+2] = (plen + FPC_IP4_HEADER_LEN + 20) >> 8;
    pkts->pkt[r+3] = (plen + FPC_IP4_HEADER_LEN+ 20);
    r += FPC_IP4_HEADER_LEN;
    //ports
    if (s2c) {
        memcpy(pkts->pkt+r, pkts->Data+FPC0_MAGIC_LEN, 2);
        memcpy(pkts->pkt+r+2, pkts->Data+FPC0_MAGIC_LEN+2, 2);
        pkts->pkt[r+4] = pkts->seqSrvAckCli >> 24;
        pkts->pkt[r+5] = pkts->seqSrvAckCli >> 16;
        pkts->pkt[r+6] = pkts->seqSrvAckCli >> 8;
        pkts->pkt[r+7] = pkts->seqSrvAckCli;
        pkts->pkt[r+8] = pkts->seqCliAckSrv >> 24;
        pkts->pkt[r+9] = pkts->seqCliAckSrv >> 16;
        pkts->pkt[r+10] = pkts->seqCliAckSrv >> 8;
        pkts->pkt[r+11] = pkts->seqCliAckSrv;
    } else {
        memcpy(pkts->pkt+r, pkts->Data+FPC0_MAGIC_LEN+2, 2);
        memcpy(pkts->pkt+r+2, pkts->Data+FPC0_MAGIC_LEN, 2);
        pkts->pkt[r+4] = pkts->seqCliAckSrv >> 24;
        pkts->pkt[r+5] = pkts->seqCliAckSrv >> 16;
        pkts->pkt[r+6] = pkts->seqCliAckSrv >> 8;
        pkts->pkt[r+7] = pkts->seqCliAckSrv;
        if (pkts->tcpState != FPC_TCP_STATE_SYN) {
            pkts->pkt[r+8] = pkts->seqSrvAckCli >> 24;
            pkts->pkt[r+9] = pkts->seqSrvAckCli >> 16;
            pkts->pkt[r+10] = pkts->seqSrvAckCli >> 8;
            pkts->pkt[r+11] = pkts->seqSrvAckCli;
        }
    }
    r += 12;
    pkts->pkt[r] = 0x50; // TCP length
    if (pkts->tcpState == FPC_TCP_STATE_ESTABLISHED) {
        pkts->pkt[r+1] = FPC_TCP_FLAG_ACK; // flags
    } else {
        pkts->pkt[r+1] = 0; // flags
    }
    r+=2;
    memcpy(pkts->pkt+r, FPC_TCP_HEADER_END, FPC_TCP_HEADER_END_LEN);
    r+=FPC_TCP_HEADER_END_LEN;
    return r;
}

#define FCP_BASE_TIME 0x601cf51a

int FPC_next_pcap(FPC_buffer_t *pkts, struct pcap_pkthdr *header, const uint8_t **pkt) {
    *pkt = pkts->Data + pkts->offset + FPC_TS_MAXSIZE;
    const uint8_t *next = memmem(pkts->Data + pkts->offset, pkts->Size - pkts->offset, FPC0_MAGIC, FPC0_MAGIC_LEN);
    if (next == NULL) {
        next = pkts->Data + pkts->Size;
    }
    if (next < *pkt) {
        //wrong input
        return -1;
    }

    memset(header, 0, sizeof(struct pcap_pkthdr));
    header->ts.tv_sec = *((time_t *) (pkts->Data + pkts->offset));
    if (header->ts.tv_sec < 0) {
        header->ts.tv_sec = 0;
    }
    header->ts.tv_usec = *((suseconds_t *) (pkts->Data + pkts->offset + FPC_TS_MAXSIZE/2));
    // Limit microseconds to 1 million
    header->ts.tv_usec = ((header->ts.tv_usec % 1000000) + 1000000) % 1000000;
    header->caplen = next - (*pkt);
    pkts->offset += header->caplen + FPC_TS_MAXSIZE + FPC0_MAGIC_LEN;
    header->len = header->caplen;
    return 1;
}

int FPC_next_tcp(FPC_buffer_t *pkts, struct pcap_pkthdr *header, const uint8_t **pkt) {
    *pkt = pkts->Data + pkts->offset;
    const uint8_t *next = memmem(pkts->Data + pkts->offset, pkts->Size - pkts->offset, FPC0_MAGIC, FPC0_MAGIC_LEN);
    if (next == NULL) {
        next = pkts->Data + pkts->Size;
    }
    if (next < *pkt) {
        //wrong input
        return -1;
    }

    memset(header, 0, sizeof(struct pcap_pkthdr));
    header->ts.tv_sec = FCP_BASE_TIME;
    header->ts.tv_usec = pkts->nb;
    pkts->nb++;
    header->caplen = next - (*pkt);

    if (pkts->tcpState > FPC_TCP_STATE_SYNACK) {
        pkts->offset += header->caplen + FPC0_MAGIC_LEN;
    }
    switch (pkts->tcpState) {
        case FPC_TCP_STATE_START:
        pkts->tcpState = FPC_TCP_STATE_SYN;
        header->caplen = buildTCPpacket(pkts, false, 0);
        *pkt = pkts->pkt;
        pkts->pkt[header->caplen-FPC_TCP_FLAGS_NEG_OFFSET] |= FPC_TCP_FLAG_SYN;
        pkts->seqCliAckSrv++;
        break;

        case FPC_TCP_STATE_SYN:
        pkts->tcpState = FPC_TCP_STATE_SYNACK;
        header->caplen = buildTCPpacket(pkts, true, 0);
        *pkt = pkts->pkt;
        pkts->pkt[header->caplen-FPC_TCP_FLAGS_NEG_OFFSET] |= FPC_TCP_FLAG_SYN | FPC_TCP_FLAG_ACK;
        pkts->seqSrvAckCli++;
        break;

        case FPC_TCP_STATE_SYNACK:
        pkts->tcpState = FPC_TCP_STATE_ESTABLISHED;
        header->caplen = buildTCPpacket(pkts, false, 0);
        *pkt = pkts->pkt;
        pkts->pkt[header->caplen-FPC_TCP_FLAGS_NEG_OFFSET] |= FPC_TCP_FLAG_ACK;
        break;

        case FPC_TCP_STATE_ESTABLISHED:
        if (header->caplen < 1) {
            return -1;
        }
        header->caplen--;
        bool s2c = (*pkt[0]) & 1;
        header->len = buildTCPpacket(pkts, s2c, header->caplen);
        if (header->caplen + header->len > FPC_SNAPLEN) {
            header->caplen = FPC_SNAPLEN - header->len;
        }
        memcpy(pkts->pkt+header->len, *pkt+1, header->caplen);
        if (s2c) {
            pkts->seqSrvAckCli += header->caplen;
        } else {
            pkts->seqCliAckSrv += header->caplen;
        }
        header->caplen += header->len;
        *pkt = pkts->pkt;
        break;
    }
    header->len = header->caplen;
    return 1;
}

int FPC_next(FPC_buffer_t *pkts, struct pcap_pkthdr *header, const uint8_t **pkt) {
    if (pkts->offset >= pkts->Size) {
        return 0;
    }

    if (pkts->tcpSingleStream) {
        return FPC_next_tcp(pkts, header, pkt);
    } //else
    return FPC_next_pcap(pkts, header, pkt);
}

Coverage Report

Created: 2025-11-16 07:09

Line	Count	Source
1		// Copyright (c) 2021 Catena cyber
2		// Author Philippe Antoine <p.antoine@catenacyber.fr>
3
4		#define _GNU_SOURCE
5		#include <stdint.h>
6		#include <stddef.h>
7		#include <string.h>
8		#include <stdlib.h>
9
10		#include <pcap/pcap.h>
11
12		#include "fuzz_pcap.h"
13
14	68.1k	int FPC_IsFuzzPacketCapture(const uint8_t *Data, size_t Size) {
15	68.1k	if (Size < FPC0_HEADER_LEN) {
16	6	return 0;
17	6	}
18	68.1k	if (memcmp(Data, FPC0_MAGIC, FPC0_MAGIC_LEN - 1) != 0) {
19	51	return 0;
20	51	}
21	68.0k	if (FPC_datalink_to(Data[FPC0_MAGIC_LEN-1] & 0x7F) == FPC_DATALINK_ERROR) {
22	2	return 0;
23	2	}
24	68.0k	return 1;
25	68.0k	}
26
27	136k	uint32_t FPC_datalink_to(uint8_t in) {
28	136k	if (in == DLT_NULL \|\| in == DLT_EN10MB) {
29	136k	return in;
30	136k	}
31	2	return (uint32_t) FPC_DATALINK_ERROR;
32	136k	}
33
34	0	uint8_t FPC_datalink_from(uint32_t in) {
35	0	if (in == DLT_NULL \|\| in == DLT_EN10MB) {
36	0	return in;
37	0	}
38	0	return FPC_DATALINK_ERROR;
39	0	}
40
41	68.1k	int FPC_init(FPC_buffer_t r, const uint8_t Data, size_t Size) {
42	68.1k	if (!FPC_IsFuzzPacketCapture(Data, Size)) {
43	59	return -1;
44	59	}
45	68.0k	r->Data = Data;
46	68.0k	r->Size = Size;
47	68.0k	r->datalink = FPC_datalink_to(Data[FPC0_MAGIC_LEN-1] & 0x7F);
48	68.0k	r->tcpSingleStream = (Data[FPC0_MAGIC_LEN-1] & 0x80);
49	68.0k	if (r->tcpSingleStream) {
50	35.2k	r->offset = FPC0_HEADER_LEN;
51	35.2k	} else {
52	32.8k	r->offset = FPC0_MAGIC_LEN;
53	32.8k	}
54	68.0k	memset(r->pkt, 0, FPC_SNAPLEN);
55	68.0k	r->tcpState = FPC_TCP_STATE_START;
56	68.0k	r->seqCliAckSrv = 0x10000000;
57	68.0k	r->seqSrvAckCli = 0x20000000;
58	68.0k	r->nb = 0;
59	68.0k	return 0;
60	68.1k	}
61
62	70.1k	#define FPC_TCP_FLAG_SYN 0x02
63	7.50M	#define FPC_TCP_FLAG_ACK 0x10
64	105k	#define FPC_TCP_FLAGS_NEG_OFFSET 7
65
66	7.48M	#define FPC_NULL_HEADER "\x02\x00\x00\x00"
67	14.9M	#define FPC_NULL_HEADER_LEN 4
68
69	20.0k	#define FPC_ETH_HEADER "\x00\x01\x02\x03\x04\x05\x00\x01\x02\x03\x04\x05\x08\x00"
70	40.0k	#define FPC_ETH_HEADER_LEN 14
71
72	7.50M	#define FPC_IP4_HEADER "\x45\x00\xff\xff\x00\x00\x40\x00\x40\x06\x00\x00\x7f\x00\x00\x01" \
73	7.50M	"\x7f\x00\x00\x01"
74	30.0M	#define FPC_IP4_HEADER_LEN 20
75
76	7.50M	#define FPC_TCP_HEADER_END "\xFF\xFF\x00\x00\x00\x00"
77	15.0M	#define FPC_TCP_HEADER_END_LEN 6
78
79	7.50M	static bpf_u_int32 buildTCPpacket(FPC_buffer_t *pkts, bool s2c, size_t plen) {
80	7.50M	bpf_u_int32 r = 0;
81	7.50M	if (pkts->datalink == DLT_NULL) {
82	7.48M	memcpy(pkts->pkt, FPC_NULL_HEADER, FPC_NULL_HEADER_LEN);
83	7.48M	r = FPC_NULL_HEADER_LEN;
84	7.48M	} else if (pkts->datalink == DLT_EN10MB) {
85	20.0k	memcpy(pkts->pkt, FPC_ETH_HEADER, FPC_ETH_HEADER_LEN);
86	20.0k	r = FPC_ETH_HEADER_LEN;
87	20.0k	} else {
88		//unreachable
89	0	abort();
90	0	}
91	7.50M	memcpy(pkts->pkt+r, FPC_IP4_HEADER, FPC_IP4_HEADER_LEN);
92	7.50M	pkts->pkt[r+2] = (plen + FPC_IP4_HEADER_LEN + 20) >> 8;
93	7.50M	pkts->pkt[r+3] = (plen + FPC_IP4_HEADER_LEN+ 20);
94	7.50M	r += FPC_IP4_HEADER_LEN;
95		//ports
96	7.50M	if (s2c) {
97	3.59M	memcpy(pkts->pkt+r, pkts->Data+FPC0_MAGIC_LEN, 2);
98	3.59M	memcpy(pkts->pkt+r+2, pkts->Data+FPC0_MAGIC_LEN+2, 2);
99	3.59M	pkts->pkt[r+4] = pkts->seqSrvAckCli >> 24;
100	3.59M	pkts->pkt[r+5] = pkts->seqSrvAckCli >> 16;
101	3.59M	pkts->pkt[r+6] = pkts->seqSrvAckCli >> 8;
102	3.59M	pkts->pkt[r+7] = pkts->seqSrvAckCli;
103	3.59M	pkts->pkt[r+8] = pkts->seqCliAckSrv >> 24;
104	3.59M	pkts->pkt[r+9] = pkts->seqCliAckSrv >> 16;
105	3.59M	pkts->pkt[r+10] = pkts->seqCliAckSrv >> 8;
106	3.59M	pkts->pkt[r+11] = pkts->seqCliAckSrv;
107	3.90M	} else {
108	3.90M	memcpy(pkts->pkt+r, pkts->Data+FPC0_MAGIC_LEN+2, 2);
109	3.90M	memcpy(pkts->pkt+r+2, pkts->Data+FPC0_MAGIC_LEN, 2);
110	3.90M	pkts->pkt[r+4] = pkts->seqCliAckSrv >> 24;
111	3.90M	pkts->pkt[r+5] = pkts->seqCliAckSrv >> 16;
112	3.90M	pkts->pkt[r+6] = pkts->seqCliAckSrv >> 8;
113	3.90M	pkts->pkt[r+7] = pkts->seqCliAckSrv;
114	3.90M	if (pkts->tcpState != FPC_TCP_STATE_SYN) {
115	3.87M	pkts->pkt[r+8] = pkts->seqSrvAckCli >> 24;
116	3.87M	pkts->pkt[r+9] = pkts->seqSrvAckCli >> 16;
117	3.87M	pkts->pkt[r+10] = pkts->seqSrvAckCli >> 8;
118	3.87M	pkts->pkt[r+11] = pkts->seqSrvAckCli;
119	3.87M	}
120	3.90M	}
121	7.50M	r += 12;
122	7.50M	pkts->pkt[r] = 0x50; // TCP length
123	7.50M	if (pkts->tcpState == FPC_TCP_STATE_ESTABLISHED) {
124	7.43M	pkts->pkt[r+1] = FPC_TCP_FLAG_ACK; // flags
125	7.43M	} else {
126	70.1k	pkts->pkt[r+1] = 0; // flags
127	70.1k	}
128	7.50M	r+=2;
129	7.50M	memcpy(pkts->pkt+r, FPC_TCP_HEADER_END, FPC_TCP_HEADER_END_LEN);
130	7.50M	r+=FPC_TCP_HEADER_END_LEN;
131	7.50M	return r;
132	7.50M	}
133
134	7.50M	#define FCP_BASE_TIME 0x601cf51a
135
136	8.91M	int FPC_next_pcap(FPC_buffer_t pkts, struct pcap_pkthdr header, const uint8_t **pkt) {
137	8.91M	*pkt = pkts->Data + pkts->offset + FPC_TS_MAXSIZE;
138	8.91M	const uint8_t *next = memmem(pkts->Data + pkts->offset, pkts->Size - pkts->offset, FPC0_MAGIC, FPC0_MAGIC_LEN);
139	8.91M	if (next == NULL) {
140	25.9k	next = pkts->Data + pkts->Size;
141	25.9k	}
142	8.91M	if (next < *pkt) {
143		//wrong input
144	3.94k	return -1;
145	3.94k	}
146
147	8.91M	memset(header, 0, sizeof(struct pcap_pkthdr));
148	8.91M	header->ts.tv_sec = ((time_t ) (pkts->Data + pkts->offset));
149	8.91M	if (header->ts.tv_sec < 0) {
150	841k	header->ts.tv_sec = 0;
151	841k	}
152	8.91M	header->ts.tv_usec = ((suseconds_t ) (pkts->Data + pkts->offset + FPC_TS_MAXSIZE/2));
153		// Limit microseconds to 1 million
154	8.91M	header->ts.tv_usec = ((header->ts.tv_usec % 1000000) + 1000000) % 1000000;
155	8.91M	header->caplen = next - (*pkt);
156	8.91M	pkts->offset += header->caplen + FPC_TS_MAXSIZE + FPC0_MAGIC_LEN;
157	8.91M	header->len = header->caplen;
158	8.91M	return 1;
159	8.91M	}
160
161	7.50M	int FPC_next_tcp(FPC_buffer_t pkts, struct pcap_pkthdr header, const uint8_t **pkt) {
162	7.50M	*pkt = pkts->Data + pkts->offset;
163	7.50M	const uint8_t *next = memmem(pkts->Data + pkts->offset, pkts->Size - pkts->offset, FPC0_MAGIC, FPC0_MAGIC_LEN);
164	7.50M	if (next == NULL) {
165	40.7k	next = pkts->Data + pkts->Size;
166	40.7k	}
167	7.50M	if (next < *pkt) {
168		//wrong input
169	0	return -1;
170	0	}
171
172	7.50M	memset(header, 0, sizeof(struct pcap_pkthdr));
173	7.50M	header->ts.tv_sec = FCP_BASE_TIME;
174	7.50M	header->ts.tv_usec = pkts->nb;
175	7.50M	pkts->nb++;
176	7.50M	header->caplen = next - (*pkt);
177
178	7.50M	if (pkts->tcpState > FPC_TCP_STATE_SYNACK) {
179	7.40M	pkts->offset += header->caplen + FPC0_MAGIC_LEN;
180	7.40M	}
181	7.50M	switch (pkts->tcpState) {
182	35.0k	case FPC_TCP_STATE_START:
183	35.0k	pkts->tcpState = FPC_TCP_STATE_SYN;
184	35.0k	header->caplen = buildTCPpacket(pkts, false, 0);
185	35.0k	*pkt = pkts->pkt;
186	35.0k	pkts->pkt[header->caplen-FPC_TCP_FLAGS_NEG_OFFSET] \|= FPC_TCP_FLAG_SYN;
187	35.0k	pkts->seqCliAckSrv++;
188	35.0k	break;
189
190	35.0k	case FPC_TCP_STATE_SYN:
191	35.0k	pkts->tcpState = FPC_TCP_STATE_SYNACK;
192	35.0k	header->caplen = buildTCPpacket(pkts, true, 0);
193	35.0k	*pkt = pkts->pkt;
194	35.0k	pkts->pkt[header->caplen-FPC_TCP_FLAGS_NEG_OFFSET] \|= FPC_TCP_FLAG_SYN \| FPC_TCP_FLAG_ACK;
195	35.0k	pkts->seqSrvAckCli++;
196	35.0k	break;
197
198	35.0k	case FPC_TCP_STATE_SYNACK:
199	35.0k	pkts->tcpState = FPC_TCP_STATE_ESTABLISHED;
200	35.0k	header->caplen = buildTCPpacket(pkts, false, 0);
201	35.0k	*pkt = pkts->pkt;
202	35.0k	pkts->pkt[header->caplen-FPC_TCP_FLAGS_NEG_OFFSET] \|= FPC_TCP_FLAG_ACK;
203	35.0k	break;
204
205	7.40M	case FPC_TCP_STATE_ESTABLISHED:
206	7.40M	if (header->caplen < 1) {
207	101	return -1;
208	101	}
209	7.40M	header->caplen--;
210	7.40M	bool s2c = (*pkt[0]) & 1;
211	7.40M	header->len = buildTCPpacket(pkts, s2c, header->caplen);
212	7.40M	if (header->caplen + header->len > FPC_SNAPLEN) {
213	644	header->caplen = FPC_SNAPLEN - header->len;
214	644	}
215	7.40M	memcpy(pkts->pkt+header->len, *pkt+1, header->caplen);
216	7.40M	if (s2c) {
217	3.56M	pkts->seqSrvAckCli += header->caplen;
218	3.83M	} else {
219	3.83M	pkts->seqCliAckSrv += header->caplen;
220	3.83M	}
221	7.40M	header->caplen += header->len;
222	7.40M	*pkt = pkts->pkt;
223	7.40M	break;
224	7.50M	}
225	7.50M	header->len = header->caplen;
226	7.50M	return 1;
227	7.50M	}
228
229	16.4M	int FPC_next(FPC_buffer_t pkts, struct pcap_pkthdr header, const uint8_t **pkt) {
230	16.4M	if (pkts->offset >= pkts->Size) {
231	59.6k	return 0;
232	59.6k	}
233
234	16.4M	if (pkts->tcpSingleStream) {
235	7.50M	return FPC_next_tcp(pkts, header, pkt);
236	7.50M	} //else
237	8.91M	return FPC_next_pcap(pkts, header, pkt);
238	16.4M	}